Wiseco overbore kits, which one?
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Thread: Wiseco overbore kits, which one?

  1. #1

    Wiseco overbore kits, which one?

    Hey guys, you helped me once and need your help agian. No one can tell me if my current setup is adequate enough for the r629 kit, instead of the r619? I'd go with the r619 but they aren't gonna have any made in 6 weeks, and I'm not willing to wait that long. The r629 kits are in stock though.. same price too. Powersports dealer told me he'd go with the r629 since it's bigger and couldn't think of how it'd be different from the r619. I mean yes, it's higher compression ratio, but I'm not certain how that gets taken into the whole equation of the engine.
    My current setup is stock FZR600 carbs, stock FZR600 engine 'cept for the soon to be overbore, all in a fzr400 frame.

    Also, I have yzf carbs that I've been wanting to use but someone said that they lost a little lower end and gained only a little higher end. Will these yzf600 carbs work better on the overbored engine? or should I still stick with fzr600 carbs?

    Sorry for long questions, but no one seems to beable to tell me why or whynot I should go with the 629.

    Thanks much!!

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  3. #2
    Eh Muh Gawd Becky!! Array Purplekawi's Avatar
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    whether the carbs will work better is a guess. putting larger carbs on generally does tend to loose a bit on bottom but put more on the top end. the big bore kit should be able to utilize the larger carbs better than a stock 600 due to the larger cylinder bore. the reason some may not recomend the 629 kit is the having to bore the cylinder out larger and therefore making the cylinder walls thinner and possibly causing more heat due to less materials there. anytime you bore out a motorcycle engine you run these risks but the gains are generally good and as long as your not trying to build a 100,000K engine, it should be fine. i used to race old oil pumper Gixxers and we used to bore em huge and they'd go for a few races before melt down but the gains were good.
    That that doesn't kill us forces us to live with a busted up bike!!

  4. #3
    *lol* I see, someone mentinoed heat but I wasn't sure what they meant. So maybe in the long run it's not a good idea to bore the engines then, due to fact it'll start warping after a while. I do want this engine to last, so that would be a thought. Would the 619 kit make it last much longer than the 629? I mean would it gain me an extra few years say?
    I'm not out so much for performance but rather a good engine. I didn't realize about the heat.

  5. #4
    Here's my 2 cents:
    #1 take the block to a machine shop and determine how much is needed to true out the bores to spec(true out-of round, taper and whatever scratches/scuffs). I am assuming you're considering a big bore kit BECAUSE your motor needs a rebuild.
    the power gains would not be worth doing for the hell of it.
    Keep in mind, that bigger bore means higher compression,which means more power, but with consequences(heat,like mentioned already), but also it will probably need higher octane gas. Also more power puts more stress on bottom end.....and any money you'll sink into boring the block and pistons and what not WILL be for nothing if it throws a rod a week later.
    your "dealer" you talked to that suggested going with the bigger bore kit.....let me guess, you talked to a parts person? he wants your money NOW,not 6 weeks later or whenever the hell, NOW.
    My advice would be to go to some yamaha dealerships and talk to actual mechanics, not sales people or parts/accesorie people.
    If you're rebuilding the motor because its starting to puff, i'd get it over-bored JUST ENOUGH to get everething in spec. and do the bottom end bearings while you're at it. and before you start one part of the motor re-build, price out EVERETHING, valve job, all the gaskets and bearings,seals,etc.

  6. #5
    yeah that's what a few people finally said that I should just find out what it needs basically.
    right, someone else mentioned the gas as a concern.

    *laugh* yes I'd rather not sink much more into it if possible, I'm broke here!

    Actually it was a Yamaha specific dealership Mechanic I talked to One I talk to a lot for advice with it too. He didn't seem to know much on the consequences of overboring, or what the difference between the 619 and 629 would be.

    Well it puffs on acceleration so I've been told and eats oil like mad.

    I'm not gonna re-do the valves, they got done last year. I've already ordered all the parts I need for the basic stuff, like gaskets, but realized today I"m gonna need to buy more due to change of plans, which is fine.

    And in terms of bearings on lower end, do you mean those spacer type of bearings the rods attach to the crankshaft on?


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