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Thread: New piston for 1985 Yamaha SRX600?

  1. #16
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  2. #17
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  3. #18
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    I looked at SRX 600's a lot at one point and I still think there is one in my future - not sure why...

    Making them bigger than they are seems to be not recommended. In fact increasing the power output full stop seems to a little fraught unless you are spending big big dollars to beef everything up. Of course this is not actual experience...

  4. #19
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    If you get one hang out for the slightly later version. Same engine and very similar chassis and styling but has three spoke wheels, rear monoshock and a way better front brake only a single disc but larger rotor and 4 piston caliper. also 17 inch wheels when the earlier one had 18's. Lot of fun particularly on a twisty road.
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  5. #20
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    Quote Originally Posted by Paul in NZ View Post
    I looked at SRX 600's a lot at one point and I still think there is one in my future - not sure why...

    Making them bigger than they are seems to be not recommended. In fact increasing the power output full stop seems to a little fraught unless you are spending big big dollars to beef everything up. Of course this is not actual experience...
    Not really...The rod and pin will take anything you throw at them. Forged piston isn't really needed unless you're racing it. The heads respond to porting very well indeed on stock valve sizes. Cam profiles as std are very mild so not much more cam gives a big boost..Carbs must be changed - the OE part slide part CV setup is so hard to retune it's not funny. decent pipe helps too.

    Biggest problem - if you'd call it that - is that while it's apart, you'll logically look at the gearbox too. Because most of them have spent their lives in town at low speeds, 2nd and sometimes 3rd gear will be through the hardening. Top can be the same too. It's the "big single" effect - bang, pause,bang, oscillating low frequency loadings on the most used gears. Can get costly....

  6. #21
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    Quote Originally Posted by Grumph View Post
    Not really...The rod and pin will take anything you throw at them. Forged piston isn't really needed unless you're racing it. The heads respond to porting very well indeed on stock valve sizes. Cam profiles as std are very mild so not much more cam gives a big boost..Carbs must be changed - the OE part slide part CV setup is so hard to retune it's not funny. decent pipe helps too.

    Biggest problem - if you'd call it that - is that while it's apart, you'll logically look at the gearbox too. Because most of them have spent their lives in town at low speeds, 2nd and sometimes 3rd gear will be through the hardening. Top can be the same too. It's the "big single" effect - bang, pause,bang, oscillating low frequency loadings on the most used gears. Can get costly....
    replacements available or is it a call to Mike Jones and a cubic foot of $10 bills later?
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  7. #22
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    Quote Originally Posted by HenryDorsetCase View Post
    replacements available or is it a call to Mike Jones and a cubic foot of $10 bills later?
    If it was the dogs it would be Mike...but it's always the teeth going through the hardening. Last time i asked , they were available.

  8. #23
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    Quote Originally Posted by HenryDorsetCase View Post
    If you get one hang out for the slightly later version. Same engine and very similar chassis and styling but has three spoke wheels, rear monoshock and a way better front brake only a single disc but larger rotor and 4 piston caliper. also 17 inch wheels when the earlier one had 18's. Lot of fun particularly on a twisty road.
    There is a later model twin SRX400 with three spoke mags, 320 rotor and 4 pot caliper, 17 front but 18 rear. Sport demons or BT45'swork well on them so the 18inch wheel isn't a problem anyway. The first model had wheels and brakes like RZ350. The bikes were the same apart from the wheels

    The later single shock bike was heaps different, and electric start I think

    http://www.srx400.co.uk/

    http://www.srx600.net/

    The front sprocket is different on the 400 to 600, fine spline and course spline, cant remember what has what. Maybe different gearbox internals?
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  9. #24
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    Hi again guys,

    Sorry for the super slow reply, I hope my old dead threads aren't clogging up the place(sorry if they are, I can delete one maybe?). I've decided to take the majority advice and spend a few extra $$
    I currently emailing around engine restorers trying to find someone who can do me a rebore and a camshaft recondition (without charging an arm and a leg). If you know anyone who fits that description and is in Auckland, I'd like to know. Once I've got that sorted I was thinking of:

    Wiseco 1mm oversized, 11.5:1 compression piston kit $180..or so (is 95 octane high enough?)
    Maybe having the lobes enlarged on my cam making it hot? (I'm really no expert on cam tinkering, I'll let the engine reconditioner tell me what I can do)
    If I'm going be cam tinkering I guess I'll need to find some custom valve springs ( Hopefully a good reconditioner can help me out there)
    full gasket set
    Also have a 2 into 1 carb manifold and a 38mm mikuni flatside ready to go ( Will
    will need a 2 into 1 exhaust collector section made up so I can fit a supertrapp I have lying around (anybody know someone who can do that for cheap?)

    I also have some pretty good nick srx400 engines and some xt400 stuff around. So I'll canabalize whatever fits.

    I figure, if I'm going to spend a few hundred getting it running, why not a couple hundred more and try squeeze 50 ponies out of the old girl. Hugely grateful for your advice guys, I'd buy you all a beer if we were at the pub.....and I wasn't a peasant

  10. #25
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    11.5:1? I personally wouldn't bother with that on a road going single you'll never pull the revs to justify it, nor will the engine flow enough to justify it either.
    Does it have an electric start? It may not like it, and you'll need some mighty legs if you haven't got a de-comp on the kick.
    Hard to say if 95 will be enough without experiencing myself how good the knock resistance is on one of those
    Quote Originally Posted by Paul in NZ View Post
    Ha...Thats true but life is full horrible choices sometimes Merv. Then sometimes just plain stuff happens... and then some more stuff happens.....




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  11. #26
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    13th June 2010 - 17:47
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    If the squish is set correctly, the knock resistance is quite good - but yeah, that's too much com for road use. If you've committed to the piston buy, I'd drop com by laying back the chamber walls around the valves. 10 : 1 for road use on pump fuel would be max as they don't have a lot of finning....maybe an oil cooler too.

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