Planet Minis

agentorange · 11-04-2008, 05:50 PM

Last Saturday I got my CT running. It was great except when I would stop I had to rev the throttle a bit to keep it from dying while idling. So, Sunday I decided to play with the pilot and air screws, and thought I had it down. I rode it for about a mile and it sputtered down, like maybe it was starved for air, or fuel, but before it died out it was idling great. I let it sit and it started fine, but sputtered out after a quarter mile or so. I adjusted the screws and the results are the same. Maybe I need to let it sit again after the last adjustment.

Any suggestions on how to get it set properly at this point?

mexicanyella · 11-04-2008, 09:10 PM

If it quit while riding, you weren't on the pilot circuit so your screw adjustments shouldn't have been coming into play. With slide carbs the pilot screw and pilot jet affects the idle-1/4 throttle range, the slide cutaway profile from about 1/4 up to maybe 1/3-1/2, the needle setting and taper from there up to about 3/4, and the main jet from 3/4 to full. These ranges generally overlap and are interactive up to a point, but that's a rough guideline.

If it's crapping out under load and taking a while of riding to do it, I'd suspect you've got some junk or water blobbing around in the float bowl until it meets the main jet and restricts fuel flow momentarily, or your float needle is sticking shut, or you've got another restriction somewhere upstream of the carb.

I had the brass fuel inlet nipple/barb thing actually come loose in the carb body once, and it didn't leak but pushed into the carb a ways without me realizing it and was restricting fuel flow into the bowl. I've only seen this once or twice before and it was on little old honda carbs each time. I'd check elsewhere first, though.

agentorange · 11-04-2008, 09:23 PM

Thanks for the reply. I have a new fuel tank and lines but I guess it could be some junk in the carb from somewhere, hopefully not part of the carb itself. Should I try to keep running it and hope it clears or remove, open up the carb & drain it to see if anything is in it?
It may not have anything to do with the air or pilot screws, but it just seems odd that it was fine until I started adjusting them.

mexicanyella · 11-04-2008, 11:19 PM

First off, the pilot screw is the air screw. At idle and just above, fuel's metered by a small fixed orifice--the pilot jet--and you adjust the idle mixture within a small, fine-tuning range by the pilot (air) screw, which restricts air flow in a small air passage bypassing the throttle slide according to how far you screw the screw into this passage. Larger, coarser adjustments to idle mixture are made by replacing the pilot jet with one with a different-sized fuel orifice in it.

The other screw on the side, the one that sticks out, is the throttle stop screw, which just adjusts how far the slide comes down when you let off the throttle. Screwed all the way out, the slide drops all the way and the bike doesn't idle. As you screw it in, you raise the slide's lowest position slightly until you get an idle speed you want.

Definitely remove, disassemble and throughly clean. In any case, a good first step would be to open the bowl-drain screw (near the bottom of the float bowl) with the fuel petcock turned on. You should see a fairly fast flow as the bowl empties, then a slower flow as fuel comes in through the float needle and drains out. Do not drink the fuel; it tastes bad--I know. And make sure you're not surging along on pissed-off-at-your-bike energy and doing this in the garage next to a hot water heater with a standing pilot or something. A fair amount of fuel will come out, enough to make fumes...

If it slows down to nothing, or to a slow drip, that's a clue...the bowl's not filling fast enough. If the flattened sides and corners of the float needle are crusty, it can cause the needle to stay seated in the seat even if the float's dropped. That happened to me before. Sometimes you can use carb spray and a shop towel to clean this stuff off, but sometimes it's hard crust like water deposits, which is pretty cleaning-resistant. In that case it's probably better to just replace the needle and seat.

But this is probably getting ahead of myself. It might just be dirt in there. Or water. The fact that it runs for a bit and then goes away could be something moving around in the bottom of the bowl as the fuel sloshes around with the bike's movement. Water's heavier than gas and collects in a blob at the bottom, and if it's enough to start getting sucked into the jet, it will block the gas flow until it sloshes away again. Same with flecks of dirt.

