kx5 biggest bore

[YUNGGUNNAZ]

saw on a post here awhile back on the subject of big bore #'s like 540 and even 6 something kits by the way of stroking but no other detail info.
would like to find more on this since we sand drag alot here.

[gowen]

If you are sand draging, there is no need to up past 2mm overbore (520) due to the fact that the more bore you have, the lower the powerband.

I sand drag my KX and am untouchable with a 520cc kit. There are other parts you can get to increase your performance in the sand besides a huge ass bore.

[YUNGGUNNAZ]

gowen, where do you race at?there doesn't seem to be many tracks here in Va. doing this.i really like to explore any other combinations to see its merits or down falls at a mechanics point of view.untouchable uh?wait til I tell katie!lol

[Brett]

Don't bother inceasing youre bore size untill you have to due to wear.  Sand drags not that i do them myself i am sure the things you should be looking at are: port timings, make wilder by lifting barrell or porting; compression, increase via machining cylinder or head; expansion chamber, find the biggest in diameter you can get your hands on; and then tune carby to suit.  All these things will give you a motor that has a s**tload more topend power that will be in a narrow powerband and give violent power delivery.  Leave the bore size alone changing from 500cc to 520cc is only about 4% increase in power statistically but why f**k up a perfectly good cylinder for meager returns.

[YUNGGUNNAZ]

brett,all of what you spoke of has been done.cylinder ported,head reworked,2mm over,jemco pipe(two of these as one was builted in 91)and other tricks.but i am always looking for more.willbe trying something new this weekend at the last drags.here is site for race,www.bikerenews.com.dirt drags

[gowen]

brett,all of what you spoke of has been done.cylinder ported,head reworked,2mm over,jemco pipe(two of these as one was builted in 91)and other tricks.but i am always looking for more.willbe trying something new this weekend at the last drags.here is site for race,www.bikerenews.com.dirt drags

Having a good port job done is the key, but the winning key was my ignition. Use a PVL. I've posted about it many times. It will cause a little more wear, but then again. So does doing sand drags. You can't' go wrong with it, unless you plan on doing trails in tight woods.. Then it sucks.

[gowen]

Also, doing the 520 kit did increase the power by noticeable amounts. Also with the PVL, you absolutely MUST gear up on the transmission or you will be in 5th gear pinned within' a hundred foot. I installed a paddle tire for grass and sand racing to help with traction. I'm even considering ice screws too. Either way, nothing comes close with a good foot. I've even been known to 2nd and 3rd start it so it acts like an automatic and just keeps on pulling.

[YUNGGUNNAZ]

i've noticed that the 89 flywheel is alot smaller(thus lighter)than the 99 i have here so i thought of turning the outside down some while waiting for pvl.i assume the pvl bolts on like old style inner rotor magneto's.i current use the left hand threads in flywheel for the outboard starter.will this apply to the pvl?we use 2nd most but this week i have 12/38 gearing so its 1st gear starts.

[gowen]

i've noticed that the 89 flywheel is alot smaller(thus lighter)than the 99 i have here so i thought of turning the outside down some while waiting for pvl.i assume the pvl bolts on like old style inner rotor magneto's.i current use the left hand threads in flywheel for the outboard starter.will this apply to the pvl?we use 2nd most but this week i have 12/38 gearing so its 1st gear starts.

Flywheel with puller in it is a stock flywheel that has been buried in water. But, for sized reasons.

[YUNGGUNNAZ]

good pic.i see how to mount nut for starter using the holes for the puller.what year is the bike?flywheel looks to be off late 90's to 04.

[Brett]

Are you guys running custom expansion chambers? I think you should be  if just dragging them

[gowen]

Running an old '90. I have kept away from custom chambers, as they limit my riding and areas that I ride. Until I move into Alk or NOS, I plan on keeping my Desert pipe. I don't like the bulk of the PSI or Jemco. Even though the Jemco is tucked under the frame, I'm so far impressed with the FMF.

[YUNGGUNNAZ]

i have a dynaport but have not tried it yet.have a jemco from back in 91 and that was different from one i just got so i am tuning in to the new one.need a left side radiator too!