2 Stroke ring end gap setting?


5 replies to this topic
  • rpt50

Posted January 09, 2007 - 07:02 PM

#1

I have a general question about setting the ring end gap for two strokes. The Weisco instructions suggest determining the minimum gap by multiplying the cylinder bore by .004. I have always found this gap to be a good bit less than what is suggested in the service manual for the bike. For example, on the bike I’m working on now (RM 125), the Weisco method gives a minimum end gap of .0085, whereas the service manual gives an end gap measurement of .018 to .024 as standard. What should I use? Should I use the Weisco method since I’m using that piston, or should I go with the service manual values? Thanks

  • 642MX

Posted January 09, 2007 - 07:09 PM

#2

Go with the Wiseco numbers. The Wiseco piston is forged and has different tolerances than the cast OEM piston. The service manual is refering to the cast piston values.

  • steve_M.

Posted January 10, 2007 - 11:11 AM

#3

I Just put a Wiseco in a cr80 and was shocked at the ring end gap instructions.

When did this start? Wiseco says to check the ring end gap and to FILE the ring down if the gap is too small?

  • cleonard

Posted January 10, 2007 - 11:35 AM

#4

The numbers are different. Normally the numbers in the shop manual are a wear limit. As in if the ring gap is greater than specified then replace the rings. I have let engines run with a greater gap than in the manual. It usually just means a little less power.

The Wiseco number is a limit for new rings. If the gap is less than what they say then the rings might expand too much and get jacked into the cylinder walls.

  • rpt50

Posted January 10, 2007 - 12:01 PM

#5

I ended up calling Weisco this morning. They said use their values (bore X .004) for their pistons, which are forged. OEM pistons, which are usually cast, have different values. That explains the large values in the service manuals.

  • Ocean

Posted January 10, 2007 - 12:29 PM

#6

I ended up calling Weisco this morning. They said use their values (bore X .004) for their pistons, which are forged. OEM pistons, which are usually cast, have different values. That explains the large values in the service manuals.


I don't understand what the piston has to do with ring gap. The ring itself may be a different material but even then there's bugger all difference in thermal expansion. Barrel material makes a difference, the old SG iron sleeves don't grow as much as chromed alloy. Maybe Weisco have a slightly different locating pin setup? Suzuki are certainly likely to be more risk-adverse, they'd rather you were a smidgeon down on power than seized....

I assume the ring is one piece? is it parallel or slightly tapered?

.





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