Power Valve Stuck Open (02 CR250r)

[goblue12n0]

Is it possible for an RC power valve to stick open or even closed for that matter? I have a 2002 CR250r. I have rebuilt the top end (5 - 7 hours ago) and have replaced the actuator. The bike runs great with exception of the power band.

At the track recently, somone indicated that when rebuilding the top end it is necessary to remove the power valve and utilze a small Dremmel wire brush tool to remove all rough edges and barbs from the power valve and the power valve housing.

I do not have superior mechanical skills, perhaps slightly above average. I have the book for the bike and it does not go into detail about maintaining the power valve. I also took the bike to Honda. They placed it upon the stand and tested the (new) actuator. They claimed the actuator moved properly.

The bike also has some "knock" sounds at certain rpm(s). Mostly low rpm or just above idle. The top end has about 5 - 7 hours. The bottom end was rebuilt by Honda 10 - 14 hours ago. The mechanic at Honda indicated that the "knock" sounds were normal. Is this true?

Lastly, how difficult is it to replace the rod?

 

[btm1948]

most the time a knock in your engine is not normal where are the nocking sounds comming from. its not to hard to replace the rod as long as you have the shop manual on hand

 

[_JOE_]

most the time a knock in your engine is not normal where are the nocking sounds comming from. its not to hard to replace the rod as long as you have the shop manual on hand

You need alot of special tools to do a proper rod replacement. As cheap as you can get complete cranks for, it can be more expensive have the stocker rebuilt by someone who knows what they're doing. Something like this isn't what you want to take a chance on.

 

[gscx]

Yea, you should just get a new crank, it is probly cheaper, taking the crank out isnt hard, esp. if you have the book, that way you wont need a mech. to take it out and you can save alot of money. And my frind has a 02 cr250 and i know what you are talking about with the knocking sound. Ive asked around and it happens to all of them, idk why. But for the powervalve take them out and take off any carbon deposits, with something that wont scratch it, a wire brush will do.

 

[mox69]

I thought my '02 CR250 had an engine knock as well. After many hours I have pinned it down to the chain. For whatever reason upon acceleration it slaps the swingarm and creates what sounds exactly like an engine knock.

It happens even with race gas, and yes the chain is adjusted properly. I've learned to ignore it now.

 

[goblue12n0]

Thanks to all and Update

All,

Thank you for your advice! The bike is still apart. The rod and the bottom end are within specification and appear solid. The knock sound was the actual exhaust power valve / flap. For whatever reason the flap was goining up and down as the bike was in low idle and it was slapping against the top / bottom of the exaust valve casing within the cylinder / jug thus, causing the knocking sound. This knocking actually created significant recesses in the bottom of the exaust valve casing. I took the cylinder / jug to Honda after removal. They (Honda) contacted support and indicated that they had put the wrong cylinder on the bike after rebuilding it 2 years ago. Our local Honda dealer, Noblesville Honda, has offered to replace the entire top end and properly adjust the power valve (RC) controls.

So, for those of you with 2002 CR250R bikes add this to the long list of things that could be a problem. It should also be noted that since the rebuild by Honda 2 years ago, when the power valve began malfunctioning, the bike started spooging. I modified the jetting significantly and could never eliminate the spooging problem completely.