Forde's 1980 Honda H100

Discussion in '2 smokers' started by Forde, Jul 24, 2013.

  1. Forde

    Forde Been here awhile

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    Well,

    Got this wee honey on sunday. 1980 H100A. Needs some work but overall a nice wee bike! Has oil injection, the fuel tank is cool its a split tank with part of it for the 2T oil instead of a seperate 2T tank somewhere else.

    Ive already removed the gross indicators and reflectors, hope to start the real work this week.


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    Bike was only running with choke on, so removed carb last night for a look.

    Pilot jet was mangled, blocked and corroded in place. Managed to get it removed but it is too wrecked to see the number and google is proving fruitless.

    Can anyone shed some light on the pilot jet size or have a H100 of their own that they can check so i can get my jet ordered and get this thing running again?

    Would really appreciate some help

    Thanks for lookin!
    #1
  2. Duck_Pilot

    Duck_Pilot Retired Roadracer

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    #2
  3. Forde

    Forde Been here awhile

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    Thanks man, I found a guy on my local forum who also has a h100 but his is the s version. He checked his and it was a 42 so I ordered a keihin 42 one on ebay but it is a bit different looking and the hole in it is clearly bigger than my old one. Going to give it a go anyway.

    I see the link you have posted is also for the s which is actually the next model of h100 my a model is only from 80 to 83. Carb is the same keihin pf25a though so should work.
    #3
  4. Duck_Pilot

    Duck_Pilot Retired Roadracer

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    Yer welcome. Finding specifications on US-destined models is a breeze, but different rules for different countries overseas makes the search a lot tougher for the models you guys get. Best to look for a factory service manual, and pay the going rate for it...... saves a lotta wasted time later on.
    #4
  5. Forde

    Forde Been here awhile

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    Hi mate, i do not know what models you guys got, but the H100A was from 80-83, then from 83 on was the H100s, and after that the H100SJ.

    I have purchased a haynes manual covering the H100A specifically, it does not list pilot jet size lol.
    However, the carb is listed as the Keihin PF25a which is what is on my bike and also what is on the H100S. A guy on my local forum has a H100S and checked his manual and bike for me. His bike had a 42 and his manual stated 42, however i have bought a 42 and it seems bigger. I think the S just used a bigger one than the A as it is the same carb? The S used some other different engine bits too.

    Im about to post my next update with more info.

    Thanks for your reply!
    #5
  6. Forde

    Forde Been here awhile

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    So first thing to sort is the bike only ran with either the choke or throttle on so there was something up with pilot circuit.



    Removed tank and carb, going to clean the tank.



    Touched up various worn spots of paint on frame with black hammerite, will probably strip it and get frame blasted this or next winter but wanted to prevent it rusting.


    Ordered new pilot jet for the carb as it was blocked and also wrecked.



    Carb apparently is a Keihin PF25a. But it says PF18 on it, but apparently this is because it is a 18mm carb in spite of being called the PF25a. But carbs are usually named by size that they actually are. i.e. mikuni VM20 is 20mm, dellorto phbg17 is 17m, etc. So i thought it was called the PF18 but apparently not. I managed to get a early haynes that only covers the A model and it states PF25A as well but does not give pilot size.



    Can only find info online for the H100S but apparently it uses the same carb? Anyway H100S manual says a 42, and mike on nibikers has an S and checked and he had a 42.


    Hole in new jet noticeably bigger than old one. And threads in different place. But all online resources i read stated that all the carbs used the same pilot jets in different hole sizes but same fitting, and this jet was listed as a keihin PF jet (but not officially made by keihin, made by some other company to fit keihin). The threads appear to be the same pitch so it should screw in so going to give it a go. I should be able to adjust with the idle speed screw to compensate for bigger pilot shouldnt i?


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    Thats all for now!
    #6
  7. Forde

    Forde Been here awhile

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    Rebuilt the carb with the new jet and the wee bike is going perfect now. Now on to the rest of the to do list lol
    #7
  8. joexr

    joexr Banned

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    Isn't this basically the same as an MB10 ?
    #8
  9. Forde

    Forde Been here awhile

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    I'm not sure that we got the mb 100 in UK, people just put the engines from these into mb50 and called it that. That's why there are very few h100 left.

    We got the 50 and 80? I could be wrong on that.
    #9
  10. Forde

    Forde Been here awhile

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  11. Forde

    Forde Been here awhile

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    Removed forks as thought there was no oil in them as they were so bouncy.

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    This is all the oil from both fork legs.

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    Thinking about adding a new set of stanchions to my parts order, they are a bit rough. I think they would probably do ok but dont wanna go to trouble of replacing seals and oil and putting it all back together to find the stanchions are duff lol. Plus the bike is so clean i think it deserves it. they are 85 quid you wouldnt get the originals rechromed for that would ya?
    #11