Spark plugs

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fl9018
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'51 FL Bobber
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Spark plugs

#1

Post by fl9018 »

Why is the front cylinder black and sooty while the rear cylinder almost looks perfect? I just started a freshly rebuilt 84" stroker pan. Do I have an intake leak on the rear?

Help,

Frank
Spark plugs
Spark plugs
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Andygears
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Re: Spark plugs

#2

Post by Andygears »

As you stated, the rear looks great, but the front...could be a few things, rich carb, high float level or is it oil on there? How does it run? Smooth idle? Start hard? Are these plugs after a ride or just started? Did you choke it a lot when starting? Timing?

Stroker? What else is there? Valves? Cam? Internet tuning is hard without a lot of info and / or background.

My two cents

Andygears
fl9018
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Re: Spark plugs

#3

Post by fl9018 »

'51 panhead, fresh rebuild with S&S 512 cam(?), 84" sidewinder crank assembly and oil pump, CV carb, points ignition in an aftermarket auto advance timer, 12 volt conversion, O-ring intake manifold conversion, triple checked timing, Genuine James Viton O-rings and oh yeah...I left the enricher on, DOH! This is the first time I got it to run for any length of time. The first few times was for about thirty seconds then quit. Just long enough to see that there was oil pressure. It's been a hard starter during those times. I did bubble test the intake manifold and nipples. It did start a little easier today and it ran good but I didn't ride it yet. I was able to rev it up but I'm thinking I still have an intake leak on the rear head. If I left something out, please let me know.
fl9018
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Re: Spark plugs

#4

Post by fl9018 »

Well here's an update. Did the bubble test and couldn't find any. Cleaned off the sooty plug after dialing in the carb. It's closer to where it should be now. I changed spark plug wires, changed the plugs from front to rear, switched plug wires position in the coil. Overall the bike is back to being a one kick wonder but...the rear cylinder pops under acceleration and the plug is always wet. So now I think I may have a faulty head gasket according to the interweb. At least there is a little light at the end of this long tunnel.
Pascal
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Re: Spark plugs

#5

Post by Pascal »

I don't think so.
You exchanged plugs and leads rear to front, and the black sooted plug (although cleaned) now sits in your rear cilinder.
Could it just be a faulty plug, a cracked cap or a rotten lead?
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