'02 CR250R will not rev out......sometimes!

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kooldad

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Apr 23, 2010
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OK, here is the deal. Got a great bike (2002 Honda CR250R two stoke) with a new carb, jetting is perfect. I have an issue that seems like it is running stopped up (lack of better analogy). It will not rev out completely in any gear. Now all I have to do is kill the engine and restart and it will run hard and rev out all the way. It will not change while the engine is running. Either it revs out all the time, or it will not rev out. It only happens if the engine dies, as in it is running good and I stall on the trail. I restart it and it has less power. A quick engine shut down and bump start is all it takes to fix the issue and it will run hard like it should.
This HAS to be an electrical issue right? Anyone have a similar experience or any suggestions about where to start?

I'm pretty confident this isn't a carb or jetting issue. It is a brand new Keihen PWK racing carb and the jetting has been fine tuned and the float level checked and set. It's even been jetted for the change in the weather. All new fuel lines, petcock and air breather. I'm using super unleaded with a racing fuel mixed 32:1.
It's just that sometimes when I start it up and get it all blowed out and ready to ride, it just doesn't rev up all the way like it is stopped up or has a governor on it. All I have to do is kill it and restart and it will rev all the way up and pull a wheelie in every gear like it should. Then if I stall on the trail or something it may or may not go back to acting up. All I do is a restart and it's back to wide open. The silencer has been repacked recently also so I don't believe that's the issue. A local shop agrees that it is electrical. I'm just trying to find out what exactly is going bad instead of just changing parts.
 

ellandoh

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my next guess personally would be powervalve you can pull up the rubber boots on the control wires and rev it up to see if they move.
 
J

_JOE_

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May 10, 2007
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The power valve was what popped into my head too. That one has the funky cable operated setup. I would think that to be a more consitant issue though.
 

whenfoxforks-ruled

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Sure sounds like the exhaust valve. Isn't the 02~07 an electronic controlled? A bad exhaust valve servo? I believe that's what Honda calls their governor that operates the mechanism aside the clutch and drive gear. The older models have a small round inspection cover on the left side of the cylinder, to check the valve function while the engine is running. Vintage Bob
 
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kooldad

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Apr 23, 2010
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Thanks for the input. I know the shaft on the powervalve is turning when I rev it up. I'll have to go back and see if it is turning enough. Does anyone think that maybe the stator is going bad? If so how to check it? How about a way to test the servo motor?
 
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2strokerfun

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May 19, 2006
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The only time I've had a problem with a stator, it was an on/off problem, not a limited rev problem.
 
J

_JOE_

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I think all the stator failures I've seen were sudden and killed the engine. I would think it to be something more like the cdi if it's ignition related. You should have specs and diagrams in your service manual for the ignition system, but I would make sure that the power valve servo, cables and internals are working properly first. Try to get it to act up and see if you can see a difference in range of motion.
 
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kooldad

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Apr 23, 2010
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I have looked again at the powervalve. I removed the cover and ran the engine, shut it off, ran the engine.......several times. My manual says fully closed at 3000 rpm and fully open at 8000 rpm. I did not have tachometer attached but notice that at idle, the shaft would constantly turn back and forth. If I opened the throttle it would slam open like it should.
Now after turningthe engine off then back on, I noticed the shaft would not move at all. If I opened the throttle it would move just a little toward the open direction. I could shut off the engine, restart it and it would go back to constantly moving back and forth at idle.

So, I feel like I am makin progress. What now? Is it the servo motor?
 

ellandoh

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this may help
 

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ellandoh

dismount art student
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get through these and let us know where youre at with it
 

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K

kooldad

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Apr 23, 2010
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I found a corroded wire at the ECM where the servo plugs in. ........Then I hooked up the cables backward and think I bent a valve. Be careful if you try this. I had to go opposite the manual to get it right.
 

ellandoh

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how could it bend i valve?
 
