Basic ring job for GS1100

[mschis@hotmail.com]

Trying to get an 82 GS1100GL running and concluded one piston has very low compression (60) and others are not great (100). The pistons and cyclinder walls appear to be OK but very little or no cross hatching exists. Putting a little oil in the cylinder increased compression from 60 to over 100. I think the valves look OK - dismantled and did some simple lapping and the seat areas seem uniform - no bubbles when blowing air into the ports with wd-40 in the cup.

Is it a viable option to get new rings, get the cylinder honed, and just put it back together? I don't see stock size rings online - have not checked with Suzuki yet. I see there are 72.5mm "oversize" rings on ebay which supposedly fit the GS1100. The only other products I see online are complete overbore kits.

Thanks.

[Nessism]

Did you check the valve clearances before tearing down the engine? The clearance decreases with mileage and after awhile all the clearance goes away and the valves hang open which destroys compression (and can also burn the valves).

Regarding your question, please download the factory manual for your bike and then measure the cylinder and pistons for wear. If they fall into the service limit than a bottle brush hone job and new rings can be installed. There are tons of OEM part sources: partzilla and parts outlaw are a couple of good options. Cruzin image may have stock rings too if money is tight. For gaskets, OEM is the safe bet. Aftermarket gaskets range in quality from passable to pure crap. Oh, and be sure to replace the valve stem seals.

http://members.dslextreme.com/users/bikecliff/

[Steve]

It may be too late, as it appears that you might have the engine apart already, but if the engine has not been run for a couple of years (or more), low compression might also be due to stuck rings. An "Italian Tune-up" might help unstick the rings.

Definitely check valve clearances first, then do another compression check to see if you need to do anything else.

NOTE: just a reminder, when doing a compression check, be sure to hold the throttle wide open.

.

[mschis@hotmail.com]

Thanks for your replies. A little more history. This is my second round of trying to get this thing running good after it sat for 10+ years. I did check the valves in round 1 and replaced a few shims but nothing was really badly out of spec. After that and a complete carb rebuild the bike did run but I was having trouble tuning it. Discovered the pipe on Cylinder #3 was not getting as hot as the others and that's when I started looking at valve seating and compression (the cylinder not firing as well was the one with low compression reading). I rode it around a bit in round 1 (with some high revs) so I would think the pistons would have "unstuck" but maybe not. Now (in round 2) I lapped the valves (and replaced seals) and concluded it might be the rings on that cylinder. Since I am not entirely sure if it is valves or rings I have decided to eliminate the rings as a possibility before putting it back together. Then if its not solved I will get a complete valve job done. I will make an attempt to measure the pistons/cylinders but I may just take it to a machine shop and get their opinion. If slight cylinder work is required are the rings called oversize (72.5mm) meant to be used with the stock pistons or is that a bad idea to use non-stock size rings on stock pistons (or is that not possible at all).
Thanks

[Nessism]

Bad idea to use oversized rings. Even a worn cylinder is not large enough for the OS rings to achieve a round shape in the stock bores.

[GregT]

Reading what you've posted of the history, I'd pick that it's got worn ring grooves in at least one piston.
As Nessism says, it's pull down and measure.
The Cruzinimage piston sets are good quality - and value.

[mschis@hotmail.com]

The compression with cylinder#3 is resolved. I ended up taking the cylinder block off and all pistons/rings looked OK. Had it inspected/honed and installed new rings. Put it together and now compression in all cylinders is OK. So visually the valves looked OK (lapped them anyway) and the pistons/rings looked OK (honed/new rings anyway). After going through this I now wonder if it was a small breach in the head gasket and I didn't look close enough. Good experience going through the motor anyway. Thanks everyone for your input.

[Nessism]

The compression with cylinder#3 is resolved. I ended up taking the cylinder block off and all pistons/rings looked OK. Had it inspected/honed and installed new rings. Put it together and now compression in all cylinders is OK. So visually the valves looked OK (lapped them anyway) and the pistons/rings looked OK (honed/new rings anyway). After going through this I now wonder if it was a small breach in the head gasket and I didn't look close enough. Good experience going through the motor anyway. Thanks everyone for your input.

Be sure to follow up and torque the head after a few heat cycles. If the torque fell off retorque, then check again in a few hundered miles more. Keep doing this until the torque doesn't fall off anymore. With OEM gaskets one retorque should be all that's necessary, but if you used aftermarket...?

[bwringer]

Nice to see the follow-up on this. Thanks, and happy riding!

*snif* I just love a happy ending...