Only have 30psi in one of the cylinders

[Guest]

I recently took my 1984 gs1150 into the shop to see why it was running so poorly. They did a compression test and said one cylinder only had 30psi. The other 3 have 90, 110, and 115. I'm fairly sure it's just blow by so I was thinking of boring out the cylinders and getting new pistons, rings, ect. Has anyone had to do this? If not does anyone have a 1150 engine for sale ?

[Nessism]

How long since your last valve adjustment?

The 1150 is a super popular engine to hot rod. Tons of guys have bored out the cylinder and installed oversize pistons/rings. The question is how fast do you want to go (how big to bore)? Also, since the cylinders seem to be tired it's strongly advised to rebuild the head as well.

Good luck

[Steve]

I, too, will ask about valve adjustment, but will also ask "how long since the engine has been run on a regular basis?

Yes, that is quite a difference between cylinders, but if the engine was cold and it has not been run for several years, it might not need anything besides a valve adjustment and several hundered kilometers of vigorous running.

How many miles (kilometers) on the engine? How much of its history do you know?

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[jeris101]

I had no idea you could even adjust the valves ( I am by no means a mechanic) i brought the bike in to get the carbs cleaned. and the shop I brought it to didn't say anything about it other than they did a compression test and that I'd likely need new pistons an rings.
I thought the carbs needed to be cleaned because I noticed a lack of power at the high end of the revs. As well as if you really leaned on it it almost sounded like the engine had a rev limiter (I know it doesn't and its probably the valves just floating or whatever)
There's about 50000 km on the engine
I haven't run it very much in the last 2 years.
I've owned if for 3 years and the guy that owned it before me was pretty old so I can't imagine he would have driven it that hard.
If I don't have to rebuild anything I'd prefer not to.

[Steve]

First of all, you are lucky enough to have a shop let your bike through the door. Most shops have a 10-year-old limit on bikes. Too many problems trying to remove old hardware, and it takes projects right out of the flat-rate manual.

Have them check valve clearances, don't worry about the carbs yet. If the clearances are a bit tight (typical) have them set to the proper spec (at the looser end of the range is preferrered) and see if the bike runs any better. You should at least get it warmed up to do a compression check, then remove all spark plugs and be sure to hold the throttle open while cranking.

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[gsrick]

I'd have them do a leak down test on all the cylinders to see where the leak actually is. More than likely it is one of the valves a little too tight and checking the clearances is something that should be done either way, but it could also be the rings.