Check the fuel flow and the internal dirt situation and see what you see, and check back in.

(There's a saying that 90% of carb problems are electrical. It never hurts to have a look at the spark plug condition just to be sure. Please report back with that too. If I've misinterpreted your description of it quitting on you, that may get me back on track...)

agentorange · 11-05-2008, 06:55 PM

I will remove & clean the carb this weekend.

I rode it today to make sure it wasn't a fluke when it sputtered out the other day. I went around the block 3 times (1 mile)and thought I was in the clear, but it sputtered out, and wouldnt start. I pushed it into the garage and let it sit for about 15 minutes and it then started first kick. Sound like junk or water in the carb?

mexicanyella · 11-05-2008, 09:05 PM

It could be that or a few other things. If I were in the same place as the bike I'd be listening to how it sputtered out, looking for telltale exhaust smoke, smelling the exhaust...but without actually being there I can't be sure. Rich vs. lean exhaust smells different. Engines with dodgy ignition coils sometimes run for awhile until they get hot, then crap out unpredictably. I've heard that dodgy condensers can behave this way, but I've not experienced that. With me dodgy condensers just caused my points to get pitted faster...and then the points condition caused the bike to run bad or quit.

A carbon-fouled spark plug can fire under light load but crap out under heavier load, I suppose due to different cylinder pressures (I am fighting with one of our tractors over this issue right now; it's got this old weak magneto that probably needs to be rebuilt and maybe have its rotor remagnetized, and I've got spark quality all over the map according to lunar phase, whether our neighbor's got the lawn sprinkler going or not, etc.) You'd look at the plug and think the mixture's rich, but the carb setting is fine. It's just got a weak spark some of the time. My Z50 has done this before too when I had the pilot screw set a little too rich and let it idle too long, or over-choked it on a cold start. I didn't realize I'd fouled the plug until I gave it some throttle. With the two-strokes I've owned over the years, plug fouling was less throttle-dependent...it either was fine or I fouled the bejesus out of it and it just wouldn't start or run.

Anyway, once I hear what you find in the carb and what the spark plug looks like, I'll possibly have a better idea.

Another thing that would be helpful to know is whether it cuts out at a consistent load/throttle opening, or whether the dependent variable is just how long it runs.

(is this a points CT or an electronic ignition CT?)

agentorange · 11-06-2008, 08:01 AM

Okay, you just hit on a few things I did not remember to mention. I swapped out the spark plug before I rode it yesterday and the business end of the plug looked sooty. Also, there is some smoke coming from the exhaust, as in from where it curves out of the engine. Not a lot, but there is some smoke I have noticed. When it cuts out, it seems like it is as I am accelerating. It just dies out with a spoot spoot spoot and flutters down. It needs to sit about 1o minutes or so, then it's up first kick.

mexicanyella · 11-06-2008, 08:15 AM

Have you drained and/or removed the float bowl yet? If it seems to be running well before it dies each time, I'm leaning towards "eliminate the possibility of dirt and water sliding around the bottom of the float bowl." What you're describing sounds like an intermittent cutting out, and that's out of the realm of carb settings most of the time. Verify the float bowl's clean and water-free, and make sure the fuel flow into it is sufficient and steady as I described above. Gotta eliminate some things here to narrow it down.

boonacka · 11-06-2008, 08:38 AM

make sure your gas cap is vented properly and your carb vents arent blocked.

agentorange · 11-06-2008, 06:43 PM

I removed the carb and opened it up; no signs of trash or water that I could see. I did notice that there seemed to be some soot on the choke flap side of the carb as well as on the engine side of the intake.I fastened it back up and did about a mile the sput sput.... The fuel flow seems to be great through the lines from the tank and the petcock.

