Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Sealing the timing cover, B50T

I have a '71 B50T that I am in the middle of restoring. The bike sat for 20 years or more in a heated dry basement. Unfortunately when I got it the piston was seized to the bore. A little coaxing got it un-stuck but upon inspection of the bore, it was simply too pitted. So far I've got EV Engineering to bore it and am using his 10:1 piston (I am building it for reliability and not performance). Overall, the farther I got into this engine, the more crap I discovered. The shift fork to 4th gear was stuck on the rod. So the transmission had to be gone through thoroughly. Most of the work was in cleaning.

I purchased what appears to be a OEM gasket kit and replaced all gaskets in the engine. I noticed that the timing cover and transmission cover did not have a gasket. Also in the parts book there was no mention of a gasket. I noticed on the surfaces, traces of old sealer. I assumed that that good old Three Bond 1011 would surely work in this instance. I buttoned everything up on the engine and filled the oil, transmission and primary. After a few minutes I noticed a small leak coming from the outer timing cover under the trans section. Since it also needs a new return spring for the kickstarter I drained the trans oil to avoid more leakage.

The question: Since there is no listed gasket used on the inner and outer housing/covers I used the Three Bond....evidently that may not be enough to form a tight seal (I applied it pretty thin so I am taking into account that I may not have done a very good job). Does anybody think that there will be a problem in cutting and using thin paper gasket material on those two surfaces?

Three Bond will make it hard to remove the cover. I would suggest Loctite Gasket Eliminator instead. Clean the surfaces with acetone or lacquer thinner. Let it sit overnight to cure.
Puting in a gasket will increase the end float of the cam gear. I believe there is an O-ring in the timing cover to seal the crank feed. A gasket might not allow the O-ring to seal.

I use coppercoat. Also Ed V can spec out a breather device that really does help lower crankcase pressure and keep oil on the inside. I had much of my shop work done by Ed and the bike has been troublefree for years and I started with a rusted basket case.

Mr Mike

A couple of thoughts:

The inner and outer timing covers were not made to take gaskets. I always use the red Permatex Anaerobic Gasket Maker. It does not take a thick layer of it to seal nicely. All you are filling are slight inconsistencies on the mating surfaces. As noted above make sure the surfaces are nice and clean.

Are you certain that the leak is coming from the gear box? Does the oil smell like gear oil? If you overfill the gear box it will tend to want to leak.

If you are leaking engine oil it is following the underside of the motor and is dripping below the gear box. If it is engine oil that might be a symptom of wet sumping probably meaning you have a stuck non-return ball valve. The problem being that there is no way to keep the motor from leaking oil if the oil tank is draining into the motor. There are enough spots where the motor can weep oil that have no seals that you will always have oil leaks when wet sumping.

Peter

Yes, it is the gearbox. I can see the gear oil accumulate in a drip at a spot just below where the kickstarter is. And yes, the smell is distinctly gear oil.

OK so we are talking about a sealing issue not a pressure issue (as of yet). The bike leaked before it was run, just sitting, from the gearbox.

A good sealer on clean surfaces should do the job.

Peter

Also yes, the engine has not yet been started.

Did you chase and chamfer the case-threads ?

While you have it back apart ,
Re-check that no-case-threads have pulled-proud into the mating-surface.

.

There appears to be no issues with buggered up threads however that is a damn good idea that I hadn't thought about. That would also explain problems I've had in the past with other bikes.

I take the cases and clean them real good and then blue them (or a magic marker work)s. I then take a fine flat file and lay it so it is touching the joint surface in two places and ever so lightly with my finger tips I slide it back and forth. Any high spots show up right away and the file will take them off. DO IT CAREFULLY! It made and timing side covers relatively leak proof. I frequently found raised metal around threaded holes.
Mr Mike

When fitting the cases after flattening and applying sealer, fit the screws finger tight .

Start to tighten in the following pattern, 12 O clock, 6 o clock 1 o clock 7 o clock and so on. If the cases have slightly bowed this pulls the centres together and spreads pressure out to the edges. This works for all casings which have a long and short dimension. , if using Allen screws only tighten with the short end of the key.

If using allen bolts put a flat washer under the head as the surface area under the head is about 1/2 that of the original philister heads and is the fastest way to distort the cover with pull through.

Trevor, have you been on holiday? Haven't heard anything out of you since spring time, that is North American springtime.


Bill B...

Not quite,
Bought a small engine repair run.
Found out I knew a lot less that I thought I did .
I mean mowers / motorcycles, all the same, not quite so I found.
Thus it has been a steep learning curve.
This was going to be a transitional enterprise but the management at the warehouse decided that at 60 I was too old and my 1.5 ton van too small to deliver wine into the city.
They now have 2 men in 2 ton vans doing what I used to do.

So I have been haunting mower forums for a while as I have to make the engine repairs pay and spending 4 hours on a $ 50 repair ain't going to pay the bills.

Funny I used to get by fine on 3 to 4 hours kip /day and when you get older you are supposed to need less sleep , Not so with this little black duck and while BSA's might be a passion, they are still just a pastime.

Thanks for asking, didn't think I would be missed