1964 FLH Spark Plugs Fouling

[T. Cotten]

The service manual states to adjust the low speed needle out five full turns from lightly seated and that the motor will start but it will be rich. My recent experience doing this on a newly rebuilt 48EL is that five turns is WAY too rich and my plugs looked just like the ones in your photo. I discovered that about two turns instead of five did the trick. Of course this is just a starting point. If that fails then any of these other suggestions should be explored. Just my 2 cents . . .

I always figured, Gitguy,

They spec'd such a fat starting place because nobody knew how to find a vacuum leak.

My assemblies went out at 3.5 turns, expecting to be trimmed in even further, and received no pertinent complaints for decades.

...Cotten

[BigLakeBob]

Even with a proper float at proper level, Otis,..

It will overflow while sitting if the petcock leaks.

No floatvalve is absolute.

....Cotten

Are you saying if I stop my bike and don't close the petcock my carb will overflow? I don't experience that.

[T. Cotten]

Are you saying if I stop my bike and don't close the petcock my carb will overflow? I don't experience that.

Ain't you lucky, Bob!

The rest of us are victims of physics;

That's why petcocks were invented.

Floatvalves were designed to operate open.

...Cotten

[BigLakeBob]

I grind my needle tapers if needed then do a light lapping job, has worked well for me over the years. I couldn't imagine walking in a store for a few minutes and my carb overflowing.

[T. Cotten]

I grind my needle tapers if needed then do a light lapping job, has worked well for me over the years. I couldn't imagine walking in a store for a few minutes and my carb overflowing.

I stopped embedding abrasives in brass seats a quarter-century ago, Bob.

After inspection for obvious flaws, I usually just set the seat on a firm bench, placed the needle within it, and smacked it with a wooden screwdriver handle, and gave it the suck-test. Maybe twice. If three times failed, I sold it a new one. Schebs no problem.

Few minutes? Now you introduce the time factor?

...Cotten

[BigLakeBob]

Yea, I get it on the time factor, same with my job. Hobbies are different, time spent isn't time trying to make a living. I guess the seating the needle with a smack is like the oil pump ball seating. Thanks for all the tips.

[T. Cotten]

Yea, I get it on the time factor, same with my job. Hobbies are different, time spent isn't time trying to make a living. I guess the seating the needle with a smack is like the oil pump ball seating. Thanks for all the tips.

Its not about the job, Bob!

Its about spending too much time in the pub without worrying about it. I had no problem either.

Its about stinking up the garage over time, which means an OHV probably polluted its oil, and soaked its O-rings.

Petcocks are our friend when they work.

...Cotten

[Iacovos]

The service manual states to adjust the low speed needle out five full turns from lightly seated and that the motor will start but it will be rich. My recent experience doing this on a newly rebuilt 48EL is that five turns is WAY too rich and my plugs looked just like the ones in your photo. I discovered that about two turns instead of five did the trick. Of course this is just a starting point. If that fails then any of these other suggestions should be explored. Just my 2 cents . . .

Thanks Otis! I too believe that 5 turns is too much!

[dukekleman]

Lacovos,

Here's a guideline I'll share with you. It's in reference to the conversation regarding 5 turns on the low speed needle...

With all things working correctly, as engineered on the stock (as designed) motorcycle, your low speed needle should land at a final setting of 1 1/4 turns to a maximum of 2 1/2 turns when adjusted correctly at proper "operating temperature".

Any setting outside those boundaries indicates that you have an issue. That indication can be thought of like a check engine light of modern motorcycles, refered to as a malfunction indicator lamp today.

There are many things that drive the low speed calibration setting to be outside of its proper range. In an attempt to share this knowledge and keep things simple, please consider the range I stated above.

Hope this helps,
Duke Kleman

[Iacovos]

Lacovos,

Here's a guideline I'll share with you. It's in reference to the conversation regarding 5 turns on the low speed needle...

With all things working correctly, as engineered on the stock (as designed) motorcycle, your low speed needle should land at a final setting of 1 1/4 turns to a maximum of 2 1/2 turns when adjusted correctly at proper "operating temperature".

