Clutch Rod Seals, wet sumping

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"Sons of Arthritus"
Jan 14, 2004
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I don't know if everyone on this forum knows about Dynodave's super cool, handy dandy clutch rod seal.
When I was bombing around 30 yrs ago with my Dunstall piped 850, along with tightening the headers every hundred miles or so, I had to disassemble the primary, clean and sand the gunk off the clutch plates somewhere around 200mi. Then pretty soon the clutch would start slipping at WOT and draggin at the lights and I'd do it all over again. I tried every combination of oil, ATF, non detergent everything. No one had an answer other than replace it with Barnett plates. I couldn't understand this because these 'bronze' plates were supposed to be state of the art.
The bike was eventually sold.

I got back into Norton's in the middle 90's and happened upon Dynodave on another forum.
He discovered the tranny oil/grease would siphen through the mainshaft via the clutch rod and contaminate the plates. Brilliant!
I made it even worse by storing my 'Dumbstall' piped bike on it's side stand. The grease just rolls unto the plates, besides dripping all over the floor. (yes I used to overfill my tranny, because I was sooo smart)
Anyway, you can check out his seals at or (formerly

The other problem I had was smoking on start up. I had bought the bike new. (My first new anything, 400 dn, 86 per mo.) It started smoking on start up somewhere around 10,000 mi. Because I was soooo smart, I assumed it was valve seals. I did a complete valve job and rings while I was at it. Didn't solve a thing, still smoked. I figured I had done something wrong. Now understand in the middle 70's there were not alot of places to go to talk Norton. I had to go to a Triumph dealership to buy parts, they didn't want me anymore than I wanted them. It was a miserable time.

So in 1978, I had a bike that hauled a#%, had to tighten the pipes every 100mi., do the clutch thing every 200mi, dripped oil, smoked on start up, NO dealer support and it didn't look like it was getting any better.
Ride on the weekend, work on it all week. This got old.

So I sold it as part of a down payment on my first house. When I saw it going away, I was happy to see it go but was wondering if I would ever regret it. The bike gave me so much joy, yet so much grief.

I see now the problems were owner ignorance.
Smoking on start up is from wet sumping. Normal
Clutch slippage / dragging is from tranny contamination further induced from side stand storage.
Overfilling the tranny, bike on side stand = oil on floor.
'Dumbstall' pipes are more trouble than their worth.

Had I been able to solve these solvable problems, I probably never would have sold it.

I am gone for the weekend, everyone have a nice "T" day.
I have a similar story I can share. Back in the late 70s I too had a Duntall-piped 850 (just Dunstall mufflers actually). I was able to maintain it fairly well for quite a while. But I put a lot of miles on that bike and eventually it needed major work, or so I thought.

It was around 1980 when I threw in the towel. NVT had gone bust a few years earlier, all the dealers dropped the bikes, and I felt parts were going to be impossible to find soon. The chassis felt really loose, the amals wore out, the mikuni conversion didn't work right, and there was no technical support available. No internet forums like this, no local clubs. So I sold it for $750. I didn't want to but I felt I had no reasonable alternative.

In retrospect I now realize it wouldn't have been that hard to restore it. The bike needed new amals, a complete iso rebuild, new fork bushings, and a swingarm spindle rebuild. Some of the chrome parts like the headlight bucket had rusted out from living near the beach. That stuff needed attention and the bike needed paint. The motor, clutch, and tranny were solid though.

I hung on to the manuals and tools over the years. I always had the dream in the back of my mind of getting another one some day. I even kept the owners manual, dealer service booklet, and a little tire booklet published by Avon that came with the bike when Dad bought it new.

But whenever I saw one in the classifieds, it was always "Norton Commando, runs good. $6500 firm." And I always thought "oh that's too expensive." I even looked at a few for sale locally. But they were in roughly the same condition as John's $300 bike and the sellers wanted $4000+ for them. Firm. Then I discovered ebay about a year ago. Say what you will about ebay, but that's what got me back into Nortons! Funny how things work out.

Happy Turkey Day for those celebrating it.

surfing before cooking
Just in case some of you blokes/sheilas haven't heard of this.

One bloke over here swears by "filling" the lower part of his primary with grease, just to the level of the "bottom" primary chain. (what a mess !)
But that is what he does........

