Planet Minis

fastbmw · 10-01-2009, 11:35 PM

My mini-Repsol ZB50 died and I don't know why. I was cruising to work and the engine died, it wasn't a sudden stop but it just slowed to a stop like someone had turned off the fuel. It wouldn't start anymore and had to push it to work. (which sucked) I got it taken home and proceeded to diagnosis the problem.

(background on the engine, 72cc bore with big valve head but stock carb. Stock everything else.)

I had plenty of fuel, had spark, it had a fresh oil change and oil level was at the proper level. I did a compression check and it was within the specs of the service manual. I took it apart, thoroughly cleaned the carb and even replaced the slow jet. The fuel was clean and the jets weren't clogged. I cleaned out the petcock and fuel flow seems fine.
The engine turns over fine, though it seems like it is easier to kick over then usual. I tested all the electrical components and everything checks out fine (coil, ignition switch, cutoff switch, spark plug cap) I even double checked the valve gap which was fine too.

I can kick and kick but it won't start anymore. I don't know where to go from here without taking the head and jug off. Any ideas?

(good thing my mini-Ducati is still running or I'd be very very sad.) haha

--X-- · 10-02-2009, 06:57 AM

I rode my CT to work one time and it just shut down on me. Couldn't figure out what was wrong for the life of me. Turns out I somehow hit the off switch on my handle bar while grabbing for the front brake while taking a corner so it shut off on me. It was a really dumb thing, but it had me guessing for most of the day as to what was wrong. Just a thought, but did you hit the off switch on the handle bars?

If you have spark and it's getting gas, then that motor should be doing something. Did you check your ground wire? They can come loose sometimes too.

RAZZO · 10-02-2009, 07:09 AM

Always start with the simple. Kill switch like X said. New plug next. Have seen plugs with spark fail to start or quit right off idle.

Check float valve in carb. May be hung up. Check the light in the glove box too. :P LOL

--X-- · 10-02-2009, 10:02 AM

I've seen the spark plug issue many many times too. Swap in a clean plug and I've been able to get numerous bikes going again. My CT was running too rich before too, and it would fool out the plug after a week. Now I ride with a spare and fixed that issue too.

schofell84 · 10-02-2009, 10:17 AM

so you have fuel, ignition and compression and it wont run? are you sure youre getting fuel?

DuckBoy · 10-02-2009, 10:28 AM

New spark plug

fastbmw · 10-02-2009, 04:56 PM

Quote:

Originally Posted by schofell84

so you have fuel, ignition and compression and it wont run? are you sure youre getting fuel?

Yeah it's driving me a bit nuts. I double checked the kill switch and even used my multimeter on it, it works fine. I'll try a new plug, thanks for the hint!

tmas · 10-02-2009, 05:03 PM

Quote:

Originally Posted by fastbmw

Yeah it's driving me a bit nuts. I double checked the kill switch and even used my multimeter on it, it works fine. I'll try a new plug, thanks for the hint!

Also..Try your ignition switch beside the speedometer too. Just try it disconnected.
tmas

fastbmw · 10-02-2009, 05:36 PM

Yeah, I did a multimeter test on that too.

z50 chopper · 10-02-2009, 06:01 PM

could it be somthing in the case not meshing up right? Check your exhaust and intake valves, compression may be good but one of the valves could be clogged or fouled up some how.
Ok so I am reaching for what could possibley cause this problem but you never know till you check.

fastbmw · 10-02-2009, 07:03 PM

Thanks alot everyone, I appreciate the ideas. I'll keep you all updated.

slapaho16 · 10-02-2009, 07:12 PM

also check the valve tappets if they come loose it wont start

hooptytank · 10-03-2009, 02:58 AM

Quote:

Originally Posted by fastbmw

The engine turns over fine, though it seems like it is easier to kick over then usual.

sounds mechanical... check cam timing, valve clearance, compression and cylinder leak down test if you have the tools, or you may need to pull the head off and check the valves and bore condition.

Way loose valve clearance could indicate a bent valve if the adjusters are still tight.

A few drops of oil through the plug hole can tell you if the rings are shot/seized.

I'd start with a fresh plug like others said, it's the easiest. And that stupid a$$ "off" switch that gives you 2 chances to screw up... it's gotten me too many times.

fastbmw · 10-05-2009, 02:01 PM

I think I found the problem, I believe it's a blown headgasket, which is weird since the compression test was within norms. I used a new NGK plug and it would start if you held open the throttle but I got that distinctive cracking sound of a cylinder with no exhaust pipe. I guess I'm going to have to tear it down for further investigation. Thanks for all the help guys.

