1920 Harley Model F

[TechNoir]

Note that its not a simple washer but a proper seat that the last spring coil fits into.







After ages fettling it, refitting it and then making more adjustments, I got it to fit OK






However, I still couldn't get the shaft to fit all the way into the case. Even when I got the spring fitting OK I couldn't get it fitting correctly. Also, when the spring gets pre-tensioned it makes it worse.




After some head scratching I noted that the original spring has 9 coils and the wire measures ~ 0.118" diameter. The new spring has 9.5 coils and the wire measures ~ 0.130" diameter. 9 x 0.118" = 1.062" and 9.5 x 0.130" = 1.235". So the new spring is 0.173" bigger than the old one with all coils touching. I mentioned above that pre-tensioning the spring makes things worse, this is due to the pre-tensioning increasing the number of coils. The extra half a coil on the new spring also means adding an additional half a turn of pre-tension to the spring which also add to the problem.







I decided to remove half a coil and if that doesn't work, remove another full coil.





Success! After removing just the first half coil.






After that it was a simple matter of reassembly.



Next I need to get it running. Last time it started and then quickly stopped and refused to start again. My first port of call is ignition timing, it has all the signs of having slipped. I am pretty certain that the mag is good After that, if it still wont go, its back to carburation.

Of course I will need fuel so I will have to time getting some to a visit to the supermarket for food due to the current travel restrictions.

John

[Steve Swan]

John how nice to see your thread return to life! Fitting these old bikes back together is one thing after another, that's what makes these old machines so charming and let's uss appreciate them more than we could ever have imagined! Hope to hear more once you have your timing reset!

[pan620]

Thank you, very nice pictures and text.

[TechNoir]

Thanks for the comments Steve & Pan. Hopefully I can make some progress on a few things whilst we are all confined to barracks.

Being a desk jockey, I am able to work from home so I will be busy weekdays which fortunately also means we have some cash coming in. I feel for those folks who have been laid off on reduced or no pay.


John

[exeric]

So good to see your post, John. I knew you would sort out your return spring issue. I think it is so beautiful to see a machine made 100 years ago, gently, and lovingly brought back to life. It's even better to see an old friend back on this forum.

[pisten-bully]

Next I need to get it running. Last time it started and then quickly stopped and refused to start again. My first port of call is ignition timing, it has all the signs of having slipped. I am pretty certain that the mag is good After that, if it still wont go, its back to carburation.

Go John, and thanks for posting the pictures along with your progress!

[TechNoir]

Thanks to eric and Pisten Bully for your comments.

Earlier today I checked the timing and I am sure that it has not moved. However to be sure I reset it again.



Then I put some fuel in the tank and some oil in the crankcases and tried starting it. On the second kick it tried to fire, after that nothing except that after about 10 more kicks I noticed fuel dripping slowly from the carb.

So it was off with the carburettor. First it conected a remote fuel supply to check the float valve. With 32" of pressure all was well, no leaks.





So I decided to strip it right down and check everything. Last time I just tinkered with it although I did make a new butterfly because the old "new" one was sticking.

In doing so I have learned something, don't screw AND solder the butterfly in. Do one or the other but not both. The old butterfly had been screwed in but when I replaced the screws they didn't hold very well so I soldered the butterfly as per the original. However I also left the screws in as if I removed them I would have had two gaping holes. Now that I need to remove the butterfly its a nightmare. I couldn't get enough heat in to free the screws so after a long time messing around I very carefully drilled them out and was then able to un-solder the rest of the butterfly. However, doing this destroyed the butterfly and shaft (which isn't an original one based on the 1988 build report).



I have some suitable brass so will make a replacement shaft and butterfly. I seem to remember eric mentioning that when he made one of these shafts it was a pita so i shall see how I go. One issue is that I don't have a suitable slitting saw for the slot so i have ordered one which will be here in a few days so I wont be able to finish it until that arrives (unless anyone has any suggestions as to how to cut a 0.050" slot in a brass rod without one?)

John

[exeric]

The fixture I made to generate the angle for the throttle disk was based on a fixture that Tom Cotten posted. It was an elegant idea and he deserves the credit for it. I'm still looking for the fixture I made to put the slot in the throttle shaft. I need to do that again so I better find it

[T. Cotten]

My cage got rattled, Folks... (thanks, I guess,..)

