1920 Harley Model F

[TechNoir]

A quick question, what pressure is recommended for testing the manifold?

John

[T. Cotten]

John!

14.7 is equal to absolute vacuum at sealevel at standard temperature and pressure, so if a cheap regulator reads 15, y'er there.

...Cotten

[TechNoir]

Re: 1920 "F" Project

John!

14.7 is equal to absolute vacuum at sealevel at standard temperature and pressure, so if a cheap regulator reads 15, y'er there.

...Cotten

Doh! Of course its obvious to go for 1 Bar.

Thanks.

John

[TechNoir]

Re: 1920 "F" Project

Hi folks. I leak tested my inlet manifold and found no leaks.

Then I tried starting the bike and continued to do so for the best part of an hour but with no luck.

I have a good spark.

The timing is right.

When I first got the bike complete it would start after 4 or 5 kicks but didn’t run very well once started.

Since then the only thing I have changed is the carburation so at the moment my money is on fuelling.

The 3 things I have adjusted (when the bike was running about 3 weeks ago) are:

1. Float height which is as per the manual.
2. Idle adjustment. The bike wouldn’t idle at all on a closed throttle the first few times I ran it and I found that the "low speed adjustment" screw was screwed right in. I wound it out 3 turns.
3. After warming the bike up I also adjusted the "Intermediate adjustment" to get it running better.

It started after about 10 kicks last night but today I have nothing after about 100 kicks. (I am knackered)

What are the recommended base settings? I have read somewhere that a starting point for the needle is 3 turns out. I have also determined a starting point for the needle on my carb by sucking on the bowl stem (following advice from Cotten on this forum).

I am off out on my Triumph now to have a think and once I get back I guess I need to go back to basics.

On the bright side my new float seems to be working OK.

John

[TechNoir]

Re: 1920 "F" Project

After doing some essential chores this morning I turned my attention to the H-D and made a new air valve.








After that I had intended to go through the bike and check the points, timing etc but I couldn’t resist having a go at starting it after finishing th air valve. On the second kick it fired and it started on the third kick so I didn’t bother checking the timing etc.


I took it for a 3 mile run to warm it up and it was running rough. It would only run on more than half throttle, anything less and it bogged down. When adjusting the needle valve adjusting knurl the bike runs best with it screwed down tight when the needle valve lift lever rests at the position where the cam strip is supported on its supporting casting.

With the knurl screwed down tight it runs better but the bike pops on the overrun.

The high speed adjustment is set in the middle.

Also the bike seems to start best with the air valve in the lowest position i.e. in the normal running position. There is minimal tension on the spring, I haven’t measured it yet but I have it adjusted so the the spring is just tight enough to keep the valve closed. If I loosen it any more the valve would be loose and would not be fully closed.

I didnt have time to do too much more today because I had other stuff to do with my family but I will have some more time tomorrow to try to get it running better.

On the plus side at least I can start it now.

John

[exeric]

I'll be following your progress, John. Some people love a mystery; me, I hate a mystery when it comes to motorcycle engines

[TechNoir]

Re: 1920 "F" Project

I'll be following your progress, John. Some people love a mystery; me, I hate a mystery when it comes to motorcycle engines

Ha ha, that made me smile Eric. I agree, I would rather not have a mystery when it comes to engines.

The air valve has made a massive difference to starting it so thats one thing sorted out. I will set it up as per Tommo's and Cotten's advice to get the right spring tension although at the moment I suspect that it is close enough.

Before I wound the "Intermediate adjustment" knurl right down it was running exactly like a later carburettor (with removable jets) would run with a way too big main jet in it.

The popping on the overrun could be a few things, timing, mixture, exhaust leaks (I have a poor seal on the rear cylinder exhaust fitting so that might be it). Now that it goes I can run it and see where it leads but I am not expecting it to be too hard to sort out. (Lets hope that by saying that I haven’t jinxed it!)

Its pouring with rain now (08:00 in the UK) but its forecast to be fine later on so it looks like an afternoon job for today.

John

[TechNoir]

Re: 1920 "F" Project

Back to Basics.

When I rebuilt my Triumph motor a couple of weeks ago I was reminded that I have been meaning to get a Magneto Timing Light so i ordered one which didnrt come in time to time my Triumph but now that I have it I figured I could use it to check the timing on the ZEV mag on the HD.

I have a couple of questions. First question is what points gap is recommended? The manual says 0.020" and I have also read on here that 0.015" is the gap to go for. Which one is it or does it matter? I have always erred on the high side with points gap so my instinct says 0.020". They were set at 0.015" when I got the bike which I left them at. What does the collective wisdom on here think?

