PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 9, 2018 19:08:50 GMT -5
Was riding home from work today no problems until I got to a traffic light about 3 minutes from work and I heard a lot of backfiring and popping sounds. I thought someone was shooting off fireworks so I went on. After about 5 miles...it acted fuel starved and I heard the backfiring/popping sound again so, I let off the gas and it slowed down to about 25. I eased on the gas and it ran fine. I stayed at about 25 the last 2 miles home and, now that I was within easy pushing distance, I opened it up and it took off fine. Got home and put it on the stand thinking I was imagining things and it died. It will not restart either by electric or kicking it. It usually starts with one kick but lately, I have had some trouble starting it with the electric. It would crank and crank but no start. I kick it once and poof...starts right up. I figured I might need a new battery as it is about time but, it was cranking at 500 rpm according to the tach.
I opened the inspection port under the seat and poked around and the intake manifold looks intact. I loosened the clamp and looked under it to be sure. The engine is too hot still to take apart further so I thought I would see what you guys thought. I put gas and seafoam in the tank this morning before riding to work and tank is still pretty full. It has been about 2 years or so since I did the fuel filter and I was think maybe that got clogged up? I have a few spares so I will swap that out first. When it began to die I was on a main road and every time I would give it gas it it would just go uhhhhhhhh (Like a bog but a little different) and keep slowing until I backed off then it kept running. A bad fuel filter in a car has done this to me years ago back in the carburated days. The only thing that has me concerned is even if the filter is clogged and can not keep up with W.O.T. operations, there should be plenty of fuel in the bowl to at least start up...unless it has cut off all fuel...not likely but possible I guess. Would a coil going bad do this? Have not checked for spark or anything as it is still 100 out there and the scoot is still very hot too.
Any and all ideas would be great especially if you have experienced similar symptoms. I am usually pretty good at diagnostics but I am not sure about this issue at all.
Thanks,
Bill
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Post by scootnewb on Jul 9, 2018 19:21:54 GMT -5
I had something similar happen but it was related to rainy weather/wet streets. Other than that, I got nothin'
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 9, 2018 19:29:41 GMT -5
It was a series of very short multiple backfires and I am thinking maybe a coil going bad? Like flipping the ignition off, on, off, on real fast might produce. I was leaning toward clogged filter or restricted fuel flow but, it still should start right up and...while trying to start...it didn't even try at all...like the ignition was turned off you know? it is still almost 100 out there so the scoot will not be cool until it is too dark to work on it tonight I think.
Bill
EDIT: I just ordered a kit with a new stock CDI, Stator and Coil and wire for $25.00. I figure it is one of these things and, even if it isn't, one day, it will be. I already have fuel filters. If it is not one of these things, I will be totally lost. I will know in a few days.
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Post by scootnewb on Jul 9, 2018 22:33:48 GMT -5
Hmm. Maybe. I know I replaced my coil and coil wire when I had problems tuning and jetting. I was getting back fires and things went much smoother after that. But the backfires were kind of a regular thing until I got the jetting down. It wasn't running good then all of a sudden...
I just stumbled onto it. I was checking the spark with a new plug and it seemed weak and erratic, I had an orange coil wire/coil lying around and when I put it on and tested, the arcs were bigger and constant.
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Post by KSR Moto on Jul 10, 2018 6:27:01 GMT -5
It was a series of very short multiple backfires and I am thinking maybe a coil going bad? Like flipping the ignition off, on, off, on real fast might produce. I was leaning toward clogged filter or restricted fuel flow but, it still should start right up and...while trying to start...it didn't even try at all...like the ignition was turned off you know? it is still almost 100 out there so the scoot will not be cool until it is too dark to work on it tonight I think. Bill EDIT: I just ordered a kit with a new stock CDI, Stator and Coil and wire for $25.00. I figure it is one of these things and, even if it isn't, one day, it will be. I already have fuel filters. If it is not one of these things, I will be totally lost. I will know in a few days. Check your electric enricher, other than that it could be that you have too small lash on the exhaust valve and at high temp it was probably leaking causing backfiring and then you were riding home with throttle not at wot and it probably cooled down a bit thats why it didnt act up when you gave it a wot again |
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Post by 90GTVert on Jul 10, 2018 6:34:28 GMT -5
Fuel supply sounds like a good call. Check for a cracked intake. Check vacuum hoses. See if the petcock is working as it should.
I'd consider checking valve lash.
