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backfireing problem

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Hey folks I was wondering if you can help me solve this problem I'm having? First off the bike is an 08 450R, ran exellent, always maintained, I did buy it used, but from a very good dealer who I have dealt with for a long time. I have put 36 hours on the bike and it may have had the same amount on it before I bought it. Now here comes the problem. We went to an indoor track in Laval Quebec, X Town. Drove 7 hours just to get there. Unload the bikes, get ready and we go out for the first 15min session. The bike ran exellent, started no problem and was a blast to ride as usual. Then we where getting ready for the our next turn, everything started out fine, but a 1/2 lap in my bike starts to bog, bang, and pop? I came off the track got a few opinions on what the problem could be? The bike would start and idle fine. We all thought the same thing, I must have gotten some dirt in the carb. Now the air filter is clean and installed correctly. When we got home I pulled the carb, cleaned it blew out all the jets and ports, reassembled it and put it back together. Kept my fingers crossed and kicked the bike over 3 times and she started . I let her warm up, but as soon as I twisted the throttle the same thing bog, bang, pop? What gives? Starts fine idles beautifully. Can anyone help? If there are any questions you might need answered I will, thanks in advance for any and all your help. Bags. Oh and sorry for the long drawn out story to.

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Have you checked your decompressioner. On the 08's they have a centrifugal weight that is supposed to disengage the decompressioner once the engine reaches a certain rpm. It may be hanging up. Happened to me once before and had simalar results. It may be bad gas too. Drain all of the gas out of the tank and try new. Bad gas happens.:thumbsup: Good luck. Keep us informed.

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I know you said you took the carb off but check to make sure your fuel screw did not fall out.Thats what it sounds like.

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Was this riding spot colder than the temps at your house? If so, it will be lean and will backfire, so turn out the fuel screw at the bottom of the carb until the popping stops, should only be a small turn out, 1/4 or 3/8's of a full turn.

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Hey thanks for the reply guys. No I did not check the auto decompression, how do I do that? Also could that happen mid ride? And would there be any strange noises coming from the motor? Because there is none. And no the fuel screw did not come out everything was there when I took it apart and reassembled it, but thanks for the idea. Also I always use supreme gas or the one with a higher octane rating at the pumps. Plus my buddy was running the same gas in his 07 YZF450 and no problem?. As far as temps go I have ridden in colder places with no issuses like this. I was wondering if it could be the accelerator pump circiut? maybe the diaphram is torn? To be honest it almost sounds like it is starving for gas? Or could the timing be out? I just don't get it, running fine then all of the sudden popping and bogging? I ride pretty easy, not bumping the rev limiter to often, I do my oil changes and air filter changes probably more than I have to. But keep the ideas coming fella's. Everone that was at this X Town said the same thing my buddies and I thought, carb problem's. But like I said keep the idea's coming, I appretiate this.

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Take the head cover off and just move it with you finger to see if it moves freely. You can push on it where it attaches to the cam gear.

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I had a similar problem recently. I own two 08's and they both have done this.I removed the left side engine cover and cleaned the rotor od residual metal shavings that accumulated from the engine oil over time.I also installed a magnetic oil filter cover to remedy this issue permanently. The other posibility could be the ignition coil or spark plug.Try the engine cover thing first because it is the cheapest to try.

Mark

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Thanks Markster I'll try that even before I remove the rocker cover to check the auto decomp. I would have done it right now but my bike is at my buddies place because he has a nice warm shop to work out of as opposed to my cold garage. And keep the idea's coming thanks!!

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Hey Markster problem solved!!! Thanks. I can't believe that is all it was. That is the first tme I have ever hear of something like that happening before? Is it a common problem on Honda's? And where do I get a magnetic oil filter cover? I plan on getting a magnetic oil drain plug to. But I wonder why it happened? I change my oil ever 4 to 5 hours? I use Honda GN4 oil all the time, and it seemed more like "slug" for lack of a better word than anything else. There was no abbrasivenes to this "slug" and there was not a great deal of it on there? But it was stuck to the sator? Should I change oil more often, or just change the oil I use? Thanks again for all the help from everyone.

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Metal flakes on the fly wheel/stator does not sound good to me. I just replaced my ignition cover on my bike (51 hours on it. 08 crf450r) and there wasn't a single piece of metal on the flywheel or stator. Could that be a sign of failure to come? Maybee the crank bearings on their way out? I'm glad that you solved your problem though:banana:. Keep us in touch on how it does over the next few weeks.:thumbsup:

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I agree metal flakes don't sound good, but like I said it did not feel gritty or anything. Just out of curiosity why did you replace the left side engine case? And did you just transfer the stator over to the new one? And yes I will keep you posted on how things go. We have a big ice ride planned for this saturday, I am keeping my fingers crossed!?

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I agree metal flakes don't sound good, but like I said it did not feel gritty or anything. Just out of curiosity why did you replace the left side engine case? And did you just transfer the stator over to the new one? And yes I will keep you posted on how things go. We have a big ice ride planned for this saturday, I am keeping my fingers crossed!?

I landed on a huge rock on my last ride:banghead:. It smashed a hole in the side of the cover. I just transfered all the parts over to the new cover. Just took it for a ride down the street a few minutes ago. It doesn't match the bike right now though. Its too pretty. I need to put some scratches on it:smirk:.

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Ha Ha, that sucks that you broke it but glad you got it fixed.

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Hi ,

No I did not do anything else. It was more like metal fuzz than flakes.Just normal metal in an engine.The oil filter does not capture everything.All engines have this minute amount metal and it just builds up over time.Every 60 hours the sidecover should come off and the stator and rotor should get the contact cleaner and clean rag treatment.If they ever mounted the stator and rotor so it was dry and not in the enginothat would eliminate this , unfortunately this is done to probably keep things cool.Anyway , Zipty and Moose make the magnetic oil filter cover and this should all but eliminate this problem.

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