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Post by nt006man on Jun 9, 2021 15:58:51 GMT 1
Hi guys I am new to this forum stuff but could do with some help.we are restoring aLC250 and got new pistons and rings . The new pistons have expander rings. Do they have to be fitted as the old pistons don't. And I am having difficulty getting the normal ring to settle in with them fitted. Would be grateful for your thoughts
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Post by headcoats on Jun 9, 2021 16:01:24 GMT 1
Can of worms and a lot leave them out
I think aftermarket ones can break up and jam the ring
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Post by midlifecrisisrd on Jun 9, 2021 16:07:01 GMT 1
I'd usually fit them but twice now I've fitted them and found them very tight in the bore. Take them out and they are fine so never fitted them
Steve
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Post by Robbieben on Jun 9, 2021 16:26:24 GMT 1
Hi guys I am new to this forum stuff but could do with some help.we are restoring aLC250 and got new pistons and rings . The new pistons have expander rings. Do they have to be fitted as the old pistons don't. And I am having difficulty getting the normal ring to settle in with them fitted. Would be grateful for your thoughts Slide the new ring into the bore at the top, push it down about 10 - 15 mm using the piston so that it is straight and square, measure the ring gap, it should be around 0.20 mm or 12 thou of an inch. If it is smaller than this that is the reason why you are having trouble fitting with the expander rings, usually if they are supplied as a kit, piston, rings and expander they are designed to be used like that but in many cases the expander is not always necessary but depends on the ring profile and the ring seat on the piston, are the rings fitted correctly on the piston as when an expander is used the ring generally has top and bottom faces.
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Post by Tobyjugs on Jun 9, 2021 18:11:57 GMT 1
Great advice from above, also make sure you piston ring grooves are clean, be carfull cleaning them you can damage them easily if you have too much enthusiasm.
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Post by freddie19 on Jun 9, 2021 23:16:28 GMT 1
I've just rebuilt my LC2 with Potenza pistons and pattern rings, pretty sure they're RIK rings as both had the R marking.
Bought these from Stan Stevens back in the 90's but decided not to use the pattern expander rings as they look so flimsy and have sharp angled corners compared to the Yamaha ones which are nicely contoured.
So I've used my original expanders that had covered about 15k miles. Carefully cleaned off all the carbon and gave them a bit of a polish and they look better than new!
Feel much more comfortable using them than the fragile looking pattern expanders!😁
And...... thanks to all the guys that recommended using Simoniz Gloss Black engine enamel on the cylinders. They look amazing..... better than when they left Mr Yamaha.
Gloss black is definitely the way to go......I was so close to painting them Satin black, so glad I didn't!😁👍
I'll post some pics when I get a minute.
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Post by bare on Jun 10, 2021 3:54:21 GMT 1
Yup the Riken rings expanders (Piston centralisers) are a poor imitation of the OEM yama ones. Flimsy and prone to breakage after not too many miles. Gotta luv the 'quality' in aftermarket bits.
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Post by abar121 on Jun 10, 2021 10:33:53 GMT 1
I also don't bother with the RIK expander rings. The other rings themselves are excellent.
I always check the ring gap and it's usually perfect, still the expander rings can be too tight.
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Post by jon on Jun 10, 2021 19:42:26 GMT 1
I’m never too keen on the expanders, but generally put them in, as I’m also not so keen on piston slap effect without them causing premature bore wear. I had to go from standard bore to 0.75 over as the pistons had rocked and worn bottom inlet side of them.
Interestingly my 31k engine has been rebored with genuine banshee pistons and these have no expanders.
I’ve asked before if Mataka LC rings will fit a YPVS piston, but not got an answer.
I’ll ask again, can anyone measure a Miktaka LC ring depth?
Jon
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fubars
Drag-strip hero
Posts: 294
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Post by fubars on Jun 12, 2021 19:46:31 GMT 1
Do you mean Mitaka ? If so does this help ?
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