Carb adjustment question

[Lipdog]

On the thread on Wet sumping, the conversation wandered to carb adjustment, so I thought it would be good to start a new thread.

My initial question on the carb was: I just went to baseline the carb adjustments and was surprised what I found. The low-speed screw was only 7/8 of a turn open from seated. The high-speed screw was 1-7/8 turns open from seated. The baseline adjustments mentioned in the book are 4 and 1-1/2 turns, respectively. So the low-speed is set far leaner than the baseline, yet the plugs still fouled at idle. Has anyone seen adjustments this far away from the baseline?

Cotten replied:

Lipdog!

Please make certain that your LS needle is 3.5" long, the spring in the knob is on top of the needle, and the lift spring collar is in place with the flat side down.

I send M344s out set at three and a half turns on the LS, and one and a half on the HS, but that assumes a sealed manifold assembly.

....Cotten

I think everything checked out ok. Attached below are photos of both the high and low speed needles. The spring loaded ball on the LS side moves nicely too, and it looks like it was rebuilt and cleaned carefully in general.

Given it seems to be fouling the (Autolite 303) plugs while idling (the bike is not registered/on the road yet) for 10 minutes, and the LS screw is only 7/8 of a turn out, do you recommend I start over at 3.5 turns for the LS and 1.5 turns for the HS, or would that just give me a richer idle and foul the plugs more?

Thanks!

[duffeycycles]

All carbs need to be adjusted for the motor.
You need to read the part after initial adjustments & do those adjustments.TWICE!!!
There is no setting that fits all motors & carbs.

[T. Cotten]

I'd first measure the 303s for resistance, Lipdog.

....Cotten

[duffeycycles]

303 is resistor copper core
Starklite calls for their Indian script = NGK B7HS or Champion J6..non resistor plugs
I hate Autolite plugs

[T. Cotten]

303 is resistor copper core
Starklite calls for their Indian script = NGK B7HS or Champion J6..non resistor plugs
I hate Autolite plugs

I just hate resistor plugs, Duffey!

Or at least all of my coils do...

...Cotten
PS: Lipdog!
Lots of 'rebuilt and cleaned' carbs crossed my benches (back when I was accepting new accounts).
The 'professional' "rebuilds" often weren't.
Please inspect the gallery plugs, as one ebay hero was selling kits with set screws, allowing both fuel and air to the wrong places.

[Lipdog]

I have a box of NOS J6 plugs so I will swap them in. I will also check to see if there is a wet sump condition and check for manifold leaks. I am thinking I should start from the benchmark that Cotton recommends (3.5 turns out LS/1.5 turns out HS) and work from there.

Cotton: I looked on a number of diagrams (like this one: https://www.jerrygreersengineering.c...y=1952&m=Chief) and can't find parts called the gallery plugs. Is there another name and are they on this diagram?

Thanks!

[T. Cotten]

They're just "plugs", Lipdog,

#1 on Greer's list, Indian OEM 102420

They plug galleries, and your M344 would have four.

I'd post a pic of the crappy kit with set screws and other issues, but the vendor isn't here to defend himself.

....Cotten
PS: Wow, mine just went up a buck, thanks!

[pisten-bully]

I just hate resistor plugs, Duffey!

Or at least all of my coils

Whoa... 303 Autolite plugs work well in my Chief...don’t go bad mouthin’ my plug choice!

In spite of two of the most knowledgeable vintage bike guys you’re likely to ever hear from, and they may be right, Lipdog...I’m thinking you just need to be patient. Slap a plate on that Chief and ride it under load for a while...see what’s up. You can chase problems all day long but without actually running the road, under load at more than an idle, I don’t think you’ll ever get an accurate picture what you’ve got going. Don’t go chasing a problem until you find out that you DO have a problem.

[Lipdog]

Yeah, I get your point about chasing problems. But I don't think this carb is right. I swapped in the J6's, drained the excess oil from the sump, and got it started (for the first time, hot as well as cold). When I turned the LS needle in all the way, the bike still ran ok. Revving it a bit and checking the HS needle, it didn't seem to have much of an effect. And it fouled the plugs after a few minutes (see photo). I pulled the carb and will check the manifold for leaks this weekend, just to be sure.

IMG_0366.jpg
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IMG_0370.jpg

[Steve Slocombe]

And don't forget to check the length of both high and low speed needles, as various types are out there and small differences have a big effect.

