Low RPM Backfire Through Carb - Kawasaki ATV Forum
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post #1 of 7 Old 05-24-2010, 05:46 PM Thread Starter
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Low RPM Backfire Through Carb - SOLVED!!

I have a 650 SRA with about 20 hours on it. It backfires through the intake at low RPM's, no matter how long I let it warm up. Did it since the day I bought it. It is now snorkeled, has K&N filter and a Dynatek box. Those mods seemed to help a little, but it still does it. Plugs are new, gas is clean, never been in deep water or mud. The air filter smells of fuel, and the plugs fowl very quickly.

I am thinking it is running rich. Any other ideas?? If it is, how hard are those pilot screws to get to? Do I need to remove a bunch of plastic?

Last edited by swampstalker; 05-27-2010 at 06:09 PM.
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post #2 of 7 Old 05-27-2010, 08:09 AM
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I had the same problem "backfire through the carb" on my 08 brute with about 10 hours on it, the fix after alot of dealers looking at it was the exhaust valves were too tight and this caused it to backfire through the carb which blew a hole in the carb boots check the carb boots ...if they are leaking or damaged it will backfire through them and the cause is most likely the exhaust valves are too tight
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post #3 of 7 Old 05-27-2010, 09:44 AM
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On the SRA the mixture screws are accesible without removing anything.

If your plugs are fouling you should check your choke plungers. Make sure they are closing completely. You can work the choke and pay attention to the choke cable travel. You will have to remove the airbox and center plastic to access the plungers. That would be a good time to check the valve clearances.

If you filter smells like gas it might need a good cleaning. That would make it fould plugs also.
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post #4 of 7 Old 05-27-2010, 09:59 AM
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intake valves are too tight

2004 RMZ250 hot cams, high comp piston, total control suspension, etc, etc


www.bigkevsperformance.com

(919) 803-0883
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post #5 of 7 Old 05-27-2010, 11:26 AM
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I had that problem on a 650 Prairie, I shimmed the needles and now it is fine.
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post #6 of 7 Old 05-27-2010, 06:11 PM Thread Starter
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I installed a Stage 1 Dynojet kit and it runs flawless now. Noticeable difference in power too. Very pleased, and the install was seamless, even though the instructions were HORRIBLE. G-rider, I had read from several people about shimming the needles, but for just over $50.00 I opted to just get the jet kit.

Thanks for all the responses.
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post #7 of 7 Old 05-27-2010, 06:12 PM Thread Starter
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Quote:
Originally Posted by KDIXER View Post
On the SRA the mixture screws are accesible without removing anything.

If your plugs are fouling you should check your choke plungers. Make sure they are closing completely. You can work the choke and pay attention to the choke cable travel. You will have to remove the airbox and center plastic to access the plungers. That would be a good time to check the valve clearances.

If you filter smells like gas it might need a good cleaning. That would make it fould plugs also.
The screws were actually covered with a little metal plug that I had to drill out. Not sure what the thinking was behind that.
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