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Some help for a frog ! ;)

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  • Some help for a frog ! ;)

    Hi guys,

    I need some advices and I think that this place is best for it.

    I ride an XJ 750 seca from 1982. I had many problems with the engine and I'm now fed up with it.

    The last one was a very low cylinder compression (4 psi/cylinder...). I cured it with a Bardhal additive and now it's ok for a moment, I hope.
    I opened this engine three times in 2 years and I'm really fed up with it, gaskets and parts are not free...

    First I was thinking to change it for an XJ 900 engine, easier to find in France. Finally, I'm thinking about another solution, change it for an XS one.

    I'm crazy of vintage bikes (I turned my XJ into a Cafe-Racer) and I always regret that my bike doesn't have a kick-start. It's also really practical when battery's over ! I know that XS have kick-start.

    So my question is, what kind of XS engine can fit my bike without big modifications in your opinion ?

    XJ seca and some XS seems to have the same frame, is it correct ?

    Any advice or suggestion will be really appreciated ! Thanks !

    Best regards from frogland

  • #2
    Engine Transplant?

    Bonjour Monsier Visant,

    That's it. I know a fellow in France who has several XS's, but I don't know how to speak it, so hopefully you'll be able to understand us? Your English was very good!

    Okay, Yamaha did away with the Kick Starters in 79-80 for the XS11's. Secondly, IF your battery is very weak to where it won't crank the engine over, then it's probably also too weak to fire the TCI/Ignition box....they require about 10 volts to work, so kick starting would NOT be an option anyways!!!

    The XJ750 frame is probably built to only hold the 750 engine, and a larger one will probably not fit, at least not without some modification. But then there's also the weight, and additional stress the POWER would put on the frame!

    Also the electrics are considerably different from the XJ series bikes and the XS series, would require a lot of changes to your wiring!? Getting an XJ1100 engine would be a closer match!

    Yes, going into your engine is a frustrating thing, especially several times in a few years. But you didn't say whether YOU were doing the wrenching, or you were having to pay someone to do this? Also, didn't say what was wrong when you were into the engine previously?
    The last one was a very low cylinder compression (4 psi/cylinder...). I cured it with a Bardhal additive and now it's ok for a moment, I hope.
    That IS a very low comp, and to "Cure" it with Bardahl doesn't sound right! How many Kilometers/miles do you have on the engine? Sounds like either worn rings, or even burned or worn valves, or poorly set valve clearances?

    The XS engine isn't much different than the XJ, 2 valves per cylinder, DOHC, bucket shim design, cam tensioner....but in the back of cylinders.....possibly more difficult to get to, possibly less likely to adjust leading to loose chain, skipping cam sprocket teeth?

    You say you made your bike into a Cafe Racer style, do you run the engine HARD? Possibly another cause for engine fatigue and failure, along with less than optimal maintanence will kill an XS11 engine just as quick!
    T.C.
    T. C. Gresham
    81SH "Godzilla" . . .1179cc super-rat.
    79SF "The Teacher" . . .basket case!
    History shows again and again,
    How nature points out the folly of men!

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    • #3
      Re: Engine Transplant?

      Hi,

      Thanks for your quick reply. I have a secret for my english, going regulary at the pub

      Thanks for the information for the kick starter

      The XS engine I'm thinking about is a 750 or a 650, I'm not silly enough to try to put a 1100 into my bike ! My objective isn't to finish at he top of a tree...

      For the many repairs I have done on it, the most technical part was realized by a friend of mine who own a repair bike shop.
      I'm sure about they're not responsible about my lastest engine troubles (which appeared suddently). The engine is in a quite good condition, the cylinders where just recondionned and have only less than 4000 kilometers. Carbs where changed too.

      About my bike customisation, I just change the look, not the engine specifications and I'm not a barbarian when I ride it. I know that this kind of engine wasn't created for racing !

      The only thing I'm sure is that they don't changed piston rings cuz they seems to be in a good condition...
      I think now that it was not really clever decision...

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