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03 CR250 Transmission problems

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Hi all,

 

I'm new here and could use some input on a problem that so far, is unsolved. Any help would be greatly appreciated.

 

I have an 03 Cr250 with a shifting issue that I can't find the source of. The problem I'm having is the transmission won't shift at times, when I'm on the pipe. At lower rpm's everything is buttery smooth, but sometimes it simply refuses to shift until I slow down or hit a bump and unload the rear tire. I notice this mostly when shifting into 3rd between obstacles and I'm afraid that one day this is going to get me hurt. I've tried several different oils and shifting techniques but nothing has helped. The shift lever just stays solid and doesn't budge until the load is removed.

 

I currently have the transmission apart, but see nothing that jumps out at me that could cause this. I spent 4 years building transmission, rear ends and transfer cases for heavy trucks and automobiles but this is the first motorcycle transmission I've had apart, so I'm not familiar with diagnosing these.

 

 

Any ideas??

 

 

 

 

 

IMG_1304.jpg

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Are you clutching when you shift?  Are you closing the throttle when you shift?

 

You have to unload the transmission to allow it to move smoothly between positions (it simply refuses to shift until I slow down or hit a bump and unload the rear tire).  If you are holding it wide open and trying to bang through the gears without using the clutch or a quick snap shut of the throttle, it will be hard to move it between gears.

 

Do you have the manual?  The service limits of the gears, washers, bearings, shift arms etc is in the manual.

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Yes, I always clutch when I shift and snap the throttle shut. Unless I really have the thing loaded it shifts great.

 

I mainly see the problem as I accelerate out of a turn and go for 3rd gear. Sometimes I'll make 3 or 4 attempts at shifting and the lever just feels solid and doesn't engage, I'll release the clutch and snap the throttle back open to find I'm still in second gear. As the bike slows from my attempts to shift, it will suddenly fall right into gear. It's been very repeatable.

 

I'll download the service manual and check the service limits.

 

Thanks for the replies.

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you can hold it wideopen but you have to flip the clutch slightly while simultaniosly shifting the gear. otherwise the torq holds the gears together.

Edited by harryhandshake

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Check for bent shaft forks or shift shafts. Also look at the shift drum grooves to see if there is anything that would keep fork tabs from sliding in the grooves.

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Everything checked out within spec.

 

The only wear I was able to find was on the center shift fork and very slight rounding of the engagement dogs of 3rd gear (mainshaft). You can see where the face is slightly polished from the opposing dogs gliding across, but not engaging. I think I'll replace the fork and gear, just for piece of mind and put it back together. At least now I know there isn't a catastrophic failure, just waiting to happen. 

 

I wish I was able to better describe the symptoms. 

 

Maybe it's just the way I ride it?

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When replacing gears it is always advisable to replace BOTH gears the mesh together. If you are seeing wear on 3rd gear, then the other gear that meshes with it probably has wear on it as well.

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When replacing gears it is always advisable to replace BOTH gears the mesh together. If you are seeing wear on 3rd gear, then the other gear that meshes with it probably has wear on it as well.

 

I can do that.

 

One thing that does seem a bit funny is the wear on the center shift fork. This shift fork actuates the gears in question and although very, very slight... has a funny wear pattern. I don't have a photo to upload right now since I'm at work, but I'll try to describe.

 

If when looking at the fork, you view the tip of the fork as the "toe", and the base of the fork as the "heel", the wear show on the "heel" of BOTH sides of the fork. This tells me the fork is cocking over when trying to shift in BOTH directions. If the fork was bent I'd find the "toe" worn on one side, and the "heel" worn on the other. The shaft checks straight and the drum shows no signs of wear at all. It seems like the fork is deflecting from the pressure of trying to change between gears.

 

I hate to just throw parts at it, but I know something isn't right. I'll replace both gears and the fork to see if that cures it.

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I would replace the shift fork shaft too.

 

Will do. I ordered that as well, this morning.

 

Thanks for the suggestions. I'll let you guys know how she works after the part replacements.

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I hate to just throw parts at it, but I know something isn't right. I'll replace both gears and the fork to see if that cures it.

 

Then don't! Keep diagnosing until you find out exactly what is wrong!!! In my opinion (take it for what is worth .02 if that) thats the difference between a good mechanic and a visit to the shop again to fix the problem again... 

 

I wish I knew of better resources to give you for troubleshooting the problem. Re read the manual again, and find the symptoms you are having issues with, then check the parts spec (listed in the manual).

 

Good luck.  

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It could actually be your clutch basket or inner clutch hub that is causing this as well.  If either are badly notched pulling in the clutch won't do much of anything and will cause hard shift like you are experiencing simply because the plates are not moving independent of each other.

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The earlier cr's did not shift well under power, this is well documented. they improved it with the 05-07 model.

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The earlier cr's did not shift well under power, this is well documented. they improved it with the 05-07 model.

First of heard of it.  Have had an 02 & 03 with 300 plus hrs. combined still on original bottom ends with no issues.   

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