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Evo 4T Banging Through The Exhaust

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#1 trialholic


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Posted 23 April 2012 - 12:44 PM

Hi guys

My beta 4T, when ride at medium speed and I shut off gas i can hear some "bangs" through the exhaust..

Is it that normal? or should I tune up the carb in some way?

Thanks mates.

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#2 pindie


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Posted 23 April 2012 - 05:40 PM

Air leak in an intake or exhaust joint.
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#3 nzralphy


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Posted 24 April 2012 - 07:40 AM

Run the engine and spray some starter fluid around the carb. Wiggle the carb and see if the idle changes -- to find the air leak.
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#4 jimg



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Posted 24 April 2012 - 05:13 PM

"Bang"? Like a loud popcorn popping sound? Perhaps several in a row? If so, this is a common sound when shutting down the throttle on the Evo 4t, especially when going down an incline. My only sugenstion is to ensure your jetting is set correct. I had to adjust my pilot and main jet as the bike was too lean and the popcorn sound diminished a fair amount. The air boots on the carb are "hard fitting" and the front boot can shimmy back causing an air leak. So, double check that fitting and don't over-tighten the boot clamp as it will cut through the boot in a short time if too tight.

#5 carl ekblom

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Posted 24 April 2012 - 09:15 PM

Needle in 4th or 5th groove and fuel mixture screw 3-4 turns out may help and check for air leaks in intake system.

#6 trialholic


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Posted 26 April 2012 - 06:01 PM

Thanks guys! :icon_salut:

it was an air leak between the carb manifold and the carb union hose, the hose clamps were too loose and the carb was a little backwards. I pushed the carb in place, tighten the clamps a bit and... problem solved! :)

Edited by trialholic, 26 April 2012 - 06:02 PM.

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