[T. Cotten]

Whoa... 303 Autolite plugs work well in my Chief...don’t go bad mouthin’ my plug choice!

Good for you, Harry!

What kind of coil/ignition are you running?

...Cotten

Yeah, I get your point about chasing problems. But I don't think this carb is right. I swapped in the J6's, drained the excess oil from the sump, and got it started (for the first time, hot as well as cold). When I turned the LS needle in all the way, the bike still ran ok. Revving it a bit and checking the HS needle, it didn't seem to have much of an effect. And it fouled the plugs after a few minutes (see photo). I pulled the carb and will check the manifold for leaks this weekend, just to be sure.

Measure the LS needle length out of the knob, Jeff,..

The 1/4"-40 threads means a lot of turns to make up any shortening at all. And they do get dressed, of course.
(Here's one from the ebay hero sold as new. I've got a pic of one of his new HS that's knicked, too.)

....Cotten
PS: Can't tell much from your assembled pics, but face it, an M344 ain't finished if it ain't black..

[Lipdog]

The LS is 3-3/8" long, and the HS is 2-2/4" long, measured from the bottom of the thread, as shown in the pix.

If I were to start by replacing some parts on the carb to get it in range, where would you start? I was thinking at a minimum I'd replace both needles with new ones, and gaskets.

[T. Cotten]

The LS is 3-3/8" long, and the HS is 2-2/4" long, measured from the bottom of the thread, as shown in the pix.

If I were to start by replacing some parts on the carb to get it in range, where would you start? I was thinking at a minimum I'd replace both needles with new ones, and gaskets.

Since the LS is our immediate concern, Jeff,..

Please remove the screw, lock, and spring, to measure the needle's length from the bottom of its spring "head".
I have found great variance in the 'fossil record'. Graciously they are adjustable.

Rarely did I ever retail a new needle (Got plenty!)
Throwing parts at it doesn't help if the new stuff needs re-worked anyway.

First patient observation and inspection: Take it all the way apart and let the gremlins out.
Any stone unturned gives you another tail chase.

Looking forward to the bubble-test..

....Cotten
PS: Every turn on the knob is .025".
So the difference between three and a half turns and seven-eighths is just over a sixteenth of an inch.
Look for grinder marks.

Or hope like Hell nobody took a drill bit to your LS seat. I can't help much then... sorry...

PPS: "Within range?"...
Are you just getting it ready to sell?

[Lipdog]

I rigged up a pretty basic rubber stopper with am air fitting threaded in, greased it with Super Lube, and held it firmly in place while I pressurized the intake manifold to about 12 PSI with the bike on the compression stroke. I then sprayed soapy water on the manifold nuts. I couldn't see any bubbling at all, and the pressure bled down *very* slowly, maybe a few PSI per minute. This could have been through the cylinders or through my rig, but everything seemed very tight. Does this seem ok?

Next I measured the LS and HS needles. The LS needle is 3.43" from the seating surface at the top to the tip. The HS needle is 2.75" from the bottom of the screw threads to the tip. I also photographed what the HS seat looks like with the needle 3.5 turns out, and what the nozzle looks like.

The low speed lifter washer/spacer is brass and seemed to be in the correct way.

Does anything stand out here? What would you check next?

IMG_0376.jpg

IMG_0378.jpg

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IMG_0381.jpg

[T. Cotten]

Its not about "bleed down", Jeff!

Its about pressure differential, and that's why a constant, regulated supply is essential to make bubbles.
The gap between the valve stem and guide alone is an order of magnitude larger than the holes we are looking for, and frankly, it isn't that easy to get both intakes shut on some Chiefs.

So we know your LS needle is 2.8 turns of the knob shorter than it should be.
(Nice Schebler/early HD Linkert screw on top! Worth a dozen 'correct' ones. Both knobs are pre-'48... and that looks like a shorter detente spring.)
If it was adjustable at all, its probably not the cause of fouling.

Unless completely shut, the HS needle does not affect idle mixture at all.

It might be just the pic, but the nozzle spigot looks short.
It should reach just shy of the middle of the bore.
Even that shouldn't cause fouling, by itself.

I see you have a correct gallery plug, but the bowlstem looks crusty to me. Please completely disassemble, and inspect the idle bleeds for obstruction, and clean with a .008" feeler gauge narrowed to a sixteenth of an inch or so.

And please don't forget the bowl assembly is a "circuit" of its own.

...Cotten
PS: If its got throttledisc wear anything like my second pic bottom right, its always going to be difficult.