Good catch on the seal! Drive shaft and shift shaft seals are the usual culprits for leaks on the drive side on RD's. Be sure to use some engine case sealant on the outside of the new seal, so that the mating between the engine case and the new seal is oil tight. Use a spanner socket to gently tap in the new seal. Use a bit of blue lock-tite on the neutral switch screws. It is easy to over tighten the screws and cracking the neutral switch cover. If your neutral switch leaks, you can replace the o ring on the cover, and you can make a gasket for the neutral switch cover from some cereal box cardboard, cut to size, painted with spray paint to seal the cardboard. Very easy and effective. Finally, check your shift shaft for free play. The air cooled RD's cases were machined to fit the shift shaft. Over time, the shift shaft opening wears, which causes leaking and seal wear. The later LC models had a pressed in bushing to address shift shaft wear. This bushing could be replaced, as needed, to keep things oil tight. On older RD's, the engine case could be bored out to accept the bushing to solve the problem. Alternatively, there is a kit available that moves the shaft seal slightly outboard, which also adds the bushing, without needing to machine the engine case. Inexpensive, easy to install, and also effective. Hang in there. You will get your RD oil tight.
Yes - to me it looks as if the shaft seal's lip is running on the bushing?!?! In this case there MUST be an additional sealing (O-ring...) between the bushing and the gear shaft. Else a leakage is unavoidable.
If you can get the seal out, I would replace both. The bush seemed quite slack, the lip on the oil seal only needs to be flattened slightly and you could well find yourself not completely getting rid of the problem. However as you have rebuilt the engine it might be a big ask. Best of luck
An rd250e back in 1979, if I remember correctly it had a clear pipe coming out the top of the gearbox, that exited near the chain, behind the front sprocket, I think it was something to do with a gearbox oil overflow, don't know if it was to release any pressure or over filling🤔
It looked like that bush behind the sprocket was quite a loose fit. The one on mine has some resistance when I pull it out. Was the seal OE Yamaha. Some pattern ones are variable quality.
@@MrGaryjames1 wow Sondel were legendary in their time. Only them or (I guess your arch rival Stan Steven’s?) were the tuners of choice. I bet you have some very fond memories
@@MrGaryjames1 I remember back in the early 80’s Clark’s motorcycles in St Albans had a beautiful white 250 e or f model in white for sale. There was this odd screw in the left hand switch gear. When I asked what it was for, I was told that the lad that owned it had had it tuned by you guys. His dad was not happy and put the screw in as a throttle stop!
Good find. Mine has the same mystery leak. I'm gonna check behind my sprocket now!
Thanks, let me know how you get on
Trials and tribulations!!! keep going with the head dow and you will get there. Never give up
Thanks Mike, we live for that one afternoon when everything comes together and the engine is singing
Good catch on the seal!
Drive shaft and shift shaft seals are the usual culprits for leaks on the drive side on RD's. Be sure to use some engine case sealant on the outside of the new seal, so that the mating between the engine case and the new seal is oil tight. Use a spanner socket to gently tap in the new seal.
Use a bit of blue lock-tite on the neutral switch screws. It is easy to over tighten the screws and cracking the neutral switch cover. If your neutral switch leaks, you can replace the o ring on the cover, and you can make a gasket for the neutral switch cover from some cereal box cardboard, cut to size, painted with spray paint to seal the cardboard. Very easy and effective.
Finally, check your shift shaft for free play. The air cooled RD's cases were machined to fit the shift shaft. Over time, the shift shaft opening wears, which causes leaking and seal wear. The later LC models had a pressed in bushing to address shift shaft wear. This bushing could be replaced, as needed, to keep things oil tight. On older RD's, the engine case could be bored out to accept the bushing to solve the problem. Alternatively, there is a kit available that moves the shaft seal slightly outboard, which also adds the bushing, without needing to machine the engine case. Inexpensive, easy to install, and also effective.
Hang in there. You will get your RD oil tight.
PS, don't forget to add a little bit of grease to the drive shaft bushing to reduce seal wear.😊
Fantastic knowledge and advice, thank you
If I remember correctly some models had a very thin ‘O’ ring sitting behind the sprocket bush/collar
Thanks, I'll look into that
Yes - to me it looks as if the shaft seal's lip is running on the bushing?!?! In this case there MUST be an additional sealing (O-ring...) between the bushing and the gear shaft. Else a leakage is unavoidable.
If you can get the seal out, I would replace both. The bush seemed quite slack, the lip on the oil seal only needs to be flattened slightly and you could well find yourself not completely getting rid of the problem. However as you have rebuilt the engine it might be a big ask.
Best of luck
Thanks for your comment, I agree, best to change them both if possible
An rd250e back in 1979, if I remember correctly it had a clear pipe coming out the top of the gearbox, that exited near the chain, behind the front sprocket, I think it was something to do with a gearbox oil overflow, don't know if it was to release any pressure or over filling🤔
I think it is a breather pipe. It was clear without any oil in it so I didn't think it was coming from there
@@RepairandRideout I jumped the gun there, I just watched the rest of the video, I see you found it👍
@@Alien937 Lets hope so
It looked like that bush behind the sprocket was quite a loose fit. The one on mine has some resistance when I pull it out. Was the seal OE Yamaha. Some pattern ones are variable quality.
Clutch pushrod seal? I had a similar issue with an old RX-S.
That was what I was expecting to see, a very common on Yamaha's
Great videos, can you tell me what you torqued the vape rotor to please? My 77 250d has the same leak so I’ll take a look at my collar too, thank you
Hi Andy, I took the torque settings from the Yamaha air cooled Facebook page. 58ft-lb folks on there suggest
Good luck with the collar too
the expansion chambers are they J&Rs or all speeds?
Hi thanks for your question, they’re all speeds
@@RepairandRideout used to work for sondel sports a Yamaha dealer in London when those were new and have had a soft spot for them since.
@@MrGaryjames1 wow Sondel were legendary in their time. Only them or (I guess your arch rival Stan Steven’s?) were the tuners of choice. I bet you have some very fond memories
@@RepairandRideout yes I do it was a great place to work and the people there were great to work with.
@@MrGaryjames1 I remember back in the early 80’s Clark’s motorcycles in St Albans had a beautiful white 250 e or f model in white for sale. There was this odd screw in the left hand switch gear. When I asked what it was for, I was told that the lad that owned it had had it tuned by you guys. His dad was not happy and put the screw in as a throttle stop!