Any setting outside those boundaries indicates that you have an issue. That indication can be thought of like a check engine light of modern motorcycles, refered to as a malfunction indicator lamp today.

There are many things that drive the low speed calibration setting to be outside of its proper range. In an attempt to share this knowledge and keep things simple, please consider the range I stated above.

Hope this helps,
Duke Kleman

Hello Duke!

This is a great guideline!!

Will check asap and revert!

[Iacovos]

Ok back on to this.
The low speed needle was out 2 turns but spark plugs came out black
Trimmed back to 1.5. Bike starts ok but i suspect again its going to foul a plug. What else is to see? Or should i ride the bike and see ?

[T. Cotten]

Can we assume, Jack,

You have installed a proper float, and bubble-tested the manifold?

The carb can only be tuned while ridden; With cleaned plugs, and initial needle settings of three-quarters of a turn on the high speed, and three and a half on the low, the motor should start, and the low speed can be trimmed in for smooth idle.

The high speed needle on the M74 series is notoriously insensitive, as the fixed jet supplies ample fuel. (The needle was meant to be trimmed in for high altitudes....)
When engine is warm, the low speed can be fine-tuned, and the high speed can be tested for effect while cruising.

Although the needles 'over-lap' each other (leaning the low speed enrichens the high, and vice versa), the effect is not as dramatic as other models.

....Cotten

[Iacovos]

Can we assume, Jack,

You have installed a proper float, and bubble-tested the manifold?

The carb can only be tuned while ridden; With cleaned plugs, and initial needle settings of three-quarters of a turn on the high speed, and three and a half on the low, the motor should start, and the low speed can be trimmed in for smooth idle.

The high speed needle on the M74 series is notoriously insensitive, as the fixed jet supplies ample fuel. (The needle was meant to be trimmed in for high altitudes....)
When engine is warm, the low speed can be fine-tuned, and the high speed can be tested for effect while cruising.

Although the needles 'over-lap' each other (leaning the low speed enrichens the high, and vice versa), the effect is not as dramatic as other models.

....Cotten

Hello Cotten

Correct proper float and bubble test (also new manifold seals).
Proper float set up and observed operation prior to bolting to the body.

Just for my knowledge how can the float alter the amount of gas going into the body from bowl?

What i have noticed with two different motorcycles of the same year. Upon opening the throttle there was hesitation and from then things went downhill.

Could it be that the high speed needle to far open?

Another question: you say the carb is adjusted whilst running. But to properly access and trim the low speed needle you need to have the air filter backing plate removed

Thanks for the input

[T. Cotten]

...Just for my knowledge how can the float alter the amount of gas going into the body from bowl?

The way I understand it, Jack,

The float acts the same as a toilet, except it doesn't flush. Instead, the float maintains a 5/8" fuel level within the bowl that can then be metered and mixed with air by the nozzle. If the float does not maintain that level, it alters the mixture:

Floatcircuit.jpg
(Armored School Handbook)

What i have noticed with two different motorcycles of the same year. Upon opening the throttle there was hesitation and from then things went downhill.

Could it be that the high speed needle to far open?

Only if performance while cruising improves; Otherwise, leave it where it performs best.
A "hesitation" upon acceleration can have many causes, and it can also be the sum of several.
If all other things are in order, excessive borewear from the throttledisc extending as far as the idle bleed is a classic culprit,..

eyebrow.jpg

..as it disturbs the flow of air in and out of the bleeds, and muddies the transition from the low-speed idle circuit to the high speed power circuit.
(Even a 'blue-printed' carb must still have the idle speed faster than a 'lope' to avoid a 'flat spot'.)

Another question: you say the carb is adjusted whilst running. But to properly access and trim the low speed needle you need to have the air filter backing plate removed..

Certainly I had to take my glove off, but I never had a problem with a stock assembly.
(But that was pre-Dupuytren's..)

.....Cotten

[Iacovos]

Thanks Cotten
Will work on the bike and revert
have a great day
awesome book by the way