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Discussion Starter · #1 ·
Hi all.



I had the gearbox out, but did not take it apart. Everything looked OK, and upon reassembly the gearbox cassette slid in with a reassuring 'clack'. When I tightened up the bolts and checked the shafts the input shaft turned freely, but the output shaft seemed a bit stiff. I attributed this to somewhat dry shafts and gears, and figured it would turn easier after oil had been added.



But now the more I think about it the less I like it. Since then I have put on the engine covers, but wonder now if I have to tear it apart again to have peace of mind. I can turn the output shaft with two fingers, but only just, using force. Any tips about what it could be? Both shims on the rear of both shafts were present, and the pics I took of the assembly before I put it together shows everything is correct. All gears go in properly.



Thanks,

Michael
 

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All the gear boxes I have ever done spun pretty freely even without oil in them. Did you oil the parts in the gears and bearings when you put it back together?



Have you tried shifting it through the gears?
 

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Hi all.



I had the gearbox out, but did not take it apart. Everything looked OK, and upon reassembly the gearbox cassette slid in with a reassuring 'clack'. When I tightened up the bolts and checked the shafts the input shaft turned freely, but the output shaft seemed a bit stiff. I attributed this to somewhat dry shafts and gears, and figured it would turn easier after oil had been added.



But now the more I think about it the less I like it. Since then I have put on the engine covers, but wonder now if I have to tear it apart again to have peace of mind. I can turn the output shaft with two fingers, but only just, using force. Any tips about what it could be? Both shims on the rear of both shafts were present, and the pics I took of the assembly before I put it together shows everything is correct. All gears go in properly.



Thanks,

Michael
Michael,oil in or out is irrelevent.you say all 5 gears go in properly.. in neutral the shaft should spin freely.

so something is adrift.

what did you do to the motor.why was the rear cover off.did you use a honda gasket on the rear case?
 

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Discussion Starter · #4 ·
Michael,oil in or out is irrelevent.you say all 5 gears go in properly.. in neutral the shaft should spin freely.

so something is adrift.

what did you do to the motor.why was the rear cover off.did you use a honda gasket on the rear case?


I have changed the camchain and tensioner, mechanical seal and oil seal. Also the head gaskets due to water leaks, then I found some corrosion in the cylinders, and had to hone them, and change piston rings. Therefore the gearbox had to go out. All gaskets and parts are OEM Honda. This problem would not be gasket related however, rather the gearbox itself. I'll take the 'box out again, cannot take the risk. Perhaps some slight misalignment between output shaft and casing? Strange.
 

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I have changed the camchain and tensioner, mechanical seal and oil seal. Also the head gaskets due to water leaks, then I found some corrosion in the cylinders, and had to hone them, and change piston rings. Therefore the gearbox had to go out. All gaskets and parts are OEM Honda. This problem would not be gasket related however, rather the gearbox itself. I'll take the 'box out again, cannot take the risk. Perhaps some slight misalignment between output shaft and casing? Strange.
agree,take it out,something is binding.
 

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Did you ever find the cause? I seem to have the same problem.



Noticed it when taking the engine out to find a slight knocking sound. Gearbox seemed OK, but when doing up the bolts that keep it in place the output shaft would bind. "fixed" it by grinding the shim on the end of the shaft so it turned freely when all bolts were in place. Yes, this was the correct shim, even compared it with one from a spare gearbox. Even checked out OK whith the rear cover back on. Engine ran well, still with a slight knocking sound when cold.



Now after only about 100kms the shaft is very tight again and can only just be turned using two fingers. So, the engine is coming out again, but a known cause would be nice.



Anyway, will report here what I find.



Frans
 

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Before taking the engine apart again I remembered reading somewhere that sometimes the caged needle bearing in the front cover of the gearbox (on the front end of the output shaft) might work its way out a bit (why is unknown). The author recommended just tapping the shaft might help, and sure enough: a smart tap with a soft nylon hammer on the output shaft and - surprise - it suddenly ran free and smooth again.



Don't ask me to explain, but if anybody can please share that bit of wisdom.



Because I now had the engine out anyway opened it and pulled the gearbox apart, but couldn't find anything wrong. Now CX gearboxes don't normally give any trouble, so replaced the whole lot from spare, problem solved. Seems to change gears a lot smoother now.





Endresult : no fault found, so replaced gearbox.



(yes, replacing the whole engine is too easy
)
 

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Discussion Starter · #8 ·
Thanks for the update brinkcx.



I never found the root cause. As in your case the output shaft was a bit thight. I dismantled the gearbox completely and found nothing wrong. I also suspected the needle bearing bush but could not see that it had crept out. Tapping the end of the output shaft did not help. Measuring showed that the shaft was tight by 0.12mm. It was possible to turn the output shaft with two fingers, although with some force. Inspection of the shims showed that the one on the needle bearing side had wear marks, indicating that the assembly must have been tight for some while, or perhaps since it left the factory. The engine only had 6300 miles on it.



I used #1000 emery paper and polished off a combined total of 0.15mm of both shims, after that the shaft rotated perfectly. After some 200 miles I took of the rubber gaiter on the final drive shaft and rotated the shaft with my fingers, it was still completely free.



When I took over the bike from the previous owner it had a clutch judder when cold, after my engine rebuild it had not, although I did nothing to the clutch. That could have been a symptom. I suspect the shaft was a bit thight since new, freeing when hot as the cases expanded. 0.12mm is not enough to cause problems for the output bearing but enough for it to feel tight.



Strange case.



Regards,

Michael
 

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I'm reconditioning and rebuilding a CX500 engine (CX500E - 2102884) which I obtained in pieces, the gearbox however was whole and looked in good condition. After fitting the gearbox the output shaft was quite stiff to turn, I was getting worried and was going to take it out again but before I did I found this thread. So, I've just given the output shaft a sharp whack with a fibre mallet and it freed-up just like magic!!

Thank you all for the information.

Regards
Mike B
 
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