Spark plugs color

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May 18, 2026 | 01:42 AM

marcelm

Thread Starter

Cruiser

Joined: Aug 2015

Posts: 190

Likes: 31

From: Arad, Romania

Spark plugs color

Hello,

My bike is a Softail from '87. Bike starts well (kickstart) and runs well also. Only the spark plugs, in my opinion are a bit white, with some deposits on them, think I run a bit lean.

> Carb is Keihin CV, (could be the original one). I run jets 48/180, needle raised 3 mm (1/8 inch) mixture screw 2,5 turns out,
> Air filter is open, foam under the steel mesh,
> Exhausts with some baffles inside,
> Stock heads.

See pics.
Thinking to raise a bit more the needle. What is your opinion?

Thanks
BR
Marcel

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May 18, 2026 | 06:00 AM

Rains2much

Grand HDF Member

Joined: Sep 2022

Posts: 4,417

Likes: 3,823

From: Florida

I think you’re running too hot of a plug. A tad lean, some mild detonation or pre-ignition.

Run a cooler plug, gap right at spec.

Last edited by Rains2much; May 18, 2026 at 06:03 AM.

May 18, 2026 | 06:04 PM

t150vej

HDF Community Team

Joined: Dec 2005

Posts: 5,402

Likes: 2,605

From: NC USA

With 2, .020 shims and a 48 low jet, the only way those plugs are that clean - an extreme intake leak.

Don't tell me you checked it, There is no way to check for an intake leak on an engine with a short manifold and basically no vacuum at or near idle.

May 18, 2026 | 06:18 PM

John Harper

HDF Community Team

Joined: Dec 2011

Posts: 8,550

Likes: 3,975

From: San Diego, CA

+1 on intake leak.

John

May 19, 2026 | 01:55 AM

marcelm

Thread Starter

Cruiser

Joined: Aug 2015

Posts: 190

Likes: 31

From: Arad, Romania

Quote:

Originally Posted by t150vej

There is no way to check for an intake leak on an engine with a short manifold and basically no vacuum at or near idle.

What do you mean by that? It is the stock manifold, between carb and heads.

Last edited by marcelm; May 19, 2026 at 01:57 AM.

May 19, 2026 | 06:05 AM

Rains2much

Grand HDF Member

Joined: Sep 2022

Posts: 4,417

Likes: 3,823

From: Florida

Quote:

Originally Posted by marcelm

What do you mean by that? It is the stock manifold, between carb and heads.

yeah, he’s suggesting for the plugs to be that clean it has an air intake leak. That’s common with shovels and does happen with EVO’s. That could be. I just assumed these were pretty new plugs that you ran a few miles and then removed to look at. I say pre-ignition because your white porcelain has little brown, grey specs all around. Too me that’s classic pre-ignition. That’s tiny little bits of your piston metal getting on the white base. I also see the ridge right around the top of the white porcelain that has a faint ring sunken in. That’s usually heat range of the plug. We actually could both be right. If you do have and fix the leak it may cure all those symptoms.

‘’He’s also more versed in your carburetor. He’s saying the way you have it jetted it should not be lean.. rich if anything… so that’s another indicator that you have a vacuum leak that’s pulling in a lot of air to your air/fuel ratio.

Last edited by Rains2much; May 19, 2026 at 06:09 AM.