Any suggestions for fixing a crankcase leak?

check your oil tank for cracks and leaks.

green53 said:

check your oil tank for cracks and leaks.

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But I think he says the oil is coming from the front of his motor and going under the bike, but if its a base gasket blown is a easy fix without pulling the motor fully apart, till he cleans the whole bike and then trace where the oil is coming from, we won't know.

Ashley

He check his tach cable seal? Simple crap first.

I think you are going to have to identify exactly where that leak is coming from rather than have us guess for you. Clean the engine thoroughly and get back to us.

I have a leak from my crank case half join [ I have never had them apart on my 850 ] Everywhere else that I have done work on does not leak. The main seal leaks into my primary housing , but after 1750 ,miles doing the NZ rally, I added only 2.25 litres, which I drained from my primary every so often. My bike is covered in oil underneath, and my drive train got plenty of lube on the run. Under normal riding where I do 50 -60 miles at a time it hasn't been a problem, but now I have started stripping the primary to get to that seal. just as well because I found the clutch hub bearing seems loose. more details to follow,.,

Hope you make it to the Tutukaka rally [ are you a club member, if not join. only $30.00 per year and good fun ]. Looking forward to it myself as its only 45 minutes from home.
Dereck

one way to pinpoint an oil leak
https://www.google.ca/search?q=oil+leak ... blacklight

Chris, I would start by checking the tightness of all of the engine fasteners, you did say that it was oil- tight after the rebuild so perhaps some of the nuts and bolts have come loose due to vibration. The bolts holding the cases together are also the mounting bolts except for the one underneath, the short one at the front and the two recessed screws at the very bottom of the case on the right hand side. I have found that the barrel nuts can come loose after a couple of heat cycles on a rebuilt engine, this is also the case with the cylinder head, so I would tighten all of the barrel bolts andmthe head bolts and then see if it still leaks.

Steve when you raise the barrel enough to fit the new base gasket, how do you get it around the conrods without cutting it somewhere ? I use gasket cement there with no gasket. Yamaha triple bond was always good stuff. I just buy the modern equivalent. It would be possible to remove the gasket by raising the barrel, but fiddley. A flap valve in the engine breather is important. It probably only creates a partial vacuum at low revs, however I've always found the engine leaks less with one fitted. I use one from an old ford six cylinder engine with a tail brazed to it. If you are doing this you need to stand the unit in water while brazing so the spring doesn't soften.

When I did mine I cut it in two places. Little Hondabond and no leaks.

First time before knowing better i took barrel off plstons but now i know than use base plate or gasket - just lift barrel with head on then tedious clean before smearing goop with natural thread embedded.

Guys - thanks for all the input.

If I said that the leak was from the cylinder head that was a mistake (but I do have some minor leaks from the tappet covers, and did have some from the rocker spindles until I replaced the gaskets on those); the main leak is between the crankcase and the bottom of the cylinder barrell; right where the barrell has been rebuilt or welded up. The suggestion that I can lift the barrell and replace the gasket with one in two parts is gold and something that I probably can do myself. If I do that will it disturb the push rods? Or should they just go back into place when it gets retightened? If they can move out of position how can I check that they are ok/fix that?

Are there any other things that I should look out for when doing that? How far up could I lift the barrell before something goes wrong? Where would be the best place to cut the gasket in two? At the sides so that there are two more or less equal halves?

Ashman - appreciate your suggestion that I should be able to do a top end disassembly; I think that I probably can too, but am reluctant to attempt that myself right now given time, family commitments, and lack of space.

I have done a lot of checking for the source of the leak; short rides after cleaning the motor, and think that I have found the source; or the major source - the leak between crankcase and barrell.

Right now I am unable to do much about it; I am in Auckland at work and the bike is still at our bach (beach house), and I will not bring it back until Easter; so the attempt to repair will be a winter job.

