Linkert Carburetor Service

[Peter Cooke]

I hope this one appears,

Got it now thanks.

[T. Cotten]

Pics can be deceiving, Duke,

Even when focused.

Although it gives the impression it was a pretty recent 'rebuild','
the only things I can be certain of is the Starklite float and -50 floatvalve.

Even if everything else was in order, the boatanchor float would be enough to curiously varnish-foul as shown.
(But I see no #13 stamping; Was the throttledisc installed backwards?)

....Cotten

[dukekleman]

Cotten,

The throttle disc was installed correctly.

The treat to me was how clean the entire carburetor was in general.

Witness marks of previous service were very minimal, especially for the vintage year. No damaged threads, no repaired threads, no body distortion, broken flange surfaces, modified fuel circuits, modified calibration, etc...

It's the nicest carburetor of its era I've personally been blessed to come across in my 39 years of service on Harley Davidsons.

Duke Kleman

[dukekleman]

Cotten,

Screenshot_20251228-103157.png
I've circled the #13 Disc ID you asked about in post #17.
If you zoom in on post #14 you can see it pretty clear, better than the circled image above

Not sure if this helps,

Duke Kleman

[T. Cotten]

I'll have to take your word for it, Duke,



There's something like a 1, but its not centered between the screws (ignore the Schebler on top):



Virtually all assemblies need a fresh refit anyway;
Is there a "keyway" worn at the top, or bottom?



That is often a good gauge of borewear, and the gap that would be left with even a perfect NOS disc.
(Beware that the ordnance-packed examples were often as much as .002" undersized!)

....Cotten

[dukekleman]

No, there is virtually no wear.
When I look through my otoscope for better inspection, there is a light sign of the start of one, maybe 0.020" off the edge of the bore hole for the throttle shaft.
It's nothing I'm going to consider addressing.

Other than the fact it has really low mileage for a 1937, I contribute the fact of little to no wear from the throttle shaft springs low tension.
The tension is noticably lighter than normal which reduces upward pressure and bore/disc wear.

Duke Kleman

[T. Cotten]

No, there is virtually no wear.
When I look through my otoscope for better inspection, there is a light sign of the start of one, maybe 0.020" off the edge of the bore hole for the throttle shaft.
It's nothing I'm going to consider addressing.

Other than the fact it has really low mileage for a 1937, I contribute the fact of little to no wear from the throttle shaft springs low tension.
The tension is noticably lighter than normal which reduces upward pressure and bore/disc wear.

Duke Kleman

How will you really know until the final assembly, Duke?

Have you inspected it for daylight with fresh bushings installed, shaft, and disc, while torqued to a stressplate as if installed to a manifold?

If your customer won't want to pay your time and trouble to get it perfect,
I understand completely!

....Cotten
PS: The only OEM throttleshaft spring I am aware of is the spiral friction spring, which should not put any wear thrust on the shaft at all. (The springy control cables contributed greatly, however!)

Please note the the vertical travel limiting bearing faces are the bottom collar of the shaft, and the bottom bushing, which was very durable Monel. Borewear is predominately a result of side-travel, which requires sloppy bushings, or control cable stress..)

(Well, I guess there were these BECK springs, but I never saw one!)

[dukekleman]

Cotten,

I have developed a process and sequence in which I check for bind and distortion. Using the OEM manifold that will be used in service, surface flatness corrections and a torque sequence value. It works well for me and has given me the results I'm looking for.

On the subject of the spring and throttle shaft. It is correct that the lower collar stops vertical travel. It is important to also note that the job performance of the spring is to maintain the home position of the shaft. Much like a valve spring returning the valve to its seat, the throttle shaft spring maintains lower throttle shaft collar contact as items wear.
My point was that a spring with greater rate wears things out quick over time. This pulls the throttle disc upward (doing it's intended job) and wears the bore of the carburetor. Similar to high valve spring rates causing faster valve wear and tulip valve distortion... This carburetor has a lighter rate spring than I normally see which I was contributing to less wear along with the low mileage for a 1937 era carburetor.

