Frequency of top end changes

T

thomas123

Member

Oct 31, 2001

94

0

• Jan 12, 2003

• #1

Hi, I just bought a 2002 cr125 that was used by a Canadian national pro in a few races, anyway it's been ported and has a high-compression head, full bills pipe, suspension, etc... It's also only run on race gas. My question is how often should I change the piston/rings? I race at the Junior level in canada ( I think that's the "C" class in the states but I may be wrong ) I've heard 10 hrs per topend but I'm not sure if that's also for modified motors. Thanks, Thomas

 

marcusgunby

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Jan 9, 2000

6,450

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• Jan 12, 2003

• #2

It also depends on the piston you use-the std one is a very sloppy fit even when new.It also depends on how big the ports are.I would think 10 hours is a safe limit and i guess you could go a bit longer say 15 hours but its a risky thing to do-it would be wise to fit a piston and run it for 10 hours-dissassemble and measure everything to see how it holds up.

 

bclapham

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Nov 5, 2001

4,340

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• Jan 12, 2003

• #3

Try to buy some digital calipers, mine cost $40 and paid for themselves X 5 recently. I thought i was ready for a full top end and clutch, after measuring the specs all it cost me was a ring set and gaskets!

 

T

thomas123

Member

Oct 31, 2001

94

0

• Jan 13, 2003

• Thread starter
• #4

What piston would you reconmend if not stock? the one time I tried a vortex piston in my 2000 cr250 it completly shattered after only 7 hours of use, not pretty... Ever since I've been using stock pistons... Thanks, Thomas

 

marcusgunby

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Jan 9, 2000

6,450

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• Jan 13, 2003

• #5

The wisecos are the strongest bar none-but you have to bed them in right and warm them up properly-the vertex's are good but they do make some race only ones-these last 7 hours like you have found.