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Backfiring
by: geh3333 - Jan 2, 2015 21:06:06 GMT -5
via mobile
Post by geh3333 on Jan 2, 2015 21:06:06 GMT -5
If you have a gravity fed system with a junk vacuum operated fuel valve just get rid of that thing and use a Manuel fuel shutoff valve . one less piece of crap to worry about.
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Post by jerseyboy on Jan 2, 2015 21:32:09 GMT -5
I agree,,
Or get a Mikuni fuel pump,,they will pump fuel 10ft up hill no worries..
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Backfiring
by: ricardoguitars - Jan 6, 2015 20:44:25 GMT -5
Post by ricardoguitars on Jan 6, 2015 20:44:25 GMT -5
I have backfiring issues as well, in my case the screws that hold the muffler to the head broke! I'm waiting for a new muffler to have it fixed. Is backfiring bad for the engine? I believe it is more an annoyance than a problem  |
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Post by JerryScript on Jan 6, 2015 20:52:07 GMT -5
Do NOT ride that scooter until you have the muffler re-attached! You will burn your exhaust valve. I have an extra exhaust stud I can send you if you need it, no charge, I got two only needed one.
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Backfiring
by: jerseyboy - Jan 6, 2015 21:14:35 GMT -5
Post by jerseyboy on Jan 6, 2015 21:14:35 GMT -5
Any home center or hardware store will have 6mm nuts,,he could just double nut it with a flat washer and that would work fine in a pinch..at least you could ride until you got the right one.
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Backfiring
by: ricardoguitars - Jan 6, 2015 21:23:12 GMT -5
Post by ricardoguitars on Jan 6, 2015 21:23:12 GMT -5
Do NOT ride that scooter until you have the muffler re-attached! You will burn your exhaust valve. I have an extra exhaust stud I can send you if you need it, no charge, I got two only needed one. Now I'm scared  The muffler is not "completely off", I got it temporarily fixed at a shop, one of the bolts was broken, they managed to take out the remaining piece and put a phillips bolt on to hold the muffler, the other bolt was ok, they put a nut to hold it, but both (bolt and nut) keep getting loose. Getting parts locally is not easy, I have to buy online from the US most of the time and wait around 2 weeks to get the package here  |
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Post by JerryScript on Jan 6, 2015 21:34:45 GMT -5
Do NOT ride that scooter until you have the muffler re-attached! You will burn your exhaust valve. I have an extra exhaust stud I can send you if you need it, no charge, I got two only needed one. Now I'm scared The muffler is not "completely off", I got it temporarily fixed at a shop, one of the bolts was broken, they managed to take out the remaining piece and put a phillips bolt on to hold the muffler, the other bolt was ok, they put a nut to hold it, but both (bolt and nut) keep getting loose. Getting parts locally is not easy, I have to buy online from the US most of the time and wait around 2 weeks to get the package here If you want me to send you the extra exhaust stud I have, PM me. |
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Backfiring
by: ricardoguitars - Jan 6, 2015 21:51:41 GMT -5
Post by ricardoguitars on Jan 6, 2015 21:51:41 GMT -5
Now I'm scared The muffler is not "completely off", I got it temporarily fixed at a shop, one of the bolts was broken, they managed to take out the remaining piece and put a phillips bolt on to hold the muffler, the other bolt was ok, they put a nut to hold it, but both (bolt and nut) keep getting loose. Getting parts locally is not easy, I have to buy online from the US most of the time and wait around 2 weeks to get the package here If you want me to send you the extra exhaust stud I have, PM me. Thanks dude, i appreciate it 8-|Don't worry, the parts are already on the way, hopefully they will be here in a week. |
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Post by lain on Jan 7, 2015 10:03:46 GMT -5
Not a problem Lain, most folks cannot distinguish from POPS or BACKFIRES or BRAT sounds a motor may make. But it is very important to know which sound it is making and WHEN because that will tell you what the problem is so one can fix it. Backfiring is not good that can damage your exhaust valve period. POPS are RICH and or LEAN conditions depends when it POPS. They can occur at low rpms, accelerating and or during decel. If they occur at low rpms and or accelerating to much fuel if on decel to lean. Brat sounds are LEAN condition and you will get this sound at higher mph. From all you say I would say it is getting to much fuel right off the bat. Check the Vacuum hose going to the PETCOCK, pull it off at the INTAKE MANIFOLD and see if it is wet. Also when you did the bbk did you change any of the JETS the one causing this would be the PILOT JET NOT the main jet. You were right about the fuel pump. I took the old pump off and cleaned it out then used water to see if there was a leak, it is very small and almost unnoticeable but it does let some through the vacuum hose. I replaced the pump with a brand new one, and started it up. It was popping a lot more often, like ever second it would pop once or twice, so I turned it off and took a look at the valve gaps. The intake and exhaust valve gaps were not at what I set them at. I originally set them at 0.004 in and 0.005 ex, but I found them at 0.005 in and 0.007 ex. I then set them both to 0.004, and now the scooter won't start! I'm thinking I will try to go back to my old settings of 0.004 in and 0.005 ex, but what do you guys think? |
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Backfiring
by: jerseyboy - Jan 7, 2015 10:45:47 GMT -5
Post by jerseyboy on Jan 7, 2015 10:45:47 GMT -5
Dewd,,
I really think you have bigger issues than valve gap..
It shouldn't matter if the valves are a little loose or even .002,,as long as they are closing it should start.
