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Backfiring
by: lain - Dec 27, 2014 20:32:12 GMT -5
Post by lain on Dec 27, 2014 20:32:12 GMT -5
So I went out for a ride to the store, the entire time there it seemed to be popping very quietly sometimes, then close to the store it popped super loud out the tailpipe. On my way back it seemed to be backfiring a lot more and it kept almost dying everytime it popped I would need to rev it when I was at a stop light to keep it alive. There is also a small bit of what seems like oil smoke coming out of the tailpipe as well. It seems that everytime I run it it is getting worse now, but it doesn't backfire when I am above about 2/5 throttle. Going over bumps or taking it off the center stand also makes it backfire or sort of cut out, sometimes it does cut out completely.
What could be causing this? Is it because of the oil getting by because the piston rings on my BBK are about 0.002 off from what they should be? Or is it because my exhaust valve seems to be building up an oil deposit on it and also seems to be broken on the edges in a few spots, not much but very small bits of it have blown off.
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Backfiring
by: wilds - Dec 28, 2014 4:42:59 GMT -5
Post by wilds on Dec 28, 2014 4:42:59 GMT -5
Broken valves is not good, I would replace the broken valve or the head a.s.a.p!
Since you didn't do anything to the carb before it started backfiring it normally indicates that there is:
A leaking exhaust valve. (which I suspect you have)
A leak between the cylinder and the header/muffler.
A leak between the carb and intake.
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Post by lain on Dec 28, 2014 8:20:21 GMT -5
Broken valves is not good, I would replace the broken valve or the head a.s.a.p! Since you didn't do anything to the carb before it started backfiring it normally indicates that there is: A leaking exhaust valve. (which I suspect you have) A leak between the cylinder and the header/muffler. A leak between the carb and intake. Actually I did clean the carb, and it has been backfiring since I installed the BBK pretty much, just getting worse. I think the enricher is broken and letting in extra gas as well. The exhaust port has a missing stud so only one nut is holding the exhaust/muffler onto the head of the engine. Got a new head and intake and rings otw, arrives tomorrow, it is already at my local post office but it's Sunday! Darnit! Hopefully the problem will be solved, if not after replacing all those parts one would assume too much gas maybe not enough air? My carb does not have a fuel/air mix screw that is accessible so I would assume going down some jets if it is too rich? I have been fouling plugs so I am assuming already it might be too rich. |
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Backfiring
by: wilds - Dec 28, 2014 12:21:05 GMT -5
Post by wilds on Dec 28, 2014 12:21:05 GMT -5
Running rich is also a cause of backfiring... If your head had a missing stud from the begining, I think your problem will be solved when you install the new head. If it still runs a little on the rich side, I would try to go down one size (or maybe two) on the slow jet. If it backfires on deccel it could be a too small slow jet. If it backfires on accleration / on a even cruise it could be a too large slow jet. Or backfiring could also be caused by a broken enricher as you said. Test your enricher |
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Backfiring
by: bashan - Dec 28, 2014 22:09:28 GMT -5
Post by bashan on Dec 28, 2014 22:09:28 GMT -5
Is it doing it when you shut down the throttle? Considering your head has a broken exhaust stud I'd say that is your problem. Air is sucked back into the combustion chamber causing a lean condition. Since there is not enough gas to provide adequate combustion the remainder passes into the hot exhaust where it ignites. I know that seems counterintuitive but that's the way it works. I'd put the new head on with a good gasket before doing anything else. I bet that will fix it.