I

In come tacks

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Feb 10, 2010
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So the problem was electrical? I need to look at mine, it seemed to be doing the same thing, but I could hear a chatter. I hope it IS corroded conectors!
 

whenfoxforks-ruled

Old MX Racer
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kooldad said:
I found a corroded wire at the ECM where the servo plugs in. ........Then I hooked up the cables backward and think I bent a valve. Be careful if you try this. I had to go opposite the manual to get it right.
Click to expand...
What brand name manual has the instructions backwards? Vintage Bob
 
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kooldad

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Apr 23, 2010
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I have the 2002-2003 Honda Service Manual. Chapter 8 section 9 on RC cable connection/adjustment. It says to connect the rear cable to the servo motor first then the front cable. I did that and started the motor and the pulley on the cylinder was slammed wide open at idle.

I had to connect the front cable to the rear of the servo motor pully first and then the rear cable.
 
K

kooldad

Member
Apr 23, 2010
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Does anyone know if it is possible to remove the exhaust valves from the '02 CR250R WITHOUT removing the cylinder and head?

I know the manual says to break down the top end. It looks to me like you can remove the shaft and slip the vlaves out of the exhaust manifold.

Any comments?
 
J

_JOE_

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May 10, 2007
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Give it a whirl. They should slide out the front and may not clear the frame as you slide them out, but it might work. I would question if the servo is malfunctioning. It's pretty uncommon for a factory service manual to be wrong.
 

ellandoh

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it may be more fun getting it put back together than getting apart. not to mention, make sure the piston is in a good spot to catch them if they fall in on you.........if it was me i would get a gasket set and some rings and pull the jug. that way if they need servicing youre good and if they dont you will have a fresh set of rings.
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Merrillville,Indiana
Check and see if you can determine if its got a sleeve or overbore before ordering parts. Most sleeves are magnetic, plated is not. Check the piston, the bore and the crank clearances while its down also. My 97CR says 7.5 hours on the piston and ring. Yes slower riders may get more, and the forged usually lasts longer than the oem cast, and if its got a sleeve? But then you know where your engine is at, wear wise. Its safer for you, and in the long run saves you money. Athena or cometic gasket kits are cheap on fleabay, and plentiful. For a laugh, compare the prices to Service Hondas, what do you have to lose, more money. If you pull the jug off, gaskets and rings are a given. It will make a seemingly great bike truly great! Vintage Bob
 
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kooldad

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Apr 23, 2010
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Thanks for all the advice. I will probably end up rebuilding the top end soon. I got it all put together and it seems to be running O.K. for now. I haven't been able to really run it, but I'll let you know.

My next project is cleaning the clutches. My oil looks like sludge after just a few hours. Someone told me to pull the clutches and wash everything down. I did that no problem following the manual. I've checked the service limits and all looks good.

One thing the manual is not clear on is the orientation of the clutch plates. I got the order down pat, but what about a front or back side. And some of the tabs on the clutch discs have little half moon cutouts. I staggered them just because. Does it really matter on the orientation?
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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Merrillville,Indiana
Now I believe you are into some solid guy figuring territory. I have set them together and staggered. WTF, no difference noted? I am pretty sure them divots are for oil sloshing. Either way, they slosh the oil around, seemingly. And some brands, do not have them. 1 thing, if it has aluminum metal plates, ditch them and get steels. I have always got longer clutch life, and cleaner oil. I have lost, seemingly nothing. It looks good on paper though, less spinning mass? I like my clutches as solid as I can get them. If they ever make a clutch that locks up solid...it will likely never work in the dirt? Vintage Bob
 
K

kooldad

Member
Apr 23, 2010
10
0
I ran my bike this weekend. It is still doing the same thing so I'm back to square one. FYI The exhaust valves will NOT come out of the exhaust mainfold so I did have to pull the cylinder off. At least the valves were so carboned up that they would not come out the exhaust side. I'll clean them up good and see if they will fit, but otherwise they have to come out throught the cylinder.

Guess I will go ahead and replace a few things while it is open.
 
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