Sounds like maybe something is bent in the valve tran..
Yes,,put it back to where it was running,,but I don't think the gap setting is causing it not to run unless it was .001 or less.
I'm really confused with some of the issues you are having,,did you ever take a video of it running while it was popping
so we can hear what you are talking about??,,don't know why you would touch the valves because of popping,,thats not really a symptom of improper valve lash.
Popping you describe is more like a timing issue IMO...popping on decel is normal for slightly lean condition,,but popping under accel is something in the CDI or ignition system.Did you do all the OHM and VOLTAGE tests on your system with a DVM according to the video Alley and I posted?
You need to start ruling things out one at a time...in order starting with the ignition system,,then move to fuel,,don't keep jumping back and forth cause its confusing to us all.
Then maybe we can figure this thing out,,its probably a very simple fix.
Tom
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Post by lain on Jan 7, 2015 11:51:05 GMT -5
Dewd,, I really think you have bigger issues than valve gap.. It shouldn't matter if the valves are a little loose or even .002,,as long as they are closing it should start. Sounds like maybe something is bent in the valve tran.. Yes,,put it back to where it was running,,but I don't think the gap setting is causing it not to run unless it was .001 or less. I'm really confused with some of the issues you are having,,did you ever take a video of it running while it was popping so we can hear what you are talking about??,,don't know why you would touch the valves because of popping,,thats not really a symptom of improper valve lash. Popping you describe is more like a timing issue IMO...popping on decel is normal for slightly lean condition,,but popping under accel is something in the CDI or ignition system.Did you do all the OHM and VOLTAGE tests on your system with a DVM according to the video Alley and I posted? You need to start ruling things out one at a time...in order starting with the ignition system,,then move to fuel,,don't keep jumping back and forth cause its confusing to us all. Then maybe we can figure this thing out,,its probably a very simple fix. Tom But I just replaced the head, so I don't think it would be bent valves. I've only ridden it twice since I installed the new head. Yes I checked everything, and switching out each and every electrical component makes no difference, and I have a brand new CDI now as well and it doesn't make a difference if I use the brand new one or the other working cdi. Besides the electrical components isn't there anything else that controls timing? I thought the valves did that, that's why I tried adjusting them when it was popping more after installing the new fuel pump. Could it be possible the popping is caused by a mixture problem? Recording or taking pictures hasn't been possible, haven't had access to a cam lately and my old one is broken still. |
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Backfiring
by: rcq92130 - Jan 7, 2015 12:54:44 GMT -5
Post by rcq92130 on Jan 7, 2015 12:54:44 GMT -5
OK, this may NOT be your problem, but I can tell you from personal experience a new head does not necessarily mean the valves are OK. When I BBK'ed I make tons of silly little errors and had to take it apart / put it back together many times. One of those times I tried to shortcut re-assembly and got a valve adjuster off to the side of the valve stem. Then, as the head nuts were tightened it was all pulled into order - bending the valve stem. The result of THAT was the valve would not close completely --- very poor compression and no start or bad running. Have you checked compression  ?? |
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Post by lain on Jan 7, 2015 13:09:19 GMT -5
OK, this may NOT be your problem, but I can tell you from personal experience a new head does not necessarily mean the valves are OK. When I BBK'ed I make tons of silly little errors and had to take it apart / put it back together many times. One of those times I tried to shortcut re-assembly and got a valve adjuster off to the side of the valve stem. Then, as the head nuts were tightened it was all pulled into order - bending the valve stem. The result of THAT was the valve would not close completely --- very poor compression and no start or bad running. Have you checked compression ?? I bought the new head with valves already assembled, it was the same price as a head without so I figured, why not cut some of the work out? I'll check the compression the crude way now. |
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Backfiring
by: rcq92130 - Jan 7, 2015 13:47:39 GMT -5
Post by rcq92130 on Jan 7, 2015 13:47:39 GMT -5
That was a misunderstanding.
Yep - many heads come with valves already assembled (like yours, like mine). But you can bend the valve when you are putting the head and rocker assembly onto the engine (like I did). Unlikely, but possible.
Anyway - I'd for sure go on down to O'Reilly, get a loaner compression gauge, and see what's up. That's kind of a fundamental first step in figuring things out.
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Post by lain on Jan 7, 2015 14:41:22 GMT -5
That was a misunderstanding. Yep - many heads come with valves already assembled (like yours, like mine). But you can bend the valve when you are putting the head and rocker assembly onto the engine (like I did). Unlikely, but possible. Anyway - I'd for sure go on down to O'Reilly, get a loaner compression gauge, and see what's up. That's kind of a fundamental first step in figuring things out. I don't have any money to put down as a safety deposit. I just went out and I tried to start it up first. It started up after about 10 seconds of holding down the starter button. It is about 20 degrees out here and the scooter has been out in it all night. I let it idle and warm up. While warming up the smoke did seem light a light blue color, I think before it seemed white because I always had sunglasses on... Yeah I know, beginner mistake. The smoke was thick, but when the autochoke engaged fully there was little to no smoke at all and the popping stopped! |
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The muffler is not "completely off", I got it temporarily fixed at a shop, one of the bolts was broken, they managed to take out the remaining piece and put a phillips bolt on to hold the muffler, the other bolt was ok, they put a nut to hold it, but both (bolt and nut) keep getting loose. Getting parts locally is not easy, I have to buy online from the US most of the time and wait around 2 weeks to get the package here 
