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Post Info TOPIC: Motor backfiring and popping when accelerating...please help


Newbie

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Motor backfiring and popping when accelerating...please help
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Hey guys, just scored my second TTR250, an 06 model with 14,000ks. The bike was a one owner from new and has sat for 6 years untouched- I was told it ran fine when parked last. So far I have changed the filters, plug, rebuilt the carby, new battery etc. The bike starts and idles awesome and revvs "ok" in neutral with a few misfires and a little hesitation. The issue is when under load being ridden it just WILL NOT revv out :( it hesitates, splutters and backfires and pops. It will gradually revv out if i roll onto the throttle super slow but still backfires and hesitates like mad. 

I have swapped carbies with my running TT250 so I know it IS NOT a carby issue, I have put another spark plug in with no luck. No idea where to look next (valves, timing chain stuffed, tensioner or electrical? Absolutely stumped and quite upset as was hoping to have the bike fixed up in the next few days so I can take the old man out for a few more rides before the cancer puts him off anything 2 wheeled.  I am still quite new to these bikes so any advice would be much appreciated! Cheers a heap, Josh



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Hi Josh and welcome to the forum!

Did you check the carb inlet stub was OK when you swapped carbs? Over time the alumimium section corrodes and parts from the rubber section allowing air to leak in.

Also, it's probably worth taking the tank and cam cover off to check the timing is OK and that the chain hasn't jumped a tooth or whatever.

Brian



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I was going to say carby but you have changed them over.  How's the inlet stub? 

At 14000 KS I'd say the timing chain and valves are OK. 

 



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cheers guys! I didn;t pay specific attention to it, is there a thread on here so I can find some more info as to what it looks like etc? also, from cold- the bike has a little flatspot but once past 1/4 throttle it will revv out fine. after2 mins it starts to backfire and bog etc. The hotter the motor- the worse it gets. Will check timing this arvo.

cheers a heap :)

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See https://ttr250.activeboard.com/t60393065/intake-manifold-stub-troubles/

If you find yours damaged then this is what you need.

Usually a flat spot like you describe is caused by a clogged or partially clogged pilot jet. The hole is very small and ultrasonic cleaning and using carb cleaner often doesn't work. The jet needs to be reamed with copper wire to be absolutely sure its clean wink

Brian



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Exeter, Devon, UK

http://www.ttr250.com  - The one and only dedicated TTR250 FAQ! 
 

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