High comp 200x piston..

[Yamaha_Rules69]

I decided to rebuild my 1985 Honda 200x auto s engine, because it seems to be loosing power and smoking. I have a brand new in the box Weisco high compression piston, with a bunch of extra parts (few cylinders too). I will be installing the high comp. piston after I have done a valve job and such of course. It is a stock size piston, going into a stock bore. Anyways, I was wondering about fuel consumption if I use the high comp piston. Will I need to re-jet my carb, get a diffrent exhaust system because of the power increase, and have a higher octane gasoline? Will it really add that much power? Let me know what you think. This is my first high compression project, so I need some guidance and ideas. Thanx again for the help. )

[samster143]

Depending on which piston you have...10.25:1 or 12.0:1 will determine what fuel you will need to use. 10.25 will run fine on high grade pump gas(93), 12.0 will need a little more probably 100 octane at least. Be sure your piston is the right size for the cylinder you will use ie. correct bore diameter, std, .020 over etc. I would have it measured by a pro, I would think it would be tough to find a cylinder that is on stock bore with proper piston to wall clearance. The piston must be measured and the bore precision honed to get the proper fit. Bad clearance #'s = short engine life. This will run fine without any other mods...in my opinion.

[thefox]

You will need to rejet but it wont have to change much. Getting a performance exhaust will help gain more power but is not needed. And yes you will need to get better gas like samster143 said.

[3WheelsForever]

I hope you decide to go with a 10.25:1 compression piston. The 12:1 is way to much if you ask me. My friend just rebuilt his 200x with a 185s motor. At first I was suprised because it didnt have as much compression as I thought it would. Now he got the timing right and adjusted the valves, your lucky to be able to pull start it! Each time he pull starts the engine it breaks the springs in the pull starter, hes still trying to find a solution.

[samster143]

I have heard the 12:1 pistons are hard on the kickstart internals as well....we all know they are not the strong point to these motors. I am gonna try the 12:1 piston in my spare motor....Always looking for a little more juice !