oil build up in crankcase on commando 850 bleeding through cylinder barrel gasket

D

Drummer99

VIP MEMBER
Joined
Oct 18, 2013
Messages
157
Country flag
Second start up on commando 850 rebuild I had good oil pressure but recovery to tank seemed sporadic After about 5 min of running noticed oil seeping from bottom cylinder gasket in the rear. Immediatly stopped the bike and checked the sump and 12 ounce of oil came out oil was also slightly cloudy. I first suspected a bad base gasket seal and tightened the bolts Bolts were fairly tight. I thought that 12 ounces of oil in the sump was a lot and then suspected the oil pump which I had rebuilt when assembling. Now have the oil pump out and apart seems ok Any ideas would be appreciated Cheers Drummer 99
 
D99 quoted:
"but recovery to tank seemed sporadic"


Pictures would help to show where it is leaking.
On your Re-build, You should see oil returning to your oil tank with the oil filler cap off. You will see a brazed tube at the back Through the filler and with the engine running oil pump return should look like a coffee peculator. (If that is what you mean as sporadic?) If you see that then that is normal.
Cheers,
Tom
 
There is no base gasket used on an 850.
12oz. in the sump is not excessive.
The "sporadic" recovery to tank is as-designed, the scavenge pump has more volume than the supply, thus, slugs of oil, slugs of air.
 
concours said:
There is no base gasket used on an 850.
12oz. in the sump is not excessive.
The "sporadic" recovery to tank is as-designed, the scavenge pump has more volume than the supply, thus, slugs of oil, slugs of air.
Click to expand...
Concours,
I am confused about the base gasket on an 850.When Jim Comstock did my head and new rings,he sent me a base gasket along with instructions on what sealer to use.This was the first time I have had the cylinder off in 30+ years of ownership and it had a gasket on it. I went to the parts book and sure enough there is no listing.Long story short,14,000 miles on it with no problems..Just confused.
Mike
 
YING said:
Concours,
I am confused about the base gasket on an 850.When Jim Comstock did my head and new rings,he sent me a base gasket along with instructions on what sealer to use.This was the first time I have had the cylinder off in 30+ years of ownership and it had a gasket on it. I went to the parts book and sure enough there is no listing.Long story short,14,000 miles on it with no problems..Just confused.
Mike
Click to expand...
Lots has been written on the topic.
If Jim supplied it with his work, there's a good reason for it. (compensate for cut surfaces, etc.)
What crankcase breather is fitted?
 
Last edited:
YING said:
Concours,
I am confused about the base gasket on an 850.When Jim Comstock did my head and new rings,he sent me a base gasket along with instructions on what sealer to use.This was the first time I have had the cylinder off in 30+ years of ownership and it had a gasket on it. I went to the parts book and sure enough there is no listing.Long story short,14,000 miles on it with no problems..Just confused.
Mike
Click to expand...

The 850 originally had no base gasket, the base joint being sealed with Loctite "plastic gasket" instead.
The thinking seems to have been that the four long barrel through-bolts couldn't be checked/retorqued if they slackened due to base gasket compression without removing the cylinder head.
However, a base gasket was introduced on (or by the time of) the 850 Mk3 and why there is an '850' base gasket (item 25) and why there's one included in the 850 gasket kits).
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk

AN lists the base gasket (item 1A) for all 850 models.
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
 
concours said:
Lots has been written on the topic.
If Jim supplied it with his work, there's a good reason for it. (compensate for cut surfaces, etc.)
What crankcase breather is fitted?
Click to expand...
Concours,
I am using a Comstock breather.
Mike
 
The oil return hole in the gasket was properly aligned? Not too much sealant around it?
Don't be offended, just confirming.
 
Drummer99 said:
Second start up on commando 850 rebuild I had good oil pressure but recovery to tank seemed sporadic After about 5 min of running noticed oil seeping from bottom cylinder gasket in the rear. Immediatly stopped the bike and checked the sump and 12 ounce of oil came out oil was also slightly cloudy. I first suspected a bad base gasket seal and tightened the bolts Bolts were fairly tight. I thought that 12 ounces of oil in the sump was a lot and then suspected the oil pump which I had rebuilt when assembling. Now have the oil pump out and apart seems ok Any ideas would be appreciated Cheers Drummer 99
Click to expand...


"commando 850 rebuild" = top end? entire bottom end?
 
Last edited:
concours said:
The oil return hole in the gasket was properly aligned? Not too much sealant around it?
Don't be offended, just confirming.
Click to expand...
I rebuilt another oil pump and installed it and my return is much better however still getting the leak at the base gasket in the rear it is quite substantial I dont think I installed the gasket backwards and I am also confused about the sealant vs the gasket Looks like I will have to pull the head and barrels and see what is wrong I think I will leave the gaslet out this time. Thanks for all the feedback I will let you know what I find
 
:
kommando said:
If you have done 14k with a gasket then keep fitting one until the next rebore, removing before risks the top ring breaking against the unworn bore at the top.
Click to expand...
Worth repeating or if you want to go gasketless you need to relieve any unworn bore above the ring travel so the top ring can travel further up the bore.
 
Drummer99 said:
I rebuilt another oil pump and installed it and my return is much better however still getting the leak at the base gasket in the rear it is quite substantial I dont think I installed the gasket backwards and I am also confused about the sealant vs the gasket Looks like I will have to pull the head and barrels and see what is wrong I think I will leave the gaslet out this time. Thanks for all the feedback I will let you know what I find
Click to expand...
Top deck not aligning after rebuild? Best to torque down barrel before tightening crankcase bolts. Also, the paper gasket is very thin, isn't it? I can't see it causing a problem for torquing the through-studs. I'd fit it again.
Have you ensured oil pump seats properly and all oilways (especially oilway to the sump) are clear?

-Knut
 
This is what Jim Comstock told me to use with the gasket.
Loctite anaerobic #515 gasket maker.
Whatever you decide,be careful to make sure not to clog the small return hole.
Mike
 
YING said:
This is what Jim Comstock told me to use with the gasket.
Loctite anaerobic #515 gasket maker.
Whatever you decide,be careful to make sure not to clog the small return hole.
Mike
Click to expand...
Ok Gasket appeared to be damaged at the oil return hole I cant imagine I damaged it putting the barrels on but its possible Do you put the locktite on both sides of the gasket
Thx Drummer99
 
Drummer99 said:
Ok Gasket appeared to be damaged at the oil return hole I cant imagine I damaged it putting the barrels on but its possible Do you put the locktite on both sides of the gasket
Thx Drummer99
Click to expand...
Yes. I also was very cautious with the sealer around the return hole.
 
I use a thin coat (smeared between fingers) of 518 on all gaskets. Seals tight, easily removable.
 
Reviving old thread.
I have seepage at two places of the 850 mkII barrel base. This was last fitted by a classic bike shop a year ago. Seems to have a gasket and some sealer evident around edges. Thinking to remove head and lift barrel enough to clean up, apply locktite sealer and torque. Trying to avoid full block lift off as I've never done ring fitting before and don't want to risk it.

Does this sound like a reasonable approach?
 
You must log in or register to reply here.
Back
Top