Linkert m74 idle control/throttle plate light leak

[CAP'N BOB]

Quite honestly, Tom, it all sounds scary to me, not being familiar with Linkert carburetors. Where do I get those intake check plates for the Linkert?

This one is an M74B, 1-1/2 Mod M, 2-418. Short of taking the venturi out and measuring it, I have no idea how to tell you, kitabel, if this is a 1-1/8" or a 1-5/16" venturi. Any recommendations for me on how to tell, would be appreciated. You said the venturi size does not relate to my problem, but it seems to me that it could since the venturi controls the air flow/pressure, right? If I cannot get it to idle properly, the throttle plate leaking air and the venturi being wrong for this carb (if it is) seems to me could/would all be connected.

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[kitabel]

Hard to tell from the picture, but that venturi looks small to me. There are only 2 that fit that body: 1-1/8" and 1-5/16". An M-74B should have the larger; the smaller is M-36A, M-61 for EL and FLE, not recommended for the M-74B main nozzle.
It's not related to your problem, but I'd find out what you have before you're done.

[T. Cotten]

A '47 would be a Knuck and a different animal, Bob,..

So let us assume you have ~'48 Pan heads where the "plumbers-style" inlet nipples have been replaced with probably COLONY O-ring conversion nipples. Thus you also have a '55 and later O-ring-style aftermarket manifold. It would be prudent to grind its flange, and replace the exhaust clamps with similar that have smaller #10 screw fasteners.

But please bubble-test the inlet replacements separately first, as they are notorious.

If that sounds scary, it should.

....Cotten
PS: Please also test thoroughly the welds, and pan cover screws over each port. And Good Luck!

[CAP'N BOB]

The intake is a complicating factor, Cotten, the heads have been modified, I believe. I have a 1947 FL, and this 1948 should have the same type of intake (I think they are called Plumber?). It does not, as you can see. I think someone, somewhere along the line "updated" these heads, and expect that is something the guy is going to have to live with, and I have to live with getting this bike on the road for him.

I do not have one of those leak testers. This being the first Linkert for me, I have never had the need to purchase those type of tools. I am not opposed to purchasing one, but wonder it if would be better to have a Linkert expert set this up, including the intake manifold, so that it is all proper.

Is there anyone out there you would recommend to me to get this carburetor and manifold rebuilt and set up? Do you do that? I do not really want to start grinding on it, not knowing much about the Linkert carbs. On my Knuck and Pan, I run S&S carbs, and understand them, but those are my bikes, neither of which is any way a restoration. He wants this to be more or less original, (a "rustoration").

Thank you for your help.

Bob

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[T. Cotten]

That's certainly enough daylight to be an issue, Cap'n!

Since it is at both top and bottom, I would suspect an 'eyebrow' of wear into the body like this:
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The remedy on the right is complicated, but frankly, there are many other things that can cause such grief, such as the manifold (which was unique for '48-'49).

Until you are certain that the manifold assembly is sound (tested as discussed at http://virtualindian.org/11techleaktest.html), no carburetor will perform properly.

.....Cotten
PS: Note also that your flange really needs a grind, and undoubtedly the manifold does as well.

[CAP'N BOB]

Good afternoon:

I am working on a 1948 FL for a customer. He brought the bike to me in multiple baskets, and I have been working to put it together for him. I have had it running and cannot control the idle on this M74 Linkert. I read a post from 2001 that discussed checking the throttle plate for light leaks if there was an idle control issue. The first attached photo is the throttle plate on this Linkert, and it certainly does leak light. I'm guessing that is the air leak but would like some help from someone who knows Linkert carburetors. Before this bike I have NO experience with Linkert carburetors.
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If that is the probable source of the problem with this Linkert M74, is the fix as simple as a new plate or do I need to have someone who knows what they are doing rebuild this carburetor? My guess is that it would be prudent to send this to someone who rebuilds Linkert carburetors and have it done right. This bike needs to run, properly.

A second issue is oil leak. When I had the bike running, oil leaked from the rocker boxes and even from the rear exhaust lifter lower tube. I read in the Restoration Manual that the 1948s were very bad for oil leaks, to the extent that Harley changed the oil pumps to fix the issue. So, I am going to put the oil leak issue out as a separate string. Just mention it here because until I had the bike running, I did not know there WAS an oil leak! :-)

Bob