i have an hpd trail mod engine,no air box,12-1 dome,hotseat pipe, 39 kehin carb. i want more low end for trail riding. i was considering the big bore kit but was tod this may be a better setup with the 15.5-1 dome what i was wondering is what compression aprox this would put my engine at, how much more often would i need rings and a piston, what octane fuel should i run. is the scrambler still reliable with this dome or a time bomb? what kind of performance can i expect over and above what i have now?

 

Right now I suppose that you are running 93 oct. w/ the 12:1???

If you want the 15.5:1 you better be ready to pay out the YANG for the 110-116 oct. stuff. Can you say $5-$7 a gallon (where I live anyway)

Ask youself this, and if your still interested then let us know.

I personally believe that the 12:1 is the most sufficient way to go especially if you are trail riding.

Do you have an aftermarket reed cage?
How about a larger carb?

EC

 

yes i have the 39 kehin. i had the v force delta reeds but now have the boysen rad valve, didnt notice much differance between the two. yes im still interested in your information. is the power increase worth the price of fuel. i now run 91 octane at 3200 feet with zero problems.

 

has anyone ran these domes or some close, i have the 12-1 and want to know if the power increase is worth the price of fuel.

 

quad buster i do want your info i have put the rest of my mods in the sight

 

PeeWee,

Personally, I do not have any exp. w/ the 15:1 dome. I do know that the only people that do have the 15:1 are running the full race porting.

I feel that w/out the added air flow of the race porting, that the 15:1 dome would be a waste of $$. If you are bent on having a new head/dome, go for the 14:1. YOu'll be able to get away w/ around 104 oct. (160lbs. compression) and probably a small amout of new torque and a little on the top end. Yes, It would be an emprovement, but expensive. If your willing to spend the cash, I say go for it. If you are really wanting more boost, go for the race porting.

Hope to have helped.

EC