10.25:1 piston in 200s.Will it be much harder to pullstart?

[Tim Hall]

I have a jug freshly bored and a 10.25:1 piston. Will it be hard to pull over?The de compression cable is missing from the pull starter.Also have a stock xr 200 carburetor. Would it be worth installing or would the engine lose torque?Any response appreciated

[El Camexican]

Can’t speak on the carb, but replacing your decompression cable and making sure it works properly would be highly recommended. Makes a huge difference and your starter assembly and your arm will will thank you for it.

[oldskool83]

I build one years ago no one could start it. Pull start low compression, kick start high compression

[ATC King]

Will it be hard to pull over?

It'll be harder than stock and even a stock eninge can rip the handle out of your hand when things aren't right.


If too many parts are missing from the recoil assembly to economically get the automatic system working again, you could use a manual setup with a handlebar mounted lever. That's the same basic system many dirt bikes use. It's just a miniature lever mounted on the left side of the handlebar and a cable run to the decomp lever on the head.

There are advantages to using a manual decomp instead of auto, like being able to hold the exhaust valve open to more easily clear a flooded engine, and if it hasn't been started in a while just holding it open and spinning the engine over a few easy times to splash some oil around before starting and clear out the cylinder.


Having any type of decompression mechanism slows wear on the recoil parts too. Even if you can start it, it's still better to have a functional decomp.

[MrConcdid]

I have read that there is very minimal HP gains from a high compression piston, you may be better off, with some porting and exhaust work.
Just a suggestion.

[350for350]

The XR200 carb would depend on how you ride it. When I put one on my AutoX, all I did was swap over the jets. I could feel a small loss of low end power and a slightly bigger gain in high RPM power. It felt like it revs out farther/longer.

[Homeless Dave]

I have dealt with an engine built nearly identical to what you described. started easy! it's now got a 12.5 to 1 piston and a super aggressive cam, just utilize the decompression system.

[oscarmayer]

you can use the decom lever off a 185 on the head assembly. it slides right in and BAM you got a manual lever to start it. next, the compression is not that much more than stock. stock is 9:1 on that motor. so not a lot of difference. you should be fine. i would use a new rope on the pull start.