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Post by g2kmobile on Oct 22, 2015 11:20:26 GMT -5
Hi guys and gals, I'm still new to the boards. I have a 2011 Peace sports 50cc scooter, that I would really appreciate your help with. The scooter always backfires on deceleration, and dies when taken off the center stand. It has either too high an idle or too low an idle once warmed up. The smog system has been removed. Adjusting the fuel/air mixture screw makes essentially no difference in rpm unless screwed all the way in (clockwise). Here is the work that has been performed thus far:
Carb has been completely torn down and cleaned thoroughly.
New cdi, stator, solenoid installed, each played with individually so as to verify integrity of each component.
Spark plug gapped at .020,.021,.022,.024,.028,.030,.035, and scooter tested to see if each gap setting made a difference. So far, .020 seems to produce the best results.
Valve clearance set to .003 for both intake and exhaust, exhaust gasket at muffler/head replaced and tightened
new wiring harness installed, new vacuum operated petcock installed.
New (keyed) ignition switch, kill switch tests good.
No air leaks at intake manifold to carb or head. No air leaks at airbox to carb, vacuum lines replaced, gas lines replaced, fuel filter replaced.
Float level adjusted, bowl does fill with fuel. No gas detected in air cleaner.
I cannot keep this scooter from backfiring when letting off the throttle from WOT. My current thinking is that SMOG removal = needs 1 size smaller jets = an always rich condition?? = backfiring??
Any help with this would be greatly appreciated. Any thoughts?
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Post by scooter on Oct 22, 2015 11:43:19 GMT -5
Hi guys and gals, I'm still new to the boards. I have a 2011 Peace sports 50cc scooter, that I would really appreciate your help with. The scooter always backfires on deceleration, and dies when taken off the center stand. It has either too high an idle or too low an idle once warmed up. The smog system has been removed. Adjusting the fuel/air mixture screw makes essentially no difference in rpm unless screwed all the way in (clockwise). Here is the work that has been performed thus far: Carb has been completely torn down and cleaned thoroughly. New cdi, stator, solenoid installed, each played with individually so as to verify integrity of each component. Spark plug gapped at .020,.021,.022,.024,.028,.030,.035, and scooter tested to see if each gap setting made a difference. So far, .020 seems to produce the best results. Valve clearance set to .003 for both intake and exhaust, exhaust gasket at muffler/head replaced and tightened new wiring harness installed, new vacuum operated petcock installed. New (keyed) ignition switch, kill switch tests good. No air leaks at intake manifold to carb or head. No air leaks at airbox to carb, vacuum lines replaced, gas lines replaced, fuel filter replaced. Float level adjusted, bowl does fill with fuel. No gas detected in air cleaner. I cannot keep this scooter from backfiring when letting off the throttle from WOT. My current thinking is that SMOG removal = needs 1 size smaller jets = an always rich condition?? = backfiring?? Any help with this would be greatly appreciated. Any thoughts? Sounds like too much air in your exhaust. If you had one of those EGR things on your exhaust pipe, you'd have to seal it off. Maybe check your exhaust nuts and also look for holes or cracks in the muffler if it's old. |
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Post by urbanmadness on Oct 22, 2015 11:51:55 GMT -5
De-acceleration valve on the carb might be bad or not getting vacuum. You have a picture of how the vacuum lines are routed?
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Post by g2kmobile on Oct 22, 2015 12:47:17 GMT -5
Muffler studs are tight and muffler gasket is new (3 days old). There is a small pinhole in the muffler tube but it won't even make a Bic lighter sputter out. It'll be tomorrow before I can post pics of the vacuum hose routing(s).
Thank you guys for the help so far. I repair scooters on the side and have never encountered a problem like this before. The scooter dying when let off the center stand is confusing me too. There are no "safety switches" on this scoot that tie into the stands like there are on a Zuma or Bergman.
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Post by urbanmadness on Oct 22, 2015 14:04:59 GMT -5
Take scooter off the center stand and see if you have spark... If you don't, you have a short or bad ground somewhere. The popping tho, is running rich on decel. usually that's either not enough back pressure in the exhaust, or the decel valve not working or leaking vacuum.
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Post by g2kmobile on Oct 23, 2015 9:15:28 GMT -5
urbanmadness I have spark when the scooter is off the center stand. What happens is when the scooter hits the ground from being taken off the stand the engine RPM either drops or it dies completely. If it dies I can simply restart it with no problems/issues. Whats curious is that I have double checked all wiring connections, and they are tight. I have also inspected the layout of vacuum and fuel lines to see if a momentary "pinching" is occurring and there is no "pinching" of any vacuum or fuel lines. I should have pictures up either later today or sometime tomorrow. From what I have read when you remove the PAIR system you should block off the hole where the "S pipe" connects to the head. On this scooter there is still a metal tube attached and it is routed to some type of device. So there may be an issue there.
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Post by g2kmobile on Nov 5, 2015 10:05:11 GMT -5
Sorry it took so long to get the pics up, the scooter is the ONLY transportation option, the customer has. We finally got it back into the shop yesterday, it died and wouldn't start at all. That turned out to be a bad CDI. Here are the pictures of the vacuum line routing and the "device" the S pipe connects to. The scooter is still having all the same issues as previously posted.     I'm not sure I mentioned this before: the scooter can't seem to be adjusted to where its idle is the correct speed without affecting something else... If the idle speed is set to 3000 rpm, light throttling will cause it to idle down to 1500 - 2000 for a second or two, then go back up to 3000. If adjusted to 1900 - 2000 rpm, light throttling will cause it to idle down to 500 - 700 rpm, which in turn causes it to stall out. Adjusting the A/F mixture screw does NOT affect this behavior. Adjusting the A/F mixture screw one way brings the expected response of light stumbling when increasing throttle from idle. Or adjusting the other way causes light stumbling when going WOT, but not when first coming off idle, as one would expect. Curious to hear your ideas on this. Again, thank you all for the help this is proving a most difficult case. |
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Post by JerryScript on Nov 5, 2015 13:05:16 GMT -5
Sounds like you need to upjet the carb.
