johnm
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- Joined
- Feb 26, 2008
- Messages
- 1,940

The mixture looks remarkably stable. Almost too good based on my dyno run experience.
I have seen a very simialar hp response when vibration caused fuel frothing at higher rpm. Expecially common when extended inlet tracts are fitted without good mountings. I recomend Mikuni fittings.
Place your hand on the carbs during a dyno run to check for harsh vibration and also look for signs of fuel frothing out the tickler.
The stable mixture does not fit this interpretation but its worth checking anyway. I guess you have checked for fuel feed rate already.
After that you will need to go for cam and ignition timing as mentioned by others. I doubt exhaust is doing this.
I have seen a very simialar hp response when vibration caused fuel frothing at higher rpm. Expecially common when extended inlet tracts are fitted without good mountings. I recomend Mikuni fittings.
Place your hand on the carbs during a dyno run to check for harsh vibration and also look for signs of fuel frothing out the tickler.
The stable mixture does not fit this interpretation but its worth checking anyway. I guess you have checked for fuel feed rate already.
After that you will need to go for cam and ignition timing as mentioned by others. I doubt exhaust is doing this.