Could this be a coil problem? I hope not, I don't have any experience changing them.

dirtbkr188 · 11-06-2008, 07:00 PM

As you slowly eliminate all the problems fuel related, it will become more apparent that it can be electrical in nature. Sometimes, a coil with a cracked housing will be fine until it warms up enough to expand the crack, letting the spark arc to the frame, taking it away from the spark plug. Sometimes the same thing can happen with a points-type ignition, with either the points or the condenser shorting itself out. Make sure you have the plug boot firmly threaded onto the coil wire, and that there is plenty of wire for the boot to get a good spark through.

mexicanyella · 11-06-2008, 07:28 PM

I wouldn't be too worried about the carb soot for now. Next step is to carry a spark plug socket and a ratchet (or the original spark plug wrench, if it's still with the bike) with you and get it to crap out (the bike, not the tools). Pull the plug--wear gloves; it'll be hot--and put it back in the spark plug wire and lay the plug on the cylinder or cases so the metal part is grounded to the engine, and kick it over with the ignition on and see if you still have a regular spark, and if that spark appears to be of normal strength. Maybe do this before you ride too so you can get an idea of what kind of spark it has when it IS running right. The spark should be bright bluish. A thin, thready purplish spark MIGHT run the engine but is a sign that something's weak in there usually.

It's starting to sound more and more like your spark's going away when the engine gets hot.

What year is your CT? It would be good to know if it has points or not.

agentorange · 11-06-2008, 07:37 PM

It's a '78. Next time I will do the spark test tomorrow. My wife is about to divorce me because I am spending every spare minute with the bike...

mexicanyella · 11-06-2008, 07:43 PM

Aw, hell. Get her one too. Then you can work on TWO of them, possibly while she taps her foot impatiently in the background. That kind of thing makes mechanical repairs FUN.

Good luck with the spark test; hopefully that will provide a clue or two.

Remember that hot spark plugs stay hot for quite a while. Do not ask me how I know this.

agentorange · 11-06-2008, 08:03 PM

That's a great idea! Thanks for your help with this, man. I had completely convinced myself that it had to be the carb, now it looks like it is electrical.

ShapeShifter · 11-06-2008, 11:00 PM

Quote:

Originally Posted by mexicanyella

....... Then you can work on TWO of them, possibly while she taps her foot impatiently in the background. That kind of thing makes mechanical repairs FUN.
.........

Love it! LOL

agentorange · 11-08-2008, 08:13 PM

Finally got a chance to test the spark. The first one was purple (but seemed weaker than last week when the bike first got going). I then put the plug back in and started it up and it was fluttery right off the bat. I t seems like whatever it is has gotten worse. Within a couple of minutes the headlight dimmed and it sputtered out. I pushed it back up the driveway and checked the spark again. Still there, but even weaker than before.
Does this sound like a bad coil?

mexicanyella · 11-08-2008, 10:38 PM

Here comes a long post. Don't take it as patronizing or condescending if you already know some or all of this. Feel free to ask more questions if I've glossed over some detail you don't get, because one thing I can do is type like a mannafanna...

Could be a bad coil, or a bad connection somewhere, or your points need adjusting/filing.

Test the coil in the following bone-headed manner, which I learned on an antique engine message board awhile back: locate the coil, on the upstream end of the sparkplug wire. On a CT, I think it's inside the frame somewhere, under the seat or something. I like a good high-voltage electrical component close to the fuel supply.

There'll be a skinny wire feeding the coil, with one of those standard japanese-bike bullet connectors you can unplug. Unplug it. Maybe clean the ends of this with some electronics spray cleaner or a brief interlude of finicky sanding. Make sure it's a good connection when you plug it back in.

Pull the spark plug AGAIN, and put it in the plug wire; lay plug/wire combo on head or cylinder or whatever was working for you on your spark test.

Get a 6V lantern battery or a battery charger set to 6V, connect the - terminal to the frame or engine and lightly brush the + terminal against the end of the little wire going into the coil. As you brush them together and then apart, you're charging the coil's primary winding and then interrupting the current, just like the points are supposed to. If the coil's working and connected to a clean, well-grounded spark plug, you'll see a healthy spark at the plug as the current source separates from the end of the primary wire going into the coil. Report findings.