Setting up a 'remote fuel supply' soaked up a lot of my expensive R&D time over the years.
It was valuable for forensic float level studies, no doubt.
But pointless for floatvalve testing. Just flip it upside down, and suck on it.

Cutting angled throttle discs requires a simple lathe mandrel, with screws in the right place.
(Beware that if you hone the body precisely with a torque-plate as if installed, and then cut a disc to precisely fit that bore, you may need to put the torque-plate back on to precisely install the disc! Particularly with 1 1/2" Model M's.)

....Cotten
PS: I learned of the mandrel from a local with better instincts than mine: Bert Sweat, the creator of 'The Sweatster": a Cushman Sportsman(?) chassis with a 'Vulcan' (or whatever B&S) motor. Wish I had a pic....
He was into Powell's, too.
PPS: I'd show my shaft slitting fixture, John,... But its "proprietary". Some of it I fashioned three and a half decades past. Expect some challenges! (The trick is to keep it simple.)
PPPS: Don't look now, but HX throttlediscs weren't that fat. Honest.

[TechNoir]

eric and Tom, thanks for the input.

Last time I did this you mentioned the mandrel to cut he angle which I did. Having done this once before I will be making a MKII mandrel with some minor changes to my last one.

Tom, thanks for the tip on the torque plate, I will use one.

This morning I will put everything in an ultrasonic cleaner and then make a start on the new parts.

The butterfly that came with the carb was about 0.050" thick, are you saying that they should be thinner than that? I have a few different thicknesses of brass so I could go thinner.

I have some ideas on slitting the shaft, I agree, as with most things, its best to keep it simple. eric, I would be interested to see your set up although no rush. (Any clues on why you need to do another? Does it involve the Merkel?)

Once the slitting saw arrives I will update you on progress.

Thanks, John.

[T. Cotten]

The original discs were ~.032", John!

A torque-plate really doesn't do anything for an HX, as the throttle is so far from the manifold, but it does make for a great handle while honing.

(Sometimes I type more than necessary...)

You lost me at 'the Merkel', but I always need to make another tool.

....Cotten

[TechNoir]

Hi Tom, thanks for the info on the disc thickness. I have a 1.0mm slitting saw on its way which is approx 0.039" so it wont be too far off.

I dont have a hone but fortunatly the 1988 build included boring the carb true and it is not too bad so I dont need to hone it.

The Merkel comment was for eric, I was wondering why he needs to fix another old carb.

Today I made a new shaft with the exception of boring the pin hole and cutting the slot. I also started making a new mandrel to cut the disc at a 12 degree angle. It all took longer than it should because I had to unpack and find numerous items of tooling that I had packed away last September.

Once the slitting saw arrives I will be able to make some more progress.

John

[T. Cotten]

You will want brass sheet to match, John!

I bought my saw and brass from MSC Industrial, but their brass varies occasionally.

Ten degrees aims best over the idle screw. Twelve could very well work, with patience to fit the notch with a jewelers' file and ink.
(Just like fitting a friction disc.)

Why would you bore the pin hole? That's the very very last operation, after assembly, and even Schebler aimed different every time.
(I used the original hole through the cam for a guide, drilling from both sides until they met.)

....Cotten
PS:

... I was wondering why he needs to fix another old carb...

I'm asking myself that a lot lately.

[TechNoir]

You will want brass sheet to match, John!

I have some. I have 1.0mm and 1.5mm so I ordered 1.0mm and 1.5mm saws.

Ten degrees aims best over the idle screw. Twelve could very well work, with patience to fit the notch with a jewelers' file and ink.
(Just like fitting a friction disc.)

I could easily adjust for 10 degrees.

Why would you bore the pin hole? That's the very very last operation, after assembly, and even Schebler aimed different every time.
(I used the original hole through the cam for a guide, drilling from both sides until they met.)

Thats exactly why I didn't bore it yet. I had assumed that it was the last thing to do after getting everything else right and then, as you say, use the hole in the cam as the guide.

Once again, many thanks for your help and advice.

John

[T. Cotten]

There are times I wish 'metric' was more available here, John!

(Recently I finished a Yale Scheb that had a 14mm bore.)

So,... How do you plan to cut the notch to fall perfectly upon the idle screw?

....Cotten