compression?

[redrider99]

Hey guys I don't have a repair manual " it's on order". I was wondering what the proper psi for compression would be in a '85 250r pretty much just stock. Might be bored over.20 but thats about all.. Thanx for all your help...

[factoryX]

155-180 psi is about stock psi...

[redrider99]

I found the oem honda 1985-86 service manual and it states that compression should be between 170.7 - 199.1 psi. should the bike be warmed up to check compression or does it matter. I had 148 psi on a cold motor not warmed up

[oscarmayer]

warmed willmake it about 15-20psi more. did you hold the throttle all the way open when you did it? most forget about that part.

[MTS]

If your up here in alberta, The readings will be a bit lower, The elevation and air-density Plays a role (so i have found) make sure you use a good gauge too, cheap ones can vary as much as 50Lbs,

[redrider99]

I'am not in alberta at the moment in Newbrunswick so I'am at sea level. yea i held the throttle wide open also. The manual tells me to flip up the starter valve I would assume that would be the choke?..Would that really make that much of a difference?

[MTS]

Not 100% familiar with the R carbs, but i think its a plunger style choke, Pretty Much a Enriching circuit, Not a butterfly- style, Should not make much of a difference in that case, 150lbs should be quite suffice to run just fine,

[factoryX]

so if my 86 tri-z motor gets 170psi at sea level your telling me when it warms up its around 180-185psi?

[redrider99]

Yea i have a small leak in the base gasket the idle is up and then plains out and then up again so i think it was sucking in air there. But i downloaded the original service manual and it said compression from 170.7 - 199.1 psi but never says at what elevation 199 is pretty high compared to what ppl have said they was running but thats just what the manual says it should be between.

[MTS]

Gota remember, Especially with the old stuff, and manuals, its all based off a Perfect motor, Production Motors all fall within the Acceptable Range, Meaning, the Clarence's Can be at the Close or Loose end of the range, The whole elevation thing didn't come into a factor till the later years, Sounds too me more of an intake tract leak than a basegasket, but one can never tell without the proper Tests.

[redrider99]

It just noticed it the other day out riding and it was seeping out of the base gasket hardly enough to wet the end of your finger tip. I'am gonna take a propane torch around the intake and see if the idling issue clears up and check the air screw.....if them manuals are off kinda makes it hard to figure things out before you chew up a cyclinder.

[redrider99]

Well I went out today and figured i would do another compression test. I warmed up the bike for 10 mins and tightened up the compression tester and I got the same reading as when I checked it when the engine was cold 148psi... To me it doesnt make sence. Is there something else wrong perhaps a stuck ring or bad reed valve. I'am not really shure what to do other then rebuild the top end?

[factoryX]

no it sounds like it is getting compression but it looks like you need a top end rebuild pretty soon,,,,Also it could be a crank seal.

[redrider99]

how would I check to see if its a crank seal? would a crank seal give me any other problems? It works fine starts 1-2nd kick everytime. I dont really wanna split the motor if i don't have to.