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GS850 odd piston

uk gs nut

uk gs nut

Forum Mentor
Hi all, I bought a GS850 complete engine to get the top end for my 77 750, to do the 750-850 conversion. So when I stripped the motor I found number 1 piston has some of the skirt milled off ?. The other 3 are as you would see as normal. I weighed all 4 and there all the same weight ?. What do you all think ?, just use it or try and find another piston, not easy I looked for months to find this engine.
View attachment 47666
 
Yep, that's weird.

And both pistons look to be in fine shape. No scuffing on the side missing the little "ear".

New pistons are still available from Suzuki, so personally, I'd replace the piston. Here in the US a GS850 piston is about $55 (rings are about $31/piston), not an outrageous amount of money compared to everything else. Those pistons are in exceptional condition, so I don't think you'll have any issues at all mixing one new with three old.

You could stuff in a used piston, of course, but it may be tough to find any in the same or better condition. That said, GS850 pistons generally suffer very little wear, even at very high mileage, so any piston in decent shape would likely work just fine.
 
Not cheap on this side of the pond, Robinsons a Suzuki parts dealer want ?81+ tax and 10 days wait. I didn't pay much more for the complete engine. Don't know what to do, strange it weighs the same as the others. The machined part is to the rear/inlet side of piston. Could it be somebody removed it to get it the same weight as the others. Looking at some GS1000 pistons I have they don't have such ears on the skirts, it must have run ok before I did a compression test and all 4 were around 95 psi with a couple drops of light oil.
 
That's still half what I paid for a complete engine, it even has the unobtainium black and silver points cover emblem. Any member in UK got a spare piston they will sell ?. Still thinking of just using this odd one, the barrels were stuck on the studs as usual so it's been in there a while.
 
This may or may not be relevant I was reading classic motorcycle mechanics today when I came across a piece by the well known and respected two stroke tuner Stan Stephens and he shows a picture of pistons he machines during the tune up stage after porting the barrels ( yes I know the gs is not a two stroke) and they have an ear missing this is done to expose the inlet port sooner.
just wondered if someone tried a test to see what happens.
 
fastbysuzuki said:
This may or may not be relevant I was reading classic motorcycle mechanics today when I came across a piece by the well known and respected two stroke tuner Stan Stephens and he shows a picture of pistons he machines during the tune up stage after porting the barrels ( yes I know the gs is not a two stroke) and they have an ear missing this is done to expose the inlet port sooner.
just wondered if someone tried a test to see what happens.
Click to expand...

Or maybe someone was a Van Gogh nut?..
 
I wonder if it got damaged and it was cleaned up just to get going. The head is a mess as the cam caps are mixed up and the cam bearing surfaces are shot, ham fisted spanner/wrench monkey maybe :crushed:
 
uk gs nut said:
I wonder if it got damaged and it was cleaned up just to get going. The head is a mess as the cam caps are mixed up and the cam bearing surfaces are shot, ham fisted spanner/wrench monkey maybe :crushed:
Click to expand...

If true it's a neat machining job.
 
Update on this problem. Member Steve has come to the rescue, he is sending me a replacement piston TOP bloke. A BIG thanks.
 
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