Maintenance & Technical > KX100 / KX85 / KX80 / KX65 / KX60

kx 85 lacking bottom end power !

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riggy:
I have a kx 85 it has  a rad valve , pro circuit platinum pipe , and some head work  I just rebuilt top end new piston and rings however this bike is all top end . where would  my next step be to get a noticeably better bottom end  for woods riding ? I was curious if a fmf fatty pipe had more bottom end . GEARING IS STOCK 12/49 . or big bore kit . not sure lookin for some input thanks .

riggy:
I advanced the timing one mark it seemed to help . however it still needs more , looking for a flywheel wieght if anyone has one ! and a 52 tooth rear sprocket .

DoldGuy:
I am not the KX85 expert and know just a little but will try to help. My freinds boy Motos a KX85 & KX100 and the 85 is alot more pipey. The 100 cylinder will bolt on and give alot more bottom & smoother transition into the mid-topend. The CDI is also different and helps smooths out the transition. You said the bike has "head" work, if you can give more detail it would help (stock cylinder?). The Rad Valve usually requires leaner jetting then stock and provides more everywhere on all the bikes I tried them on. The Pro Circuit & FMF both shift the power to the topend (my buddy has the FMF on both) the stock pipe would better suit your needs. In my testing advancing the timing makes the bike Hit Harder in the mid range, try retarding the timing to see if it helps (stator counter clockwise). Also confirm your powervalves are operating correctly closing. Hope this will help.

riggy:
I was mistaken I moved the timing 1 notch counter clockwise / retarding it . That helped not advanced my mistake . The squish angle was cut and head saved . 49mm wiseco piston .  Thanks for the response hope this info helps looking for some ideas .

DoldGuy:
Riggy,
If you have confirmed your power valves are functioning properly and your jetting is correct and you still want more Bottom End (KX85 Has one of the best) then an affordable fix is to remove the cylinder and have the Base turned down (Bottom of the Cylinder) which will retard your port timing (Giving more bottom but taking away some top). You will also need to have your head Re Chambered to compensate. Again, Confirm your valves are operating correctly and jetting is correct before doing anything else. Hope the info helps out.

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