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Japanese Import 650 Maxim, '81

Discussion in 'XJ Technical Chat' started by Minimutly, Feb 19, 2018.

  1. XJ550H

    XJ550H Well-Known Member Premium Member

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    could be a replacement motor
     
  2. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    The Maxim uses one single long bolt. The Seca uses two short bolts, since they also hold the footpegs in place.
     
  3. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Parts are cheaper than for most bikes of this era, and still cheaper to fix up than buying a new bike.
     
  4. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    This was covered earlier in the thread. JDM engines only had a 3 digit engine number stamped onto them.
     
  5. Minimutly

    Minimutly Active Member

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    The rh switch was from a 650 turbo. It has a four plus two plug, as well as the three. Looks like there is a spare yellow wire.
    The switch itself has a large rocker, a lights off po on, and there is the start button. I don't see many relays on this at all -two under the tank and thats it.
    I put a battery on it and spun it over today, turns over nice. Can't wait to unpack the carbs when they turn up - will the be 28s or 31s? Either way they're going on to start it up.
    Put a battery on it and spun it up today, sounds sweet.
     
    Last edited: Mar 13, 2018
  6. Minimutly

    Minimutly Active Member

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    My haynes manual doesn't cover jdm wiring, so again I'm floundering a bit. It does look like the p,off,on switch is instead of the light relay, but the lighting circuit is a bit convoluted, so we'll see how it works once I have the right switch. As for the switch, just bought a 600 switch, throttle, and cable. Between this and my existing one I'm fairly confident it will work.
     
  7. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Start a conversation with Yu Tanaka. He has been helpful in getting JDM manuals and documents.
     
  8. Minimutly

    Minimutly Active Member

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    Thanks again k-moe, I'll keep it in mind - the colour diagrams i have are pretty good, and once I set to with a meter and pencil it shouldn't take long to amend one of them. One thing I've seen is that the ignition switch connections have been butchered - bit of deja vu for me, my gt750 trike was not making sense for a while electrically, untill I sussed that the American import had been retrofitted with a UK ignition switch, and then butchered to make it "work". The kawasaki was a little more complex though.
     
  9. Minimutly

    Minimutly Active Member

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    Postman brought me two sets of mikunis today:)
    The tatty looking set externally open up, smell ok, and generally without looking inside seem the better pair.
    The cleaner looking set stink of varnished fuel, as do my hands, the kitchen where I opened the parcel, and soon my workshop will I guess.
    The big plus, and probably why my hands stink, is that they measure up at 31mm as close as I can measure without my vernier.
    Result then. Will make the best set up with any spares I need from the other, and buy new bits like float valves etc. I hope. With any luck soon get it running, then decide its fate. (In all honesty though, I think it will be saved - if you can call a flat seat cafe racer style thing saving it).
     
  10. a100man

    a100man Well-Known Member

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    Hmm not how teh Mikunis will work out. They were used only on the chain drive 550/600 models and not shafties from what I can gather. If they will align with the rubbers
    and fit snugly then you might get lucky. Otherwise I would look for a set of Hitachis from a Seca 650. BTW I thought Mikinus only cames as 28 (550) 30 (FZ600 and Radian) 32 (XJ600)..
    Cheers

    James
     
  11. Minimutly

    Minimutly Active Member

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    They were from a 600 xj, that's all I know. Why wouldn't they fit? I did say as close as I could measure them without using a vernier. And assuming they do line up, why would I carry on looking for Hitachis?
    Thanks
     
  12. a100man

    a100man Well-Known Member

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    I don't know for sure, give them a try and let us know. In fact I'd go for a trial fit before spending time stripping them down. If they're from an XJ600 then they'll be 32s.
     
  13. Simmy

    Simmy Active Member

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    I read this entire post, although the title clearly says 650 Maxim, are we sure that's what you have?
    If your bike is shaft drive then in most cases it will need Hitachi carbs, (there are exceptions).
    If your bike is chain driven it will need Mikuni.
    The carb spacing is tighter on the smaller chain drive bike and won't fit the shaft drives.
    XJ600 carbs will not fit 650 Maxim.
     
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  14. Minimutly

    Minimutly Active Member

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    Wow, that's something new - are the heads different between the 600 and the 650 then? Or is it the angles of the inlet manifolds? I can't see why the carbs would need to be narrower (or wider etc), but I can see that supply/cost issues would dictate different carb suppliers at different times. I guess I need to go into work to trial fit the rack I haven't split. Was the 600 based on a smaller head? I will report back.
    Thanks.
     
  15. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Yes. The 600 engine is based on the original 400cc JDM XJ engine, and is quite a bit narrower. The 650/ 750 was an all new design. Even within the shaft-driven XJ engines there are differences in intake port spacing (YICS vs. Non-YICS).

    A bit of relevant reading: TECH TOPIC: The History of Yamaha
     
    Last edited: Mar 15, 2018
  16. Minimutly

    Minimutly Active Member

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    I don't want to argue with anyone, but I believe my carbs are off the later 600, not the original one:-
    "In later years, a new XJ600, with all-new frame and a mono-shock rear suspension system, was marketed as the Seca II in North America and the Diversion elsewhere" From that writup, which I had read previously.
    Now, I've just popped into work, fitted the mikunis up, and they fit just fine, if there is any issue, it might be that the manifolds are a little snug on the carbs - can anyone with a Hitachi carb tell me the dia at the face please?
     
  17. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    The HSC 32 carbs measure 38.1 mm OD at the engine side of the carb. The retaining groove is set back 7.62 mm from the face of the bore, and is 2.54 mm deep (measured from my spare set).
     
    Last edited: Mar 15, 2018
  18. a100man

    a100man Well-Known Member

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    They won't be off a Diversion Seca-II I can promise you. They were of a 'down-draft' type due to the incline of the head/cylinders on those bikes. As I suggested in my first post 'you might get lucky' and it seems you have, as far as fitment goes. Now you 'only' have to strip and clean them. Knowing what I know now I would still rather get the
    right ones - there's a set on ebay germany.. https://www.ebay.co.uk/itm/YAMAHA-XJ-650-4K0-Vergaser-fur-Bastler-100/332487374193
     
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  19. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Look at the bottom of the float bowls. There should be ink stampings on them identifying what carbs they are.
     
  20. Simmy

    Simmy Active Member

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    The op called it a 650 Maxim.
    Have we verified with certainty that’s what he has? Is it a shaft drive bike?
    Pic please
     

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