I have a 1979 750 Bonneville engine. Recently, I developed a leak which appears to be coming from the gear box side of the front sprocket and the gear box fluid level is dropping. It would appear that the primary would need to be disassembled in order to replace this seal. Is this correct? Will I need any special tools? What parts (other than the seal) will I need? Any help is appreciated.
I would add to RFW's excellent article the following.
Be prepared to lap oilseal/shaft interfaces with a very fine abrasive film/paper to remove localised shaft polishing which will have the seal running dry.
Use a vacuum pump type oil extractor to pull oil out of the oil tank and primary, leave well sealed drain plugs in place, the primary drain plug/tensioner adjuster plug is in the crankcase and if you strip that or crack the crankcase through overtightening you are in deep trouble.
Alemite make a really good sump sucker and draining the primary through the drain/adjuster plug will take a bloody week.
Last Saturday I had the primary case off my unit TR6 and the sump sucker fitted with smallest supplied hose left maybe 20cc of ATF in the case, you can refill with the correct 300cc confident that you are not overfilling.
Story goes on and on, do not overtorque the dome nuts at the front of the primary case, I stretch a couple of "o" rings over the studs and fit fresh fibre washers over them, fibre washers settle a bit so be prepared to nip them down a little with use.
My bike does not leak oil and only drops a little from the crankcase breather filter [under the gearbox]and if I run the bike hard with too high an engine oil level I get some oil from the froth tower vent which is piped back to the rear lip of the rear mudguard.
Originally posted by Tiger: ...20cc of ATF in the case, you can refill with the correct 300cc confident that you are not overfilling.
FYI, Tiger's bike is a dry frame....yours is OIF. Your primary case (assuming stock breather system) shares the oil used in the engine. After you replace the primary cover, prime the chaincase with 150cc (~4oz.) of the oil you use for your engine (motorcycle-grade 20W/50).
Altho I don't doubt Tiger's oil-tight bike, I find the stock copper washer set-up for the dome nuts on the primary more than sufficient. The key is to anneal the washers before reinstalling them......
The real key to good seals on these bikes are flat smooth mating surfaces. Get rid of any old sealant, gasket material, etc. on those surfaces...
'77 T140J "Vintage Bike". What's in your garage?
"The paying customer is always right."
Fitting round pegs into square holes since 1961...
I might add to Steve's comments about the sealing surfaces that they be free from ALL oil. This includes any residue!
Your success is dependant on how free from oil the surfaces are when you use just a new gasket or any of the many sealants that have been mentioned on this forum.
Oil wicks. Oily surfaces promote wicking. By providing an oil free surface you provide a surface for the sealant or modern gasket a surface to bond to. This bonding of the gasket or sealant prevents the oil from wicking and keeps it where you want it..
A good test is to take some painter's tape. You know the type that doesn't stick very well and comes off easily not damaging the paint it is stuck to and try to stick it to the surface you just cleaned with your favorite cleaner. If the tape doesn't stick you have not removed all of the oil.
Not all cleaners remove oil. I was just working with Btour using a new to me enviromentally correct brake cleaner "CRC Brakleen" in a green can. While it removes a lot of the grime it did not remove the oil from the surface. If I had used it to prepare gasket surfaces my sealant of choice would not have worked. We switched to conventional CRC brake parts cleaner in a red can and it removed all traces of oil from the surface. The sealant bonded as expected.
A modern gasket, or almost any of the sealants mentioned on this forum, will work better if the surface to be sealed is free from any oil residue.
I normally use methyl alcohol, the kind you buy at the local hardware store. (I was out and the hardware wasn't open and I ended up at the auto parts store and they didn't have any alcohol) It is an excellent oil solvent and leaves gasket surfaces free from any oil residue. I also use it when putting the clutch hub on the mainshaft taper to remove any oil from that surface. John
You have to remove the whole primary drive and alternator on a 750. If the chain has stretched enough you can slacken the tensioner and maybe only have to take off the clutch. This works on mine but it has a duplex chain rather than triplex. If the chain is new it is very difficult or impossible. Once all that is out you can remove the circular cover, remove the gearbox sprocket and get to the seal.
You would need two or three tools- clutch extractor, engine sprocket extractor and, possibly, the gearbox sprocket extractor but I think this is the same tool as does the engine sprocket. The gearbox sprocket is supposed to be tight on the splines but it often just comes off by hand because the nut tends to work loose which allows spline wear, I suppose. You can fix this by blue loctiting the nut.
If the gearbox leaks all the time you may have a joint leak. My bike has a leak in the gearbox sprocket area and the seal only leaks when the machine is on the move. The oil that has collected under the gearbox area may drip off at a stop but then no more oil comes out. The same thing happens with the clutch oil seal. You can tell which is leaking by smelling the oil- gearbox oil normally stinks! Change both seals while you are in there but the high gear oil seal is pretty tight.
If the leak isn't too bad I would just leave it until you have to do a strip when there is a more serious problem. There is no way I am stripping mine for the little leak it has.
RC, After cleaning the mainshaft and sprocket splines of oil fill the splines with silicone sealer(RTV) after fitting the sprocket but before fitting the nut. This is one of the few places RTV has no downside. It keeps the gear oil from migrating down the shaft via the splines. Also in this exercise it does not matter if the RTV squeezes out as you tighten the nut and looks like a 10 year old did it, just so it seals. Jack
Guys, Thanks for the quick responses. It is a significant leak. I fill the gear box to the bottom of the fill plug before I ride and the biggest leak seems to be after it is parked. I suspect that it leaks until it gets below the seal.
Cannot recall if the '70 needs this but on the '69 the selector shaft hole in the LH case [about 1/4" diameter and just in front of the seal you are replacing] carries right through the case and can be the source of gearbox oil weepage, easy to clean with contact cleaner [or JH's red can brake cleaner] and wipe a bit of Threebond or similar over the hole. The '70 cases may have a blind hole in that location. Check that the three countersunk screws in either side of the clutch centre [cush drive] are tight. If you feel the need you could remove either the front or rear cush drive plate and replace the internal cush drive rubbers, not a difficult job in itself but getting the primary off a stock bike is a fair bit of work and I check/replace anything required to avoid having to go in there again before necessary.
RC - Btour's issue is quite common with 35 yo oil seals; they just finally give up due to hardening and general age. You had best count on replacing every o-ring and oil seal you find doing this one job. Each one will be equally hard and ready to give up.
PS.... Buy a correct clutch puller before you screw up the clutch hub and have some real fun.