Piston Replacement

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2cycle
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Piston Replacement

#1 Post by 2cycle » Tue Jun 19, 2018 1:28 pm

One of my fuel petcock outlets plugged on my 350lc and as a result a piston seized. Once the cylinder was cleaned up it appears to be ok. Just some visual marks that cleaned up after a cylinder hone. However the piston is toast. How do I replace the piston while making sure the piston to cylinder clearance is ok or do I need to bore next size over ?
1973 ct70
1974 xr75
1977 rd400
1981 rd350lc
2002 zrx1200

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T.RexRacing
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Re: Piston Replacement

#2 Post by T.RexRacing » Tue Jun 19, 2018 1:46 pm

Measure the bore. Use a bore gauge not calipers. Measure for size,taper and out of round. Then decide. if you don't have a bore gauge buy one if you'll be doing this regularly if not the local machinist should do it for a reasonable fee if not free.

You can pick up a Fowler kit for about $200 USD.

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2cycle
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Re: Piston Replacement

#3 Post by 2cycle » Tue Jun 19, 2018 3:02 pm

I haven't measured the bore.......had a total rebuild 1500km ago. If the bore is good and only need a piston, I guess its just luck that you get a piston close to the proper size to end up within the piston to cylinder clearance values.
1973 ct70
1974 xr75
1977 rd400
1981 rd350lc
2002 zrx1200

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Re: Piston Replacement

#4 Post by T.RexRacing » Tue Jun 19, 2018 5:50 pm

Well made pistons vary little from one to another.
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waltmil
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Re: Piston Replacement

#5 Post by waltmil » Tue Jun 19, 2018 8:35 pm

Quality pistons from the same manufacturer should be interchangeable, especially if from the same production run. How long did the 1500km take?
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Re: Piston Replacement

#6 Post by hondaror » Wed Jun 20, 2018 4:12 am

You don't rely on luck when fitting an engine with parts. What matters is how much material was removed with the hone and where. Your bore measurements will have to be compared to that of the piston, with recommended clearances from the piston manufacturer.
Rory
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Yellow and Black RZ
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Re: Piston Replacement

#7 Post by Yellow and Black RZ » Wed Jun 20, 2018 3:02 pm

If it was me, and the cylinder bore is ok, I'd verify what size the piston is and buy the same piston from the same manufacturer.
Would be a good idea to verify size but .25mm is .0098. Pretty tough to have much variation when the tolerances have to be so tight.

With that said pick up some bore gages and eliminate any fears you might have.
'85 RRZ350 - Hacked.

2cycle
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Re: Piston Replacement

#8 Post by 2cycle » Wed Jun 20, 2018 3:32 pm

Does anyone know who sells pro-x pistons in Canada ?
1973 ct70
1974 xr75
1977 rd400
1981 rd350lc
2002 zrx1200

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Yellow and Black RZ
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Re: Piston Replacement

#9 Post by Yellow and Black RZ » Wed Jun 20, 2018 3:50 pm

2cycle wrote:Does anyone know who sells pro-x pistons in Canada ?
Have you tried PMC? http://www.pmcanada.ca/" onclick="window.open(this.href);return false;
'85 RRZ350 - Hacked.

2cycle
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Re: Piston Replacement

#10 Post by 2cycle » Wed Jun 20, 2018 4:09 pm

I just tried them but when i start to search I get access denied. will pistons from banshees fit my 1981 350lc and is there specific years that fit ?
1973 ct70
1974 xr75
1977 rd400
1981 rd350lc
2002 zrx1200

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two-stroke-brit
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Re: Piston Replacement

#11 Post by two-stroke-brit » Wed Jun 20, 2018 7:01 pm

2cycle wrote: will pistons from banshees fit my 1981 350lc and is there specific years that fit ?
there is a sticky just about this.

viewtopic.php?f=15&t=9739" onclick="window.open(this.href);return false;

mark
350LC,Athena 392 big bore,stock porting,swiss cheese air box,stock reeds,spec11 pipes.(now TSA big bore pipes)
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2cycle
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Re: Piston Replacement

#12 Post by 2cycle » Mon Jun 25, 2018 8:24 am

Thanks for all of the advice.
1973 ct70
1974 xr75
1977 rd400
1981 rd350lc
2002 zrx1200

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Re: Piston Replacement

#13 Post by silverstrom » Sat Jun 30, 2018 10:08 pm

Assuming you had matching left and right pistons to start with you might want to consider the weight of the piston being replaced. If you use a different brand/manufacturer, ideally the new piston should be very close to the weight of the undamaged piston or you could end up with a larger than desired weight difference between left and right. If balance is at all important to you.

If you have a damaged bore and need to go up 1 size you can replace just that one piston with the next size up and balance that piston to the weight of the other cylinder's piston. As long as both piston weights are the same (or very, very close) the difference in bore size won't matter. It saves the expense of having to bore and go up 1 size on the undamaged cylinder.

2cycle
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Re: Piston Replacement

#14 Post by 2cycle » Wed Jul 04, 2018 3:57 pm

Yellow and Black RZ wrote:If it was me, and the cylinder bore is ok, I'd verify what size the piston is and buy the same piston from the same manufacturer.
Would be a good idea to verify size but .25mm is .0098. Pretty tough to have much variation when the tolerances have to be so tight.

With that said pick up some bore gages and eliminate any fears you might have.
\



Do you mean make a request to the manufacture for a piston as close as the same size as the good piston or buy any 64.50 piston from the same manufacture ?
1973 ct70
1974 xr75
1977 rd400
1981 rd350lc
2002 zrx1200

MK
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Re: Piston Replacement

#15 Post by MK » Wed Jul 04, 2018 4:41 pm

I have successfully used Prox and Wiseco of 0.5mm different size in one engine - I guess you won't find more of a mismatch in aftermarket pistons.
(That's what you do as a weekend repair when that bloody Seizco failed and you had a complete used cylinder to swap ... if it weren't for the different piston. But hey, the wish to ride was stronger than the fear it won't work)

It didn't vibrate more - just differently in different rpms.
Bye
Martin

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