Linkert MR-4 A

[T. Cotten]

A hot air gun,heat the carb up a bit usually helps.Doesn't take much heat...no torch!Same with the little plugs.

I always torch out frozen plugs, Duffey!

But its a special torch.

....Cotten

[duffeycycles]

Cotton,If I said use a torch I could see a potential problem with some of the group!

[T. Cotten]

Cotton,If I said use a torch I could see a potential problem with some of the group!

Divas and trolls, Duffey!

....Cotten

[41craig]

I'll try to remove the nozzle this afternoon.
Robbie; A pic would be great and thanks for the info.
Cotten; Thanks for your pics and info. I'll have to look through my junk and misc. boxes and see if I have a plug like that.
Duffey; Thanks for your help.

Craig

[41craig]

Well, after about 3 1/2 hours and a lot of *#@^!#^! language. It's time to leave it alone until tomorrow. I've tried Mapp Gas, and a cable ( the soldered end came off the cable ). I got it to move even with the throat of the carb., but that is as far as I can get it now. The bore that the nozzle tube comes up through is about the the same I.D. as the O.D. of the nozzle tube. Unlike regular Linkerts. I looked to see if I had a junk nozzle that I could cut the top off of and use it as a guide to pull it out with. I'll have to check my carb. collection to see if one of those have a junk nozzle that I can use.

Craig

[T. Cotten]

Can you imagine doing this for a living, Craig?

The nozzle 'tube' (I call it a spigot) depends upon a sweet fit to its hole in the venturi, or the body, if it seats in a blind 'well' in the casting like a bombsight model.

(I make seals..)

GX models are much, much worse to deal with.
Its scary with any model when it makes loud snapping sounds under torque.
That's actually good, except when its the puller that snapped, again.

....Cotten

[41craig]

Success !! I finally got it out !! The pictures included show the nozzle in between a Side Valve and a late Big Twin OHV nozzle. The spigot is obviously tweaked. Probably the reason for the troublesome removal.
Kitabel; The I.D. measurements are approximately 1 11/32 at the nozzle hole. 1 15/16 at the air cleaner end. And 1 9/16 at the manifold end.
CraigCIMG1172.JPGCIMG1173.jpg

[kitabel]

Thanks, the venturi is larger than the -41.
The nozzle doesn't look like the ones I've seen, which are beveled all the way up on the sides.

[T. Cotten]

I'm way out of my zodiac here, Folks,..

But a couple of observations:

A 32nd of an inch might make for a little more highspeed flow, but from my experience, that's within one-off tolerances of the blueprint, especially if your digital lathe control is emery on your index digit.
(The best way to measure a venturi is to drop it on a pool cue, mark the spigot hole with a marker, and then put a caliper on it. Common OEMs vary, as any potmetal part will...)

The M53 series nozzle was short like that, but as Kitabel notes, 'square' like the M74B, and a couple more holes.
(My photo collection has one nozzle labeled "MR-4" that matches the M53, for what that's worth.)
Craig's appears to be another link in the evolution.
(It doesn't appear to have an eighth" whacked off the spigot as the blueprint suggests.)

I don't think the wear at the base of the spigot was a 'tweak', Craig!
Usually that's from a potmetal venturi that shrank and rattled upon it.
Does the nozzle well in the body go all the way through to the bore at the same diameter, or is it shouldered at the top?

....Cotten

[41craig]

Cotten; It is shouldered at the top. I have included a pic of the MR-4A with an M-61 to compare lengths. Also a pic of my Vernier Caliper laying on the M-61 with the depth part of it shoved in the bottom of the MR-4A to show where the shoulder starts.
CraigCIMG1174.JPGCIMG1176.JPG

[T. Cotten]

I expected the body to capture the nozzle instead of the venturi, Craig,

(Your air correction hole appears to point downward into the body, instead of straight in like common models.)

But the caliper pic confuses me a little;
A standard 1 1/2" model is 2 3/8" deep, so yours has a .065" shoulder?

A sixteenth makes sense I guess,
Who has literature about similar M53 series to tell us about gaskets, both upon the nozzle and bowl?
And what was the float setting for M53s?

3/16"?

...Cotten
PS: Thanks in advance as always....

[41craig]

Cotten; Tomorrow I will get a better look inside. Also, I noticed from the beginning that ( rubbing your finger inside the carb. bore ) there seems to be a negligible lip, close to the nozzle hole. That you can feel, coming from the manifold side. It's almost like, instead of an aluminum venturi, it has a brass venturi that goes from the nozzle to the air cleaner end.
Craig

[Rubone]

This is an MR3, MR4 and M53 for size comparison. As for M53 float height, I have an NOS M53A1 with the float bowl on it s shipped from H-D. I'll check it for grins.