If the coil seems to be working, next I'd check the points. They get pits and bumps on the contact faces after squizillions of open/close cycles at many thousands of rpm, and you have to file the contact faces flat again. You can get a points file at NAPA or somewhere similar for a few bucks, or if you're really in rat mode you can rip off one of your wife's fingernail emery boards. Get the points file if you can. Emery boards will make the points flat but also scatter sand particles around which will make for more cleanup. Plus they're clumsier. On a tractor with a big old distributor, it's less of an issue. It's pretty tight under that CT flywheel.

It's sort of possible to do this through the holes in the flywheel, but it's better to obtain a flywheel puller and remove the flywheel. Flywheel pullers for Z50s/CT70s are about twenty bucks or so at your local motorcycle shop. Ask to order one from their parts unlimited or tucker-rocky catalog. Good tool to have with a points-equipped bike.

You want to be able to get the filing device between the contact faces and move it back and forth in a repeating linear motion with the spring pressure of the points spring holding the contacts against the file on either side. Do this a bit, check your progress, do it again until the faces are flat and clean. Don't file the entire face away, and keep them meeting one another squarely when they're allowed to close.

Once you've done that, and I hope you've done it with the flywheel off because you just know that's more betterer, you need to clean off the fuzz, shavings, and squizz that you've just sent all over the immediate points area. Best way is to spray electronics cleaner aerosol spray in there, because it's a strong solvent that evaporates away immediately without dissolving the insulation off anything in there. If you didn't get a can of that you can sort of clean things enough to run by pulling a clean business card through the closed points until it comes out clean. But this is less betterer.

While you've got the flyweel off look at the little wire to the points and the condenser (small silver canister which is supposed to absorb enough current when the points open to keep them from arcing and burning) and make sure it's not shorting out on anything metal and it's secure in there.

Now you need to put the flywheel back on to set the points gap, because the cam that opens and closes the points is part of the flywheel. Once it's on, rotate the flywheel until the points are as far open as they get and measure the gap with a feeler gauge. It should be in the range of .012"-.016," where a feeler gauge in that thickness range feels like it has light drag coming through the gap. You don't want the feeler gauge shoving them open farther, or flapping around between them. There's a screw on the fixed points contact you can loosen to allow them to pivot. Loosen it just enough to allow a screwdriver, inserted into the little adjustment slot, to move the base, but still tight enough to hold that adjustment while you tighten the screw back down. If you stuck a dirty, oily feeler gauge in there to measure them, you've just crapped up your points-cleaning efforts and need to clean them again. Oil on the points is bad.

With a good coil, plugged back in after the coil test of course, and clean, flat and correctly gapped points, you should have a fat blue spark. Do you?

Disclaimer: under no circumstances would I discourage you from buying a tune-up kit and actually REPLACING the points and condenser with new ones. It can't hurt, but you still need to pull the flywheel and as far as I know, my two running 1971 Z50 engines are running the original points and condensers and have needed no ignition work other than occasional filing and gap-setting for 37 years; I've owned them since about 1991 and have never replaced anything under there. My old Suzuki DS100 ate condensers and needed lots of points attention for some reason (but made up for it by being slow and having crappy suspension). The Hondas rev just as high...but seem to be more reliable. WTF?

agentorange · 11-09-2008, 02:29 PM

Awesome information, no problem with stuff I already knew, trust me. Well, no way around getting into the engine. While I'm at it, might as well replace the gaskets. Better get the flywheel puller ordered too. If it's not the coil, it's the points or condenser.
I will try to get this taken care of this week & will report my findings. Thanks Mexicanyella!

mexicanyella · 11-09-2008, 03:36 PM

Gaskets? You don' need no steenkeeng gaskets. Not to pull the flywheel or set the points, anyway.

Maybe there's supposed to be a gasket under the flywheel cover, but neither of my bikes has one nor ever has in the time that I've owned them, and I've done my share of riding in rain/sleet/snow/mud/hail/flying sea snakes and never had a problem without it...

