Maintenance & Technical > KX500 Original
the 250/500 project
John:
Thanks,
I might take you up on the offer and come back to you with one or two questions.
By the way, don't worry about your English. I am also a "stupid foreigner" i.e. non-English. You have to see the benefits - how many English speaking persons are bilingual?
/John - the Swede (as in Swedish - not the vegetable)
K5RACER:
Ok step 5. what fittings dont fit? can we get a closer pic of exactly where and what you had to cut and weld?
supermotokx:
I'll upload all the closeups in a week or so. I've got pics of all my mods, so hang tight.
Martin
kxtaz:
i would be willing to weld pipe together for you.im fairly experience welder i own a mig welder and tig welder.ive posted some pics of my welding in forum a while back.i welded some stuff for a couple different pitbull members.i will even do it for free.From my experience with welding dirtbike pipes in the past its much easier and you will get a much cleaner looking weld if you modify brand new pipe.riding bike causes exhaust pipe metal to become brittle [this is especially true with stainless,chrome or nickel finished pipes]this is caused the heating and cooling process.another problem is carbon buildup inside used pipe.during weld the carbon in pipe is ignited and causing hot spot in sheetmetal making it very easy to burn through material harder to run long consistent beads with carbon buildup inside pipe. materials tempature will be very inconsistent the heavy carbon areas will burn thru easy. you can use lower setting to prevent burning through then you dont get good penetration in area where there is no carbon buildup.Repairing a dent or sm. holes in a used exhaust pipe is pretty simple and simple wirefeed welder will usually work fine.its a little trickier to weld factory looking seams throughout a complete pipe.if you are interested in me fabricating or modifying pipe for your bike.let me know.You would definitely need to have pipe already cut,pieces formed,fitted and well marked as to how they are supposed to go together.best way to mark is by careful fitting pieces together when you have good fit,proper bends and everthing aligned properly.use a crayon and scribe lines across areas or seams where parts join together.crayon marks can then be used as alignment points when fabricating. if you use a couple different colors its even easier
kxtaz:
i looked at pics of your pipe.i think your better off using kx250 pipe with kx500 exhaust port flange.since you are using kx250 radiators,shrouds ,sidepanels and really didnt do any modifications to the 250 frame.a 250 pipe should still fit pretty good from radiator all the way back to rear fender.you would just need fabicate about a 8 in. section from exhaust port to somewhere just below radiator or wherever you choose to chop 250 pipe.it looks pretty tight around airbox.you should either make a new sheetmetal airbox or try and find a airbox off another model bike that can be modified so exhaust will fit inside subframe. 500 performance losses with 250 pipe really not a big deal.theory behind 2 stroke exhaust is very simple.there are a ton of books on how to tune and modify 2 stroke pipe to give desired powerband.the kx 250 pipe doesnt come out of cylinder and make the sharp looping turn like the kx 500.kx500 exhaust makes that big loop to increase backpressure for better bottom end.if you use a smaller piece of slightly smaller diameter pipe in 8 in. section you fabricate you can achive similar increase in backpressure [length and diameter of the smaller section can will determine how much bottom or top end performance will be affected.]
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