How tight for MKII Primary cover?

I have a slow leak on my Combat. (Not a surprise eh?) As soon as the engine gets warm, I get oil that slowly seeps out the primary cover and on to the header. How tight should the primary cover bolt be? I don't want to tighten it too much and have it crack... or does it stop when it's fully tightened? Thanks.

Is the best gasket for the primary cover the one from Old Brits? or is there an aftermarket one elsewhere that is better? I recently got the neoprene gaskets for the rocker covers and they worked really well.

You gotta start by shimming the inner cover support bolt so that inner primary sits perfectly flat. Use a steel ruler along it to view for any slight bending/ warpage= try again. Only then are you good to go with a new rubber band, the band join placed up top of the loop as this is a potential drip point. Some use smeared grease or silicone in the inner groove.

Johnny, you have three choices.

1) I got so damn sick of my primary leaking that I converted to a blessedly dry belt primary.
And my clutch plates said thank you and now stay perfectly dry also.

2) You can go to Lowes or any place that can sell you a couple feet of 1/4 inch rubber tubing.
Goop that sucker up on the bottom half with an oil resistant seal and try it again.

3) But, it seems that maybe maybe you are missing the spacer washer that goes on the right side of your inner cover.
Can you look from the right side and see if it is missing?

4) Mine was and you don't have to take off the inner cover and entire primary to put one there.
I found a thick washer that would fit and cut out enough of it to slip over the bolt on the right side of the inner cover. I might have been able to just tap it into place, can't remember, but I also may have had to take off the alternator stator to get to the three little bolts that hold the front of the inner cover on and loosen them up enough to be able to move the inner cover enough to locate the shim/washer cut out.
If I remember, this gave me enough room so that I did not have to take the clutch plates out and loosen the hub.

If you think you will die with an excess $500 on hand, then just convert to dry belt drive now and never worry again!

Thanks guys. What kind of oil resistant sealant woul dyou recommend? I have a tube of the RTV silicon gasket stuff in my toolbox.

Johnnymac said:

Thanks guys. What kind of oil resistant sealant woul dyou recommend? I have a tube of the RTV silicon gasket stuff in my toolbox.
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The high temp red should work fine but Permatex doesn't stress its oil resistance. Ultra Black, however, is mentioned as an oil resistant sealer and Ultra Grey is supposed to be "highly" resistant to oils. Both the Black and Grey have worked well for us in my shop and both are good for 500 degrees (the "hi temp" red is good for 650).

The grey also is billed as resistant to the effects of vibration and I use it to build vintage 2 stroke kart engines. I like it especially because it seems impervious to their gas/oil mix and I really like the cleanup when the engines are disassembled later.

Hope it helps.

Hey Johnny,
I replaced my O ring, only to find it still dripping oil onto the Pipe after about 100 miles.
My mate who rebiult the engine reminded me of the brocken (rear) chain guard on the inner cover,
the one that should protect the rest of the cover if there were to be a brocken (rear) chain.
Anyhow, with a piece of the guard missing, it allows oil to throw forward off the (rear) chain and run down
the inner primary case, which appears to be an oil leak.
I still have the Oil tank overflow/breather line going to my rear chain, and am happy to see the chain with some
oil on it. It's minimal in my case but enough to drip occasionally and the chain is happy.
Just a thought, check yours out.
An O ring chain might be the go for me when the chain needs replacing.
AC.

I put some Ultra Gray RTV in the groove on the inner side of the bottom half of the primary, installed a new rubber o-ring from a gasket set and haven't had a leak. But you have to make sure your inner cover is straight and not warped from improper shimming of the center stud. Outer one needs to be straight too. Torque center bolt onto stud to 25 ft/lb with a large washer under it.

Sometimes the crank to inner cover leaks and you think it's the cover. Make sure it's not that. I installed studs and nuts for the 3 bolts into the crank with red locktite after cleaning with carb cleaner and rtv'd the crank to cover gasket too. DomiRacer has a nice rubberized gasket for that area. It's a bit thick so you may have to re-shim the inner primary.

Dave
69S

A.C. , Chain lube for chains and engine oil for engines.Seal that puppy up. Yes Dave to belt end of issue +reminder that I have a new kit in box from R.G.M. and will need tips myself for this when the snow flies.Put Big Money Wasted into garage winter hibernation mode just an hour ago.Snow just to north.