When ignition components are weak, it will more commonly mimic a rich condition. Could be a bad connection though. Doesn't hurt to check all connections though. You can also check spark strength by making it jump a large gap (bend back or cut off the ground strap from an old spark plug to use as a tester or get an HEI or adjustable gap tester). You can check reluctor air gap (gap between the pickup an bump on the flywheel) to see if it's about 0.010" to 0.030". You can check output of the exciter and pickup wires from the stator. Exciter wire should be something like 50VAC cranking with the stator unplugged from the scoot's harness. Pickup should be closer to 0.5VAC. There are also resistance checks in service manuals for the stator and coil. You can make sure there is no ground on the kill wire to the CDI when the key is on and kill switch is set to run. When checking that, play with the switches a little just to be sure nothing is malfunctioning and intermittently grounding that wire. That stuff will keep you busy for a few if you want to explore the ignition side of it.
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 10, 2018 9:16:58 GMT -5
It was a series of very short multiple backfires and I am thinking maybe a coil going bad? Like flipping the ignition off, on, off, on real fast might produce. I was leaning toward clogged filter or restricted fuel flow but, it still should start right up and...while trying to start...it didn't even try at all...like the ignition was turned off you know? it is still almost 100 out there so the scoot will not be cool until it is too dark to work on it tonight I think. Bill EDIT: I just ordered a kit with a new stock CDI, Stator and Coil and wire for $25.00. I figure it is one of these things and, even if it isn't, one day, it will be. I already have fuel filters. If it is not one of these things, I will be totally lost. I will know in a few days. Check your electric enricher, other than that it could be that you have too small lash on the exhaust valve and at high temp it was probably leaking causing backfiring and then you were riding home with throttle not at wot and it probably cooled down a bit thats why it didnt act up when you gave it a wot again I was thinking about maybe checking the enricher to see if maybe it was not cutting off entirely making it too rich when warmed up so, thank you. I just did the valve lash about 4 weeks ago and set both to .0026 and have been riding the same route in much hotter weather than this so...I don't think that is it...I am concerned maybe it jumped timing or something so I am going to check that as well. Thanks, Bill |
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 10, 2018 9:27:14 GMT -5
Fuel supply sounds like a good call. Check for a cracked intake. Check vacuum hoses. See if the petcock is working as it should. I'd consider checking valve lash. When ignition components are weak, it will more commonly mimic a rich condition. Could be a bad connection though. Doesn't hurt to check all connections though. You can also check spark strength by making it jump a large gap (bend back or cut off the ground strap from an old spark plug to use as a tester or get an HEI or adjustable gap tester). You can check reluctor air gap (gap between the pickup an bump on the flywheel) to see if it's about 0.010" to 0.030". You can check output of the exciter and pickup wires from the stator. Exciter wire should be something like 50VAC cranking with the stator unplugged from the scoot's harness. Pickup should be closer to 0.5VAC. There are also resistance checks in service manuals for the stator and coil. You can make sure there is no ground on the kill wire to the CDI when the key is on and kill switch is set to run. When checking that, play with the switches a little just to be sure nothing is malfunctioning and intermittently grounding that wire. That stuff will keep you busy for a few if you want to explore the ignition side of it. Thanks Brent. Except for that vibration I had written about before, the scoot has been running beautifully. The only thing I noticed is that cold, it will not start electrically but will always start with 1 or 2 kicks. That had me confused but I did not have a chance to look into it as it just started doing that last week. Maybe the enricher is stuck halfway or something making not rich enough to start with the starter but too rich to run when warmed up? In cars I was taught that too rich makes it backfire out of the tailpipe and too lean makes it backfire out of the carb. The distance I rode from work prior to this happening was just enough for it to be totally warmed up...maybe 1 mile but, I always let it warm a bit on the center stand when I first start it before driving off...maybe 3 minutes or so. I will check everything you suggest and yes, that will keep me very busy for a while. Unless my locking nuts on my valve lash adjusters have come loose and changed the lash suddenly, the lash should be fine. I was always worried about that happening so I cleaned the oil from the threads and applied a little blue locktite to them just in case. I make them tight but always am afraid of stripping them by going too tight you know? Thank you for your detailed reply. I think I have some good clues here I just need to figure out what they are telling me. I have 2 enrichers at home...one used from the original carb. and one sitting on a brand new carb. shipped to me in error when I ordered a clutch. I could swap that out just to see and I will pull the valve cover and check lash again just in case. Thanks, Bill |
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Post by KSR Moto on Jul 10, 2018 9:28:23 GMT -5
Check your electric enricher, other than that it could be that you have too small lash on the exhaust valve and at high temp it was probably leaking causing backfiring and then you were riding home with throttle not at wot and it probably cooled down a bit thats why it didnt act up when you gave it a wot again I was thinking about maybe checking the enricher to see if maybe it was not cutting off entirely making it too rich when warmed up so, thank you. I just did the valve lash about 4 weeks ago and set both to .0026 and have been riding the same route in much hotter weather than this so...I don't think that is it...I am concerned maybe it jumped timing or something so I am going to check that as well. Thanks, Bill I think that is very unlikely unless your chain tensioners are seriously worned out |
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 10, 2018 10:59:25 GMT -5
I was thinking about maybe checking the enricher to see if maybe it was not cutting off entirely making it too rich when warmed up so, thank you. I just did the valve lash about 4 weeks ago and set both to .0026 and have been riding the same route in much hotter weather than this so...I don't think that is it...I am concerned maybe it jumped timing or something so I am going to check that as well. Thanks, Bill I think that is very unlikely unless your chain tensioners are seriously worned out Glad to hear that. Is it possible for the chain tensioner to loosen up over time? I have 5,000 miles on this scoot and never checked or messed with the tensioner. Bill |
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Post by GrumpyUnk on Jul 10, 2018 11:35:47 GMT -5
My bet is lack of fuel, based on the clue(to me) that it seemed to improve when fuel demand was lessened(you backed off on the throttle==less fuel needed to match airflow).
