My 75 MK3 has an annoying leak coming from the gear shift shaft in the outer primary. It has been filled correctly. I use ATF. I have replaced the seal and the shaft appeared to be in good order. It is not a big leak but on a long run a small amount of ATF will run down and then blow spots of fluid along the right exhaust as it drips off the bottom of the primary. On stopping it will leave one drip on the floor. Thats it. Maybe I'm been fussy but has anyone else had this? Also I was a bit lazy in re torquing my head down. I think I left it too long after running the bike in. Now I have a very slight mist build up around the push rod tunnel. I used a composite gasket. Would the time between initial torque and secondary torque affect this?
Mk III Outer Primary Cover Leak
- Thread starter rags
- Start date
- Status
If you have not re-torqued your head yet, doing so now may stop that slight mist from the push rod tunnels. if you have re-torqued it and it still leaks, I'm afraid you'll have to give it another go if it really bug you. In regards to the primary, I'd not use ATF in a MK3 as I don't believe it has the viscosity needed for proper automatic chain tensioner operation, and I'd worry about the sprag too for the same reason, assuming you are running the electric start. Book calls for 20w50 I believe and I'd use a bike specific oil (as I do) to assure the weight is correct for the hydraulic tensioner and additives are good for the sprag and to a degree the clutch. Don't know if this will stop the slight misting though.
- Joined
- May 28, 2003
- Messages
- 2,591
I don't have a full grasp on the percentages , but any MKIII that has ever been laid down on the left side (even gently) has potential to have a cracked outer primary at the shifter. 15 years ago we made a set of jigs to hold the primary cover on angle to allow heliarc repair and remachining. IIRC also the shifter will feel sloppy while shifting.
Any MK3 that has been down on its left side, will usually suffer damage from the footrest moving in on the primary cover rather than the gear change pedal, unless bits are getting ripped from the bike during the mishap. I get a little from mine but not enough to notice it on the the exhaust. I know it sounds daft, but has the seal been fitted correctly.
- Joined
- Jan 1, 2005
- Messages
- 196
I chased the same oil leak on the primary case for many years; new bushings, new seals etc. etc. etc. Then after my recent rebuild I installed a new seal that came with the gasket set from Fair Spares. The gasket was soft on the outer diameter not a hard metal ring and it was green in color.
This seal hasn't leaked a drop in 2k miles and I have been riding 'Pa', my trusty Norton, like I stole it!
Ride On
Dave
This seal hasn't leaked a drop in 2k miles and I have been riding 'Pa', my trusty Norton, like I stole it!
Ride On
Dave
Thanks to all replies. The head has been tightened down but as I said, I may have left it a little long between 1st and 2nd torqueing. It's not a big leak. Maybe after a few hundred Ks I can wipe a tiny amount off the top fin of the barrels at the front. The primary isn't cracked and shows no sign of being dropped. The seal I put in had a metal outer so may try to get the all rubber one mentioned. I did have trouble fitting it as in when I pushed the shaft through it it kept popping out due to the shoulder on the shaft. I put the shaft in first then and supported it on a wood block whilst I pushed the seal onto it. Its such a tight fit though I think the edge of the lip gets damaged somehow doing this maybe. I read many discussions on oil v ATF in the primary. Some say oil isnt good on the plates.
It's been discussed here and I found it true that you should add only the amount of oil called for in the primary rather than filling 'til it runs out the witness hole as that overfills it giving more chance to soak the plates. The last time I filled mine I used 15 40 Rotella as that was close at hand. The 20 50 box was empty. It's working fine.
- Joined
- Nov 20, 2004
- Messages
- 20,786
rags said:
When I bought my Mk3 it had also ATF in the primary, and was what I continued to use until I was informed that engine oil suited the hydraulic tensioner better, and with (motorcycle)20w/50 in the primary, I immediately noticed a marked reduction in transmission snatch when riding slowly at low revs in all gears and the primary drive seemed quieter, also the heavy 'knocking' or 'clonking' often heard on first start-up before the tensioner re-primed itself almost completely disappeared. The only clutch problems (dragging and slipping) occurred before I fitted dynodave push rod seal and also replaced a worn (notched) clutch centre.
The tensioner system is not really very sophisticated. It is somewhat spring assisted but relies on oil to work. The plungers have a weep hole each, which sort of acts as a controlled leak back down into the primary. The oil is re-supplied to the unit via a funnel at the top that catches sling-off oil from the primary chain. I believe that if too thin an oil (ATF) is used, the plungers will leak down too quickly in use and also the thinner oil may get slung off the chain too soon or not even pick up enough oil in the first place to replenish the mechanism via that funnel.
- Status