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Backfiring
by: lain - Dec 28, 2014 22:46:31 GMT -5
Post by lain on Dec 28, 2014 22:46:31 GMT -5
Is it doing it when you shut down the throttle? Considering your head has a broken exhaust stud I'd say that is your problem. Air is sucked back into the combustion chamber causing a lean condition. Since there is not enough gas to provide adequate combustion the remainder passes into the hot exhaust where it ignites. I know that seems counterintuitive but that's the way it works. I'd put the new head on with a good gasket before doing anything else. I bet that will fix it. It is doing it constantly pretty much, less when at higher RPMs |
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Post by tvnacman on Dec 29, 2014 6:39:27 GMT -5
Is it doing it when you shut down the throttle? Considering your head has a broken exhaust stud I'd say that is your problem. Air is sucked back into the combustion chamber causing a lean condition. Since there is not enough gas to provide adequate combustion the remainder passes into the hot exhaust where it ignites. I know that seems counterintuitive but that's the way it works. I'd put the new head on with a good gasket before doing anything else. I bet that will fix it. It is doing it constantly pretty much, less when at higher RPMs this is starting to sound like timing , the other day I had a hard time getting my scooter started . when it did start it backfired via the muffler .. The ran really bad . I keep a few cdi's under my seat , I plugged in a different cdi perfect . Can you shoot a video with you magneto on the "T" mark and the position of the cam . I would like to check that/see that . John |
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Post by lain on Dec 29, 2014 9:30:51 GMT -5
It is doing it constantly pretty much, less when at higher RPMs this is starting to sound like timing , the other day I had a hard time getting my scooter started . when it did start it backfired via the muffler .. The ran really bad . I keep a few cdi's under my seat , I plugged in a different cdi perfect . Can you shoot a video with you magneto on the "T" mark and the position of the cam . I would like to check that/see that . John Well, I am replacing the piston rings, head and stator today. I will take a video while I am reassembling everything later today. |
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Backfiring
by: lain - Dec 29, 2014 22:55:58 GMT -5
Post by lain on Dec 29, 2014 22:55:58 GMT -5
After changing the head, and everything the scoot still backfires. The backfires seem to be coming from the muffler into the engine and out the tailpipe at the same time. There is a decent amount of oil and gas buildup from when the scoot wasn't running well stuck in the muffler to the point where it seems much heavier than it was before. Also, it's spewing out TONS of white smoke for about the entire warmup, after it gets on the road it stops smoking.
I am guessing this may be a cause or THE cause of the backfires, I think my piston rings may be letting out too much oil, since my engine seems to EAT OIL. I am also suspecting running rich due to too large main jet, but I have a jet set on the way. I did get new rings but the new ones had gaps that were already too large so I am sending them back and getting new ones.
How do I remove the buildup so I can ride without the backfires? Brake cleaner? I already know about the torch method but I do not want to do that method because my muffler is already a bit messed up. Money is a problem otherwise I would have got myself a new muffler already.
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Backfiring
by: tvnacman - Dec 30, 2014 9:07:25 GMT -5
Post by tvnacman on Dec 30, 2014 9:07:25 GMT -5
where are the pictures I asked for yesterday ?
John
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Backfiring
by: lain - Dec 30, 2014 10:46:28 GMT -5
Post by lain on Dec 30, 2014 10:46:28 GMT -5
where are the pictures I asked for yesterday ? John Damn dude, I know you asked for a VIDEO but my friend cannot send it. I do not have a camera, I have friend's record for me and then have them send them. Sometimes doesn't work out the way you planned it and sometimes you record a video and the person who recorded it is an idiot and can't figure out how to send the video. All you will see in the video is that everything is TDC, so what would you have done after seeing that anyways? Rest assured everything is TDC and not off. Do you have any tips to remove large amounts of buildup from a muffler pipe? |
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Backfiring
by: tvnacman - Dec 30, 2014 11:09:17 GMT -5
Post by tvnacman on Dec 30, 2014 11:09:17 GMT -5
is the muffler and engine pipe one piece ? take it off and with a vacuum in reverse blow it in reverse .
John
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Backfiring
by: lain - Dec 30, 2014 11:21:51 GMT -5
Post by lain on Dec 30, 2014 11:21:51 GMT -5
is the muffler and engine pipe one piece ? take it off and with a vacuum in reverse blow it in reverse . John Yes it is all one piece, I do not own a vacuum, I only have a broom. Poor life sucks. Have you cleaned out wet oily mess from inside a muffler, and what did you use? It seems it's very thick and has coated the entire inside in a very thick layer of oil/gas. |
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Backfiring
by: tvnacman - Dec 30, 2014 11:27:31 GMT -5
Post by tvnacman on Dec 30, 2014 11:27:31 GMT -5
take it off and put some gas in it let it soak , turn it to an end for a to drain . then blow it out with compressed air .
John
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Backfiring
by: lain - Dec 30, 2014 11:32:35 GMT -5
Post by lain on Dec 30, 2014 11:32:35 GMT -5
take it off and put some gas in it let it soak , turn it to an end for a to drain . then blow it out with compressed air . John Put some gas in it? That sounds counterproductive, what does gas do to the oil and gas buildup? How much gas? The same gas from my tank? Why gas? Why not brake cleaner? Not strong enough to penetrate the buildup? BTW, my friend uploaded the video to some weird site, here is that video you wanted: mega.co.nz/#!lcVWSbhT!3DiSzdXgkqQwko_buUx-rk0RggRkS0EziC86GFxlyaY |
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