Oil leak

Hi
Now I've also got the classic oil leak from pushrod tunnel ahead of the cylinder head. It's small but irritating
Planned to do something about it in the winter.
My question is: What is the best solution?
Thinks it is composite fiber gasket that I have now.
My plan was to use the same type of gasket again, but then take a bit of blue Loctite 5926 around the tunnels. It is approved to to 200 degrees celcius. Do not know how hot this area will be?
Vidar

Hello Vidar,

Have a look at Jim Schmidt's solution : annealed copper gasket + copper wire around the pushrods tunnel.

His website : jsmotorsports.

I can testify that it works!

Laurent

Thats odd, so have I. Never suffered with a head leak before but when I refitted the head (rings)last December I minimised my use of silicone around the front studs and pushrod tubes (just a really thin smear). Seems it was a mistake as its leaked there for the first time in 16 years. Its not leaking at the gasket but seems to be coming up the centre stud (unlikely) or the front ones. No leaks from the rocker shaft ends or covers. I know the front studs dont break into the tubes so tis a mystery. Of course I may have a cracked head so only another strip down will tell me (maybe). A 4th retorque stopped it for 2000 miles but its back.

Keith1069 said:

Thats odd, so have I. Never suffered with a head leak before but when I refitted the head (rings)last December I minimised my use of silicone around the front studs and pushrod tubes (just a really thin smear). Seems it was a mistake as its leaked there for the first time in 16 years. Its not leaking at the gasket but seems to be coming up the centre stud (unlikely) or the front ones. No leaks from the rocker shaft ends or covers. I know the front studs dont break into the tubes so tis a mystery. Of course I may have a cracked head so only another strip down will tell me (maybe). A 4th retorque stopped it for 2000 miles but its back.

Click to expand...

Keith1069,

If you are lucky oil is leaking from the pushrod tunnel via the threads of the front 5/16" studs. Easy to fix by fitting the studs with Loctite. However the 850 Commando head is prone to crack in the front between the third and fourth fin (right behind the two front 5/16” nuts at the bottom of the recess). This crack is often caused by over tightening the two front 5/16” nuts (they need only 20 pounds instead of 30 pounds for all the other head fasteners). The problem is the thin part of the head between the pushrod tunnels to the recess for the 5/16” nuts. This crack is quite common and for that reason I made a special tool set to pressure test 850 heads for that specific crack.

Good luck,

Constant Trossèl
http://www.hollandnortonworks.eu

Hi
Tries again.
The area around the pushrod tunnels. Does anyone know how hot it gets. Will it be over 200 degrees celcius?

Vidar

vidar hjelm johansen said:

Hi
Tries again.
The area around the pushrod tunnels. Does anyone know how hot it gets. Will it be over 200 degrees celcius?

Vidar

Click to expand...

I don't know how hot it gets, but do know that Mick Hemmings uses Well Seal in on the head gasket faces to good effect.

Hi again

How hot can the oil be?
These area may well not differ much from the oil temp.?
Vidar

Are you presently using anything to reduce the pressure in your crankcase?

I have a 1970 commando. All the early bikes, up to '70, have a timed breather port which is insufficient to move the volume of air that is displaced by the pistons as they rise and fall, so my gaskets were always subject to those pressures and needless to say I had minor oil seepage on various joints of my engine over the years I've had my bike. I lamented over those leaks and other riders pointing to the drips on the ground under my bike saying, "Look, your bike is marking it's spot". I decided to install a reed valve crankcase breather to eliminate that pressure on my gaskets, and now I have virtually no leaks on my engine.

Depending on what model commando you have, you may be able to buy a "bolt on" reed valve breather (from Jim Comstock here) and lower the crankcase pressure significantly, which is the cause of a lot of commando leaks. I've had my commando for 40 years and I recall smug commando owners back in the 70's saying how they could build a commando that would not leak by being meticulous when assembling their bike. As it turns out, the flaw of leaking oil wasn't a deficiency of the builders as much as a design flaw in the regulation of crankcase pressure. A reed breather modification is the proper first step in curing leaks on any parallel twin engine... Don't be surprised if you add a crankcase reed breather and your leaks stop completely...

I run one of the MotoMite valves. What it did was amazing given the cost. I recently had the same leak being mentioned show up out of the blue. I found the valve had crapped out so I replaced it. Problem solved.

I have spent a XS650 valve a few years, but this year it began to leak.
I have now ordered a Ducati valve and will try it. Has anyone tried this:
http://www.ebay.co.uk/itm/271159259267

Vidar

If your existing reed valve is operating correctly, then I wouldn't think that crankcase pressure is causing your leak.... After I installed my breather modification (mikes xs type) and I was satisfied that it worked well enough, so I bought 2 extra reed valves to have in my parts bin so I could replace the valve if I suspected it's failure.

Your leak could suggest a reed valve failure,... or a cracked head, or just a gasket that finally let go, or maybe your head needs retorqueing... I don't think the ducati valve will make a difference if your XS valve was working correctly.

850cmndo said:

I run one of the MotoMite valves. What it did was amazing given the cost. I recently had the same leak being mentioned show up out of the blue. I found the valve had crapped out so I replaced it. Problem solved.

Click to expand...

I too have used a motormite valve on my Commando, for 9 years. It immediately stopped most oil leaks. About 2 years ago
some leaks began re-appearing. I replaced the 7 year old motormite valve with a new one and the leaks immediately went
away. So, my question is, with no disrespect intended towards anyone, why is the reed valve touted as such a great solution
to oil leaks vs. a simple one way flapper brake valve which costs less that $10 and can be plumbed in just a few minutes? I
understand that a race bike might need a more effective manipulation of crank case pressure in order to increase engine
efficiency, but I'm guessing the vast majority of Commando's aren't driven that way. :?:

Just trying one beats the hell out of pulling a head..and who knows what else it'll dry up?

lazyeye6 said:

I too have used a motormite valve on my Commando, for 9 years. It immediately stopped most oil leaks. About 2 years ago
some leaks began re-appearing. I replaced the 7 year old motormite valve with a new one and the leaks immediately went
away. So, my question is, with no disrespect intended towards anyone, why is the reed valve touted as such a great solution
to oil leaks vs. a simple one way flapper brake valve which costs less that $10 and can be plumbed in just a few minutes? I
understand that a race bike might need a more effective manipulation of crank case pressure in order to increase engine
efficiency, but I'm guessing the vast majority of Commando's aren't driven that way. :?:

Click to expand...

First, I have an early commando, so the only place I could add a motormite valve would be on the timed camshaft breather hose. I think it might act as a second seal so my crankcase breather wouldn't let air back into the bike on the upstroke, but I would still be venting air pressure through the tiny holes in the camshaft. For my model bike, I had less other options than to do a timing chest breather because a frame crossmember blocks Jim's sump plug breather from being mounted on my model bike.

I'm not an expert on all the different variations of commandos but if you can put an inline motormite valve on your existing breather hose in a few minutes and that lowers the pressure pushing outward on your gaskets, then you are lucky to have that option. As I said, I had less easy options. I really wasn't going to disassemble my crankcase to have it machined for a combat style breather, so adding the mike's xs type gave me the best result with the least headache. Interestingly enough to me..., people say that the timed camshaft breather port should be blocked off after adding the timing side modification. I left mine operational. I've yet to hear a logical reason why they can't both work together...