ak105 · 10-12-2009, 08:29 PM

i think that one of ur piston rings have popped

conant19 · 10-12-2009, 09:35 PM

make sure a vavle didnt tighen up causing it not to run right

10-01-2009, 11:35 PM	#1 (permalink)
fastbmw 2nd Gear Member Join Date: Sep 2005 Posts: 643	My ZB50 died... My mini-Repsol ZB50 died and I don't know why. I was cruising to work and the engine died, it wasn't a sudden stop but it just slowed to a stop like someone had turned off the fuel. It wouldn't start anymore and had to push it to work. (which sucked) I got it taken home and proceeded to diagnosis the problem. (background on the engine, 72cc bore with big valve head but stock carb. Stock everything else.) I had plenty of fuel, had spark, it had a fresh oil change and oil level was at the proper level. I did a compression check and it was within the specs of the service manual. I took it apart, thoroughly cleaned the carb and even replaced the slow jet. The fuel was clean and the jets weren't clogged. I cleaned out the petcock and fuel flow seems fine. The engine turns over fine, though it seems like it is easier to kick over then usual. I tested all the electrical components and everything checks out fine (coil, ignition switch, cutoff switch, spark plug cap) I even double checked the valve gap which was fine too. I can kick and kick but it won't start anymore. I don't know where to go from here without taking the head and jug off. Any ideas? (good thing my mini-Ducati is still running or I'd be very very sad.) haha Last edited by fastbmw; 10-01-2009 at 11:40 PM.

10-02-2009, 06:57 AM	#2 (permalink)
--X-- 2nd Gear Member Join Date: Mar 2006 Location: New Lenox, IL Posts: 568 My Mood:	Re: My ZB50 died... I rode my CT to work one time and it just shut down on me. Couldn't figure out what was wrong for the life of me. Turns out I somehow hit the off switch on my handle bar while grabbing for the front brake while taking a corner so it shut off on me. It was a really dumb thing, but it had me guessing for most of the day as to what was wrong. Just a thought, but did you hit the off switch on the handle bars? If you have spark and it's getting gas, then that motor should be doing something. Did you check your ground wire? They can come loose sometimes too.

10-02-2009, 07:09 AM	#3 (permalink)
RAZZO Old School Z50s Join Date: Jun 2005 Location: NEW JERSEY PINELANDS Posts: 1,971 My Mood:	Re: My ZB50 died... Always start with the simple. Kill switch like X said. New plug next. Have seen plugs with spark fail to start or quit right off idle. Check float valve in carb. May be hung up. Check the light in the glove box too. :P LOL

10-02-2009, 10:02 AM	#4 (permalink)
--X-- 2nd Gear Member Join Date: Mar 2006 Location: New Lenox, IL Posts: 568 My Mood:	Re: My ZB50 died... I've seen the spark plug issue many many times too. Swap in a clean plug and I've been able to get numerous bikes going again. My CT was running too rich before too, and it would fool out the plug after a week. Now I ride with a spare and fixed that issue too.

10-02-2009, 10:17 AM	#5 (permalink)
schofell84 2nd Gear Member Join Date: Feb 2007 Location: Ogdensburg Posts: 278	Re: My ZB50 died... so you have fuel, ignition and compression and it wont run? are you sure youre getting fuel?

10-02-2009, 10:28 AM	#6 (permalink)
DuckBoy PM Newbie Join Date: Feb 2009 Location: Central Texas Posts: 87	Re: My ZB50 died... New spark plug

10-02-2009, 05:36 PM	#9 (permalink)
fastbmw 2nd Gear Member Join Date: Sep 2005 Posts: 643	Re: My ZB50 died... Yeah, I did a multimeter test on that too.

10-02-2009, 06:01 PM	#10 (permalink)
z50 chopper 2nd Gear Member Join Date: Jun 2009 Location: Nanaimo, BC, Canada Posts: 504 My Mood:	Re: My ZB50 died... could it be somthing in the case not meshing up right? Check your exhaust and intake valves, compression may be good but one of the valves could be clogged or fouled up some how. Ok so I am reaching for what could possibley cause this problem but you never know till you check.

10-02-2009, 07:03 PM	#11 (permalink)
fastbmw 2nd Gear Member Join Date: Sep 2005 Posts: 643	Re: My ZB50 died... Thanks alot everyone, I appreciate the ideas. I'll keep you all updated.

10-02-2009, 07:12 PM	#12 (permalink)
slapaho16 3rd Gear Member Join Date: Apr 2006 Location: Fort Worth TX Posts: 5,382 My Mood:	Re: My ZB50 died... also check the valve tappets if they come loose it wont start

10-05-2009, 02:01 PM	#14 (permalink)
fastbmw 2nd Gear Member Join Date: Sep 2005 Posts: 643	Re: My ZB50 died... I think I found the problem, I believe it's a blown headgasket, which is weird since the compression test was within norms. I used a new NGK plug and it would start if you held open the throttle but I got that distinctive cracking sound of a cylinder with no exhaust pipe. I guess I'm going to have to tear it down for further investigation. Thanks for all the help guys.

10-12-2009, 08:29 PM	#15 (permalink)
ak105 PM Newbie Join Date: Oct 2009 Posts: 1	Re: My ZB50 died... i think that one of ur piston rings have popped

10-12-2009, 09:35 PM	#16 (permalink)
conant19 1st Gear Member Join Date: Nov 2008 Location: Mtv Posts: 171 My Mood:	Re: My ZB50 died... make sure a vavle didnt tighen up causing it not to run right

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