Very minor hesitation after headwork.

While apart for routine maintenance, I decided to have the head cleaned up and flowed. Just looking at it, my very meager amount of common sense noticed many areas that could be improved. Now that it is back together, WOW ---- look out. Very impressed. I would just say a very healthy gain accross the entire board (meaty).

:confused:It has left me with one nagging side bar. 15% of the time, I now have a VERY minor hesitation from 0 to 1/8 throttle. The bike ran flawless before. This glitch has caught me a few times, you know a little blip to clear something etc. I guess my question is what circuit should I look at which would correspond to a better flowing head? Too rich or too lean? I am very un-knowledgable on the FCR. Any ideas would be great.


I did the exact same work to my head during my 540 conversion. Very simplistically, the touch-up work on your valve seats makes the motor breathe better, and without knowing what your existing settings are, I bet a 1/2 turn out on the fuel screw will do away with your hesitation.

My bike now sucks an intake charge in with a throttle blip hard enough to make my airbox sides cave. It never did THAT as a 400!!!

More thoughts... if you really felt an impressive increase in power from just the headwork, then I bet going up a size on the main would help too. I don't know how much I gained from my headwork because it went in with a 140cc increase!!! But I know this bike is a different animal entirely from the 400. And the way it revs out BETTER than as a 400 leads me to believe the headwork helped out the flow. What main are you running with the EMN? Screw setting? Clip? Have you timed your accelerator pump?

Right now I am running a 165 main, 48 pilot(stock), EMN 2nd from top, 2.5 out on the fuel screw and 1 second pump time.

I will definetly try your recomendations. Thanks for the input.

Your main sounds OK w/ the EMN, and your fuel screw is already "out there". Maybe the 2nd clip position could be liberated a bit, I'm running #4 on mine. But you're pretty close to my settings.

Just for comparison I'm running a 162, EMN #4, 1.75 out, 1-sec pump, 48 pilot. The motor is 97mm bore, Wiseco 12.5 piston, 520 crank, 525EXC cam, and the aforementioned clean-up, blending, radiusing and polish of the port areas from the valve seats to about 10mm up into the port bowls.

Tucson is only around 2,500ft right? Are you riding up Flagstaff area, high altitude stuff? Does it get better when the engine is hot, or worse?

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