Dog T - the outlet on the oil tank that I attached a rubber pipe to was the one on the front face of the tank that leads straight out to the air cleaner; I understand that is the overflow? I have the timed breather exit hose routed to the inlet on the top of the tank (and another change that I intend to make is to redirect that to a catch bottle too; the bike had that when I bought it; I rerouted to stock but now think that the past owner mod was a good one).

I did use quite a flexible hose to attach to the oil tank exit, and that hose crumpled up - presumably from wind and vibration; which might have blocked the outlet and created an air pressure point; and might have been the cause or a significant factor in the leak. I have tried to strengthen that hose by putting another short length of wider hose over the hose for a couple of inches where the hose is inside the air filter and joins the oil tank; but that may not have worked; so I think that the first thing that I will do is remove that hose until I can source a firmer hose. That might at least get me able to ride home so that I can attempt the fix with all of my tools; and might be a significant factor in depressuring the crank case; as has been suggested in one of the posts above.

And like any Commando this bike does wet sump; and I ride it reasonably irregularly, so that it has the opportunity to wet sump quite a lot; up until now I have been in the school of ignoring that and just starting the bike and letting it clear itself; but I am now also conscious that the wet sumping might have also been a major contributor to raised oil pressure in the crankcase. Jim C, I'm really hopeful that you can help us early framed bike's owners out with this one...

Kerinorton, yes I am a member of the local NOC, but will not be coming on the ride.

I will report back on progress, but it may be a while given that it will take me until at least after Easter to work on it. In the meantime if anyone has any further suggestions or answers to the questions above they will be gratefully received.

That is good now we know where the leak is coming from so just lifting the barrels high enough to cut the old gasket out and just sealing it with a good sealent without a gasket will be a easy fix, my last rebuild of my mates 750 Commando I didn't use a base gasket just Yammy bond, that was few months ago and my mate just fired it up 2 weeks ago and all is well with no leaks at all, even in the workshop manual they say to disregurd that base gasket and only use sealant.

Ashley

Have you tried simply tightening the barrel base nuts as I previously suggested?

I've been following this thread with interest, and have a couple suggestions. Some of this is a repeat of what others have already suggested, and I'm just adding another voice in the same direction.

The first one is to leave the breather system the way it is, stock. Running the hose from the timed breather to a catch bottle won't really help relieve crankcase pressure any more than the stock system. The vent from the oil tank to the air cleaner already does that. If you want to use a catch bottle, just run the vent hose from the tank into the bottle, as you appear to have already done.

Regarding the leak, you've identified it as coming from the cylinder to crankcase joint right at the area where the cases have been welded. Can you tell at this point whether it is coming from the actual cylinder to crankcase (base gasket area, if you have a base gasket), or from the joint in the crankcase halves where the repair is?

If it is from the gasket joint, and re-torqueing the base nuts doesn't help, then I don't see any solution except lifting the cylinder and re-sealing it. If it was me, I'd remove the base gasket completely and just use a good joint sealant (My favorite is Hylomar blue). I've not had real good luck with using base gaskets.

If it is from the crankcase joint, I'd suggest you try a wicking sealant like Loctite 290. Info here

http://www.henkelna.com/adhesives/green ... -13227.htm

I've had good luck with it for sealing leaks in joints without disassembly. Be sure and clean the area as much as possible by flooding it with brake/parts cleaner, or acetone, etc., scrubbing with small brush, and letting it dry thoroughly before applying the Loctite. High pressure air and blow gun help. The problem here is that oil in the joint will make it difficult for the Loctite to wick in properly, but it's worth a try. I've also seen a fair number of repairs to crankcases at the track using JB Weld that lasted surprisingly well, so you might want to try that instead, or try both. Again, thorough cleaning is necessary.

That's all I can think of. Good luck with it.

Ken

On my Triumph I cut the gasket in two at the middle of both sides. Used a thin layer of Hondbond on both sides of the gasket. Make sure the pistons are at TDC. Just lift the barrel enough to clear the studs. If you start to see the wrist pins you are getting close to rings. The hardest but most essential part is cleaning both surfaces. I used a razor blade and rag soaked in acetone and its a slow process but get them squeaky clean. Stuff some rags around the rods to keep crap from falling in.
I would take a close look where the case was welded. A little judicious dress-up with a fine file might be needed.

