View Full Version : Small hole right side of linkert? Plug or not?

06-28-2005, 09:25 PM
What is the small hole on right side of my linkert for? Vaccume lock? Is that an over flow hole? What's it for? What if I plug it? What would that do?

Perry Ruiter
07-01-2005, 02:08 AM
I thought Cotten would jump in on this one. I'm no carb expert, but as I understand it that's the main nozzle vent. The nozzle can be externally vented (hole outside as you have) or internally vented (notch cut into bottom of venturi). Harley was one way and Indian the other. If you mix up the bodies and venturis you're hosed, either no venting or double venting (too much of a good thing). So ... given you have an externally vented body, make sure your venturi isn't internally vented. If it is, either change out the venturi for the correct type, or plug the hole ... Perry

T. Cotten
07-02-2005, 10:28 PM
Gimme a break,.. my evil server's been down!

Paul, I thought you had an Indian. They had no nozzle vent in the body, so please let us know which model we are speaking of, and exactly which hole, as there might be as many as three if it is a Harley model.

At any rate, none should be plugged with a proper assembly. And I even doubt that running both a vented venturi and a vented body would make an appreciable difference. And since most venturies have shrank to allow air around them, a carb with neither vent might still run!

07-04-2005, 02:04 AM
Ahhhh.... thanks for info.

Linkert M641. I'm going to leave it alone and see how the bike runs. If it runs.

T. Cotten
07-04-2005, 09:01 AM
Your M641 should vent through a slot on the bottom side of the venturi, and not through the side of the carb.

The only hole that I can think of would be indeed be the bowl vent or "overflow" as indicated in the attachment, although I don't have an M641 in my hands.

(It appears that previewing the post eliminated the attachment, and the edit function doesn't offer the option to add one.)

07-04-2005, 09:33 AM
Sorry if this isnt the place for my question, Would you be able to help me find a good carb 441 for my 41 Four??? I have a bad one have tried everything to fix it and now need to find one! THANKS Carbman!

T. Cotten
07-04-2005, 10:28 AM
I don't wheel and deal carbs outright (yet), although I make 'marriages' occasionally.

In the meantime, nearly any 1" model can be made to service.

Now I can try this attachment again.....

07-05-2005, 01:27 AM
Yes - that's the hole I was refering to. The "bowl vent hole". Now I know what it's for. What happens if I plug it?

T. Cotten
07-05-2005, 07:13 AM
The bowl won't fill.

10-03-2005, 10:02 PM
okay, i have a m74 on a knuckle and when i am priming the motor, and the choke is closed gas blows out the venturi vent.
could this mean i have the wrong venturi in th carb???

i had never had this happen before and this post is in perfect time for it!!!


other than that the carb seem to work fine, and it only does it when the choke is fully shut.

T. Cotten
10-04-2005, 07:44 AM

I doubt that you have the wrong venturi,... but you may very well have it installed backwards.

More than a few have arrived at my shop like that which have been reported to run "fine".

Linkerts are very forgiving.

10-04-2005, 03:08 PM
could that make it shoot gas out like that???


im gonna check that this afternoon!


10-07-2005, 01:17 PM
While we are on the subject of this overflow vent, maybe someone can offer some advise on my problem. My '42 knuck has a consistent problem, ever since it was put together last year, with gas pouring out of the overflow. The carb has been completely redone. It cut up big-time in Wauseon (late July), and my buddy replaced my foam float with a brass float, hoping that was the problem (though the foam float appeared fine). That seemed to solve the problem, as it did not do it again there. The bike sat until Jefferson (October 1st), and when I started it up there, presto, gas out the overflow! I bought an NOS needle & seat and hope this will cure it, but it is a shot in the dark. Trash in the gas does not seem to be the issue (100% restored orig. fuel ystem). Does it hot or cold, but not consistently. Sometimes, when I crank it with the gas off, then turn the gas on once it is running, it will be okay but not always. Any ideas?
Thanks - Lonnie :confused:

T. Cotten
10-07-2005, 08:06 PM

Even the best of floatvalves will seep over a matter of time if the petcock is not "positive".

If, however, your problem shows itself quite quickly, then a very likely culprit to suspect would be the brass boatanchor float, which certainly weighs at at least three or four times as much as an original.

Thus, to operate anywhere close, it must be set very deep in the bowl. Otherwise it allows the fuel level to rise to a flood.
Even when set to 3/8" or more when necessary, it will rob you of reserve volume for accelleration, and gas mileage as well, but should service for a 'parade machine'.

Nobody really cares about gas mileage anymore,....right??

If you desire better, post me direct, lest I spam the forum.

