My buddy just added 16cc domes to his cool head. He had 22 cc in it. His other mods are:
K&N, Reeds, Reed spacers, Vito power piston, Ported cyl., 360 main jets, FMF pipes, timing adjuster, and boost bottle. His bike ran awesome until he put in the 16cc domes. Now it has a miss at high RPMs. It kind of sputters when it gets into the higher RPMs, and won't rev. He tried jetting it up thinking it was too lean, and this didn't help. He tried taking the pug gap down some, and that didn't help. He adjusted the timing down, and that did nothing. He pretty much out of things to try. Any of you Banshee guys ever experience this? What might his problem be? Does he need bigger carbs?

Thanks,
Dan

 

Put a gauge on it and see where its at...

Between the 16cc domes (read about 190-200 psi, good enough to run alky) and Power Pistons which raise the compression too....its a recipe for problems...

Carb size really wouldnt be the problem. Stock carbs are most often adequate. Dirty carbs could cause some problems...

What gas is he running?

 

He's running pump gas 92 octane, plus octane booster. Could this be his problem. He has a friend running the same setup without issues on pump gas, and octane booster. I thought he should have to run race with all that compression. I'll tell him to at least try running some race gas. What race gas would be good for his setup? We have some speed shops around that have 110-118 octane VP race fuel. Would you run that straight or mix it with some pump gas? Thanks for the help.

Dan

 

Sounds like your buddy is building a hand grenade not an engine. 16cc domes/Vitos pistons/porting/advanced timing are a bad combination for pump gas.

 

Bad660r, you have already answered your own question! "it ran awesome until he put in the 16cc domes." Why does this guy want to go so crazy on the compression? What is the objective? Those small domes are primarily to compensate for hi-altitude compression loss due to the thinner air! (when used in that environment) The effect of higher compression, in general, on a two stroke is to add low and midrange power. Many times however, it will detract from top end power due to added pumping losses, and the engine will be more reluctant to rev out for the same reasons. (less overrev) Again, what is your friend trying to accomplish? I have a feeling he "shot himself in the foot" instead. And then, to add insult to injury, he cheaps out and does not buy race fuel to run in this thing! Stupid!!! He may be able to get by with race fuel mixed 50/50 with pump premium...but no less. I think your buddy would have been better off with 19 or 20cc domes instead. Do him a favor, and clue him in. Proper consultation with a reputable engine tuner before blindly going out and buying whatever the whim dictates will save a lot of headaches. Good luck.

 

Sounds like a pritty hot motor, I would have been running race gas in the first place.

 

I talked him into getting some race gas. His objective is to increase the gap between my Raptor, and his Banshee. He's all ready ahead by a little after my 3rd gear. He's just looking for cheap HP. The domes were a fairly cheap mod. It may be a step in the wrong direction. Good for me, bad for him! I guess when I step the Raptor up this winter he'll be looking into a stroker kit. Thanks for the insight guys. I kind of knew that may be the problem, but needed some support. I know cars, not 2 strokes. I guess the same basic principles apply.

Thanks,
Dan