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A thought about an exercise in fuel efficiency

Discussion in 'Modifications and Projects' started by Netterhead1, Jul 13, 2007.

  1. just a thought that came into my head reading a scooter thread.

    i own a 1984 rg250 gamma. enormous amount of fun. love it to death. but it really doesnt get very much as far as ks per litre is concerned.

    does anybody know how difficult/possible it would be to (when the current one dies of course*) replace the engine with a more efficient four stroker. i'd love to keep the thin light frame.

    * odometer just ticked over 98000 :shock: i dont have a full history and my bet is that either the engine has been replaced or the speedo has. but it still has heaps of compression. so this wont be the near future i dont think.
  2. Some people have stuck 4 stroke singles in them...do some searching :?:

    Looks like a straight forward swap.
  3. I've seen mention of Aprillia RS250s (which use the RGV engine) being fitted with the engine from a DR800 - that's an 800cc single :shock:. Should change the riding characteristics of the bike a bit ;) :cool: .
  4. It probably wouldnt be worth the bother, rg250 are getting pretty old, and the amount of $$ and effort to mainatain the bike will be greater overtime.
    The engines are rebuildable, but it would be hard to find parts for them (cranks especially).
    2 strokes are known for there fuel consumptions, so save up and get a 4t.
  5. SR500 engines should go in easely... but I have heard of people fiting a Yamaha 660 single into a TZR250 frame...
  6. Isn't that a SZR
  7. LOL I will have a look at the frame design... what a spin out it would be if they do share a frame...

    Err I did... different... way different... the SZR is a two pice frame while the TZR is one... with an engine cradle...
  8. it is possible to put nearly any motor in nearly any frame.
    its how much mucking around you are prepared to do, and how much money you are prepared to part with that is the determining factor.
  9. I beg to differ...check this photo

    against this one


    My SZR's frame looks identical except for a steel subframe under the seat where the one in the TZR photo appears to be alloy.

    One key difference is that the SZR has a recess let into the frame to make space for the starter motor. The bolt lugs are in different spots and there are a few "afterthought" bits of plate TIGged on, but aside from that it's TZR through and through.
  10. If I remember rightly, the old (Pre V) RG had a cradle frame, in which case you might be limited in height when trying to squeeze in a four stroke. Strokers are compact, low profile units by comparison, without all the cambox/drive gubbins to make the engine tall.

    That said, many years ago there was a Reader's Special in Performance Bikes that was a Suzuki GS550 (I think) engine shoehorned into an RG500 (I think) frame, although it could have been a 250 as my memory isn't what it should be. To make it fit, the builder had had to cut out the lower frame rails and use the engine as a stressed member. He claimed it worked, but there were an awful lot of RS bikes that quite obviously didn't so I'd take that with a pinch of the proverbial.

    It won't help your fuel consumption much but have you considered turning it into a YamaGamma (RD350YPVS lump in RG250 frame)? It was the hot setup in the UK for a while, giving better reliability, tuneability and spares availability. Again, PB did an article on the conversion years ago, which was available online on one of the many RD sites until quite recently (may still be there). I forget the exact details but it seemed pretty straightforward, mainly consisting of making up engine mount adaptor plates from steel sheet and fiddling around with radiator hoses.
  11. hmmm there were far more models of the TZR than I thought at first... (I have to re check my files/data... I think I have a picture of every model somwere)

    Also some did share the frame with the FZR250... defenately the 2KR...
  12. i did read up on the yammagamma and i gotta say it seems like a pretty S&*^hot setup. from what i read it was one plate one pipe and some right angled radiator hose to go from 45bhp to 80 bhp.

    but with todays 4-strokes getting very similar power output as the old two smoker i cant justify double the fuel consumption. rough estimate, its worth $500 a year in fuel at my current riding rate, which would increase if efficiency was greater. anybody know how much a cbr250rr engine goes for from a wrecker. it seems wider than the rg engine.

    as far as height goes, i have a bit more room to play with as its a postmix two stroke :p. has an oil reservoir that is directly above the engine.that gives a bit mroe height. i'll have a look around.