CR 250 topend job

[TRAIL]

I am getting ready to install a topend in my 2001 cr 250 and in the wiseco paper it says i may have to drill 2 holes where the piston contacts the exhaust bridge. So do I have to? Others with the same bike what have you done?

 

[250aderacer]

i dont think you will find your exhaust port has a bridge the instructions in the box cover several year ranges.

 

[Dirtvet]

The 2001 CR 250R does not have an exhaust bridge. The Wiseco piston can go right in without a problem. I've replaced two pistons in this bike without a problem (not bad for a rookie).

 

[TRAIL]

Thanks for the replies

 

[ML536]

Two things to be careful of on this model when you replace the top end are to be careful not to twist the cylinder when you are putting it back on the bike. If you do, its easy to pop a ring out of its groove and catch it on the intake port. Second, be careful when slipping the cylinder back on that the "U" shaped groove on the power valve's arm on the bottom of the cylinder aligns with the arm on the bottom end. If they don't line up, you can damage the arm. If you miss the groove completely, the powervalve wont work.

I learned first of these tips the hard way, and bent one of the new rings. What a treat that was!

If this is the first time that you replaced the top end, which I am guessing that it is because of your question, I just wanted to mention these things to help you to avoid any problems. Good luck!

 

[crkid]

Well said ML, I did the second mistake once and had to replace the pieces to the powervalve. But yep the Wiseco works great without a hitch.

 

[NCPaulD]

What about the 2002?

Is there an exhaust bridge on the 2002 CR250? I just received my new top end and also saw that I may need to drill.

 

[bedell99]

Yes there is an exhaust bridge on the 2002. . If the holes are not there, it has been my experience that they need to be drilled.

Erik

 

[pace]

In order to preempt the inevitable "..what about model year XX" questions, could one of you knowledgable guys list which years require the holes for the exhaust bridge and which do not. 2003, 2004, etc. I'm sure this info is valuable for a number of folks here. I'll be replacing my topend soon using a Wiseco piston, and I was not aware of this requirement either.

Thanks!
-Pace

 

[shnalln]

Being a rookie myself, how do you identify if you've got an exhaust bridge? What is the purpose of an exhaust bridge? And probably more importantly, can any damage be caused if the holes are not drilled when they should be?

 

[shnalln]

Ok, did a search and answered my own questions...I didn't drill the holes on my wiseco 'cause there were no holes on the stock piston...guess I got some work to do...man, I hate doing $%!^ twice...that's the price of learning though I guess...

 

[bedell99]

An exhaust bridge separates the exhaust parts into 2 channels. It is 2-3mm strip. When u remove your syslinder you will see what i mean.

Erik