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Big Bore kits

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I've got to do a valve replacement on my '99 KLX 300, and I'm thinking of going big bore, since it's just a few more bolts. Kustom Kraft, FSW, Bill Blue, or Thumper Racing? Plated cylinder or cast iron liner?

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Even though I didn't go that direction, I don't think there's much reason in not going with the BB351 kit. You already have a 300, so why go for less? I have an '06 250S and got an exceptional deal on a 300 kit, and that's the only reason a 351 isn't in mine right now.

On the plated or liner consideration, the plated is aguably marginally superior, but it's not a big span whatsoever. I think the break-in for the liner style cylinder may be a tiny bit more critical but hardly a big difference. Plated cylinders also cool a bit better, but again, you have to do something really dumb to screw up either design.

I'd also put in a new cam chain if you have many miles at this point.

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Hi Bob,

I have the KK 330 kit and it was a huge improvement over my tired 300! I also did a little but of a port and polish work on the head when I replaced the valves. If I had to do it again I would more than likely go with the Bill Blue 351 set up. What it comes down to is steel sleeve over the Nikasil plated liner from KK.

Dennis

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I also want to do the cam chain, and I have a Stroker idler gear sitting on the shelf. I have been kind of leaning toward the BB 351, I just wish I could get more feedback on the reliability.

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More money, but you can use a alum sleeve and have it plated if you think nicasil will be an advantage? Not sure what sleeve they are using but many are VERY hard, almost like nicasil when you go to port them (twostrokes). Problems I've see has more to do with the sleeve install and machining for fitment, gasket failure ect. Being iron vs nic is rarely an issue.

the crank on the klx is balanced for a 300 piston weight, so if smooth running at high rpm is important? not that the big bores throb too much, certainly less than many factory motors.

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Bills 351 is very nice, He does excellent work. can't wait to get time on her.

DSC00008a.JPG

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Man, that's huge! Just got word from Bill yesterday that mine is in the mail, along with a TM33/34. WooHoo! Now, if I can only find/make some time to put it on!

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