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Poor Running Evo


smallboy
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Hi all

Since fitting Boyesen Reeds to my bike,it runs poorly,stutters from idle,but more of a problem is when the throttle is backed off the revs are slow to go back down.

I have checked for air leaks but all seemd tight,i have oiled the throttle cable all is fine.The clip is on the bottom ring on the needle and it has 125 main jet,the plug is a NGK BR7ES.

Any ideas.......................?

Thank you in advance.

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Other than the check for airleaks - did you use a new manifold gasket. Always wise as you can then be more confident that leaks should not occur. I suspect you have adjusted your airscrew already. Take the carby off and do a thorough clean with an aerosol carby cleaner and compressed air jet if you have access. It could be as simple as crud stuck in the pilot jet.

But with the clip on the bottom groove then that will make the 1/8 to 3/4 throttle really rich. I fitted Boyesen Dual Action Power Reeds #6125 to my 2009 Evo 125 and in doing so, had to drop the main jet to 115 and slow jet to 45. The standard needle is a jjh and I had to drop that to 2nd clip from the top (it was in the 4th clip from top). However, I might have been better to go up one size in diameter of the needle to jjj and keep the needle in middle clip position. In setting my carb up I used these instructions http://www.smellofde...ydy/jetting.htm but subsequently have used a spreadsheet that gives graphs of how different jet sizes and needles interact - search for James Dean jetting. I have also now fitted Boyesen reeds to my 2012 Evo 200 (the 200's now come with the Keihin carby) and I have fitted a main jet of 118, slow jet of 45 and needle jjj in 3rd clip position.

I was very pleased with the Evo 125 performance after I fitted the Boyesen Reeds. Good luck with problem solving, the result is worth it.

Edited by peterH
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