1920 Harley Model F

[TechNoir]

Thanks for the picture, interesting. There is nothing like that in the parts book so I assume its an aftermarket part.

First thing tomorrow I will have a quick game of darts.

John

[Steve Swan]

as always, following this conversation to learn what i can, otherwise i'll stay out. looking at my 22-26 factory parts book on the carb support, the book calls for pm 1110-25 "manifold support" to fit "1925-26 twins (fits earlier models)"...... (i would suggest perhaps the pre-25 models did not have this support, but by 1925 the factory realized it was not a good idea to have the carb unsupported, hence the factory's mention, "fits earlier models").

Comp.D sells pn 1110-25 - https://www.competitiondist.com/prod...-61-74-1110-25

[T. Cotten]

My notes now show it is a DLX support, Folks,...

But it still aught'a fit!

(Or something like it.)

...Cotten
PS: Or get a bowlnut with a stud, and "farmer" a bracket down to the cases, somehow.

[Steve Swan]

oops.... thanks for catching that, Cotten!

[TechNoir]

Thanks Steve for that clarification on parts, my book only goes up to '21.

Checking CD's website they list one for $22. By the time it gets to me it will be about $75 with shipping and taxes. I will speak to them tomorrow.

John

[Steve Swan]

John, i just sent you email.

[T. Cotten]

... By the time it gets to me it will be about $75 with shipping and taxes...

*GASP!*

Let's make sure it will fit with an HX first!

.....Cotten
PS: Sure enough, as I now see on the bench, the bowl of an HX is closer to the manifold flanges.

[TechNoir]

Thanks Cotton.

[T. Cotten]

Thanks Cotton.

You can stop thanking me for leading you in circles now, John!

...Cotten
PS: I didn't do it on purpose.

[TechNoir]

Hi folks and Happy Christmas to all.

For various reasons too long to explain here I have only recently got back to sorting this bike out, suffice it to say that I have been preoccupied with other issues.

Since the last installement I retraced my steps with regard to the air side of things to make sure all was well. The carb had previously been bored out by someone else and I carefully measured it and found it to be approx 0.0005" out of round. Also, following some comments about air leaks elsewhere, I had some small doubts about my new shaft with the seperate washer.

So I made another new shaft, this time as one piece. I have also honed the bore to make it round, it is now good to within 0.0001" and I then made another new disc and then fitted everything. Again.

With the carb refitted this made no difference whatsoever.

However at this point I was now certain that they are not the problem so at least that is progress in that they are now ruled out.

My attention then turned to the cam mechanism.

For those reading this who are not familiar with these Schebler carbs here are some pictures showing the cam mechanism.


Build 420.jpg


Build 418.jpgBuild 419.jpgBuild 421.jpg


Previously I was commencing with the low speed cam adjustment screw in roughly the middle of the adjustment and making quarter turn adjustments. However even with the cam adjustment screw wound out as far as it would go, the carb was only slightly less bad. I haven't said "better" because it was still bad, just less bad.


John

[TechNoir]

Looking at the cam strip and wheel closer I was sure that they could be contributing to the issues. The wheel is not exactly round and so resembled a very mild cam as it turned and the cam strip did not have uniform wear on it either. The movement of the needle from fully closed to fully open is very small and so even small variances in the cam and wheel seemed to me that they could affect the rocker adversely and in turn the needle.

So I ordered some 0.025" stainless steel shim stock to make the cam strip and milled it to the correct width. (the existing cam strip turned out to be copper but stainless is a good replacement because it wont corrode)

Then I needed to remove the old cam strip. Cotton has previously stated that this is difficult so I approached it carefully. I held the cam assembly in a small Engineers clamp which in turn I held in the vice. I sharpened a very small cold chisel, the blade is only about 3/16" wide, and I carefully used it to loosen the peened over metal that holds the cam in position. Without much trouble at all the cam strip freed up and I was able to slide it out.


Build 422.jpg



Build 423.jpg


Build 424.jpg

Build 425.jpg


John

[TechNoir]

Next job was to make a jig so I could bend the new cam strip into the right shape.


Build 426.jpg


Reassembly was the reverse procedure and was pretty straightforward.

I have read somewhere else that an alternative to the cam wheel is a fixed PTFE wheel. I don't know if its a good long term solution but I figure that using a fixed wheel would eliminate any wobble or irregularity in a proper wheel so it would be a good starting point to test the new cam strip. So I made a PTFE wheel and screwed that on.


Build 427.jpg


All of this made absolutely no difference to the carb no matter how I tried adjusting it.

John

[T. Cotten]

The cam strips were beryllium spring alloy, John!

Hard brass works, so I'm sure stainless could too, but I would fear the wheel would just slip, instead of roll.
(Some later models just had a little Micarta finger that was intended to slip.)

With the carb in hand and the bowl removed, first make certain that at idle position, the needle can fully shut the seat, by sucking upon the nozzle tube where it is soldered and ground away on the bowlstem. Then, as you back the needle out a turn or so, you should sense if you are drawing fuel to run, and then open the throttle gradually for a feel of how the cam is proportionally opening the needle further for higher speeds.

Fine-tuning the screws on either end of the cam (some have none, and some have two and no dial) is something I've never had the opportunity to play with.

Happy Holidays!

....Cotten
PS: Is that where you have the bowl indexed when running?

[ihrescue]

Good to see you are back and working on the old bike again. You may recall I did a summary article on your build thread for the AMCA Newsletter with the intent to entice interest in the member bike build threads and the forum. It was the first of a few articles I wrote to send in the Welcome email I send to new forum members. I feel if we can get people interested in one of these threads and all the side projects, problem solving and helpful solutions that fellow members offer then they can see one of the many values of the AMCA Community Forum.

Good luck and progress

Mike Love

[TechNoir]

Hi Cotton, thanks, as always, for your input. My original cam strip has been plated and only a bit of metal is showing which is why I mistook it for copper.

I did the sucking on the stem thing numerous times to get the idle position and have adjusted both ends of the strip dozens of times. I want to ride this bike a bit so I am making an alternative arrangement for now, see my next post.

Hi Mike, thanks for the comments.

John