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Question about piston rings

  • Thread starter Thread starter cereal_killer
  • Start date Start date
C

cereal_killer

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I have a 1977 GS550. I have had a valve job done. I did this because of low compression. Dry test yeilded desired result on 3 of 4 cylinders. A wet test inproved compression on the 4th. After the valve job, compression dramtically improved across all cylinders however the rings on the 4th are are still a problem. This cylinder is right at the line for compression spec.

My question is, which component typically wears most? The cylinder or the rings?

I am unsure of the mileage on the bike the speedo say 35k but I dont know if that is accurate. PO did alot of hack work on the bike.

Thanks in advance.
 
The rings will wear out first but not by much. You have to pull it apart and measure the bores to see if a hone or rebore is required. Ohh the joys of engine rebuilds. lol
 
Thanks Sharpy.

I am eager to move on from engine work on this project which is making me impatient about the little things that I want to ignore, but know if I want it to be right, need to be done.

Can I buy over sized rings and then size them to fit? Or is it best to measure then purchase? I want to have what I need on hand so I can minimize downtime and not have my garage tied up with an engine in pieces.
 
Don't try and buy oversize rings and file to fit. That's fine for your old Panther or whatever but this is the next generation on in terms of precision engineering.

You're going to have to measure the bores and see if they're still in spec. If they're ok then hone and put in some new rings. If they're not in spec you'll need to rebore and fit oversize pistons and rings. Starts getting pricey for a 550 and you might be better to just buy a secondhand lump - there's loads out there and they sell for peanuts.
 
If the engine hasn't run for a while the rings may need some good hard miles before they show their true condition. Some Marvel Mystery Oil in the gas helps loosen up any carbon that may be sticking the rings to the pistons. If the engine truly needs rings, order the standard size, along with some OE factory gaskets. If by chance the cylinder/pistons show excessive wear, just pick up a low mileage used cylinder/pistons out of the classified area here or on ebay. You can typically pick up good low mileage parts for about 1/4 of what it will cost you to bore your old cylinder oversize. I've done this two different times with GS1000 engines and it's fairly easy to find good parts that need nothing other than a bottle brush hone to break the glaze, and a good decarboning of the pistons.

Good luck
 
There are a few miles on the engine since the valve job, just a trip or 2 around the block while fine tuning carbs.

I appreciate the suggestions. I am looking for the inexpesive fix but aren't we all. I have tossed the extra engine idea around and have come accross a few but just haven't jumped yet.

I know though that if I go deep enough to do the one cylinder then I am going to want to do them all. Cost is the issue though.

Chef where in Bakersfield are you located?
 
Most likely it just needed the valves adjusted, unless it's very well over 100,000 miles.
The 550s tend to go on and on forever, or until the neglect and lack of use catches up with them, whichever comes first.
 
I checked clearances and shimmed accordingly. The rings were a problems before the valve jobs and still are the culprit for low compression on cylinder #4. A wet test verified this. I was under the assumption that a valve job would remedy my compression issues based on a comparison of results for each cylinder. All cylinders were low but 3 of 4 were in spec and did not waver with a wet test. I concluded that valves were the bigger issue.

#4 is border line spec. I got the devil on one shoulder telling me to forget it and the angel on the other telling me you'll be glad you didn't.

Stupid conscience.
 
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