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Turbo XJ650 Maxim (Maybe)

Discussion in 'XJ Modifications' started by LPKirby, Dec 29, 2020.

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  1. LPKirby

    LPKirby New Member

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    They had 2 on hand. I was shocked at how good the condition was. Paint is still a mirror reflection no dents only very light surface rust inside the tank. Paid $200 for it. Absolute steal.

    I love this idea, thanks for persuading me away from the maxim motor. If it doesn't work out I'll just swap my good motor back in.

    I'm likely going to overhaul all the electronics in this build. It'd be neat to be able to monitor all the aspects of the engine. A/F ratio with a wideband (this could help dial in jet size?) Create a profile to retard ignition if knock is detected (Maybe not need to see how complicated this is). I'm really into the instrumentation and measurement aspects of mechanical systems. It'd be cool to compare theoretical numbers to real world.

    This is awesome to hear. I was really worried anything past 12 PSI would result in detonation problems.

    I'll keep this in mind. I was considering getting a larger oil cooler to help with the fact that these bikes are air cooled.

    Yeah, a recently saw a schematic of the turbo system and was fascinated when I saw the reed valve. Pretty neat concept.

    Here is that article if you haven't seen it already : https://badcurator.org/resources/Magazines/CG_Sep82/Yamaha-XJ650-Turbo.pdf
     
  2. Mechanic1978

    Mechanic1978 Active Member

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    I see this thread is slowed down from Jan 4th, is he still going on this?

    I personally don't recommend any psi greater than 5 on that engine, the head/cylinder studs will likely pop, plus the connecting rods are not strong enough. I have not been inside the lower section of the maxim, but I'm pretty sure they don't have factory "H" beam connecting rods in them. Also the 4 carb setup can be replaced with a 4 tube aluminum intake, and a single carb can be placed before the turbo, meaning the carb sits just before the inlet side of the turbo. but then you have to worry about fuel washing out the turbo bearings on cheap turbo's. unless you go with a high dollar sealed ceramic bearing turbo. single carb on inlet side will be much easier to tune, and does not have to be a "turbo" rated carb, as it is not under pressure, but rather a higher velocity vacuum.

    hope this continues, my intrest is peaked!! lol
     
  3. Simmy

    Simmy Well-Known Member

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    you mean like this...
    s-l1600 (4).jpg
    s-l1600 (2).jpg
     
  4. Mechanic1978

    Mechanic1978 Active Member

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    Yes sir... Much easier to tune..
     
  5. Simmy

    Simmy Well-Known Member

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    10743310_8344f1aea0a2b5b2f04716d718974b9c_t.jpg
    10743310_613a2a2374fc3d2e80f50e9cc8d61b9a_t.jpg
     
  6. Mechanic1978

    Mechanic1978 Active Member

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    Lol.. what's the turbo size and boost pressure on that thing
     
  7. Simmy

    Simmy Well-Known Member

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  8. Mechanic1978

    Mechanic1978 Active Member

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  9. Simmy

    Simmy Well-Known Member

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    I read that, it’s like a prehistoric Britten.
     
  10. Minimutly

    Minimutly Well-Known Member

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    That turbo i is a bit of a mongrel - 650 maxim with seca bars and clocks?
    Fine 40 yrs ago, but now you would go fi with a high pressure pump and ecu to control fuel and sparks...
    Problem is, where to put the turbo - low down you need an oil scavenge pump, high up you struggle to fit throttle bodies or plenum?
     

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