Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

   Crossposting is not so nice and I've posted about this in other places but I don't think I'm going to get an answer so here goes.

I got some rings that were thin.  I asked some savy people about them and the answer was the thin rings are due to government regulations.  They said I would have to get a piston which had thicker grooves that matched the thiness of the rings.  I called some suppliers but they never heard of this.  The supplier where I got the rings said they sold 40 sets without an issue.  I cannot find any Tecumseh pistons that indicate they are special.  There are superseeded number but I've never seen any mention about thin rings being required.  I suppose it's possible for a piston and ring to both be superseeded and that it's due to having thin rings and the piston changed to match but I've never heard of this.

The problem is the replacement compression ring was 10 thousands thinner than the original ring.  The end gap in the ring is just where it shoudl be on the low end of Tecumseh specifications. 

The width of the old ring is 10 thousands more than the new replacement ring.  The width is in the dirction of 90 degrees to the bore.  That is the width of the outside radious minus the inside radious so not the outer width or thickness of the ring surface that faces the bore.

The rings for the H70 130210D are pretty much not available in Tecumseh NOS stock.  Most suppliers have their own sources for this ring.  None of the suppliers lists anything about the rings being superceeded or needing a different piston.

Anyone heard about this thin ring ruling?

What effect will a ring 10 thousants thinner have?

Correct me if I'm wrong but you're talking about how far (deep) the ring sits in the groove right?   If so, I don't think that I'd be too concerned with the difference.  As long as the end gap is good, and the ring doesn't slop vertically within the groove, it should be OK.  Compression rings work not only by expansion of the ring against the bore just by the force of the spring effect of the ring.   Much of the sealing effect of the ring is caused by combustion gasses being blasted down behind the ring forcing it against the cylinder wall.   By allowing additional space behind the ring, one could theorize that more space would be available for more gas and possibly a better ring seal.  Can't say for sure if they'll work alright but I'd give the new rings a shot.    

   It turns out there is a ruling about rings in 1997 that affected rings in new motors.  The rings had to be thinner.  The rule does not apply to rings currently made for older motors though.  The information I got about the thin rings I received was incorrect.  I was told I’d have to get the matching piston which should have a ring groove to match the thin ring.  The information was not correct and a mis-application of the 1997 rule to an older motor.  It had obvious major implications if true but it is not the case.

 

  After looking around it seems the thinner ring will not have an impact in a motor like this used in standard service as long as it has the right end gap and side clearance which it does.  It looks like the ring manf is saving a few bucks by making a thinner ring.