Fouling plugs

[dave51fl]

Hi Guys,

I was wondering if anyone could help me with the following problem. I’ve just finished putting my Pan together and been out for a couple of runs and I can’t seem to get anymore than about 50 miles out of it before the plugs foul.

The low idle jet is set properly, the float level is set properly, and the fixed high speed jet has number 17 stamped on it which is correct as per Palmers book. Regardless of how far down I screw the fixed jet trimmer the bike runs exactly the same.

Any help would be much appreciated.

Thanks

Dave

[panhead]

Have you used new plugs?

[Cotten]

First, let us check out all of the possible things it could be that are not carburetion:

Are you by any chance running resistor plugs or wires with a conventional points ignition?

Timing and valve adjustment have been double-checked dead-on?

Is the battery keeping a charge?

And of course, a manifold pressuretest is mandatory, or you might just chase your tail. Better snoop the headgaskets and plugs while you are at it.

After those considerations:
Are both plugs exactly the same?
Can you see fouling? Does it extend deep into the insulator?
Do they appear wet or dry? If wet, do they dry out quickly under a heatlamp or hotair gun, or stay greasy?

If they are not oiled, and all of the above conditions are inspected, then we can address the carb.

...Cotten

[keys55]

I was wondering what brand of plugs you use. I was wondering if any of the members had a favorite, through trial and error.I know they are all not created equal. [copper, copper plus, platinum,splitfire, u groove, fine wire, etc.]

[caschnd1]

I simply use plain old Autolite plugs. Nothing fancy. No split electrodes, no platinum. Replace them every year or about 10,000 miles.

-Craig

[Tricky]

On the needle assembly there is the needle, spring, adjuster screw and screw to keep it all together. I once made the mistake of fitting the spring over the needle, rather than behind the needle....this meant the needle was never close to its correct position. Amazingly it ran, and gave the symptoms you talk of.....just a thought.

[dave51fl]

Hi All,

Thanks for your quick response. I'll try and answer the questions as I go.

Panhead & Keys55 - I've put several new sets of plugs in and all different brands.

Cotten - I have a repro coil on the bike and I'm using the leads that came with the. I've checked these with my local harley expert and he thinks they are OK. His website if your interested is http://www.hddev.com.au

I will double check the timing but it seems OK.

Its a brand new battery with a rebuilt generator and that seems to be OK.

I will double check the manifold.

Both plugs are the same and it seems to extend down into the insulator.

When you take them out they appear damp but dry out very quickly when out of the bike. Once dry if you wipe them with a cloth they clean up.

Doing some more research last night it says early 51's had a #17 jet and later 51's had a #19. Would this make a huge difference?

I didn't mention in my first post that it starts well; idles well and goes well. Until we get to 50 miles and then it starts missing and it ends in tear.

Thanks again gents.

Dave

[jellero]

you didn't mention where you are, like elevation? i am at 7,000' and had a #19 (#45 drill size, .082"). i could get 50-60 miles before fouling out. i worked my way down by taking out main jet, soldering it and re-drilling four times in steps, ending up with a drill size #54, .055". plug looks right, bike runs great. i used to get a black smoke when revving engine and pipes were black. i also bent float down 1/8" because the 1/4" figure is for a cork float and i have a brass float, much heavier. i also had the high speed trimmer all the way in, meaning too rich, can't be adjusted here. after re-jetting the final time, i took bike out and it wouldn't go over 30 mph until i backed out the trimmer and it took off just like twisting the throttle. j

[Sidecar]

"Until we get to 50 miles and then it starts missing and it ends in tear."

Your coil is bad !!!

I had two of these Repro coils do this EXACT SAME THING to me.
After the third one died I went to a round canister style one with no problems. Later I changed to electronic ignition and had to take the canister coil off and get a Dyna coil.

[jellero]

if the bike will even run one mile with the trimmer turned in all the way tells me it is jetted too rich. it isn't even using the high speed jet. plus the black gas fouled plugs... where do you live dave51?? j

[dave51fl]

Hi Jellero,

I live in Melbourne, Australia so i don't think altitude is an issue.

I think you're right that jetting is an issue so I'll replace the float and get a smaller jet and see what happens.

Cheers

Dave

[Cotten]

Dave!

What float are you running?
If it is an original and your fuel has not soaked it, it should be serviceable at book spec.
I used to weigh them, then place them under the hot sun or a heatlamp for a while, and then weigh them again. If there is no change, your float is fine.

(That's assumeing your fuels are not digestive like in the USA!)

Changing the jet is an option, but please only change one variable at a time.

By "Until we get to 50 miles and then it starts missing", do you mean 50 miles distance, or up to 50 MPH?



....Cotten

[jellero]

melbourne... got me there. do jets wear? get some numbered bits and measure it? i didn't find any jets available that were much leaner, that's why i filled & drilled mine. but like cotten said, you don't want to go too far at one time.
hey, maybe the high speed needle/seal is bent or worn letting fuel through?? have you pulled the needle? that would be an easy fix and make some sense. good luck, j

[stevo]

I was not told resistor plugs bad in points distributor panhead??
Oh Oh.

[dave51fl]

Hi Guys

Once again i really appreciate your help.

Cotten
The float is a brass float and I've left in petrol overnight and it hasn't sunk or sprung a leak so it seems OK.

Your suggestion of one variable at a time is a great idea and I'll start with the jet and see what happens.

The 50 miles is in distance and doesn't really seem to matter if its round town or highway work.

Jellero
Melbourne is the second largest city in Australia behind Sydney. That another good point you've mentioned which I'll investigate while the carbie is apart.

I've just stuck a picture of her on the site so you can have a look.

Cheers
Dave