Maintenance & Technical > KX500 Original
KX 500 Flat on Mid and top end
suicyde:
possibly a sheared stator woodruff key?
lsampson:
I don't think its electrical, it starts great and everything, it just doesn't have the 2-stroke kick upwards of midrange, and isn't as wheelie prone as I remember when my uncle had it. The exhaust valves were pretty gummy, so I think it is related to that. They are cleaned up, and I'm hoping to have it back together Friday night.
One more question, for the left and right exhaust valve guides with the rubber o-ring, how often does the o ring need replaced? They appear ok, but I did notice some oil at the gasket when I took it apart. I'm thinking of using silicon around the guides to keep oil off the gasket. I have new o-rings coming, but they wont be here in time for the weekend. Do I need to wait for the o-rings, or can I get by with the silicon?
motopunk:
the o-rings on the exhaust valves are really only there, that it is not falling out when you pull the cylinder. a little oil there is normal, because the exhaust valves are also lubricated with 2stroke-oil. the o-rings need to be replaced only when the valves fall out when you pull cylinder ...
i think, you should ask your uncle, which jetting and needle position he used, as he rode the bike... this could be the keye to find back the 2stroke-punch out of the middle... :-)
lsampson:
Thanks motopunk, thats EXACTLY what I wanted to hear! Now I can ride this weekend! As far as jetting, I bought several sizes up for both pilot and main jets, so I will fine tune it this weekend. The plug is a little light brown, so one size main should do it.
DoldGuy:
Sampson,
Check the power valve as I'm sure if it's a "91" model they have had a lot of time put on them since new. In the open position, see if the "center" valve lifts all the way up flush to the port window, even if it hangs down just 1mm or 2, it will cause a big loss in top end power. There has been a lot of info posted about the cause & fixes for such on here, give it a search & see if it answers any questions.
Hope it's as simple as this.
DoldGuy
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