Planet Minis

shiftmx11 · 09-04-2009, 04:15 PM

ok i give up on this one i try almost everything i could think of maybe someone could give me some new idea to try. ok it is a 76 xl 70 i got talk into fixing. it came to me with no fire and wiring was gutted. repair all of that got it to fire up and it runs now. but, when it is on idle it runs fine. as soon you give it gas it revs up and then blogs and the revs down and back up. ok what i have tried, 1. adjusted float 2. clean the whole carb 3. the needle was in the lowest postion when i got it so play with that. 4. check the points and clean them again 5. change spark plug 6. made sure all the jets are stock and exhaust is stock. when i change the spark plug it ran good for about 3 min then started messing up again. that makes me think it is running to rich and foul a plug. but i dont know i am so sick of this bike and want it gone.

help plz

mexicanyella · 09-04-2009, 04:51 PM

Need more info: for starters, where's the needle positioned now? What does the spark plug look like when you pull it out after the bike quits?

The bogging thing...does it do it any time you crack the throttle above idle, or just at a specific range of throttle? For instance, can you just whale on it at full throttle and it runs okay, but bogs at midway throttle openings? Or does it die at anything above an idle? Is the bog point more throttle opening dependent, or does it seem rpm dependent, or can you tell?

Dirty or incorrectly gapped points can cause weak spark which the engine will idle on okay but not accept large handfuls of throttle or much of a load, because at higher cylinder pressures the spark won't jump the gap like it will at idle.

The needle being too far down causes midrange leanness, which can cause midrange bogging. In that case the plug should look pretty clean unless you're also burning a bunch of oil or have weak spark.

An air leak between the carb and cylinder can cause bogging if it's bad enough, or a crappy and hard-to-adjust idle if it's just a little air leak...but if it's the latter, usually the bike won't run too bad at higher throttle openings because there's not much vacuum in the intake then and the lean mixture effect of the air leak is proportionally less.

Are you sure your float bowl is filling reliably? If your float needle is hanging up in its seat even when the float drops, you'll have a fuel starvation problem, which sometimes shows up at higher throttle openings even though the bike idles okay. Pull the bowl off, hook up the fuel line, turn the fuel petcock on and work the float up and down gently and look for how responsive the fuel flow is to the float position.

That ought to keep you busy for a little bit; good luck.

Also, XL70s are cool. Maybe now would be a good time to buy it cheap!

shiftmx11 · 09-09-2009, 01:02 AM

it was a bad coil all along. i founded out the coil came off a z50a with 6volt coil whitch is ok to do but, the z50a had spark problem too with a lifan 125 12 VOLT SYSTEM lol.

09-04-2009, 04:15 PM	#1 (permalink)
shiftmx11 PM Newbie Join Date: Aug 2007 Location: TN Posts: 21	xl 70 help ok i give up on this one i try almost everything i could think of maybe someone could give me some new idea to try. ok it is a 76 xl 70 i got talk into fixing. it came to me with no fire and wiring was gutted. repair all of that got it to fire up and it runs now. but, when it is on idle it runs fine. as soon you give it gas it revs up and then blogs and the revs down and back up. ok what i have tried, 1. adjusted float 2. clean the whole carb 3. the needle was in the lowest postion when i got it so play with that. 4. check the points and clean them again 5. change spark plug 6. made sure all the jets are stock and exhaust is stock. when i change the spark plug it ran good for about 3 min then started messing up again. that makes me think it is running to rich and foul a plug. but i dont know i am so sick of this bike and want it gone. help plz

09-04-2009, 04:51 PM	#2 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 984	Re: xl 70 help Need more info: for starters, where's the needle positioned now? What does the spark plug look like when you pull it out after the bike quits? The bogging thing...does it do it any time you crack the throttle above idle, or just at a specific range of throttle? For instance, can you just whale on it at full throttle and it runs okay, but bogs at midway throttle openings? Or does it die at anything above an idle? Is the bog point more throttle opening dependent, or does it seem rpm dependent, or can you tell? Dirty or incorrectly gapped points can cause weak spark which the engine will idle on okay but not accept large handfuls of throttle or much of a load, because at higher cylinder pressures the spark won't jump the gap like it will at idle. The needle being too far down causes midrange leanness, which can cause midrange bogging. In that case the plug should look pretty clean unless you're also burning a bunch of oil or have weak spark. An air leak between the carb and cylinder can cause bogging if it's bad enough, or a crappy and hard-to-adjust idle if it's just a little air leak...but if it's the latter, usually the bike won't run too bad at higher throttle openings because there's not much vacuum in the intake then and the lean mixture effect of the air leak is proportionally less. Are you sure your float bowl is filling reliably? If your float needle is hanging up in its seat even when the float drops, you'll have a fuel starvation problem, which sometimes shows up at higher throttle openings even though the bike idles okay. Pull the bowl off, hook up the fuel line, turn the fuel petcock on and work the float up and down gently and look for how responsive the fuel flow is to the float position. That ought to keep you busy for a little bit; good luck. Also, XL70s are cool. Maybe now would be a good time to buy it cheap!

09-09-2009, 01:02 AM	#3 (permalink)
shiftmx11 PM Newbie Join Date: Aug 2007 Location: TN Posts: 21	Re: xl 70 help it was a bad coil all along. i founded out the coil came off a z50a with 6volt coil whitch is ok to do but, the z50a had spark problem too with a lifan 125 12 VOLT SYSTEM lol.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)