I would check the vacuum petcock to see that it allows full flow when suction is applied to the diaphragm. It should flow full-stream as long as there is fuel in the tank. If not, work your way back to the tank - including fuel line, filter, outlet(with standpipe filter built in). Check also for 'crud' that will block the standpipe/outlet.
I would have expected ignition problems to show up as possibly intermittent power, with an 'on - off' operation, nothing in the middle, and NO effect from operating the throttle control. {Close the throttle, and no difference, not the engine starting to 'pick up' and run again.}
tom
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 10, 2018 13:15:14 GMT -5
My bet is lack of fuel, based on the clue(to me) that it seemed to improve when fuel demand was lessened(you backed off on the throttle==less fuel needed to match airflow). I would check the vacuum petcock to see that it allows full flow when suction is applied to the diaphragm. It should flow full-stream as long as there is fuel in the tank. If not, work your way back to the tank - including fuel line, filter, outlet(with standpipe filter built in). Check also for 'crud' that will block the standpipe/outlet. I would have expected ignition problems to show up as possibly intermittent power, with an 'on - off' operation, nothing in the middle, and NO effect from operating the throttle control. {Close the throttle, and no difference, not the engine starting to 'pick up' and run again.} tom Tom, I thought so too...until I could not even start it after kicking it for over 30 minutes. No vacuum petcock here, removed that and installed a manual one a long time ago after it began leaking gas into vacuum lines. I would think some fuel would have dribbled through a clogged line or filter by that time...enough to start and run. I smell gas coming out of the muffler after my starting attempts but, as of yet have not been able to pull it apart to confirm gas is flowing to the carb. Going to do that tonight if I get home early enough. That why I ordered the electrical stuff. I had a coil go bad on my 1970 440 cu. in Police Interceptor back in the mid 70's and, it only failed under hot conditions when the secondary would break down. When it was cold it ran fine but once it got hot under the hood, it misfired all over the place. I was young then and it took me a week to diagnose that little issue. It still could be a fuel issue and, I actually hope it is as it would be free and easy to fix. Thanks for your input. I will also check the standpipe filter. (Didn't know it had one.) I will report back once I find out what it is. If it is not the fuel supply then I will need to wait until my electrical parts arrived to see what is what as I also ordered a flywheel puller. Thank you, Bill |
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Post by KSR Moto on Jul 10, 2018 13:30:50 GMT -5
I think that is very unlikely unless your chain tensioners are seriously worned out Glad to hear that. Is it possible for the chain tensioner to loosen up over time? I have 5,000 miles on this scoot and never checked or messed with the tensioner. Bill It can not loosen up because chain tensioner constantly adjusts itself with the spring and locking mechanism to keep it from loosening up |
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 10, 2018 14:30:48 GMT -5
Glad to hear that. Is it possible for the chain tensioner to loosen up over time? I have 5,000 miles on this scoot and never checked or messed with the tensioner. Bill It can not loosen up because chain tensioner constantly adjusts itself with the spring and locking mechanism to keep it from loosening up Excellent news. Thanks. One less thing to be worried about. Bill |
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 10, 2018 19:07:40 GMT -5
Update: I pulled the seat tub out and checked the fuel filter and it was 3/4 full of fuel. (Normal for this scoot) I opened the fuel drain at the bottom of the carb. and turned on my manual petcock and drained half a cup of gas into a clear container. It flowed out fine and, after letting it sit for a bit I examined it and it was clear, no bubbles or globules and no separation into layers of water and fuel like I have seen once before. I am still going to install a new fuel filter but it appears there is no restriction of flow from the tank. Just for the heck of it, I tried starting it and after using both the electric starter and kicking it a bunch...it didn't even light off even for a second...not even a little bit. My electric parts are due in next week so I will not be able to swap in new parts. This weekend I will have time to open it up and check the valve lash to make sure my lock nuts have not spun off or loosened up. That's it for today.
Bill
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