Second question is am I right with the timing at 3/8" BTDC fully advanced?



Also I had a look at the build report from 1989. The carb rebuild did not mention the needle so I pulled the needle and had a look.

There are a couple of ridges on the tip. You can feel them better than see them but I have tried to show them in the picture below. I guess it is best to replace it. Where is the best source of these needles? Also I have read somewhere that different lengths are available, is this correct?






John

[T. Cotten]

Well John,

You can take a chance on paying for a modern one-size-fitz-none needle,...
Or you can just stone-dress what you have.

....Cotten
PS: I charge five minutes, but only with a complete overhaul.

[TechNoir]

Re: 1920 "F" Project

Well John,

You can take a chance on paying for a modern one-size-fitz-none needle,...
Or you can just stone-dress what you have.

....Cotten
PS: I charge five minutes, but only with a complete overhaul.

Thanks Cotten, the answer now seems obvious, I need to stone dress my original.

John.

PS. Does anyone else have any advice on points gap and timing setting?

[Steve Swan]

I don't have the btdc settings at my immediate disposal, but they can be readily found under "Files" at jd yahoo groups. Once you are in "Files," you will see "Timing."

[TechNoir]

Re: 1920 "F" Project

I don't have the btdc settings at my immediate disposal, but they can be readily found under "Files" at jd yahoo groups. Once you are in "Files," you will see "Timing."

Thanks Steve, I have asked to join the group so once they have accepted me I will be able to see the files.

John

[ihrescue]

Hi Steve - FYI I sent you a PM with a question about carbs. Thanks

Mike Love
AMCA 19097

[TechNoir]

Re: 1920 "F" Project

Back to basics has improved things.

The timing was out due to 2 factors 1, I had forgotten that the mag pinion was keyed to the shaft so it was impossible to get the timing right with the key. I had left it where it was when I checked it many months ago before the motor went in the frame. I have removed the key and timed it 3/8 Inch BTDC (which is also 32 degrees BTDC) at full advance.

Secondly I am not sure if the advance/retard mechanism has been returning the mag back to fully advanced when I turned the grip. I have made some adjustments but I am still not 100% happy. I think it will be one of those jobs that seems minor but will take ages to get right. One for a winter evening I think, until then it is easy enough to push the rod connected to the bell crank down by hand to make sure it is fully advanced.

Also I have honed the carb needle and it has made a noticeable difference to the throttle action. The bike responds much more smoothly than before.

I took it for a ride around the block to warm up and have been trying to make some adjustments. I still have 2 issues. First I cant get it to idle at a closed throttle. It will idle reasonably OK at a slightly open throttle but if I close it it stalls. I started with the slow running air screw at 3 turns out as per the manual and opening to 6 turns has only made a slight impact and it still stalls. I have adjusted both the air screw and throttle cam screw but still cant get it to idle. I will persevere but I need to sort out the second issue first

This other issue is that it is burning a lot of oil and also spitting out a lot of unburned oil. I am using 50 weight non detergent oil that is correct for these old engines. There is oil in the exhaust and the plugs are fouling and there is loads oil smoke.

I have been told on here 5 ounces (US ounces) of oil is required. By trial an error I have established that 4 pumps = 5 ounces. However the HD manual says 2 pumps is what is required (page 37 at the end of the instructions for flushing the motor with kerosene).

If that is the case then am I putting double the amount needed in?

I have read on here that two and a half pump fulls is needed and I have also read on here that 3 is needed. I am looking for advice because I have just drained the motor and have drained exactly 5 ounces. If 5 ounces is 100% correct then I guess I will need to pull the jugs but I dont want to if I don’t need to because I am putting double the amount needed in.

Thanks,

John

[TechNoir]

Re: 1920 "F" Project

OK, I now know why its been so oily.

Currently the bike looks like this:



And the engine was here:



Before I took the jug off I took a picture of this. Is this correct? There are spacers under the cylinder and the nuts dont go all the way onto the studs.



I had hoped that the rings were stuck, unfortunately that was not the case, here is the reason that that it burns oil.










Ther corrosion is old and so are the score marks. If the engine has been kept in a house as a display item then it was like this when it was assembled in 1989 and was a result of decades of being in a leaking shed.

Looking back at the build report (post #67) there is no mention of a re-bore or even honing them but it does say new rings.

I assume that these can be re-bored?

I guess my first port of call will be Steve Slocombe as he is here in the UK.

Any ideas as the the best place to get oversize pistons?

John