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G: Gearbox Gearing - Series ‘C’ Black Shadow


Bill Thomas

Well Known and Active Website User
VOC Member
Just a thought, If the Bike has been standing for long, Our Bikes sometimes ," Wet Sump", That makes them Smoke like mad !. Sorry, Don't know how long you have had the Bike. Cheers Bill.
 

Kiwi_Tim

Website User
VOC Member
As soon as I left the motorway I was caught up in heavy largely stationary traffic and was burning a lot of oil and I mean a lot. the bike struggled on, but was noticeably throwing out a huge smokescreen finally dropping a cylinder at which point the oil did clear (which had me thinking a problem with the front cylinder.
When I limped home I turned off the oil and pulled the plugs, both were black but the front one was solid with carbon.
I will drop the sump oil to check she wasn't wet sumping. No sound of anything mechanically failed. The bike has used oil since it was brought back into service 6 months ago, but its evident the oil burning (not leaking) has increased to a point I cannot ignore it.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Sorry to hear that Tim, Have you checked the oil returning to the tank, I would not think it's wet sumping,
After a run.
If it's got old type Rocker feed bolts, You could try or check that they have the small wire in the hole ?,
We were playing with a Twin some time ago, That didn't smoke bad, And Brother Ron changed the oil feed pipes and thought he would take the wires out, Next time we started it , Smoked like hell,
So we put them back in !!.
My poor old Comet is a Smoker, The only way I can ride it is with single grade 50 oil, Been doing it for a few years now, I don't go far !, I don't want to strip it out unless I have to.
I hope you are not running yours on very thin modern oil ??.
Good Luck, Bill.
 

Albervin

Well Known and Active Website User
VOC Member
Tim, when I bought my Shadow in the UK a couple of years ago I rode it for several hundred miles. It was very fast but smoked. When it arrived in Australia I pulled the heads off. The exhaust ports had been well and truly "ported" taking too much metal off the boss for the lower exhaust valve guides. This allowed the guides to rotate and allow a lot of oil to pass. I then decided the safest thing to do was split the cases. I then found the main bearings were rotating on the crank. If you don't know what is inside then the safest thing to do is strip it. There is no doubt your gearbox is non standard as it should not have the high first gear, so what else has been changed? The only way to find out is a strip down. During the strip down I also discovered a large crack in the rear wheel hub, a couple of very suspect wheel bearings etc. etc.
 

Kiwi_Tim

Website User
VOC Member
I'll start off checking the sump oil content for volume, the mag had previously made its low speed running excellent, but definitely oiling up big time now. So possibly not scavenging properly.
funnily enough it did have joggle wires but I took them out. The bike has been running a straight 40 and the last few tops ups straight 50.
If the sump is fairly clear then I guess the top end needs investigation
theoretically the engine is Dec 53, a very late number.
 

oexing

Well Known and Active Website User
VOC Member
Could be the engine breather too, in that case a lot of oil gets burnt.

Vic
 

MartynG

Well Known and Active Website User
VOC Member
When I first got my Comet it smoked like a WW2 destroyer laying a smokescreen!

Turned out to be incorrectly fitted valve guides - the lower guides were out of alignment with the top guides resulting in very ugly wear on the valve stems and the guides thus lots of oil getting past into the combustion chamber to be burnt.

Fix was new valve seats, new guides (with valve stem seals) and new valves - Oh and a fair bit of $$$$. This time the lower/upper guides were line reamed. 50,000 miles later and still smoke free.
 

Bill Thomas

Well Known and Active Website User
VOC Member
I would put the wires back in !!, Unless you want to take it off the road and spend a lot of money.
A lot of people start stripping these out and the Bike is off the road for years.
Cheers Bill.
 

vibrac

Well Known and Active Website User
VOC Member
I don't think I have ever had an engine with joggle wires in. My take on them was based on what people like Ron Kemp said that with high mileage early oils and infrequent oil changes they stopped the small oil holes getting blocked. I change oil regularly and any racer I had was on R never seen a problem
 

Bill Thomas

Well Known and Active Website User
VOC Member
I'll start off checking the sump oil content for volume, the mag had previously made its low speed running excellent, but definitely oiling up big time now. So possibly not scavenging properly.
funnily enough it did have joggle wires but I took them out. The bike has been running a straight 40 and the last few tops ups straight 50.
If the sump is fairly clear then I guess the top end needs investigation
theoretically the engine is Dec 53, a very late number.
Tim, You will always get some oil out the sump drain !, Not too much I hope.:)
Cheers Bill.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Tim, I have never checked it, But that don't sound too much,??, It has to have some, If you look in the tank when running, As long as it's returning, Vin's don't have a steady stream, It comes back in fits and farts,
Again, Try and look at another Bike. Cheers Bill.
 

chankly bore

Well Known and Active Website User
VOC Member
I remember P.E.I. saying "more harm is caused by oil not getting where it's needed than by it failing when it gets there." Especially in cold weather heavy oils tend to form "tunnels" with an outer layer adhering to pipe walls and causing the mechanical equivalent of a coronary occlusion, or perhaps a Colonial Delusion. Other things to check are valve stems gumming up and stuck rings. Personally, I run 30 or 40 grade in my Comet even in the hottest Aussie weather. P.E.I. used to like the old formula Castrol GTX because, to quote him directly, "it is messy stuff."
 

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