ERIC A "C" piston in a "B" bore??

MikeT

~SPONSOR~

Jan 17, 2001

4,095

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• Mar 25, 2002

• #1

Eric, I was wondering what you think about throwing a Yamaha "C" piston in a "B" cylinder. My bike is a 1996 YZ125 and has a stock bore. I'm getting my suspension done this winter, so I really can't do anything to the bore just yet. I am thinking it will freshen up the top end a little better than a "B" piston would. What do you think?? Also, I haven't had the bore measured yet. I am not sure what the bore size is supposed to be either. Could you point me in the right direction on that?

 

Last edited: Mar 25, 2002

Y

yzeater

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May 21, 2001

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• Mar 25, 2002

• #2

Hey Mike, I'm probably just as good at this stuff as you, but I think it's a good idea to step up a size if your cylinder has had a lot of wear...That's just what I've read on the forums here

 

MikeT

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Jan 17, 2001

4,095

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• Mar 25, 2002

• Thread starter
• #3

I'm sure it has some good wear and I need it to last this season before I give it to Eric for the 133 kit. I just want to make sure I won't ruin anything if I do this. I'm just not sure if I can.

 

J

jmics19067

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Jan 22, 2002

2,097

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• Mar 25, 2002

• #4

I believe it was the piston that is egg shaped not the cylinder

 

MikeT

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Jan 17, 2001

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• Mar 25, 2002

• Thread starter
• #5

You're right, I corrected the post.

 

B

bruce j

Member

Dec 14, 2001

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• Mar 25, 2002

• #6

Basically you need to measure your cylinder and see what the clearance will be with the piston you want to use. It's best to use measurements from an actual piston rather than just published specs. Your owner's manual should have the specs you need for the cyl. and for the piston clearance. If the C piston has adequate clearance, you should be fine. If you don't measure it, you won't know.

bruce

 

W

whyzee

Never enough time !

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Dec 24, 2001

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• Mar 25, 2002

• #7

Mike,
Cyl A 54.000 - 54.002
Cyl B 54.004 - 54.006
Cyl C 54.008 - 54.010
Cyl D 54.012 - 54.014

Pist A 53.957 - 53.960
Pist B 53.961 - 53.964
Pist C 53.965 - 53.968
Pist D 53.969 - 53.972

With 6 years of wear on your cylinder, even the D should fit your needs. Measure the cyl., you may be able to get another year with just a ring. With your oil rates the dome maybe perfect. What did you say your PSI was,... 130' ish?

 

MikeT

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Jan 17, 2001

4,095

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• Mar 25, 2002

• Thread starter
• #8

I've been running a Weisco Pro lite piston. Does anybody know what the dimensions of that piston is? If anybody knows what the weisco wensite is or a number to contact them at please post it, I'll call them. Thanks

Ya, 135 or so.

 

W

whyzee

Never enough time !

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Dec 24, 2001

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• Mar 25, 2002

• #9

Mike,
Think it goes something like this:
http://www.wiseco.com/

 

D

demographic

Member

Jan 21, 2002

128

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• Mar 25, 2002

• #10

Please go to a machine shop and get your bore measured, then we can work with the facts cos we/I don't know how much you ride your bike or how hard and how much oil or whatever.Cheers and good luck:)

 

MikeT

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Jan 17, 2001

4,095

11

• Mar 25, 2002

• Thread starter
• #11

Check, I'll do that before my next ride. Thanks guys.

 

A

ACGUY

Member

Feb 6, 2001

61

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• Apr 1, 2002

• #12

Bore Measurement tools

Find a shop that has 3 point INTRAMIK tools. The bore diameter can be measured down to the 1/10000, which I would surely want the accuracy to determine what kit to buy. For example, I just measured a XR250 cyl with a mic. It read 1.957, which is at limit. With the intramik, it measured 1.9556, which is within limit. I would have bored a cylinder that didn't need it if I had not spent the time to use a accurate tool. :D