Oil Leak from barrels? How hard to change gasket?

Guys, I finally got some time to work on my JS Carbs, fine tuning them. I think that I finally have them the way that I want them as she really pulls nicely now through the range. I was very excited as I rode home... pulled into the garage, and notice that I had oil slowly leaking from the bottom of the barrels.

How hard is it to replace this gasket? I have never actually done any engine work so this seems like a rather huge task. Might be one that I should have done professionally.

Thanks in advance!

Not quite as bad as taken whole engine out. I resealed my Combat once by just undoing headsteady and the base fasteners to lift like 1/2" to get goop back in.
To replace a base gasket mean lifting barrel off pistons which means head may have to come off to clear the pistons. I think pistons can lower enough but never did it that way. I've left the carbs just hanging from the air box boots or zip tied up. Coils have to come off as head/barrel need to tip forward to lift off and out. About the simplest major surgeical task on a Cdo considering. For me its a test of will power and mechanical attention to details with hi forces. When it works right it does increase my sense of self worth as a handy man. Once put back on then the re-torque ritual begins, but by then it will be second nature to torque beyond the manual wimp levels or guess what, new leak may develop that no torque will stop, so guess what ya get to do again...

Do you have Mikes XS breather valve (or the like) in place?

pvisseriii said:

Do you have Mikes XS breather valve (or the like) in place?

Click to expand...

Yes. I have the breather. My bike wet sumps but i usually have no problem with just starting it and letting it work the oil back up to the tank. Howevr today, when i moved the clip on my needles and started it up for the first time cold.... The throtle cable wasnt seated in the junction box so right away, the engine revved too high at cold with the sump probably full which i am sure contributed to the problem.

Are you sure it is coming from the base and not drizzling down from somewhere else. Sometimes its pretty hard to tell.

Recheck the base fasteners? Do you run a base gasket or a compression plate?

If it becomes a real problem, the head and all related items will have to come off then the cylinders. Sorry.

pvisseriii said:

If it becomes a real problem, the head and all related items will have to come off then the cylinders. Sorry.

Click to expand...

Not necessarily as all pre 850 twin barrels can be lifted from the crankcase without removing the head (exception: 750 short stroke and aftermarket bolt through barrels). Clean both surfaces and use silicon based gasket which provides better sealing and no need to re-torque the nuts.

nortonspeed said:

pvisseriii said:

If it becomes a real problem, the head and all related items will have to come off then the cylinders. Sorry.

Click to expand...

Not necessarily as all pre 850 twin barrels can be lifted from the crankcase without removing the head (exception: 750 short stroke and aftermarket bolt through barrels). Clean both surfaces and use silicon based gasket which provides better sealing and no need to re-torque the nuts.

Click to expand...

This is a 72 Combat...so you're saying I can remove the nuts holding the base on... raise it enough to clean the old gasket off and clean the surface.. then apply silicone gasket, lower base, then tighten the nuts?

What would be the best way to raise it and keep it raised while I clean and apply the silicone?

You can not put on an intact gasket w/o lifting barrel off pistons but could if a slice was made in gasket to pass around the rods. If just sealer used w/o base gasket then yes, just unscrew base fasteners till the nuts support the barrel/head up almost 1/2" and try to apply goop w/o losing much inside. Be aware that supporting the barrel with the nuts run to top of threads can bugger the top thread and make a bugger to restart again. Go around evenly or may find one twisting a nut on last thread against force of others not yet topped out. To place a gasket back in would have to lift barrel higher than just sitting on top of the case studs. I back off head banjo oil feeds to get purchase for zip ties or such to hold up hung form spine tube. Careful of pistons so low rings pop out of bores or lifters drop so far they unseat the push-rods. A fast wet sump start up could hydraulic ram oil to blast the base seal, but keep in mind there may be excessive blow by nothing will solve till new bore surface and ring job. I resealed Trixie this lazy man's way and got like most 1000 miles thinking I've solved it till new leaks and then smoking to reveal meaner task to deal with for the long run. I don't mind the simple job of undoing stuff and resealing non broken items but it beats the will power snot out of me and strains neck trying to get the push rod puzzle to work right over many trys till somehow finally fumble em up in head enough. Its such a bothersome task to me I'd sure try keeping head on and sealed til nothing else for it but lift head off too, ugh. To me nothing looks so aged long in tooth pitiful than dirty oily Cdo yet nothing looks so cool sleek and sexy all clean and dry.

Hi,

I've never done this on my Norton but I'd advise anything you use put a piece of wire on it or something you can pull it out with if it goes plonk into the sump!!!

I have experience of loosing bits from messing around with the top end, I hope I have learned my lesson!!


Kevin

Thanks guys, I thinkt hat this is one that I will just continue to monitor and if need be, get it done at my local shop..this is something that I don't want to mess with.

On another subject... you see the blanking plate on the back of the timing side with the 3 bolts... I would like to clean that up. Can I just unbolt it no problem? Or will nuts on the inside fall into the timing case?

Johnnymac said:

Thanks guys, I thinkt hat this is one that I will just continue to monitor and if need be, get it done at my local shop..this is something that I don't want to mess with.

On another subject... you see the blanking plate on the back of the timing side with the 3 bolts... I would like to clean that up. Can I just unbolt it no problem? Or will nuts on the inside fall into the timing case?

Click to expand...

Yes, 2 screws into the casing and 1 through with a nut. Oh well. You can take care of that this winter when you fix that leak.

pvisseriii said:

Johnnymac said:

Thanks guys, I thinkt hat this is one that I will just continue to monitor and if need be, get it done at my local shop..this is something that I don't want to mess with.

On another subject... you see the blanking plate on the back of the timing side with the 3 bolts... I would like to clean that up. Can I just unbolt it no problem? Or will nuts on the inside fall into the timing case?

Click to expand...

Yes, 2 screws into the casing and 1 through with a nut. Oh well. You can take care of that this winter when you fix that leak.

Click to expand...

I guess it is a very good thing that I asked before I unbolted that! Thanks!

On another note, I tightened the two bolts above where the leak was occurring and took her for a 30 minute ride yesterday.... no more leaks. I think it was due to wet sumping and the high revs when I first started her up after adjusting the carbs (cables weren't seated properly in the junction box).

I asume you cleaned the oil off before taking that picture? I can't see any leaking oil & I can tell you from experiance you realy shouldn't over worry about every little drip or clunk or sound. Ride the piss out of it & enjoy it. It's tougher then you think. Two months after owning my 2nd Norton & 1st (Combat) 750 I got worried about a noise after a long ride on a very hot day & before consulting someone smarter I tore the whole bloody thing apart thinking (ya right) I would find a broken part. After rebuilding it and still hearing the noise a well known Norton guru told me in no polite terms it's supossed to make that noise !!! Can you say " Dumbsh%#t""!!??

If the blanking plate has two outside bolts at the rear--as does one of my crankcases--it might be possible to remove the two rear bolts, swing the plate up and remove the captive bolt carefully from the inside. A locking tab on the bolt head--like those on the primary chaincase bolts--would keep the internal bolthead from rotating when you're ready to cinch things up. My timing-side case doesn't have enough metal at that bolt to anchor a stud--which no doubt explains the internal-bolt setup


Tim Kraakevik
kraakevik@voyager.net
'72 Combat, '74 RH10 850