OzVMX Forum
Clubroom => Tech Talk => Topic started by: evo550 on September 06, 2013, 08:59:11 pm
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O.K. so after a W.W. search I've located a piston kit that I've needed, it arrived today....minus a ring >:( >:(. The piston shares the same size bore as a common as muck Japanese piston, whose ring I could use, but the ring locating pin is positioned differently between the two (mine has the pin offset up from the center of the ring slot on the other piston it uses a locater that is centered in the ring slot).
Question is, is it possible to modify the ring end to suit different types of locating pins?
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Why not just get the right ring or move the peg? Modifying a ring wouldn't be something I would attempt.
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Lozza, I thought i was going to have to move a pin, but things worked out OK for now. Would you remove the old pin if so how? or just slit it flat with a 0.5 mini thin cutting blade?
Brett
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O.K. so after a W.W. search I've located a piston kit that I've needed, it arrived today....minus a ring >:( >:(. The piston shares the same size bore as a common as muck Japanese piston, whose ring I could use, but the ring locating pin is positioned differently between the two (mine has the pin offset up from the center of the ring slot on the other piston it uses a locater that is centered in the ring slot).
Question is, is it possible to modify the ring end to suit different types of locating pins?
Yes points file will do the job
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Then take the piston off to the local dentist to get it drilled for the new pin> LOL
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Why not just get the right ring or move the peg? Modifying a ring wouldn't be something I would attempt.
It's from a lem 65 and has taken me about 3 months just locating this much from Canada, it shares all dimensions with a kx 65 except for gudgeon size :( So my thoughts were to use LEM piston with kx ring, but they have different ring ends. I hadn't considered the option of moving the pin to suit the ring.
MY theory is that I only have 1 piston...can't stuff it up, I have a unlimited supply of rings..can afford to stuff a few up to get it right.
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So the locating pin is in the right position but just the wrong shape?
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So the locating pin is in the right position but just the wrong shape?
Yeah the piston is right for the bike (LEM 65), but the ring I can use (KX 65) has a different end that closes around the locating pin.
On the LEM the locating pin sits offset high in the ring groove, so as you look at the ring end it has a semi circle cut out of the top.
The KX has the locating pin centered in the ring groove and the ring groove has the semi circle cut out of the back of the ring.
Make sense?
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Why not swap the rod to use the KX 65 piston?
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Why not swap the rod to use the KX 65 piston?
That's the next step, although I don't know the difference in rod/big end dimensions between the two. Knowing my luck they will be nothing alike. I would probably consider a ktm 65 engine swap before going down the path of crank/rod/pin mods.
I don't particularly want to sell the problem on to someone else, it's quite a sexy piece of Italian engineering...
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Somewhere OEM Rings will be available
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Why not swap the rod to use the KX 65 piston?
That's the next step, although I don't know the difference in rod/big end dimensions between the two. Knowing my luck they will be nothing alike. I would probably consider a ktm 65 engine swap before going down the path of crank/rod/pin mods.
I don't particularly want to sell the problem on to someone else, it's quite a sexy piece of Italian engineering...
There is no 'problem' swapping the rod There are a few 44.5mm pistons out there.
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There is no 'problem' swapping the rod There are a few 44.5mm pistons out there.
Maybe not for you Lozza, but to most of us it's a major undertaking. Not everyone has the expertise or equipment to do crank rebuilds in their suburban shed. ::)
Somewhere OEM Rings will be available
Simple. Why complicate a simple undertaking....or am I missing something here?
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Lozza might shoot me for this theory but--all good fun--i think!!. Ok, not sure if i fully understood but think rings don't fit around/under/over the peg. Now going back a lifetime to my RM125S 1985, i got a set of rings [genuine] & sat them in the bore to check gap & thought fk, has about 20+thou gap then looking at the piston [genuine] the ring peg sat flush with the ring land & covered all the groove. New rings had heaps of tension & this is how it was meant to be & was gaped to the peg [for clearance/expansion etc. So, it appeared that ring gap wasn't the important thing but wear on the ring where she slides past the ports is what kills the sharp edge of 2 stroke power. Digressing slightly, new rings in my "86 KX125 days always sharpened it up even though the rings taken out looked ok for gap, but slide them down a bit & hold up to the light & could see past the rings in line with the ports [or exhaust in particular by memory]. Sorry about the long story but thinking just gap the rings square on to the peg with a bit of end clearance & go for it. [if your stuck for the proper parts that is]. Cheers.
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Why not swap the rod to use the KX 65 piston?
That's the next step, although I don't know the difference in rod/big end dimensions between the two. Knowing my luck they will be nothing alike. I would probably consider a ktm 65 engine swap before going down the path of crank/rod/pin mods.
I don't particularly want to sell the problem on to someone else, it's quite a sexy piece of Italian engineering...
There is no 'problem' swapping the rod There are a few 44.5mm pistons out there.
Do you have access to dimensions to both the kx and the lem rods for comparison ?
Somewhere OEM Rings will be available
Not unless you know something that I don't, although your prob right, it's finding them that's the issue.
