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[Rodders]

Can anyone advise me how to seal the primary chain case cover on my 1955 500 Twin. I've just finished the restoration and partial engine re-build. It was non running when I got it so don't know what the history is. I cannot stop the oil leak (or even staunch it to an acceptable level). I've done the following all to no avail:

1. New rubber gasket, new stud and central nut and washer. Helicoiled the thread on the engine casing.

2. I've torqued the nut to 12 and then 14 ft lbs

3. I'm using AT fluid oil as recommended.

On my second run out after 6 gentle miles I had lost about 100 mill of oil.

4. On an earlier attempt to seal it I used silicone instant gasket to support the rubber seal. The rim is not distorted as far as I can tell (by placing it on a machine bed - it doesn't rock). I haven't yet tried to use the silicone with the extra torque.

Any suggestions would be much appreciated.

[Mark M]

Rodders, a couple of questions: have you checked both halves of the chaincase for truth? And where did you get your sealing rubber gasket from? I have found some for sale which are too small in section or the rubber is too soft, compressing too much to form an effective seal. Some folk have had success using a 5mm nitrile rubber bead bought from Ebay, like this: item number121060637076 Finally, are you completely sure it's from the joint and not the crankshaft seal?

REgards, Mark

[Rodders]

Hi Mark, thanks for responding. I haven't checked the engine block part of the chaincase - not quite sure how to do that in situ. I bought the rubber gasket from our hosts. I found it a little too long so put a small cut in the top circumference to make sure it is seating in the groove. I'm certain itt's not the crankcase becauseof the colour and I can see it seeping out along the bottom edge. I'll look at other types of gasket.

[Bullet Whisperer]

Hi Rodders, ATF as recommended? By who? Better off using the same as what you have in the engine. It won't cure the leak, but ATF is thin and will leak faster than engine oil. The leak might be from the hole in the inner case where the mainshaft goes through it. Crankcase pressure can get past the crappy felt or cork seal outboard of the driveside main bearing and pressurize the chaicase. Oil is flung around by the primary chain and clutch and can get blown out through the afore mentioned hole, it then runs down and looks like it is coming from the bottom of the outer cover joint. Worth checking. Regards, Paul.

[Rodders]

thanks for this guys. I've ordered some nitrile rubber. I don't think it's coming from the crankcase hole because this is leaking before I even start the engine. I'll keep trying.

[PeteF]

Who recommends ATF in the chaincase? Hitchcock's do.

[PeteF]

So do I.

[Bullet Whisperer]

R.E. don't and I don't use it in any R.E.'s. Each to their own, though.

[Tim NZ]

Fitting the inner chain case has to be done with care, as it is very easy to damage or pinch the felt washer. Do you have the correct packing shims in place around the felt?


If you have upgraded from the felt to the latter type of lip seal, have you fitted it the right way around?


The potential to leak worse is if the engine breather is not sealing correctly; stuck discs or blocked outlet?


Typically I fit the post 57 breather (duckbill type) as I find them more reliable that the steel discs and the long thin copper tube outlet...

[Rodders]

Thanks for all the observations here. Just another thought. I put 420mml of fluid in but wonder if this is too much. I took it from a bullet article but is the primary chaincase on the 500 smaller? I say this because the plug at the bottom, which is described in the handbook as the level plug, let out approx 200mml when I was preparing to dismantle the case again. If I was to use this plug as the level plug I would probably only be putting in about 250 mml. What is the correct volume of oil/fluid? Thanks again Rod