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Discussion Starter #1
I'm putting new rings in the right cylinder of my KT17 series 1 engine.
The piston has STD stamped into it so I understand it's probably the original.
The bore is not obviously scratched or scored but oil is seeping into the cylinder when the engine's not running (and blowing smoke when it is).

I'll take the rings off today, but how do I decide what rings to replace them with?
Can I use oversize rings without getting an oversize piston?
The manual mentions service rings - what do these do?
Thanks!
 

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It is possible to use .010 rings with the stock piston but the end gap must be fitted to the cylinder. It is really a poor fix and I won't say I haven't done it but the repair will not last real long. Looking at the picture I think the engine needs to be bored oversize but would need to mic it to know for sure. Roger
 

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Discussion Starter #3
Thanks Roger. I see more scoring on the cylinder now.
I tried to take out the cylinder jug without removing the engine, but I can't get access to the bottom left bolt. When I get the engine out I can remove the cylinder and look at the rings and see how worn they are.
 

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looks like you need a bore job, there is too much clearance wall to piston
 

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The problem is that a Series 1 KT17 is hardly worth the expense of boring, new pistons ( $$$ ), rings, etc.
 

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I just rebuilt a KT17 series II. Governor fell off and was ground up by the crank. While i had it apart i put new rings in it and a gasket kit.

The cylinder picture looks like there are marks from where the ring gap is. I Would pull the jugs off and run a stone hone through them. It will be very evident what the shape of the cylinder is once it has been honed.

I bought my ring sets off of epay. They were not that expensive...

Yes, oversize rings can be file fitted and work great. These are not race cars they are tractors. I remember reading an article in popular Mechanics from the 70's that recommended knurling a worn piston to make up the gap.
knurling piston.jpg
What does this all mean? I think it is worth some time and a little money investigating...
 

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If rings a a hone get 100 hrs its worth something thats 3-4 years for me on grass and snow duty.
 

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Discussion Starter #8
Thanks everyone. I know it might not be worth it for a series 1 so a repower is always a possiblity! Keeping my eye open for a cheap series 2. I really don't want to put too much money into this thing - fun though it is.
Jenson, that is my plan - to remove the jug and hone + rings and see if that helps. That'll be about $150. Too bad I have to get the engine out to get off the jug!
Another option is to get a jug of ebay and drop it in. I haven't seen one for that side of the engine yet.
 
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