No Compression on 1 cylinder

[Shug1e]

GS1000en_Can anyone help me figure out why i`m getting very low compression on one cylinder when the rest are ok 20 100 95 100 ? All the valve clearance`s are within tolerence, Being 0.03 - 0.06mm. If i install a spark plug into cyl1 and turn the engine over while placing my hand onto the intake boot, its sucking air in fine but still hardly any compression in that cylinder. Would a damaged oil seal cause this problem?. Any help would be appreciated. Shug1e

[Nessism]

Valve stem seals do not effect compression, only oil consumption.

Could be you have a burned exhaust valve. Intake suction is okay as you indicate but there is no compression since the compression is excape past the exhaust valve. Just a guess.

[Dave8338]

Take the oil fill plug out and re-run your test. What you will be listening for is a "woosh" sound in the crankcase. If your rings are bad enough to cause that low of a pressure reading, you'll hear it. Then, to rule out or conclude the rings question, add about 1/2 ounce of 5w-30 to the #1 cylinder and run your compression test again, WOT. If the #'s improve significantly...there is a good chance that you'll need rings. All your numbers are a bit low...did you have the throttle wide open while doing the first test? How many miles are on the bike? If it's not the rings, it will be the exhaust valve as Nessism mentioned. Not always though...

[Shug1e]

Problem Cylinder

Hi Dave and Nessim, Thanks for your quick reply. My rings were ok after testing with oil,so i had to take my cylinder head off to diagnose the problem. Took it up to a friends machine shop and it turned out to be a badly seated valve! .He fixed the seat and skimmed the head so am going to reinstall it tomorrow. The engine has only done 1000miles so the rings and barrels are ok. The compression test was done dry two days ago, do you think this will improve after reinstalling and trying again with oil?. The cylinder head is off a GS1100E and is pretty much identical to the origional GS1000 head with one more fastener to the front of the rocker cover, a problem i think Suzuki fixed on models post 1980 to do with a common leaking oil problem. The other difference hopefully you can help me with is to do with the intake boots being larger, and the fasteners are further apart 70-75mm. The spacing of each boot seems to be the same. I have rebuilt a set of mikini VM26ss and am hoping there is an aftermarket set of boots that will mate these carburators to the cylinder head. Do you know of any? hopefully some good news, thanks shug1e.. ps greetings from Scotland