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1982 Suzuki GS750T Cylinder Bore

  • Thread starter Thread starter FocusMG
  • Start date Start date
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FocusMG

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Hey Guys, I've been checking out this site for awhile and decided to join and ask a question that's been nagging me.

I recently bought an '82 GS750T with about 35,000 miles on it. It didn't have the airbox so I installed a dynojet kit and pod filters and aside from it running just a little bit rich it's running pretty good.

Initially, I was having a little trouble with cold starting and I attributed that to it running rich, but I finally decided to do a compression test and I was getting in the 90's all the way across, so I thought that this might be a contributing factor as well.

After a wet test all the way across, it looks like it is the cylinders that are leaking compression and although I don't know the service history of the bike, judging the guy I bought it from I am pretty positive the engine has never been rebuilt. Also, there is a nice ring worn into the top of the cylinder.

My first question is this: Does it sound like the next step I am planning on taking in boring out the cylinders and going up in piston size and rings sound like a logical next step? I like to do whatever work that needs to be done myself, but I will have to take the cylinder somewhere to do this.

And if that is what I should be doing, I live in Mississippi, and I have had to do a considerable amount of calling around to find someone who even does this. Most mechanics want to send it off and I know I would be paying much more than necessary.

But I finally found a shop about a hour and a half away that will do it and they charge $68/cylinder in labor and they charge an hour per cylinder putting it at about $272 total for the boring alone. Does this sound reasonable, or should I keep looking for a better deal. This isn't a stealership and I've heard good things about the work they do, but I don't want to pay more than necessary. I only paid $300 for the whole bike!

And sorry, but one more thing, I have priced OEM pistons and rings and wow! Any ideas where I can get a deal on some pistons and rings, not necessarily OEM, but they should be of decent quality.

Thanks!
 
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Tight valves are known to cause hard starting like you described. Your next step should first be to adjust the valves especially if they haven't been done in awhile. Do that and I'll bet your numbers will start to come up.

I did that a couple of years ago and a cylinder that had low compression came up to match the others very quickly.

EDIT: DON'T trust shops to do the work. It's easy and if you have been lurking for long you'll know Basscliff will be along later with his mega-welcome and site chocked full of good info.
 
Oh yeah, I've been all over Basscliff's site. I got all the info on adjusting my carbs from him. I was planning on adjusting the valves as well as I can do that myself, hopefully it will help. Thanks for the suggestion!

I think that since I am going to have the bike apart and judging by the pretty prominent ring worn into the top of the cylinder, I need to give them some attention while I'm in there.
 
Just curious what you did with the throttles as you did the compression test?
 
I opened the throttle wide open on the compression test. I said I was in the 90's all the way across for simplicity, but in actuality, I was in the 90's on three cylinders and one cylinder was in the 60's.

After putting a few drops of oil in the cylinders, compression on all cylinders was between 120 and 140, which led me to believe it was the cylinders leaking compression.
 
Yes, very common with bad petcocks.

Running rich will hurt compression too.

How much has this bike been run in recent years?
 
A lot of these bikes, after siting will have low compression. Usually three cylinders are a little lower, the one with the vacuum line is a lot lower. On most of them the compression will come back up after a few thousand miles of hard riding. Do the other maintenance, replace the petcock, clean the carbs, most importantly adjust the valves. Get the electricals working correctly. If it runs at all OK, which it should with the 90 and 60 compression, ride it hard for a few months and check the compression again.
Chances are pretty good you won't need to take it apart.
 
Sounds Great. Thanks a lot! That's the kind of news I was hoping to hear.
 
How do you know there is a ring worn into the top of the cylinder?
 
I've got the entire top end off right now. Just to be safe I have measured the cylinders and I'm still within specifications. I have honed the cylinder to get a fresh crosshatch and I have placed an order for new rings.
 
Order new valve seals too while you have it apart & use ONLY Suzuki head & base gaskets. Ray.
 
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