Cylinder Bore Diameter

[minimag79]

Can anyone tell me the service limits for the 1980 Suzuki GS850 GLT?

I am having someone hone my cylinders, and all my manual gives me is a nominal dimension of 69.0mm for the bore.

[Nerobro]

minimag? Do you play paintball?

Service limits... Well if you're going to be doing any kind of a rehone, there are overbore pistons available from the factory. I think they go in .5mm increments.

why are you doing anything more than just stoning the bores? is there something seriously wrong with your bores as is?

[minimag79]

Yes I used to play on the tournament side before all the electric guns came in and turned it into how much paint you can sling at someone. But down to business there is rust in one of my cylinders, and I am having a friend re-hone them, I'm just looking for the acceptable limits for the stock configuration (ie not having to buy oversize pistons/rings). If i have to go to the next size up, thats fine. I just want to see if I don't have to.

[Nerobro]

*grins* I've got a micromag, RTpro, cocker, and the worlds fastest spyder ;-) Up untill tom bailed from paintball I was fairly buddy buddy with the whole AGD crew.

I dunno, if you're just honing it.. I don' think you'll be doing any real metal removal. how bad was the rust? the #4 cylinder on my 650 barrels had a nice solid ring of rust in it. I just knocked it down with a little thousnad grit and burnished the worst of it off with a shop rag. I'm havnig issues with cylinder #2 But not the one with the rust in it. If it's not TO bad... I'd just ignore it, and run the engine anyway. Rings are really effective at removing rust. Usually without any permanant effects.

[bwringer]

I cleaned up a pretty badly scuffed cylinder on my GS850 (a siezed #4 bearing created, um, a bit of a problem in that cylinder) in about 30 seconds with a flex-hone and a cordless drill. Many thousands of miles later (and a new bottom end and piston), it has excellent compression and uses no oil. Flex-hones are pretty foolproof and effective.

Now, to actually answer your question, stick a new oiled piston ring in there, square it with a piston, then check the ring end gap with a feeler gauge at several points. A description of the procedure and the specs for maximum and minimum gap and allowable variation are in your manual. You can use an old ring to check variation, of course, but the ring end gap may read a bit loose.

If the ring end gap is within specs at all points (you may need to grind new ring ends a bit if they are too tight throughout), then you're fine with stock bore. If they are too loose, even with a new ring, then you need to go up .5mm and get new pistons and rings.

I would bet that if you hone the rusty cylinder just enough to clean up the rust (hone the others, too) and drop in new stock rings, you'll be peachy keen.

[SqDancerLynn1]

Cylinder bore 69.000-69.015 n limit 69.080 (2.7197)

[flyingace]

An important measurement is the gap between piston and bore measured at the thrust skirt. New rings will not work if that measurement is > .06 mm.