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Thread: 1920 Harley Model F

  1. #141
    Join Date
    Sep 2005
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    Sarasota, Florida
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    4,157

    Default

    I'll be following your progress, John. Some people love a mystery; me, I hate a mystery when it comes to motorcycle engines
    Eric Smith
    AMCA #886

  2. #142
    Join Date
    Dec 2015
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    Blighty
    Posts
    272

    Default Re: 1920 "F" Project

    Quote Originally Posted by exeric View Post
    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 havenít 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

  3. #143
    Join Date
    Dec 2015
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    Blighty
    Posts
    272

    Default 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

  4. #144
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    4,276

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    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.
    Attached Images Attached Images
    Last edited by T. Cotten; 10-01-2016 at 03:42 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  5. #145
    Join Date
    Dec 2015
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    Blighty
    Posts
    272

    Default Re: 1920 "F" Project

    Quote Originally Posted by T. Cotten View Post
    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?

  6. #146
    Join Date
    Aug 2013
    Location
    1 mile east of the Rocky Mountains.
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    870

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    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."
    Last edited by Steve Swan; 10-01-2016 at 08:58 PM. Reason: addtn'l text

  7. #147
    Join Date
    Dec 2015
    Location
    Blighty
    Posts
    272

    Default Re: 1920 "F" Project

    Quote Originally Posted by Steve Swan View Post
    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

  8. #148
    Join Date
    Jun 2015
    Posts
    265

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

    Mike Love
    AMCA 19097

  9. #149
    Join Date
    Dec 2015
    Location
    Blighty
    Posts
    272

    Default 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
    Last edited by TechNoir; 10-09-2016 at 09:46 AM. Reason: Typo

  10. #150
    Join Date
    Dec 2015
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    Blighty
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    272

    Default 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

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