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sr400 vs sr500

Discussion in 'Bike Reviews, Questions and Suggestions' started by jse, May 10, 2008.

  1. what is the difference? apart from thebigger displacement.

  2. That's it. The bike was originally designed as a 500 but a 400cc version was made alongside it for the Japanese market and it's restrictions on anything over 400cc.
  3. I own a 400, and have ridden a 500 a bit.

    The main difference is the displacement and the stroke of the engine. Apart from that, most components are interchangable with the exception of -

    Ignition Unit
    Front disc brake

    Several things are designed slightly differently, including the lubrication to the exhaust/inlet valves, some internal components are lightened to allow lubrication, the front forks have recessed drain valves at the bottom rather than the plugs at the side. The fuel tank on the 400 is also 1 litre bigger. Off the top of my head, that's about it. Oh, and it's spokes only now rather than the mags.

    The engines behave quite differently. The SR400 revs a lot freeer and you can get away with shifting just about anywhere. The 500 is a bit more picky and you have to 'think' your way a lot more when you're riding.

    Both are fantastic bikes. Check out the SR500 forum if you're interested.
  4. I'd concur with the others. If anything the SR - which is still being made and going strong after 30 years! - is getting better over time : spoked wheels, modern drum brakes all round on some years, bigger more rounded tank. I believe you can simply buy a shorter piston, bolt it in place, and your 400 is a 500 (is this right QuarterWit?).

    If you had to choose between them and you wanted the vintage bike 'chug chug' then the 500 is more the way to go, and if you want the revvy cafe racer, then the 400; but at the end of the day they're the same great bike. The longer I own mine the more I love it! A reliable, simple, cheap and very beautiful and charismatic bike to own and ride.

  5. Yep, that's right!

    I was going to change it to a 500 when i first bought it but decided to leave it stock until the head needs work, at around 60,000k's. The more i see your bike too, the more i love it Matt! full of character.
  6. I think I'm getting to that point! :( I believe a rebore (and cam chain while they're at it) should do the job - not looking forward to spending the money, but at least it's much cheaper on this bike than on any other. Have to do the swing-arm bearings before anything - that's one thing with a 30 year old bike, so much needs replacing / rebuilding.

    Is your bike back on the road yet?
  7. No, she's not yet.

    The guy who was supposed to do my wheel spacers broke his hand. I was going to call him and ask for the original spacers back, but while putting the front brake on i stuffed them a bit, and by trying to unstuff them, i stuffed them more.

    Oh, and i need to change the jetting on the carb for the new muffler. Have you ever done that before?
  8. Never done that - would love to come along if you're going to do it yourself, as I'm keen to learn (on a guinea-pig other than my bike! :grin: )
  9. Rumoured to be getting fuel injection very soon to meet emissions regs - not sure if that could be classed as an improvement though.
  10. Yeah, that was supposed to happen at last years Tokyo Motor Expo but apparantly they had some problems with it.

    It can go either way, personally, Carbs scare the living bejesus out of me. If there is a bolt-on performance upgrade that i can just whack straight in my bike, dial it up and away i go it'll save all the stuffing about that will come as a result of sticking my new muffler on.

    But that's just me. :grin:

    Matt, you're more than welcome anytime mate! I hope and pray it's as simple as swapping the jets over. I've got half a dozen or so ready to go. Oh, and PM me your mobile number, i keep losing it.
  11. I think there may be something amiss with your description of a "shorter" piston increasing the displacement. I think you might find that it will be a larger diameter piston required. Or a crank with a longer throw combined with a shorter skirt piston creating a longer stroke. Any idea which it is?
  12. No. Shorter distance between the connecting pin and top of the piston = greater distance between the top of the piston and the cylinder head.
    So displacement is increased.
  13. Afraid not jd. All you have done is lower the compression ratio. Swept area or displacement is still exactly the same no matter how long or short the rod & piston are.
  14. Ah yes, you'd still need to change the crankshaft for that to work.
    Both engines are the same bore though.
  15. Joe Minton and Paul Vonderhey both developed re-jetting plans for the SR. They differ slightly because one focuses on the 32mm carby (1981 and later, I think) while the other uses the 34mm. They also differ in that one uses a Kerker exhaust and a replacement airbox. You can find a summary at

    (Sorry about the URL -the original page has vanished and all that remains is a Google cached version)

    I've used Vonderhey mods - I have an (almost) straight through exhaust and a K&H slip-on air filter. I've machined the carby slide, moved the needle to the richest setting and upped the main jet to a #330 (I have the Mikuni VM34SS carb).
  16. Thanks for that Chairman!

    I'm going to head into this thing armed with as much information as possible, the link is appreciated!