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Oval Pistons?

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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Dear gs'ers
I am a newbie to the list and would appreciate any comments about the following;
I am in the process of renovating the top end of my GS1000E circa 1978, due to low compression across all four cylinders(1=100 2=110 3=80 4=80psi).
I have checked the bores with a internal micrometer and the bores are ok? with a reading of 2.756in(within service limit 2.759).
Removed a piston ring and placed squarely into all four bores,end gap was well within tolerence.
However, when checking outside diameter of all pistons(2x readings at 90degrees to each other up from the lower skirt )all pistons were below service limit of 2.748.
Is this relevant ? and should I hone the bores and fit new rings or purchase new pistons?
In addition I am having the valves &seats recut with new guides and seals.
Thanks for taking the time to read this post.
Regards Bilbo. 8O
 
If the pistons are outside of tolerances they should be replaced, when you replace pistons you should replace the rings as well,might as well get it lightly honed whilst you at it.
Dink
 
Also check the bores for out of round, taper, etc. If you find any of this and since you have to get pistons anyway it would be best to bore the cylinders. More money I know but would also be more CCs and the motor would last much longer. Safe Riding, Bill
 
(2.7559-2.7565 =0.0006! not much leway is there!!) 2.756in is ok, but was that the same reading for all four cylinders? did you take multiple readings at various depths of the bore? (make sure the cylinders are not egg shaped!)

So you should be ok with new standard size pistons and new rings.

On my 1000g when I got it, the cylinders varied from, 2.7953in. to 2.796!! 8O It had allready bored it's self out 1mm (.040) over sized!! (it had 112,000 miles on it at the time, and stock sized pistons)
 
oval pistons- thankyou's

oval pistons- thankyou's

Dear gs'ers,
Thankyou for the replies to my earlier post. I've decided to dial gauge the bores to ensure (un)even wear, mainly due to the cost of new pistons ?45.00(approx$68u.s)each!!!!!!!!!!!
If the bores are egg shaped, then the standard pistons would be a waste of money.
I shall have to wait until the weekend, when the equipment becomes available, I'll let you know the results.
Thanks again
Bilbo 8O
 
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