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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Sputtering and backfire with throttle
Post Info TOPIC: Sputtering and backfire with throttle
TimAus


Newbie

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Sputtering and backfire with throttle
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Hi there,

I have cleaned out my carb recently and replaced the spark plug because the bike kept stalling on idle. Now the engine idles erratically (doesn't stall) when warmed up, but now it is sputtering and backfires when i give it a bit of throttle.

 

I am assuming this is a fuel/air mixture problem. I have set the air screw to 1.5 turns. I tried 2.5 turns as suggested in a sticky but i still have the same problem. There is a very very slow fuel weep out of the diaphragm needle gasket, could this be causing the issue? My bike is a TTR250 2007.

 

I was looking at the sticky and noticed that instead of a diaphragm needle and two seperate o'rings, my carb has a gasket that is one piece linked with the diaphragm needle. Also, the jets are all clear of any residue/grit build up, as i cleaned it with some carb cleaner quite thoroughly. I took the air filter off to see if it was causing a problem, still getting the same response on idle and backfiring with throttle. I'm guessing it's just getting to much fuel in there and not enough air? Can the clearance on the spark plug be causing the issue as well? i don't have the measuring tool to check, i just popped it in as it was straight off the shelf.

Everything is stock, nothing has been altered on the bike.

 

Tim



-- Edited by TimAus on Friday 31st of March 2017 09:48:12 AM

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TTRfan


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Hi Tim and sorry to hear of the problem.

Looks like you have done a bit of research so am guessing you know about the common issues such as leaking inlet stub (unlikely on such a new bike I know), and blocked or partially blocked pilot jet which can only properly be cleaned by reaming with copper wire or similar.

I haven't come across a diaphragm such as you describe before. If and when you have it out again can you please take a photo and post it up please?

Brian



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Chellejune


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Tim, 

Did you ever figure out the solution to this?  I am having the same exact issue.... it's as if I wrote your post myself!!

 

Rachelle



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