2008 kx450f with '86 kx500 motor, bad idea??

[byron909]

been told by a few that this motor is not a good candidate for a aluminum frame swap. was wondering why? not worried about not having the center powervalve. other than that and the 5 spring clutch, what is so different?

was planning to start this project soon, maybe need to put on back burner untill a newer engine is found?
thanks for any help.

[jfabmotorsports.com]

Need I repeat my self! 

http://www.kxriders.com/forums/index.php/topic,5982.0.html

[byron909]

thanks, but i figured i'd ask in the appropriate place. why is the older cylinder more bulkier?? the parts thing is no big deal, i have a few spares for this motor. anyway, it seems the some of the major items interchange with 89 up, i don't care about having the latest engine design if i don't have to, but if there is another reason than i should i'm all for it.
thanks

[don46]

The reality is that very few items interchange with 89 and up. tranny shafts are different, crank is different, clutch setup is different.  you could use the ignition if you have it complete, the right cover would work, reeds will work, intake manifold is different, cases are different. There are more parts that are different than there are the same.

[kaw rider]

The real problem is finding spare parts or new parts when something breaks or wears out.

[pc500rider]

i personally think the 86 engine is an awesome engine and many parts from the 88 engine will fit including the pisto,rod clutch and many others and with a few modifications to the engine it is an insanly powerfull engine

[kwakman]

i can see me and everyone who has a newer than 86 500 fightin.and you can all watch out cos im bringing my handbag too.
i have done a lot of research into the differences between the 86 and others for parts and this is wot i found.
cases are supposedly 83-87 but only 86 & 87 have powervalve drive.
tranny shafts are 83-87. gears too.
86 piston is stand alone but later ones fit.
clutch is 83ish thru 86.a whole 88 on clutch CAN be fitted as a unit.
(you may have to adjust the length of your clutch pushrod)
side p/valves are like rocking horse s&%t.but mine are mint so i dont care.
one of the tranny shaft needle bearings is discontinued.
gaskets are all readily available,oil seals too.
86 thru 88 barrel are almost identical,although the 86 has superior port timing in my opinion.the 86 thru 88 heads are squarer and bulkier as jerry has already mentioned.And the 86 HAULS!!!!!h.t.h,kwakman.

[byron909]

thanks for the info, i actually just started getting back to this conversion, i have since found a '94 motor to use for the 450 chassis. i decided to restore the '86 bike, once it is finished will get back to the 450f conversion.

thanks again

[The Flyin Hawaiian]

83-84 500 was aircooled, I would recheck the case fitment. Otherwise, go for it! If you have all the spare parts or can get them, I dont see it as an issue. If my memory is correct, having ridden a 86 and 88 500 when new, the 86 felt faster. My 88 was a big pussycat and worked well for the type of racing I did (enduros and harescrambles) with it.