Vintage Dirt Bike Q & A

1979 CR125 shift issue - Just fired up the CR125 for the first time. rode it up/down the driveway in 1st. Went to try 2nd and I find that the shifter seems to be ``locked up``. When I did the bottom end everything was fine and it shifts 1-6 & back no problem. Now that I have it running, only 1st & neutral.

Further investigation shows that the selector arm lateral movement of around 1/4 inch. When it is all the way ``out`` it won`t shift. But if held ``in`` it shifts fine. My dumb question is if there is a missing clip or spacer on the selector arm for a 1979 CR125R?

Further investigation:

OK, the diagram shows a small collar that is on the selector arm, that is between the arm on the wet side and the outer case. Looks to be about 1/4 inch, which is the amount of in/out play that I have. Part number is 24620-444-000

Found the collar, NOS, from a supplier down south.

Well I installed the collar (it was missing) and that took up the slack (side to side) movement. Put in fresh oil and ran it thru the gears. Seemed a bit funky, but did shift.

Primed it and fired it up. 1st gear no problem, neutral and then it won't go any higher under power.

So I'm thinking it could be a bent shift fork or the shift drum is bad. Anybody else have this problem? Looks to be a total lower end tear down and maybe a transmission. Did want to ask before doing this. With the number of cobbled fixes I have found on this one, it wouldn't be too surprising to find more missing/bent/broken things.

Just for grins, check the sector ring gear on the shift shaft end. The earlier CR gearboxes look like mirror images of yours, and I had a '77 that took a mega upward hit to the shift lever and distorted the sector gear; it would shift down fine but up only a little, just enough to get into neutral frrom 1st (the spring stopper pin had also been tweaked a bit, but I just retightened it). Or it could be a bunch of other things too, I'm sure.

If you want to rule out the gearbox internals before splitting the cases, try removing the shift pawls etc. and shifting the drum by hand (I cut up the end of a wood trim strip to fit the drum indents, and spun the countershaft for easier shifting).

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Ray,

Will give that a try. It did bench shift fine, nothing funky at all. It appears that the "kid" who bought it from me back in 88/89 tried to do his own work and was really good at losing things. I was guessing that it shifted fine when I had it apart over the winter, simular to what you are saying.

Will pull off the clutch cover (again) tonight and see about any broken parts and will be droping the chain and running the gears. Really don't want to split if I don't need too!

Jim

OK - I'm sure you'll be verifying that every part is there and installed correctly (especially the detent wheels/springs and shift pawls) so here's a diagram you surely already have:

http://www.powersedge.com/pages/OemParts?aribrand=HOM#/Honda/CR125R_A_(79)_MOTORCYCLE%2c_JPN%2c_VIN%23_JE01-2000010_TO_JE01-2010778/GEARSHIFT_DRUM/CR125R-79-JPN-A/2Y14444ZE14444Z08B

For what it's worth - every 70's Honda transmission I've had has been reluctant to shift into 4th gear on the bench without both shafts turning, although they all worked fine on the bike. I notice this when riding too - when I pull in the clutch and coast, sometimes I can't downshift until I let the clutch out briefly.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Ray - stripped off the side cover, clutch basket, ect. I can manually shift the bike into the gears using just the star wheel on the shift drum. Nothing appears to be bent/damaged. I did notice a tweaked shifter, nothing too horrible and it clears the side cover fine. Thinking that possibly the shift drum was 180* off at assembly???

Have a manual to verify the correct position and I'll see if I can get things together and have it shifting right before the side cover goes back on.

How about the hollow-ring sector gear on the clutch end of the shift shaft, the shift spring centering post, and the shift pawl assembly? These all have to be in good shape for proper shifting. Does the shift shaft bind in the case holes? Are both detent wheels / levers / springs in place and working correctly?

Sorry for all the questions.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

hi, is your shift return spring spread over the bit where it sits into? its been ages since ive been in my 1980 cr125 box, but can remember the legs on the spring need to be tweaked onto a higher point or it wont shift properly.
cheers, bill.

Ray & Bill

Here is what I found over the weekend. The shift pawls, A&B, are present, but are reversed in thier respective locations. I'll swap them around tonight and see what that gives me. If this won't do it, then the shift drum may be 180* degrees off (don't really think that is the case).

To hit the 1st gear postion I rotate counter clockwise on the shift drum. I'll need to recheck that tonight as well. The punch mark should be on the shift arm gear (at the punch mark, center of the shift gear) if I'm reading the book correctly. Good news was that the drum rotates freely and gears are meshing as they should.

Bill - everything went together as it should originally (except above), all springs & detents function correctly.

Ray - Shift shaft wasn't binding, but I did notice that there was a very large amount of play on the upward shift (that did not happen). Thinking that the "notch" on the pawl was allowing that to happen (excessive play). With the cover off, I can get it to shift as is, but the arm travel is wrong. With the cover on, just has a large free play area on upward shifting. I'll let you know in the morning what happens.

Thanks,

Jim

Jim,

I'd carefully check items 19, 20, and 21 on the diagram for bending or other damage. With the shift pawl removed and shift shaft assembled, the shift lever should move the same distance up from center as down. One of my motors had the 'sector gear' section of #19 bent way down and cracked, and #20 cocked in the case threads.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Ray - I got some time in the shop last night to really look at the motor. I thought I had movement in all of the gears, but not so. As I rotated the shift drum I could only get about 3 gears. Even if I was spinning the rear wheel, only 3 gears. From what I read in the manual, the drilled hole (witness mark) on the shift drum should be at the 3 O'Clock position, and in line with the post, or neutral position according to Honda.

At that point the punch mark on the star wheel and the mark on the selector shaft are to be lined up.

Well, I think there is a problem. The witness mark on the drum stays between 8 & 10 O'Clock, or 180* out of position. So is it possible to assemble the transmission and have the drum 180* off? If so, I have to split the cases and go thru the trans.

Thoughts????

OK, got the call yesterday on the '79 CR125. Seems that the previous owner was able to assemble the lower end with the L & R shift forks reversed. Cases, bearings & trans are all fine. Putting in new crank bearings & seals at the same time. Hope to be running by next week.