I wish aftermarket throttle shafts were more consistent. I see to many variations in machining of them. This includes measurements taken throughout the shaft. This issue causes me more problems than dealing with bushing alignment, distortion and bind.

Hope this helps understand my statements,

Duke Kleman

[T. Cotten]

My simple inspection, Duke,

Was to arbitrarily lathe-cut or grind all manifold and carb flanges flat, because they almost never are.

1¼" Models clean up last at the gallery hole:

flangcut.jpg

Your example certainly has a shiny flange and may have been serviced, but one overtorqued assembly is all it takes to stress it again. (1½" Models are much worse; I warn against going over ten foot pounds upon a 5/16"-18 fastener, seven on ¼"-24.)

Bronze DLXs didn't use the spiral spring, and they suffered the same borewear;
My contention is that you should not get borewear until there is bushing/shaft wear.

...Cotten

[dukekleman]

Cotten,

One thing to note on the bore wear is it's location. The location of the wear is always consistent in its throttle
disc position/opening degrees.

We see the same general position/area of wear on all carburetors that used a throttle disc as well as EFI throttle bodies cable and DBW operated.

There is a great amount of velocity/force at that throttle position location. The vacuum is very high and creating a lot of force on the throttle disc and shaft!
Broken throttle shafts on certain throttle bodies are not uncommon in the Harley Davidson world. More noted on bigger cubic inch engines with small millimeter throttle bodies.
This is very easy to monitor in the EFI data world however the same exact thing is occurring in the carburetor engine as well...

My point is that you will always note the wear of the bore in a similar area where this scenario is occurring.

Hope this helps,

Duke Kleman

[T. Cotten]

I just honed them clean and be done with it, Duke.

If I found a cause I cured it; Never found a broken shaft, and only one 'body', and that was the customer's impact wrench's fault:

JWCRACK.jpg

JWCARBF.jpg

He abused two fresh rebuilds, and then wondered why they ran bad:
JWPLUME.jpg

...Cotten
PS: I know what you mean when you say its hard to find quality shafts; These were American-made!:

popshft.JPG

EASTSHFT.jpg
The slots are so wide, they flex and bind inside the bushings when the screws are tightened.

[dukekleman]

Cotten,

We are on the same page and it's frustrating at times dealing with things and trying to come up with solutions.
It's stressful/frustrating at times when you actually care... striving for the best results verse just getting it out the door.

Duke Kleman

[T. Cotten]

Cotten,

We are on the same page and it's frustrating at times dealing with things and trying to come up with solutions.
It's stressful/frustrating at times when you actually care... striving for the best results verse just getting it out the door.

Duke Kleman

If you think Linkerts are frustrating, Duke,

Don't go near an HX Schebler.

Back to overtorque distortions,... ... ..

Three-bolt flanges are easily resurfaced, but really bad four-bolt models must be straightened first:

FLNGDSTX.jpg


FLNGDST3.jpg

Can't bubble-test for this leak...

FLNGPLUM.jpg

A puck and steel rod are needed to keep the bushings aligned,

flngprs3.JPG

This is NOT in a hydraulic press!

FLNGPRSS.jpg

.....Cotten

[dukekleman]

Cotten,

Some of the Linkerts need a lot of attention from years of operation and dis-service.
Explaining the bill to fix these can be just a challenging at certain times.

[T. Cotten]

Cotten,

Some of the Linkerts need a lot of attention from years of operation and dis-service.
Explaining the bill to fix these can be just a challenging at certain times.

Particularly since a ""rebuilt"" cobble can be picked up on ebay for less than it takes to fix one right, Duke!

.....Cotten
PS: Just for thread continuity,
Since machining the flanges takes costly set-up time, and inevitably removes more stock than desirable, I found it more efficient to grind both flanges (and even intake flanges), by hand.

But I had the advantage of several "Polish Mills".
(It stays in one place, and you 'run around it'.

POLSHMIL.jpg

(The white small stone is used to dress the larger blue ones; The one beneath the wood tabletop is a 42" Cincinnati Milacron, and I have a pink one, too.)