85/86 250r compression ?

[3wheelrider]

Well, i'd like to know if someone can please tell me if they have safely run 200 psi. comp. with pump gas.(92). (all there is locally- that i know of). I'm asking cause i recently bumped the compression up on my bike from 175 to 200 psi. I've run the 3 layer stainless trx headgasket (thickest) for 5+ years and i wanted to do this before but never did till now. I drilled the rivet and used the 2 outer ones. anyway- I had 100% distilled water in the cooling system,hot day, and i ran a tank of fuel with no detonating or overheating. Everything seemed fine my exhaust plating didnt change color yet either:lol: I wanted to bump the main up at least, maybe move up the needle too. but i didnt change jetting yet. i wanted to try it first. Plug didnt seem to scorche either. color was brown still. This thing is a whole 'nother motor now! Pulls the gears (14/38) with ease. Oh yeah-the honda shop manual does state the range of comp. to be from 171 to 199 psi. using something like 92 to 100 octane in stock tune. mine has many mods.;)---anyone know that can tell me?

[SWIGIN]

I have never owned an R but I raced a lt250R in the 90s and I used to run 220-230psi and it ran fine with no detonation on 92-93oct gas.

[cr480r]

cranking pressure is a product of static compression ratio and port timing... so what fuel works for one guy may not work for another and there is no magic number for pump gas... Even the pipe is a factor... I had an LT250 that needed good gas at 215psi.. And I have a KX250 that cranks 245psi and I have trail ridden it several times on pump..

[phil53]

I ran mine on 93 pump gas at 195# compression with no problems. I overheated the engine one time and warped the cylinder deck and had it cut down a hair, now I have an extra base gasket because compression was at 210-215 psi which changes my port timing slightly. Go to advanced or pep boys and get some "water wetter" from redline and put some in the coolant to help with the pump seal & maybe some lower temps. I run WW mixed with distilled water in my track bike w/ no problems. The Sunoco on US27 and Stirling rd sells 108 octane race gas at the pump if you need to mix a little bit.

I guess you got the 38FS jetted?

[3wheelrider]

hey thanks for the replies everyone. yeah phil53,-i owe you for helping me with that nightmare of a carb.

[NOS_350X]

typically at 195-200 is where a R swaps over to needing race gas.