10-10-2005, 07:11 PM
we got the carb figured out for the most part, but it still blows gas out the venturi vent when the choke is closed....

oh yeah, the bike is my buddy nelson's, he bought durable float for this carb in davenport from you

we got it pretty well dialed...

should we sorry about the gas blowin out then???

T. Cotten
10-10-2005, 10:51 PM
Sorry? Aside from $3 a gallon, the major concern is the fire hazard.

Which way is the venturi aimed?
(The tight part should be to the front.)

Assuming it is in correctly, the next aspect to consider is daylight around the venturi. (See attachment, note arrow).
Venturies were made of potmetal, which is a liquid like window glass, and slowly shrinking, moving, and crystallizing over the decades. The airgap plays havok with tuning as well.

The solution is to swage and machine it back to a pressfit.

10-10-2005, 11:53 PM
cool, that makes sense...

its weird, i have done tons of these carbs, mostly m74 b's and neverhad this as a problem...

but damn, does this knick start easy!!!!


10-11-2005, 07:40 AM
Thanks for thiis nice little tip just when I thought I was tooooo old to learn anything of great value...... this comes along ! ;)

T. Cotten
10-11-2005, 08:54 AM

We are all learning, and I learn more and more about how little I know about Linkerts (and Schebs) daily.

(Anyone who says they are "simple" carbs is just as mistaken as those who insist they need an accellerator pump.)

If there are any true experts out there, then someone please explain for me:

Is the transition from the idle circuit to the highspeed circuit instantaneous once the proper RPM is reached, or is there an RPM where the fuel is entirely metered by the highspeed but not enough to completely pull air backwards through the idle circuit? Or does it gurgle back from the idle spring collar first?
Is there a state where no air is drawn at all, yet nothing is purging from the idle bleeds?

And why do I find different heights of spring collars with no mention in the literature? (Or is there?)

And why are there "tit"s upon the idle bleed well cap and rear gallery plugs on some models?

Thanks in advance for any clues!

10-11-2005, 05:38 PM
I don't know a thing.

I feel you would see some over lapping.

I don't feel the idle circuit would ever contain air. Vaccume.

2 cents. and by the way- great tech photo Cotton!

T. Cotten
10-11-2005, 09:10 PM
At moderate speeds (~35 mph on an HD 45" for example), the idle circuit completely reverses itself to draw air from the idle bleed holes all the way back down to the bowlstem, and then into the nozzle well to emusify the highspeed circuit.

(Reference: The '43 Armored School handbook)

There is nothing simple about Linkert and Schebler carbs. They are very forgiving, but quite enigmatic.

10-11-2005, 10:02 PM
What the heck did ya'll bring me into this for? "I ain't did nuthin !!"

T. Cotten
10-11-2005, 10:22 PM

Sorry, I shoulda typed INLINE4NUT

Too many Wigwam fans and nuts among us, myself included.

None the less, nobody was getting shot at.

I was only begging for some guidance when I wrote:
>If there are any true experts out there, then someone please explain for me <

Somebody's got to know how these thing work. They weren't designed by aliens, but it seems like nothing short of a glass carburetor will make it all clear to me!

10-11-2005, 10:34 PM
emusify? How about "mix". Mr. fancy words.... Your as bad as some writers.

I did not know that. Humm.... I can visualize that. Makes sense. And your initial multiple question is very good. In my mind _I see the importance of ensuring the idle circuit is clear. Cause and effect. Thanks.

you could tap a verticle vaccume line!

Hopefully someone will speak up for some insight here.

I need to tune my hi-speed. Any tips?

T. Cotten
10-12-2005, 07:49 AM
At the risk of sounding pedantic,
there is a very important difference between a mixture and an emulsion.

Observe how tap water will slowly develop airbubbles upon the side of a glass after sitting for some time. This is air that was dissolved and slowly coming out of solution. It was a mixture. Air dissolved in gasoline does little to help its atomization for combustion in a motor.
Add a drop of detergent to the water and shake it up, and an emulsion forms, where the tiny bubbles of air do not mix with the water, but in effect separate the water, thus increasing its total surface area thousands of times. When this happens to fuel within a carburetor, it allows for the rapid vaporization that is critical to a internal combustion engine.

"Never use a big word when a diminuative one will do."....Ridnick Wysdom

10-12-2005, 08:22 AM
Exactaully the word I was looking for to disribe this threade. Enouff of the hole in the side of the carby....


10-12-2005, 04:49 PM
Your slurring yer werds a little there Louie! It looks as though you may have found the truck load of beer! Now we just need to find a drive-in for the Fastest Indian movie!!!!!