Building a 1981 Yamaha YZ465 Factory Replica...

Discussion in '2 smokers' started by FJ_Kevin, Mar 11, 2012.

  1. FJ_Kevin

    FJ_Kevin Been here awhile

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    Thanks! I am going to look into it.

    -Kevin
  2. mudmantra

    mudmantra Been here awhile

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    I have a decompression valve on my YZ465G and YZ490J. Well worth it. I'm putting together a IT465J and I'll put a decomp valve on it too. On all three bikes, I had to rebuild or replace the kick starter parts. Now they'll last a lot longer. Picture of the yz490 with decompression valve. And yes, it makes bump starting much easier. [​IMG]
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  3. wfopete

    wfopete Suffer Fools; Gladly!

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    Yup, cut the fin and you're in.
  4. Michael N.

    Michael N. Adventurer

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    What valve do you use for this mod?
    Which brand and model?

    Thank you, Michael
  5. mxbundy

    mxbundy Long timer

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    kevin,

    That shock you have labeled as a 85 is a 86 one. The 84 and 85 shocks will interchange with the exception of the bass linkage which is no big deal as the bass system is a waste of time and should be disabled anyway. The attached pi is of an 85...



    Bundy
    csteel93_1.jpg



  6. FJ_Kevin

    FJ_Kevin Been here awhile

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    Thanks for chiming in and filling in the gaps on this point... we'll update the knowledge base!
  7. mudmantra

    mudmantra Been here awhile

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    This is the valve I'll use on the IT465 motor I'm building now. Pretty sure it's the same as the one in my YZ490.
    [​IMG]
  8. Andr32

    Andr32 n00b

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    Hello! I knew it would come to this conversation.

  9. mudmantra

    mudmantra Been here awhile

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    If you lose your kick starter, you can bump start. YZ465G, with a decomp valve, bored 86.5, so over 481cc's and 14/48 sprockets. Try that without a decompression valve in the dirt, and it's just going to skid to a stop.

  10. Michael N.

    Michael N. Adventurer

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    Fiiinally it´s here!
    :)

    Just got my new Moto3 Helmet from Bell, at least we can ride a modern standard Helmet with vintage look to match our bikes and apparel.
    Fits good, the old classic Moto3 look is maintained and the overall processing is nice.

    Attached Files:

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  11. ozadvntr

    ozadvntr Planning that trip, again

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    Got mine as well last Thursday in Australia. I desperately wanted a Blue one as I did in 1980 but got a white one as I did in 1980. I like how the MOTO III is sublamintated not a decal like the original and it is so much lighter than the original.
  12. spdtrpl

    spdtrpl Red Coat MagnoliaTx

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    When riding today 5th gear turned into another neutral, before I dissassemble it does anyone have any suggestions of what has gone wrong?
    As it's going to have to come apart, are there any changes I should make to improve the gearbox?
  13. wfopete

    wfopete Suffer Fools; Gladly!

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    The rest of the gears ok? Could be several things. Something as EZ as a shift drum pin that you could fix without splitting the cases or something as complicated as a shift fork or broken gear engagement dogs (unlikely). Start with pulling the clutch side cover and checking the shift shaft paw that activates the shift cam/drum for a broken return spring, segment plate missing or loose parts. If all that seems in order I'm afraid it is time to split the cases.
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  14. FJ_Kevin

    FJ_Kevin Been here awhile

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    Ok, I know, I know.... I have been very distracted by all this euro crap and have completely neglected this thread and updates on the 83 YZ490 build.

    Let's see if we can rectify the situation somewhat today. First off, I am happy to say, this bike is finished. I think the tuning is about right on and can say the bike really flies.

    But it sure did take a lot to get there, as it always does. There are many things I like about it and a few things that I don't and we will get to that soon enough.

    But 1st, here are a few photos of the finished product.

    [​IMG]

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    As a reminder, this one has a 510cc IT490 motor and IT490 pipe. These motors have a heavier crank and hook up well. They have good bottom end grunt and I find them to be very fast but still very controllable.

    The jetting is exactly the same as I am running in the blue IT and posted some pages back. The bike starts well, often 1 kick so long as I am perched up high enough (using a milk crate or stand) so I can give it a good spin.

    I had an initially problem with slipping clutch even though the plates I used were in spec. This was fixed once I put in new plates and HD clutch springs. It would not lift the front wheel as fast as big blue as power was lost in the clutch.

    I am using a clutch extender to make up for the HD clutch springs. Also using magura levers as they do not flex like the cheap stuff and so give me a nice firm front brake.

    The forks are believed to be off an 84 YZ490. The wheel hubs are powder coated black, spokes are stainless and rims are Excel. It is a nice wheelset.

    The side panels are from DC, I like the DC side panels and use them on my other bikes. The fenders are from Yamaha.

    The silencer is an FMF turbo core II as used on the IT and YZ465 bikes. I like this part too. It took some fitting but has worked out well, sounds good, like it means business!

    I rode it a bit last fall but no too much due to the clutch slipping. I finally fixed it sometime in December and then put it away. I pulled it out again about two weeks ago... big thrill around the farmadilla test track after clutch fix.

    It's fast. And feels much lighter than the IT as it should. The tank is slimmer than the IT as you would expect but also slimmer than the YZ465 tank. I like that. Handling seems very good as does stability, of course I need to ride it more.

    OK, so what's not to like?

    One thing that bothers me is the seat/tank junction and the rise of the tank as you move forward. It seems like front of the saddle is too low for me, I am not sure.

    I like the flat saddle and tank of the YZ465 (same with the CR250 Husky) better but I suppose I will adjust after some more time on it.

    Other bikes of the era, with these safety seats, like the 81 and later Husky, Maico, etc, also seem to have this characteristic, so I guess the 490 is not alone here.

    So there you have it... my very rare YZ490 GP Winning H Mikkola Replica!

    [​IMG]

    [​IMG]

    More to come!

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  15. wfopete

    wfopete Suffer Fools; Gladly!

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    Very Nice!

    farmadilla; lol. :thumbup
  16. FJ_Kevin

    FJ_Kevin Been here awhile

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    Thanks Pete... I am suppose to be working on my taxes today but, haha, well you know!
  17. ozadvntr

    ozadvntr Planning that trip, again

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    Here are a few pictures from Classic Dirt 12 held in Queensland Australia last June.

    Was privileged to have Broc Glover ride my 1984 YZ490L and I also won best MX bike at the show and shine with my 1979 YZ400F.

    Heiki Mikhola was also at CD and rode the legends Lap with Broc

    [​IMG]

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    That's my IT250G in the background and I also had a YZ250F on show.
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  18. ozadvntr

    ozadvntr Planning that trip, again

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    Here are a few more. Including my 1979 YZ250 and 1981 YZ465. Broc rode the 465 on the Sunday as the 490 cracked DG chamber.

    [​IMG]

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    [​IMG]
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  19. wfopete

    wfopete Suffer Fools; Gladly!

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    Whoa! More nice work! Congrats.

    I always wondered how Broc and Jeff Staton would have done if they had got thier hands on the factory water cooled, aluminum framed YZ500s. It gotta be a bummer to race those air hammer bikes when Yamaha had some really great stuff accoss the pond.
  20. JCool

    JCool Long timer

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    You mean Rex Staten or Jeff Stanton ?