Plug fouling

[johndee138]

I cant seem to keep a plug in the front cylinder (47 EL) from fouling. A new one will last about 15 miles , and then it starts to sputter. Made it home on one lung this last weekend. Perhaps a new set of plug wires? Any suggestions would be appreciated.

[bmh]

What brand and heat range are you running? Also how's the oil control on that cylinder? Might just need a different heat range of front for the type of service.
Brian

[johndee138]

Plug fouling

I'm using Champion D-16s in both cylinders, gapped at .025 as per the HD specs. THe rear displays a nice light tan char the front is sooty black

[johndee138]

Not sure as to oil control, I will investigate.

[Erdos]

I had the same problem on my 45 except my rear plug was fouling and I tried everything including hotter plugs. One winter I decided to pull the motor and found my front head had a compression leak. The bolts where slightly too long and were bottoming out in the cylinder keeping the head from being torxed correctly. So I would say check for a leek on your rear cylinder.

[koanes]

Are your plug wires metal core? They either work or they don't. Put your hand on the coil after ten miles or so to see if it is hot, if so it may be shorted internally. Easy to check by installing a plug in the wire and grounding the plug to see if it has a crisp blue spark when it is warm. If your plug is oil fouling, it will have a shiney black deposit, if fouled because of weak spark it will have a dull sooty look. Look for any sign of blue smoke before the plug fouls as that would indicate an oiling problem. Good Luck.

[bmh]

Koanes brings up a good point on the wires so make sure to check them. As long as you don't think it's oil fouled, try a plug one step hotter up front and see how it does.although I suspect it is something else as the front cylinder usually likes a colder plug than the rear, but not always. I would deffinetly check for intake leaks and do a comperession test and maybe a leak down test too.
Brian

[35chief]

I have been struggling with the front plug fouling on my Chief. It is a 1935. Rear cylinder has thousands of miles and is always clean. Front fouls in 20 miles. Black soot. No oil burning. I run autolite 303. I can not find a vacuum leak. I have changed coils and wires with no change. Idea's ???????

[Skirted]

You could do a simple compression test or a leak down test and see how close the readings are between cylinders. If there is a significant difference, you can direct troubleshooting efforts to find the root cause.

What method did you use to check for an intake leak?

When did the problem start?

[AFJ]

I have been struggling with the front plug fouling on my Chief. It is a 1935. Rear cylinder has thousands of miles and is always clean. Front fouls in 20 miles. Black soot. No oil burning. I run autolite 303. I can not find a vacuum leak. I have changed coils and wires with no change. Idea's ???????

Maybe incorrect sump valve plate positioning?

[T. Cotten]

Echo Skirted's reply:

"What method did you use to check for an intake leak?"

Did you use a constant, regulated air supply to bubble-test, and not a hand pump, air mattress compressor, shop vac, etc.?

...Cotten