Lap the halves.

Chris T said:

Dog T - the outlet on the oil tank that I attached a rubber pipe to was the one on the front face of the tank that leads straight out to the air cleaner; I understand that is the overflow? I have the timed breather exit hose routed to the inlet on the top of the tank (and another change that I intend to make is to redirect that to a catch bottle too; the bike had that when I bought it; I rerouted to stock but now think that the past owner mod was a good one).

I did use quite a flexible hose to attach to the oil tank exit, and that hose crumpled up - presumably from wind and vibration; which might have blocked the outlet and created an air pressure point; and might have been the cause or a significant factor in the leak. I have tried to strengthen that hose by putting another short length of wider hose over the hose for a couple of inches where the hose is inside the air filter and joins the oil tank; but that may not have worked; so I think that the first thing that I will do is remove that hose until I can source a firmer hose. That might at least get me able to ride home so that I can attempt the fix with all of my tools; and might be a significant factor in depressuring the crank case; as has been suggested in one of the posts above.

And like any Commando this bike does wet sump; and I ride it reasonably irregularly, so that it has the opportunity to wet sump quite a lot; up until now I have been in the school of ignoring that and just starting the bike and letting it clear itself; but I am now also conscious that the wet sumping might have also been a major contributor to raised oil pressure in the crankcase. Jim C, I'm really hopeful that you can help us early framed bike's owners out with this one...

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OK, it sounds like you've got things hooked up right. I too have a catch bottle off the pipe out of the front of the oil tank, I put it into a catch bottle. I'm not sure I'd run the timed breather port to a catch bottle, but it's possible, I did it for a short time. If you have a lot of oil from wet sumping, you will end up with the excess oil (lots) in your catch bottle. Actually I tried venting the timed breather to below the engine, but the wind still took it to the bottom of the engine/cradle/etc. The vent out of the front of the oil tank is what I call the oil tank air vent or breather, it keeps pressure from building in the oil tank in my thinking. The best of all worlds is to change the breathing system to something other than the timed breather, there are a few options, but they involve changes to the crank cases unless Jim can come up with something off the sump that's not in the way of the brace.

With regards to lifting the barrel and head in a one-et, you don't have to worry about the pushrods as they are trapped between the tappets and rockers. I'm guessing you haven't got a workshop manual. Well worth the investment along with a parts list and the "INOA tech digest" IMHO

Get the bike back to Auckland and seek help from another Norton owner.
If you already have a gasket between the crank case and the barrel, I would be wary of removing it and just using sealer. Remember, the pistons go up to a point in the barrel. The rings rub up to a specific point as well and they wear the barrel. They don't wear the barrel above where they run so lowering the barrel could result in the rings hitting the ridge, and breaking.
Your call.

Dereck

kerinorton said:

Get the bike back to Auckland and seek help from another Norton owner.
If you already have a gasket between the crank case and the barrel, I would be wary of removing it and just using sealer. Remember, the pistons go up to a point in the barrel. The rings rub up to a specific point as well and they wear the barrel. They don't wear the barrel above where they run so lowering the barrel could result in the rings hitting the ridge, and breaking.
Your call.

Dereck

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For sure. Never chacge the cylinder height, in either direction, without honing. Although there are ridge cutters for the top, this doesn't take care of the lower one if applicable and I really don't think a ridge cutter is applicable unless it is severe.

kerinorton said:

Get the bike back to Auckland and seek help from another Norton owner.
If you already have a gasket between the crank case and the barrel, I would be wary of removing it and just using sealer. Remember, the pistons go up to a point in the barrel. The rings rub up to a specific point as well and they wear the barrel. They don't wear the barrel above where they run so lowering the barrel could result in the rings hitting the ridge, and breaking.
Your call.

Dereck

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Quite correct. I assumed you would be removing the top end completely, but still didn't think to mention removing the top ridge. Mea culpa.

Ken