Plug fouling

lwmcd1 · Jul 4, 2008

Hey guys,
Any ideas on where to look for a gas fouling right cylinder?
1974/Rita electronic ign. Sparx 3 phase 220 alt. and regulator. 34 mm mikuni single.
Ive tried many things like checking wiring (all new by the way) switching coils,plugs wires etc. no effect. Keeps fouling the right cyl.
thanks,
Larry

cash · Jul 4, 2008

The cause is usually oil, though it can be ignition timing related but usually if it is ignition both plugs foul. Try a hotter plug say a N8Y or even N9Y if the fouling is bad.

Cash

BrianK · Jul 5, 2008

I've found "fine-wire" (platinum or iridium) plugs much more fouling-resistant in my 73 850. FWIW/YMMV. - Brian

iusedtolikehondas · Jul 5, 2008

are you sure it's fuel fouling? having the single carb would foul both, right?

kommando · Jul 5, 2008

With a single carb you can get bias to one cylinder due to differences between the cylinders eg compression, valve clearances, wear on the cams etc etc.

mikegray660 · Jul 6, 2008

kommando said:
With a single carb you can get bias to one cylinder due to differences between the cylinders eg compression, valve clearances, wear on the cams etc etc.

yes but thats not so much a function of carb through, but rather condition of cylinders/motor - sounds more like one cylinder is a little off - have you run a compression test on them? maybe guides worn - like someone suggested you can run a hotter plug if worn guides to "mask" the problem until you have the time to fix should that be the problem

Scheffy.G · Jul 6, 2008

One more relatively easy electrical thing to try - swap the wiring itself that's going into the coils, assuming you don't have a single coil setup. Since the coils are wired in series, there's always one that's further upstream electrically than the other one. If this changes the firing cylinder it could indicate a grounding issue. Don't assume that everything's good just because the wiring's new. That's what I did and I ended up chasing my tail for weeks.

lwmcd1 · Jul 19, 2008

Scheffy.G said:
One more relatively easy electrical thing to try - swap the wiring itself that's going into the coils,"
Yep tried that. I change all Elect. over including plugs, plug wires, coils,wires from ign amp. ect. It made no difference.
I've used a hotter plug, and I've chased down all wiring to their source to confirm all connections were good. I did find a couple that were iffy. Fixed those and though it did improve things over all it did nothing about the fouling. The only thing I can think of that I have not tried and it probably won't make and difference is to increase the gap on that cylinder's intake valve so it does not open as wide and so sends less fuel/air to the right side. It is set at the called for 6 right now.

tpeever · Jul 19, 2008

What about valve seal? My right side fouls a bit as well and I am pretty sure it's a valve issue, either worn guide or seal.

lwmcd1 said:
Hey guys,
Any ideas on where to look for a gas fouling right cylinder?
1974/Rita electronic ign. Sparx 3 phase 220 alt. and regulator. 34 mm mikuni single.
Ive tried many things like checking wiring (all new by the way) switching coils,plugs wires etc. no effect. Keeps fouling the right cyl.
thanks,
Larry

mikegray660 · Jul 20, 2008

lwmcd1 said:
Scheffy.G said:

One more relatively easy electrical thing to try - swap the wiring itself that's going into the coils,"
Yep tried that. I change all Elect. over including plugs, plug wires, coils,wires from ign amp. ect. It made no difference.
I've used a hotter plug, and I've chased down all wiring to their source to confirm all connections were good. I did find a couple that were iffy. Fixed those and though it did improve things over all it did nothing about the fouling. The only thing I can think of that I have not tried and it probably won't make and difference is to increase the gap on that cylinder's intake valve so it does not open as wide and so sends less fuel/air to the right side. It is set at the called for 6 right now.

Click to expand...

again - compression test?

lwmcd1 · Jul 20, 2008

tpeever said:
What about valve seal? My right side fouls a bit as well and I am pretty sure it's a valve issue, either worn guide or seal.

The top in is very fresh. But I will be running a compression check as soon as I can find my tester. A compression check is something I should have done already I'm sure. I love tinkering but this problem has gone on entirely too long.
Thanks for the input.

lwmcd1 · Jul 20, 2008

iusedtolikehondas said:
are you sure it's fuel fouling? having the single carb would foul both, right?

Not if the problem is electrical/ignition

lwmcd1 · Jul 22, 2008

[/quote]again - compression test?[/quote]

Compression is the same for both cylinders.

cash · Jul 22, 2008

If you look down each plug hole using a torch, turn the motor over until you can see the inlet valve. If it's oily you've a stem seal gone, or hopefully not a lose guide. Now here is the long shot, or, if the oil pump gasket is put on the wrong way round the return can be restricted. Too much oil in the sump will give you oiling problems.

Cash