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Post by g2kmobile on Nov 5, 2015 14:34:07 GMT -5
I don't understand mechanically,why it would need up jetting, when it is a stock 50cc motor. The carb should be able to prevent gas seepage into the system by way of the float (assuming I have adjusted the float properly).
Even if the carb needs up jetting, it should run consistent to whatever degree of tuning we do. Albeit, said tuning, would not necessarily produce the correct balance needed.
The muffler may have been "gutted" by its previous owner, thereby causing excessive loss of back pressure/baffling, which allows more of the backfiring to be heard. I don't have a stock muffler on hand to try.
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Post by JerryScript on Nov 5, 2015 15:33:54 GMT -5
If the muffler was gutted, that would be a reason to upjet.
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Post by lain on Nov 5, 2015 20:34:24 GMT -5
Sorry it took so long to get the pics up, the scooter is the ONLY transportation option, the customer has. We finally got it back into the shop yesterday, it died and wouldn't start at all. That turned out to be a bad CDI. Here are the pictures of the vacuum line routing and the "device" the S pipe connects to. The scooter is still having all the same issues as previously posted. I'm not sure I mentioned this before: the scooter can't seem to be adjusted to where its idle is the correct speed without affecting something else... If the idle speed is set to 3000 rpm, light throttling will cause it to idle down to 1500 - 2000 for a second or two, then go back up to 3000. If adjusted to 1900 - 2000 rpm, light throttling will cause it to idle down to 500 - 700 rpm, which in turn causes it to stall out. Adjusting the A/F mixture screw does NOT affect this behavior. Adjusting the A/F mixture screw one way brings the expected response of light stumbling when increasing throttle from idle. Or adjusting the other way causes light stumbling when going WOT, but not when first coming off idle, as one would expect. Curious to hear your ideas on this. Again, thank you all for the help this is proving a most difficult case. Sounds like a leak maybe. Is the intake on there nice and snug? Is the intake spacer between the engine and the manifold cracked or worn out? Is any of the gaskets or rubber rings between the manifold and engine bad? Are you sure the carb was reassembled correctly? Maybe one of the diaphragms is not sitting correctly or is torn or have a small pinprick hole in it? |
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Post by g2kmobile on Nov 6, 2015 8:15:38 GMT -5
I applied high-temp silicone gasket maker to the intake manifold/carb spacer to ensure a good seal. and sprayed all around the jug/carb spacer and carb spacer/intake manifold with brake cleaner. No leaks detected.
Sprayed air intake to carb junction and intake manifold to carb junction, no leaks detected.
I agree gutting the muffler could create a need to upjet. I'm looking to swap with a known stock muffler to see if this corrects the problem.
I'm also going to rebuild a different carb and try that too. I'll keep updating the thread as I do these things.
The latest development is scooter lost ALL lights, turn signals, instrument cluster, etc....BUT...grounding out the solenoid terminals causes it to start right up and run. Had all the lights working the day before then nothing today.
We had put a new wiring harness in it, but we still don't seem to be running off the stator ( lights don't get brighter when revved). So I'll have to do some electrical diagnostics today as well.
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Post by lain on Nov 6, 2015 9:44:19 GMT -5
I applied high-temp silicone gasket maker to the intake manifold/carb spacer to ensure a good seal. and sprayed all around the jug/carb spacer and carb spacer/intake manifold with brake cleaner. No leaks detected. Sprayed air intake to carb junction and intake manifold to carb junction, no leaks detected. I agree gutting the muffler could create a need to upjet. I'm looking to swap with a known stock muffler to see if this corrects the problem. I'm also going to rebuild a different carb and try that too. I'll keep updating the thread as I do these things. The latest development is scooter lost ALL lights, turn signals, instrument cluster, etc....BUT...grounding out the solenoid terminals causes it to start right up and run. Had all the lights working the day before then nothing today. We had put a new wiring harness in it, but we still don't seem to be running off the stator ( lights don't get brighter when revved). So I'll have to do some electrical diagnostics today as well. High temp gasket maker is the LAST thing you want to put anywhere near your intake! That stuff breaks and gets sucked into the engine very easily as it doesn't hold up to the vacuum pressure of the engine. |
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Post by g2kmobile on Nov 6, 2015 19:21:42 GMT -5
Gasket maker was used to repair a leak, soon the new spacer/intake/intake O-ring will be here, and I'll use her old one as a testing unit. The electrical gremlins are really busting my chops... She has NO electrical systems working at all other than the motor runs when the solenoid is jumped.
No rear lights, brake lights, turn signals, head lights, running lights, no kill switch, no electric start. Bulbs test good....Didn't have time to ohm everything out with the volt meter, just do a few quick continuity tests.
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Post by lain on Nov 6, 2015 21:32:20 GMT -5
Gasket maker was used to repair a leak, soon the new spacer/intake/intake O-ring will be here, and I'll use her old one as a testing unit. The electrical gremlins are really busting my chops... She has NO electrical systems working at all other than the motor runs when the solenoid is jumped. No rear lights, brake lights, turn signals, head lights, running lights, no kill switch, no electric start. Bulbs test good....Didn't have time to ohm everything out with the volt meter, just do a few quick continuity tests. Is the thinner red wire loose or frayed? Sounds like the only thing you have power in is the solenoid you are saying, and that is actually what that thick red wire goes to from the battery. If only the thick red wire is connected then only the solenoid will work when you jump it. |
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