11-04-2008, 05:50 PM	#1 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Carb setting issue? Last Saturday I got my CT running. It was great except when I would stop I had to rev the throttle a bit to keep it from dying while idling. So, Sunday I decided to play with the pilot and air screws, and thought I had it down. I rode it for about a mile and it sputtered down, like maybe it was starved for air, or fuel, but before it died out it was idling great. I let it sit and it started fine, but sputtered out after a quarter mile or so. I adjusted the screws and the results are the same. Maybe I need to let it sit again after the last adjustment. Any suggestions on how to get it set properly at this point?

11-04-2008, 09:10 PM	#2 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? If it quit while riding, you weren't on the pilot circuit so your screw adjustments shouldn't have been coming into play. With slide carbs the pilot screw and pilot jet affects the idle-1/4 throttle range, the slide cutaway profile from about 1/4 up to maybe 1/3-1/2, the needle setting and taper from there up to about 3/4, and the main jet from 3/4 to full. These ranges generally overlap and are interactive up to a point, but that's a rough guideline. If it's crapping out under load and taking a while of riding to do it, I'd suspect you've got some junk or water blobbing around in the float bowl until it meets the main jet and restricts fuel flow momentarily, or your float needle is sticking shut, or you've got another restriction somewhere upstream of the carb. I had the brass fuel inlet nipple/barb thing actually come loose in the carb body once, and it didn't leak but pushed into the carb a ways without me realizing it and was restricting fuel flow into the bowl. I've only seen this once or twice before and it was on little old honda carbs each time. I'd check elsewhere first, though.

11-04-2008, 09:23 PM	#3 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? Thanks for the reply. I have a new fuel tank and lines but I guess it could be some junk in the carb from somewhere, hopefully not part of the carb itself. Should I try to keep running it and hope it clears or remove, open up the carb & drain it to see if anything is in it? It may not have anything to do with the air or pilot screws, but it just seems odd that it was fine until I started adjusting them.

11-04-2008, 11:19 PM	#4 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? First off, the pilot screw is the air screw. At idle and just above, fuel's metered by a small fixed orifice--the pilot jet--and you adjust the idle mixture within a small, fine-tuning range by the pilot (air) screw, which restricts air flow in a small air passage bypassing the throttle slide according to how far you screw the screw into this passage. Larger, coarser adjustments to idle mixture are made by replacing the pilot jet with one with a different-sized fuel orifice in it. The other screw on the side, the one that sticks out, is the throttle stop screw, which just adjusts how far the slide comes down when you let off the throttle. Screwed all the way out, the slide drops all the way and the bike doesn't idle. As you screw it in, you raise the slide's lowest position slightly until you get an idle speed you want. Definitely remove, disassemble and throughly clean. In any case, a good first step would be to open the bowl-drain screw (near the bottom of the float bowl) with the fuel petcock turned on. You should see a fairly fast flow as the bowl empties, then a slower flow as fuel comes in through the float needle and drains out. Do not drink the fuel; it tastes bad--I know. And make sure you're not surging along on pissed-off-at-your-bike energy and doing this in the garage next to a hot water heater with a standing pilot or something. A fair amount of fuel will come out, enough to make fumes... If it slows down to nothing, or to a slow drip, that's a clue...the bowl's not filling fast enough. If the flattened sides and corners of the float needle are crusty, it can cause the needle to stay seated in the seat even if the float's dropped. That happened to me before. Sometimes you can use carb spray and a shop towel to clean this stuff off, but sometimes it's hard crust like water deposits, which is pretty cleaning-resistant. In that case it's probably better to just replace the needle and seat. But this is probably getting ahead of myself. It might just be dirt in there. Or water. The fact that it runs for a bit and then goes away could be something moving around in the bottom of the bowl as the fuel sloshes around with the bike's movement. Water's heavier than gas and collects in a blob at the bottom, and if it's enough to start getting sucked into the jet, it will block the gas flow until it sloshes away again. Same with flecks of dirt. Check the fuel flow and the internal dirt situation and see what you see, and check back in. (There's a saying that 90% of carb problems are electrical. It never hurts to have a look at the spark plug condition just to be sure. Please report back with that too. If I've misinterpreted your description of it quitting on you, that may get me back on track...) Last edited by mexicanyella; 11-04-2008 at 11:31 PM.

