Maintenance & Technical > KX500 Original
1988 & older VS. 1989 - 2004 : Engine Performance | Output Shaft Nut | Swingarm
manco:
If this is something already covered I am sorry to bring it up again. I did some reasearch and haven't found as much engine performance charcteristic comparison info as I was hoping for. If anyone has any solid input I would appreciate it.
I have recently found myself in possesion of two KX500s. One is a 1987 the other is a 1998. The 87 has the older motor, the 98 has the newer one of course. I have ridden the 98 at the track a bit and it runs pretty good. I just aquired the 87 and haven't had a chance to take it out yet. When fired up in my shop the 87 seems to sound a bit meaner though. It could be the sound characteristics are that my 98 is running lean with an airbox, stock carb, Fatty pipe & a freshly packed FMF TurbineCore while the 87 is running rich with a Mikuni, no air box, a rag for an airfilter & a stock pipe with a performance silencer that needs repacked.
When I get both bikes out for a spin I will have a better overview of the two engines. In the meantime I was interested to hear what others thought on the two different motors. Is one better suited &/or does one outperform the other under various conditions? MX track vs trails vs drag strip? Is there much difference between the two motors?
Another few questions I have are about the output drive shafts on the two motors. The 87 has the old lock nut style output shaft and the 98 has the newer snap ring to hold the front sprocket. The reason I ask about the output shafts is that my 87 is missing the obsolete drive sprocket lock nut. A custom nut could be made I am sure though I would rather purchase one if something is avaliabele. Is there a known readily available nut that can be purchased to fit the 87 output shaft? I am also wondering can the output shaft in the 87 be swapped with a snap ring output shaft from a newer motor?
Also once the suspension changed to the newer style without the rod is the swing arm interchangable then from 1987 - 2004?
Thanks for any info you have.
manco:
I found the info I needed on the output shaft sprocket nut here at this thread. http://www.kxriders.com/forums/index.php?topic=11819.0 I am gonna go see if the hardware store has a M24x1.0 that will work.
Still wondering about swapping the output shafts between motors.
RoostiusMaximus:
i've checked the assembled lenths and the -1988 set is wider than the 89+
dave916:
--- Quote from: RoostiusMaximus on April 27, 2015, 06:06:38 AM ---i've checked the assembled lenths and the -1988 set is wider than the 89+
--- End quote ---
I guess u mean pre88 is wider than 88+ as 88 has circlip
manco:
--- Quote from: RoostiusMaximus on April 27, 2015, 06:06:38 AM ---i've checked the assembled lenths and the -1988 set is wider than the 89+
--- End quote ---
Can you clarify what you mean by "...set is wider" Are you talking about internal differences or external differences?
Externally the 1987 & older shaft is approx 15.3 mm out from the case while the 1988 & newer is approximately 10.3 mm out from the case. The extra external length is what holds the nut on the 1987 & older. The loss of 5mm on the 1988 & newer is because the clip takes up less space then the nut. The sprocket positon/space itself is the same on both shafts with approximately 5.3 mm of space. Below are pics of my 1987 & my 1998 showing these measurements.
Does anyone have 1983-1987 and a 1988-2004 output shafts loose in their shop? It would be great too see some side by side pics of the the two shafts.
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