CR overbore problem

[Mxracer510]

I blew up my 00 CR250 engine a month or so ago due to springin a leak in my radiator and running it out of coolant :scream: Pretty much toasted the cylinder. I sent it off to Eric Gorr to do an overbore job on the cylinder and to port it (mo better everywhere) I've got it back together and rejetted. It doesnt have any hesitations or blubbers and the plug is a nice brown color. But So far its pretty much just anemic in its power department. It just doesnt run good at all. From as far as i can tell it actually has less power than it started out with. I need help...baaaaaad. Any Ideas of what it could be?

 

[Rich Rohrich]

Check the powervalve operation.

 

[Mxracer510]

Powervalve opens fully...and closes fully. That was my initial response as well but i did take the left side peep hole cover off and checked it out. It opens when reved and closes when just above idle. any other ideas?

 

[NEWHONDAS4US]

I'd start with a compression test.

 

[Mxracer510]

haha...i just put in a new piston...it isnt worn. Why would i need to check compression?

 

[Rich Rohrich]

Originally posted by Mxracer510
haha...i just put in a new piston...it isnt worn. Why would i need to check compression?

To verify that the rings are sealing properly. It'd the next logical place to look if you are sure it's jetted correctly. How did you verify the jetting?

 

[Mxracer510]

Well to start off with..it was jetted good to begin with before i sent it off. I did the normal...full wide open 1/4 mile to check the main jet. then by how it responded on the slow speed jet. In the end i had to lean up the main jet and fatten the slow speed jet each by a step such as eric suggested. but it just doesnt have the power that it used to have.

 

[Mxracer510]

I just went and kicked over a 96 CR compared to my 00 and they were both about the same. Both of them have top ends that have only been ran a few times...

 

[madmxracer]

My 00 CR265 was done by eric gorr and there is definetly not a power problem. Did you use the same rings in it and i would also say to try a compresion test and if taht is to spec then look at the power valves.

 

[Mxracer510]

Use the same rings in it? Its a new piston...new rings..new bearings...

 

[Mxracer510]

Im also pondering ignition timing?

 

[NEWHONDAS4US]

timing is a possability.
where does it feel down on power ? across the board?

 

[Mxracer510]

yup...kinda across the board. mainly low/mid

 

[Mxracer510]

any other ideas?

 

[marcusgunby]

I would do a comp test to establish the rings are seated and the bore isnt glazed.A bore may glaze if the rings dont seat for ant reason.

 

[Mxracer510]

what would cause the bore to be glazed?

 

[marcusgunby]

too much oil on installation of piston?im guessing but to get to the answer we need to esablish what is right and what isnt-once you do a comp test we can rule out a glazed bore or rings not seating.

 

[Mxracer510]

There isnt any blow by on the piston..would that indicate rings sealing properly or a glazed cylinder.

 

[Jon Sosa]

What is your gearing?

js

 

[bscottr]

Back to the PV. :think:

Not only does it operate, but is the spring tension set correctly? I didn't have enough tension on my '99 CR250R after a rebuild and it felt dead, except on the top end. I put additional tension on the spring which delays the PV opening, big big difference. Just a thought. ;)

Good Luck,
Scott

 

[smrmx]

how did you change it .

 

[smrmx]

I was wondering what you did to change the delay?
and what do you think about 160psi on a 200 cr250 top end time?