11-05-2008, 06:55 PM	#5 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? I will remove & clean the carb this weekend. I rode it today to make sure it wasn't a fluke when it sputtered out the other day. I went around the block 3 times (1 mile)and thought I was in the clear, but it sputtered out, and wouldnt start. I pushed it into the garage and let it sit for about 15 minutes and it then started first kick. Sound like junk or water in the carb?

11-05-2008, 09:05 PM	#6 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? It could be that or a few other things. If I were in the same place as the bike I'd be listening to how it sputtered out, looking for telltale exhaust smoke, smelling the exhaust...but without actually being there I can't be sure. Rich vs. lean exhaust smells different. Engines with dodgy ignition coils sometimes run for awhile until they get hot, then crap out unpredictably. I've heard that dodgy condensers can behave this way, but I've not experienced that. With me dodgy condensers just caused my points to get pitted faster...and then the points condition caused the bike to run bad or quit. A carbon-fouled spark plug can fire under light load but crap out under heavier load, I suppose due to different cylinder pressures (I am fighting with one of our tractors over this issue right now; it's got this old weak magneto that probably needs to be rebuilt and maybe have its rotor remagnetized, and I've got spark quality all over the map according to lunar phase, whether our neighbor's got the lawn sprinkler going or not, etc.) You'd look at the plug and think the mixture's rich, but the carb setting is fine. It's just got a weak spark some of the time. My Z50 has done this before too when I had the pilot screw set a little too rich and let it idle too long, or over-choked it on a cold start. I didn't realize I'd fouled the plug until I gave it some throttle. With the two-strokes I've owned over the years, plug fouling was less throttle-dependent...it either was fine or I fouled the bejesus out of it and it just wouldn't start or run. Anyway, once I hear what you find in the carb and what the spark plug looks like, I'll possibly have a better idea. Another thing that would be helpful to know is whether it cuts out at a consistent load/throttle opening, or whether the dependent variable is just how long it runs. (is this a points CT or an electronic ignition CT?)

11-06-2008, 08:01 AM	#7 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? Okay, you just hit on a few things I did not remember to mention. I swapped out the spark plug before I rode it yesterday and the business end of the plug looked sooty. Also, there is some smoke coming from the exhaust, as in from where it curves out of the engine. Not a lot, but there is some smoke I have noticed. When it cuts out, it seems like it is as I am accelerating. It just dies out with a spoot spoot spoot and flutters down. It needs to sit about 1o minutes or so, then it's up first kick.

11-06-2008, 08:15 AM	#8 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? Have you drained and/or removed the float bowl yet? If it seems to be running well before it dies each time, I'm leaning towards "eliminate the possibility of dirt and water sliding around the bottom of the float bowl." What you're describing sounds like an intermittent cutting out, and that's out of the realm of carb settings most of the time. Verify the float bowl's clean and water-free, and make sure the fuel flow into it is sufficient and steady as I described above. Gotta eliminate some things here to narrow it down.

11-06-2008, 08:38 AM	#9 (permalink)
boonacka 3rd Gear Member Join Date: Mar 2006 Location: SolomonRacing.net Posts: 1,191 My Mood:	Re: Carb setting issue? make sure your gas cap is vented properly and your carb vents arent blocked.

11-06-2008, 06:43 PM	#10 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? I removed the carb and opened it up; no signs of trash or water that I could see. I did notice that there seemed to be some soot on the choke flap side of the carb as well as on the engine side of the intake.I fastened it back up and did about a mile the sput sput.... The fuel flow seems to be great through the lines from the tank and the petcock. Could this be a coil problem? I hope not, I don't have any experience changing them.