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maybe something like these could work :-\
http://www.ebay.com.au/itm/Piston-Ring-44-5-x-1-5-mm-Chainsaw-Trimmer-Brushcutter-/170915008702?pt=LH_DefaultDomain_0&hash=item27cb5410be&_uhb=1 (http://www.ebay.com.au/itm/Piston-Ring-44-5-x-1-5-mm-Chainsaw-Trimmer-Brushcutter-/170915008702?pt=LH_DefaultDomain_0&hash=item27cb5410be&_uhb=1)
have purchased from this seller a few times wih no issue at all.
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make that 1975 for my RMS
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i put in LEM 65 on ebay & keeps coming up with KTM--? & shows a 'vertex' piston kit & rings available--not sure this helps or not. Item 331015113921
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maybe something like these could work :-\
http://www.ebay.com.au/itm/Piston-Ring-44-5-x-1-5-mm-Chainsaw-Trimmer-Brushcutter-/170915008702?pt=LH_DefaultDomain_0&hash=item27cb5410be&_uhb=1 (http://www.ebay.com.au/itm/Piston-Ring-44-5-x-1-5-mm-Chainsaw-Trimmer-Brushcutter-/170915008702?pt=LH_DefaultDomain_0&hash=item27cb5410be&_uhb=1)
have purchased from this seller a few times wih no issue at all.
Could be worth a go, although at 1.5 mm thick it may be a bit wide...wonder if they do a piston to match ?
Will have to do some searching...
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i put in LEM 65 on ebay & keeps coming up with KTM--? & shows a 'vertex' piston kit & rings available--not sure this helps or not. Item 331015113921
Yeah, even google does that. The KTM 65 runs a bigger piston, so no go there.
Has anyone ever sleeved the pin holes in the piston to accept a smaller pin?
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There is no 'problem' swapping the rod There are a few 44.5mm pistons out there.
Maybe not for you Lozza, but to most of us it's a major undertaking. Not everyone has the expertise or equipment to do crank rebuilds in their suburban shed. ::)
Google 'crankshaft rebuilding services' and $50 and a week or so later you have a rebuilt crank with 0.00mm run out on a single, twin($90), triple($120) or 4 cyl($160) press up crank. I don't bother rebuilding them myself now unless it's rush rush.
Evo I have the KX rod dimensions but not the LEM, I do have the KTM 65 rod dimensions
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can you use a little end baring with smaller diameter rollers & use the proper pin for your kx piston--or no room for that.!!
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Development...Development.
Just found this, thanks to Docs lead
http://www.meteorpiston.com/Lists/Cross/Catalog.aspx?SortField=Diam%5Fx0020%5F%5Fx00d8%5F&SortDir=Asc&View=%7B356748F3%2DCB52%2D40CF%2DB7ED%2D5D22B1EA0369%7D&FilterField1=Diam%5Fx0020%5F%5Fx00d8%5F&FilterValue1=44%2E5000000000000
Can anyone confirm that "compression" measurement (23.6mm)is from the top of gudgeon pin hole to the top of dome and the "head" measurement (1.9) mm is from top of piston (outside edge above ring groove) to top of dome?
It would appear that the kx 65 piston is closer than I thought.
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Euro comp height is from centre of pin bore so - 6mm from that is from top of pin bore. Dome height is from timing edge to top of dome.
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Took 20 seconds to find Wiseco Piston Kit 696PS which uses 1693CD Rings
Should be available from your local bike shop from SERCO or A1 Accessories
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That's a 43mm piston isn't Evo after a 44.5mm piston????
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That's a 43mm piston isn't Evo after a 44.5mm piston????
Yep...
Euro comp height is from centre of pin bore so - 6mm from that is from top of pin bore. Dome height is from timing edge to top of dome.
Is it possible that they are measuring from the top of pin, as 6mm lower would make it very close to the cut out below the pin and a very "top heavy" looking piston.
The LEM piston measurer 23.6 mm from top of gudgeon to crown...
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That's a 43mm piston isn't Evo after a 44.5mm piston????
Yep...
Euro comp height is from centre of pin bore so - 6mm from that is from top of pin bore. Dome height is from timing edge to top of dome.
Is it possible that they are measuring from the top of pin, as 6mm lower would make it very close to the cut out below the pin and a very "top heavy" looking piston.
The LEM piston measurer 23.6 mm from top of gudgeon to crown...
What's a top heavy piston? Did you remember what said about conrod length ;)
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That's a 43mm piston isn't Evo after a 44.5mm piston????
Yep...
Euro comp height is from centre of pin bore so - 6mm from that is from top of pin bore. Dome height is from timing edge to top of dome.
Is it possible that they are measuring from the top of pin, as 6mm lower would make it very close to the cut out below the pin and a very "top heavy" looking piston.
The LEM piston measurer 23.6 mm from top of gudgeon to crown...
What's a top heavy piston? Did you remember what said about conrod length ;)
:) What are the chances the KX rod would be 6mm shorter...
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KX rod/piston ;)
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The fog is lifting and I am beginning to see Lozza logic more clearer....now where's that spec sheet on the LEM rods....
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Either 85 or 88mm C to C