Other people do not put any oil in the primary at all but remove the top middle inspection cap & spray RP7 or similar periodically, depending on mileage ridden.

Others will say that "ATF" will Not lubricate the chain correctly & hence wear out quicker.
I too have heard all kinds of things people do to their primary but it doesn't address the real problem. That being the tranny grease/oil syphoning down the mainshaft into the primary.
My prevous post mentions 200mi., that may be a little short afterall it was 30yrs. ago, but it was before oil changes.
What I will say is since I put one on my Mark III. I have had no problems. As you know the Mark III needs oil in it's primary!!
Also, CNW uses them on their machines and Les Emery sells them.
I also want to mention I have no financial interest / partnership in Dynodave's products.


norbsa is visiting oz in Feb & I have asked him to bring 2 of the seal kits with him :D The problem you talk about hasn't been an issue for myself.

I am also getting one norbsa's spring "kits", I reckon that will be a good thing :!:

I bigger problem at the moment for me is that pressure is pushing engine oil out through my drive side crankshaft seal into my primary. From there, because it is sealed, oil is being forced out of my primary case, past the gearshaft felt seal. From there it is being "blown" straight onto the left side of my rear tyre :evil: This is my 3rd "combat" engine & the first time this has happened.

So I am thinking of installing a relief vent in the intake rocker cover as ppl do. Then t-piece it back into the oil tank. I am also thinking about drilling another hole in the inner primary & running a relief vent from there also. As the primary is sealed with the rubber o-ring & has the rubber grommet for the alternator wires, there must be a bit of pressure in there if oil is being "blown" through the crankshaft seal.

Any thoughts on this issue ?
In hindsight, it may be "leaking" through one of the 3 bolt holes that hold the front of the inner primary onto the crankcase.
About to remove and do some detecting.

Re: your crankcase pressure problem.

Have you tried the one-way check valve in the crankcase vent line? Others have told me that this has greatly reduced oil seepage by keeping a slight negative pressure in the crankcase. Haven't needed to do it myself, but does make sense.
Ron L,

Thanks for your response. Delayed thanks for the Drouin Info also.

Tonight I replaced the crankcase seal & "plumber taped" the 3 bolts that hold the inner primary case in place.
First thing in the morning I will pull the breather off the rear of the combat engine & see if it "blocked". Will advise on outcome.

I would like to post some info here that was sent to me by BP Bob, another Norton Enthusiast. Some of what he says may be helpfull to other forum members. it is long but informative!!

Hi Reg,
this is something that happens to a lot of pommy bikes, not only
Nortons, not only Combats. I've had this happen in the past, but not
recently. Even after giving the old bike a good thrash. Oil shouldn't be
comming past the crank seal, if the seal is in good condition and it's
properly in it's place. Often the seal gets blown out of the case and is
just sitting on the shaft behind the sprocket. How bad does your bike wet
sump when it's been sitting for a while? Do you think you might have started the bike when the cases had a high level of oil in them. This is often the cause of the seal blowing out. If your breather is in the regular combat location of down low at the rear of the cases then this would have been full of oil and would have offered no breathing at all and the normal crankcase compression as the pistons came down to BDC would have blown the seal out.