11-06-2008, 07:00 PM	#11 (permalink)
dirtbkr188 3rd Gear Member Join Date: May 2004 Location: New Jersey Posts: 2,973	Re: Carb setting issue? As you slowly eliminate all the problems fuel related, it will become more apparent that it can be electrical in nature. Sometimes, a coil with a cracked housing will be fine until it warms up enough to expand the crack, letting the spark arc to the frame, taking it away from the spark plug. Sometimes the same thing can happen with a points-type ignition, with either the points or the condenser shorting itself out. Make sure you have the plug boot firmly threaded onto the coil wire, and that there is plenty of wire for the boot to get a good spark through.

11-06-2008, 07:28 PM	#12 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? I wouldn't be too worried about the carb soot for now. Next step is to carry a spark plug socket and a ratchet (or the original spark plug wrench, if it's still with the bike) with you and get it to crap out (the bike, not the tools). Pull the plug--wear gloves; it'll be hot--and put it back in the spark plug wire and lay the plug on the cylinder or cases so the metal part is grounded to the engine, and kick it over with the ignition on and see if you still have a regular spark, and if that spark appears to be of normal strength. Maybe do this before you ride too so you can get an idea of what kind of spark it has when it IS running right. The spark should be bright bluish. A thin, thready purplish spark MIGHT run the engine but is a sign that something's weak in there usually. It's starting to sound more and more like your spark's going away when the engine gets hot. What year is your CT? It would be good to know if it has points or not.

11-06-2008, 07:37 PM	#13 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? It's a '78. Next time I will do the spark test tomorrow. My wife is about to divorce me because I am spending every spare minute with the bike...

11-06-2008, 07:43 PM	#14 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? Aw, hell. Get her one too. Then you can work on TWO of them, possibly while she taps her foot impatiently in the background. That kind of thing makes mechanical repairs FUN. Good luck with the spark test; hopefully that will provide a clue or two. Remember that hot spark plugs stay hot for quite a while. Do not ask me how I know this.

11-06-2008, 08:03 PM	#15 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? That's a great idea! Thanks for your help with this, man. I had completely convinced myself that it had to be the carb, now it looks like it is electrical.

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11-08-2008, 08:13 PM	#17 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? Finally got a chance to test the spark. The first one was purple (but seemed weaker than last week when the bike first got going). I then put the plug back in and started it up and it was fluttery right off the bat. I t seems like whatever it is has gotten worse. Within a couple of minutes the headlight dimmed and it sputtered out. I pushed it back up the driveway and checked the spark again. Still there, but even weaker than before. Does this sound like a bad coil?

