Sooty plugs, running rich - where do I start?

[muskrat]

"Basically the bike starts beautifully on new plugs, ticks over evenly and runs beautifully. But after about 20 miles on new or cleaned plugs, they gather enough soot to cause a misfire. "
If you put new plugs in then does the misfire disappear till another 20 miles are covered? If the misfire continues straight away I'd be looking at the magneto.
Could also be that running in has been too gentle and glazed the bores.
Cheers

[trevinoz]

The oil leak, is it engine oil, primary oil or gearbox oil?
Gearbox oil has been known to escape when parked on the side stand.

[morris]

I'm also starting to think that there may be an ignition problem.
I remember some time after building the SA round to 12V and electronic ignition, I started to suffer sooted up plugs up to a point that it wouldn't start unless I changed the plugs for a new set. After that it started immediately and ran again for some 30-50 miles when the misfire occurred again. Experimenting with hotter plugs showed no improvement.
I had noticed right after the conversion that the battery wasn't keeping it's 12V, at times even going down to 11V, but blamed it on the dynamo that I thought couldn't keep up so I hooked it up to a charger after each ride. By the time the plug problem came up it went sometimes even as low as 10V.
At that point I started to suspect the battery anyway and although it was only a couple of months old I changed it for a new one. Since then no more sooted plugs, no more misfires and as a bonus a battery which always keeps its 12V even when running with the headlights on.
Moral of the story; don't get tempted to rule out an ignition problem when everything points in the direction of the carburettor.

[victortrry]

I have a 1970 Firebird and it always ran poorly, sooty plugs.  I pulled the carbies off so many times but couldn't get it to run right
then I bought new Wassel carburetors it started well but after a few kms the plugs would foul,
I took the carbys off a major job on the firebird because of the high pipes.  Adjusted the height of the floats to 5mm below the lip of the bowl and put it back together, no other changes the bike starts idles evenly doesn't foul the plugs, never used to do that before.

Victor


1954 A10 Plunger, 1956 B31, 1968 Enfield 350, 1981 XS650

[CrispinA10]

Right. Might be getting somewhere. It is definitely wet sumping. The pool of oil is clean sae 30 engine oil, although I haven't yet worked out where it is coming from. Doesn't leak when running nor when left on main stand, but does when on prop stand. Could oil in the sump account for thick soot on plugs? It was slightly sooty from the start, but problems seem to have started when I fitted new SRM oil sump plate at first 400 mile oil change (380 actually, as recommended) and new tank of sae 30.
What could I have done to trigger wet sumping? Hmm. Off to have a think and a stare at the Haynes manual.

[trevinoz]

The main culprit for wet sumping is the check ball behind the oil pump. Also oil leaking along the pump shaft and between the pump segments.
The pump gasket could also play a part as could a loose pump but I think that a loose pump would cause other major problems.

[chaterlea25]

Hi Crispin,
I had a problem with a customer bike where the magnetic drain plug prevented the sump ball valve from opening, so make sure the magnet is away from the pickup pipe
The usual culprit when the bike leaks on the side stand is oil leaking from the gearbox mainshaft
so what oil is in the gearbox?

John

[CrispinA10]

Not sure what oil is in the gearbox - it is whatever the previous owner put in after the rebuild some 400 miles back. But it wouldn't look like clean sae 30 would it? Perhaps it would. I'd better go and check the level before I do anything else! I am assuming that it's engine oil, because the level in the tank drops a fraction when there is a pool on the shed floor, although not hugely, about a quarter inch I'd say. But that amount of oil would probably look quite a puddle I reckon.
Whatever the ultimate cause (I'm now searching wet sumping in the archive) I have certainly learned a lot from the answers. And I might well have been over cautious running in causing possible glazing. That hadn't occurred to me, so I'll give it a little more exercise when I get it back on the road with soot free plugs.
All suggestions much appreciated - many thanks.

[Greybeard]

Gearbox oil has a distinctive smell

[muskrat]

The oil on the floor would have to be gearbox (only leaks when on the side stand).
The magnetic drain plug should be facing forward to avoid holding the ball valve closed, or use a non-magnetic plug. After a run there should only be 1 to 1.5 cups of oil in the sump, drain it and replace the plug. leave it overnight and drain the sump again. How much comes out?
Cheers

[CrispinA10]

I have a strong feeling that the drain plug is facing backwards rather than forwards, although I seem to recall that the new SRM unit only fitted one way round. Can't check at the moment because the bike is with a Goldie owning chap who seems to know a lot about wet sumping and the causes. Rather hoping that he might be able to sort the problem. It will be a tad embarrassing if it turns out to be because I fitted the SRM sump the wrong way round...

[muskrat]

G'day Crispin.
The SRM sump can be fitted in any (4) directions. It's the gauze filter that only goes 1 way.
Really hope he finds an answer for you.
Cheers

[bobandbec]

The drain plug on the SRM sump should face to the back shouldn't it? Otherwise I've fitted two incorrectly!

Peter

[Greybeard]

The drain plug on the SRM sump should face to the back shouldn't it? Otherwise I've fitted two incorrectly!

I didn't think there was any preference except, maybe to make it easier to reach when the bike is on its sidestand; however I am now worrying about the drain-plug magnet affecting the return pipe ball!

[stu.andrews]

I always had my drain plug at the front-so much easier to reach to drain off before starting.