There was a member here that gave this advice which I thought was good enough to follow. If I could remember who it was I would give them credit.

Remove the outer primary, remove the seal from the inner primary, apply high temp silicone to the groove and put the seal back in. Tighten the outer cover just enough to squeeze out some of the sealant. Let it sit overnight so that the sealant cures. Remove the excess and tighten the cover.

This process allows the sealant and the O-ring seal to form to the outer cover.

I thought it was brilliant. It also works which is even better.

Russ

Johnnymac said:

I have a slow leak on my Combat. (Not a surprise eh?) As soon as the engine gets warm, I get oil that slowly seeps out the primary cover and on to the header. How tight should the primary cover bolt be? I don't want to tighten it too much and have it crack... or does it stop when it's fully tightened? Thanks.

Click to expand...

I don't think you have to worry about cracking the cover so much as bending it. You can see it by looking at the gap between the covers when you tighten down on the nut. It closes up in the center over the nut compared to the front by the engine or towards the rear. Between the inner and the outer, it's the inner that's doing most of the flexing. I put a little spacer on the stud under the outer cover that's thick enough so when the nut is tight the cover bottoms out before the covers touch. There is still a slight gap between the covers without the o-ring in place. I like to put down some Hylomar in the grove under the o-ring. O-rings don't last forever. They harden and deform. When you pull one out and it looks more like a D-ring than an O-ring then it's probably time to replace it. $5.

There should be no need for sealant and as often as I go into the primary, I glad there is none.

You need to true up the inner cover, get a fresh seal, and stay away from bull crap solution that substitute for proper procedures. It may take a little more work, but when it's right, it's righteous.

The proper tightness will be evident by the feel of the outer cover coming to the home position. The mounting bolt will suddenly stop when the oring is compressed universally around the covers

The best gasket (big oring) is generally a fresh one.

Thank you guys! great advice. What is the best O ring.... Or are they all oractically the same? I will probabaly order it from old britts.

I'll bet they are all going to be the same. I guess the jury's still out on using anything extra on it.

I think rappton's comment is worth highlighting: "I put a little spacer on the stud under the outer cover that's thick enough so when the nut is tight the cover bottoms out before the covers touch. There is still a slight gap between the covers without the o-ring in place."

When you take off most outer primary covers, they are warped. You can then spend half an hour rubbing them flat. And if you don't put in the small spacer, and you torque the centre nut until everything sucks up hard, next time you take off the primary cover, you will find it has warped again. If insanity is doing the same thing again and again and expecting something different.........well try something different. Use a spacer between the innner and the outer.

Stephen Hill
Victoria, BC

Well, as it turns out I'm an idiot. My Primary case wasn't leaking... what I thought was an oil leak from the primary cover was actually a slow drip from the left carb float bowl which would ooze and make it's way to the bottom.... I am going to be replacing the Amals with the dual carbs from JS Motorsports in the next few weeks anyway so that will fix that issue. Thank you guys for the advice. I'm sure that it will leak in the future and your advice will certainly come in handy.

Guys,

For those of you who use RTV and an Oring gasket on the primary...what do you use to clean it up? I just pulled my primary cover off after it had been sealed this way and the RTV and gasket are impossible to remove from the inner cover groove! Wire brush? I don't want to scratch anything though. Any ideas? Is there a solvent that removes rtv?

Don't know what kind of RTV that is, but mine always comes off the case and the o-ring too with a bit of rubbing. It's always good to keep a new o-ring around just in case too.

Dave
69S

99 out of 100 primary case leaks are from the poxy felt "seal" on the gearshaft plate behind the clutch. The oil runs down the back face, forward and drips onto the left head pipe.

Mick

I have gone through a couple primary O-rings.... there seems to be two kinds that I get from my local Brit Bike shop. The first two were a hard rubber material. The past two were a spongy foam material. The reason I have had to replace them is that the foam ones suck up the RTV so when I take off the primary cover, they rip apart to pieces. No way to clean the silicone of the ring(I use RTV Ultra Gray).

Hey John Boz here. The best sealant I have used in years of Britt bike ownership was the old Yamabond grey. They don't make it anymore because some chemical in it was banned or some such garbage. The best replacement I have found is 3 Bond also grey. For cleaning up the old sealant try brake cleaner. I have a tube in my garage and I have an extra O ring that I don't need since I went to a belt drive and dry clutch. I can bring them to the open house tomorrow if you are going.