11-08-2008, 10:38 PM	#18 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? Here comes a long post. Don't take it as patronizing or condescending if you already know some or all of this. Feel free to ask more questions if I've glossed over some detail you don't get, because one thing I can do is type like a mannafanna... Could be a bad coil, or a bad connection somewhere, or your points need adjusting/filing. Test the coil in the following bone-headed manner, which I learned on an antique engine message board awhile back: locate the coil, on the upstream end of the sparkplug wire. On a CT, I think it's inside the frame somewhere, under the seat or something. I like a good high-voltage electrical component close to the fuel supply. There'll be a skinny wire feeding the coil, with one of those standard japanese-bike bullet connectors you can unplug. Unplug it. Maybe clean the ends of this with some electronics spray cleaner or a brief interlude of finicky sanding. Make sure it's a good connection when you plug it back in. Pull the spark plug AGAIN, and put it in the plug wire; lay plug/wire combo on head or cylinder or whatever was working for you on your spark test. Get a 6V lantern battery or a battery charger set to 6V, connect the - terminal to the frame or engine and lightly brush the + terminal against the end of the little wire going into the coil. As you brush them together and then apart, you're charging the coil's primary winding and then interrupting the current, just like the points are supposed to. If the coil's working and connected to a clean, well-grounded spark plug, you'll see a healthy spark at the plug as the current source separates from the end of the primary wire going into the coil. Report findings. If the coil seems to be working, next I'd check the points. They get pits and bumps on the contact faces after squizillions of open/close cycles at many thousands of rpm, and you have to file the contact faces flat again. You can get a points file at NAPA or somewhere similar for a few bucks, or if you're really in rat mode you can rip off one of your wife's fingernail emery boards. Get the points file if you can. Emery boards will make the points flat but also scatter sand particles around which will make for more cleanup. Plus they're clumsier. On a tractor with a big old distributor, it's less of an issue. It's pretty tight under that CT flywheel. It's sort of possible to do this through the holes in the flywheel, but it's better to obtain a flywheel puller and remove the flywheel. Flywheel pullers for Z50s/CT70s are about twenty bucks or so at your local motorcycle shop. Ask to order one from their parts unlimited or tucker-rocky catalog. Good tool to have with a points-equipped bike. You want to be able to get the filing device between the contact faces and move it back and forth in a repeating linear motion with the spring pressure of the points spring holding the contacts against the file on either side. Do this a bit, check your progress, do it again until the faces are flat and clean. Don't file the entire face away, and keep them meeting one another squarely when they're allowed to close. Once you've done that, and I hope you've done it with the flywheel off because you just know that's more betterer, you need to clean off the fuzz, shavings, and squizz that you've just sent all over the immediate points area. Best way is to spray electronics cleaner aerosol spray in there, because it's a strong solvent that evaporates away immediately without dissolving the insulation off anything in there. If you didn't get a can of that you can sort of clean things enough to run by pulling a clean business card through the closed points until it comes out clean. But this is less betterer. While you've got the flyweel off look at the little wire to the points and the condenser (small silver canister which is supposed to absorb enough current when the points open to keep them from arcing and burning) and make sure it's not shorting out on anything metal and it's secure in there. Now you need to put the flywheel back on to set the points gap, because the cam that opens and closes the points is part of the flywheel. Once it's on, rotate the flywheel until the points are as far open as they get and measure the gap with a feeler gauge. It should be in the range of .012"-.016," where a feeler gauge in that thickness range feels like it has light drag coming through the gap. You don't want the feeler gauge shoving them open farther, or flapping around between them. There's a screw on the fixed points contact you can loosen to allow them to pivot. Loosen it just enough to allow a screwdriver, inserted into the little adjustment slot, to move the base, but still tight enough to hold that adjustment while you tighten the screw back down. If you stuck a dirty, oily feeler gauge in there to measure them, you've just crapped up your points-cleaning efforts and need to clean them again. Oil on the points is bad. With a good coil, plugged back in after the coil test of course, and clean, flat and correctly gapped points, you should have a fat blue spark. Do you? Disclaimer: under no circumstances would I discourage you from buying a tune-up kit and actually REPLACING the points and condenser with new ones. It can't hurt, but you still need to pull the flywheel and as far as I know, my two running 1971 Z50 engines are running the original points and condensers and have needed no ignition work other than occasional filing and gap-setting for 37 years; I've owned them since about 1991 and have never replaced anything under there. My old Suzuki DS100 ate condensers and needed lots of points attention for some reason (but made up for it by being slow and having crappy suspension). The Hondas rev just as high...but seem to be more reliable. WTF? Last edited by mexicanyella; 11-08-2008 at 10:49 PM.

11-09-2008, 02:29 PM	#19 (permalink)
agentorange PM Newbie Join Date: Oct 2008 Location: Memphis, TN Posts: 37	Re: Carb setting issue? Awesome information, no problem with stuff I already knew, trust me. Well, no way around getting into the engine. While I'm at it, might as well replace the gaskets. Better get the flywheel puller ordered too. If it's not the coil, it's the points or condenser. I will try to get this taken care of this week & will report my findings. Thanks Mexicanyella!

11-09-2008, 03:36 PM	#20 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: Carb setting issue? Gaskets? You don' need no steenkeeng gaskets. Not to pull the flywheel or set the points, anyway. Maybe there's supposed to be a gasket under the flywheel cover, but neither of my bikes has one nor ever has in the time that I've owned them, and I've done my share of riding in rain/sleet/snow/mud/hail/flying sea snakes and never had a problem without it...