Vintage Dirt Bike Q & A

my 1981 cr250 developed a issue where it sticks in fifth gear. i have split the cases ,inspected all parts ,replaced everything that appears worn ,now when i install trans in right side case everything turns freely and shifts through all gears smoothly, however when install both side cases and torque to specs the sprocket shaft will only turn freely for about 3/4 turn then it locks up. the clutch shaft continues to turn freely. it will still go through gears freely but seems to freeze up regardless of what gear it is in. i have had it apart and back together countless times and have tried everything i can think of. i even have another complete tranny from another bike that develops the same problem whenever the cases are bolted together. any suggestions would be appreciated .what am i doing wrong when installing the trans into cases? how do i measure end play on the shafts?

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Now I dont have this bike but I have worked on plenty of hondas. Did you remove the shift drum? It looks like its a press fit make sure that if it is you press it in before you put the case together. I destroyed the tranny in my mt because I didnt press the shift drum back in I assumed the case was enough but I was wrong. So after I got a new mr tranny put in I used an impact hammer to seat the bearing on the shift drum and everything went together well and shifts fine to this day. Somthing on your trannys not lined up right and if somthing is a press fit and not pressed in all the way that will cause the problem you are having. Ya I bet everythings good till you put the case together cause the shift drum isnt going in like it should and causing problems. I could be wrong but thats my guess.

that was the first place i looked was the shift drum i replaced the bearing on the one side.i even went as far as swapping the shift drum with another one from a different engine. i have tried different shift forks,different shafts,replaced all the gears,thinking that one might be out of specs,i have checked the schematic every time i installed it to make sure all shims and thrust washers were in the right place.for some aggravating reason no matter which parts i use the sprocket shaft seems to hang up after i install it in the cases. it seems to be shifting properly but there is something i am overlooking cuz it will not spin freely only when i put the cases together. i am exhausted i must have had this thing apart and back together twenty times and no matter which parts i use i get the same results every time.its puzzling because when installed in right hand case half everything spins free and shifts normally.

Are all the bearings the correct Honda ones and fully seated in the cases? Are you using a Honda center case gasket?

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

Aftermarket center case gasket? Will tighten everything up by a couple thousands.

ok, thanks. i have all oem bearings and they are fully seated. i will try again with a new gasket from honda. the last one was a cheap replacement i got off e-bay. i had a oem gasket when i started this project and had the same results.Im doubtful if it will solve my problem but its worth a try. thanks for the good advice. any more will be greatly appreciated

at first you have to start with the left case, cause the transmission is fixed/positioned to the left side. install the shift drum in neutral position and fix it with the stopper plate and arm.
than the spindles with gears, the shiftforks and at last the shiftfork spindles. now testing through all gears.
be sure all parts are the right ones for the 81 model, 82 and 83 have many different parts.
maybe you have mixed some shims.

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80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

Honda trannies have a "gotcha" that's caused by two gears. Both gears have the same
number of teeth, both gears have the same cutout and will fit the main and countershaft.
The only difference is one gear is a little wider than the other. If you put the gear on the
wrong shaft, the tranny will spin freely and normally while mounted in the Left side case,
but it will bind and freeze solid once the right side case is installed. You want to make
sure the wider of the two gears is mounted on the countershaft cluster.

Might be what's ailing your tranny.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

well i finally got it back up and running today. i measured every shim and thrust washer and reinstalled and once again it was bound up. i took it apart one last time and installed new shifter forks and a new shifter drum. put it all back together and finally everything was free rolling and working right. took it out and rode it for about an hour or so and it shifts perfectly. i guess one of the forks was bent slightly but i cannot see any difference between the old and new. amazing that that slight of difference can cause so much grief. heck it could have been that old shifter drum was wore slightly but once again i cannot tell a difference just by looking at em.anyhow its all back up and running good. thanks for all the advice and suggestions. you guys have kept me motivated to get this thing back together as i was ready to give up on it after countless hours of trying to get it right. thanks again!!! this forum is awesome!!!