Hi,
Im about to have a 150 cylinder bored out for a 175 conversion piston. What clearance should i ask for, and what is your reference? I have looked through the forum and saw 3 thou mentioned a few times, but no one mentioned where this number came from.
I'd lime to know if that is correct and how authoritative it is.
Tx in advance
David
What is the recommended piston to bore clearance?
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carpe scooter diem
1974 Rally 200
1965 Li150
1963 TV175
1974 Eibar Jet200
carpe scooter diem
1974 Rally 200
1965 Li150
1963 TV175
1974 Eibar Jet200
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here we go!!.....3.5 thou is good. I tend to do mine now at 3 thou (in old money). On some alloy cylinders I've done 2.5 thou.
Running in needs to be careful. I tend to do short sharp cycles. Cold run in for a couple of miles, then back to base. Cool down then another cycle. Give it some "welly". Repeat over and over. Don't be afraid of giving it some revs in all gears..
Chris
Running in needs to be careful. I tend to do short sharp cycles. Cold run in for a couple of miles, then back to base. Cool down then another cycle. Give it some "welly". Repeat over and over. Don't be afraid of giving it some revs in all gears..
Chris
Scootering since 1968.
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Was told that way years ago by Dave Webster. It's never let me down either.Run in all my iron barrels that way.bristolmod wrote: Give it some "welly". Repeat over and over. Don't be afraid of giving it some revs in all gears..
Chris
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Not forgetting ring gap 15thou.
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Fantastic. Tx. Exactly the info i needed. Thunderbirds are go.
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carpe scooter diem
1974 Rally 200
1965 Li150
1963 TV175
1974 Eibar Jet200
carpe scooter diem
1974 Rally 200
1965 Li150
1963 TV175
1974 Eibar Jet200
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What they all said about running in, absolutely.
10-11 thou ring gap seems to work. The pi(3.14159) theory kicks in, every .001 of piston to bore clearance gives .00314159 of ring gap = .009something , so 10-11 gives a little wiggle room. Bore to .003. without a doubt.
10-11 thou ring gap seems to work. The pi(3.14159) theory kicks in, every .001 of piston to bore clearance gives .00314159 of ring gap = .009something , so 10-11 gives a little wiggle room. Bore to .003. without a doubt.
That's not going anywhere...
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How many times (ish) is 'over and over'? 10, 50, 200? Or do you still think in total miles?bristolmod wrote:here we go!!.....3.5 thou is good. I tend to do mine now at 3 thou (in old money). On some alloy cylinders I've done 2.5 thou.
Running in needs to be caereful. I tend to do short sharp cycles. Cold run in for a couple of miles, then back to base. Cool down then another cycle. Give it some "welly". Repeat over and over. Don't be afraid of giving it some revs in all gears..
Chris
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Great calculation but another case of simple issue complication.dirtyhandslopez wrote:What they all said about running in, absolutely.
10-11 thou ring gap seems to work. The pi(3.14159) theory kicks in, every .001 of piston to bore clearance gives .00314159 of ring gap = .009something , so 10-11 gives a little wiggle room. Bore to .003. without a doubt.
Would it not just be easier to adopt a rule of thumb approach and say ring gap should be 3.5 X piston/bore clearance?
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my bad- I tend to think in total miles but around 400.hendy wrote:How many times (ish) is 'over and over'? 10, 50, 200? Or do you still think in total miles?bristolmod wrote:here we go!!.....3.5 thou is good. I tend to do mine now at 3 thou (in old money). On some alloy cylinders I've done 2.5 thou.
Running in needs to be caereful. I tend to do short sharp cycles. Cold run in for a couple of miles, then back to base. Cool down then another cycle. Give it some "welly". Repeat over and over. Don't be afraid of giving it some revs in all gears..
Chris
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Scooterdude wrote:Great calculation but another case of simple issue complication.dirtyhandslopez wrote:What they all said about running in, absolutely.
10-11 thou ring gap seems to work. The pi(3.14159) theory kicks in, every .001 of piston to bore clearance gives .00314159 of ring gap = .009something , so 10-11 gives a little wiggle room. Bore to .003. without a doubt.
Would it not just be easier to adopt a rule of thumb approach and say ring gap should be 3.5 X piston/bore clearance?
No, because the actual ring gap figure should be 3.14159 for every .001 piston/bore clearance. Going to be a tad difficult to read .00942477 on a feeler gauge though. Therefore nearly spot on would be .0095000 and, as said, .010 gives a little wiggle room for when you press on the file too hard when setting ring gap.
What the pi theory part of all does also, is let you know you have the correct rings for the piston
That's not going anywhere...