If I leave either of my Nortons for anything over a week and a
half I can guarantee the oil level will be off the dipstick. I then drain
the cases and tip the oil back into the tank before start up. Even when the
oil level is low I start the bike and try not to rev it untill a few minutes
have passed and the oil return in the tank starts to splutter and the oil
level in the tank has returned to where it should be. My 69 model which
should have a camshaft timed breather, has been altered by a previous owner
so now it has a Combat type breather low at the rear of the cases. I have
made some modifications to my Combat motor. The Combat motors had a
reputation of wet sumping while on the move. Norton saw fit to do a couple
of dumb things to these motors. One was to do away with the large sump drain
plug that incorporated a screen filter before the oil went back to the pump.
The oil pick up was relocated up the wrong end of the sump which meant that
the oil was flung away from the oil pickup by the flywheel while the engine
was running and an accumulation of oil could gather without being pumped
away, this would be flung back up into the cylinders under the piston,
overoiling the cylinders and getting back into the combustion chamber, going
off as blue smoke out the zorst. Also getting blown up the breather back
into the tank in big gobs, sometimes comming out the oil tank breather and
dumping onto road back tyre etc or if the oil tank breather went into the
air filter this would saturate the filter and also appear out the zorst as
big heaps of blue smoke. Altogether this was an exception to the normal
rule. I can only ever remember it happen to me once. I was belting along
trying to get ahead of a bunch of other bikes so I could stop and take a
picha. I was hard on the brakes and went over a big woopdi in the road. Blue
smoke went every where and bikes comming from behind thought I'd dropped
it!!! There is a modification you can do to the internals of the cases.
Araldite up the old oil hole and with some grinding and drilling, relocate
it to a more suitable position. I did this years ago and can't remember much
about it, but I followed info from a magazine, this same info is now
available somewhere on the net. If I find it I'll post you a link. Also to
add with this I relocated the Combat crankcase breather from down low behind
the cases to up behind the timing cover where the maggy / starter motor
went, a la 850's. Also to go along with this was to drill three (I think)
3/8 inch holes through the crancase wall between the timing chest and the
crankcase to allow better breathing from inside the crankcase into the
timing chest thence out the breather pipe. I have since done the old
breather in the inlet cover trick and have T 'd that into the same breather
line from back of timing cover to oil tank. At present all is well with that
setup and I like it. I just drilled and tapped a hole in the cover for a 1/4
BSP fitting and put some rubber tube on it and I was away. Initiall I ran
this tube to a catch bottle. Big mistake. There is quite a bit of oil goes
out this way and soon filled up the catch bottle and smeared all down the
side of the bike. Go straight back to the oil tank. There are a few other
ideas like putting a PCV valve in line to induce some negative pressure
(vaccuum) into the cases. Not a bad idea, but I found no reason to go that
To me, blowing the drive side seal indicates lack of crankcase
breathing. Do you still have your breather down in the originl position??
These big lumpy things contained a gauze type screen and a lump of filter
type stuff. To do with trying to get the oil mist to condense and droplets
remain in sump and go back to tank via the pump. I think this lot can clog
up, severely limiting the ability of the breather to work properly. I don't
have anything in either of these contraptions, free flow all the way. If the
bike were to wet sump over night, I think I already mentioned, upon engine
startup, the oil blocking the breather can restrict the breathing and you
could blow the seal out. Only needs to happen once in an instant and it's
done.....bummer, then on it's oil pumping into the primary. Do you use some
sort of gasket goop around the outside of the seal when you put it in?? I
do. Make sure you lube the lip of the seal where it runs on the shaft so you
don't start the bike and run the seal dry in that first instant. Burns the
sharp lip off the seal and stuffs the seal. I guess you know you can get the
seal out without splitting the cases. Remove primary chain and engine
sprocket, carefully punch a hole in the seal with a sharp nail or similar
and gently screw a self taper screw in there and pull on the screw with a
pair of pliers, pulling the seal out. The only other reason you will blow
this seal out is from severe piston blow by and I'm sure thats not the case.
All I can recomend is replace the seal, don't start the engine if
you think there is too much oil in the cases and put the extra breather on
the inlet cover. Just one more of the other guys in the club
here had wierd oil consumption. One minute the oil tank was full, then it
was empty. He topped the tank up and oil went every where, out of every
orifice. The engine was badly wet sumping. What had happened was the oil
seal in the timing cover, the seal that fits on the timing side end on the
crank and delivers oil to the crank, had blown inside out. Some seals have a
spring reinforcing around behind the lip, you can clearly see it when you
look at the seal. Some seals don't have this and are more for low pressure
applications. This seal had blown inside out and oil was being pumped
straight into the sump, causing quick smart wet sumping. Also if this seal
were to be old and worn and stuffed and leaking, some oil would be bypassing
the crank and going directly to the sump. This means more oil than normal
would be accumulating in the sump and may not be getting pumped away quick
enough. This oil will be filling valuable crankcase, blocking the breather
and causing your only other seal to blow out, the primary seal. Is the
camshaft seal weeping????
Hope all this doesn't freak you out and get you tearing down your
motor for nothing. Just trying to give you a few ideas.

All the best
Combat crankcase mod

The Combat crankcase / breather mod can be found in the INOA tech digest. also has a nice write up with illustrations. A lot of shops can do this. I haven't done yet, but probably will when I decide to split cases.
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