Maintenance & Technical > KX500 Original
porting
brucegregory:
well i bought the bike last year it is an 2003 for $1700 dollars it had maybe 10 hours on it the first thing i did was put a good clutch in it and changed the reeds just the petals,it is in excellent shape starts first good kick and it really is strong but i want more power i bought another cylinder and i want to port it and mill the head but i still want to run pump gas,i like the bike and it will wheelie in the first 3 gears just rolling the throttle it will in 4th but only if the tire has quit spinning so much but i have a one tooth larger front sprocket on it i didnt like the orignal counter sprocket it was geared too low i thought i weigh 240 so i am not a light weight and i have had a lot of bikes i just thought the kx would hit harder when it got on the pipe i remember my friend had a honda cr450 they only made it one year in 1981 and it would flip over in all 4 gears when it hit but that was years ago when i rode it and i was 100 pounds lighter my bike was running 92 on the gps and it probably could of got a little more if i tucked in but it is hard to do when i was on the street holding my trucks gps in my hand
ShadeTreeFab:
i just went through my motor, i could not believe the amount of casting flash in cylinder. clean up the ports, windowed piston, cometic hi per gasket kit, v2 reed block, pc2 pipe. with the piston, v2 and gasket kit you would not even know its the same bike.
Hillclimb#42:
--- Quote from: ShadeTreeFab on December 25, 2009, 08:16:27 AM ---i just went through my motor, i could not believe the amount of casting flash in cylinder. clean up the ports, windowed piston, cometic hi per gasket kit, v2 reed block, pc2 pipe. with the piston, v2 and gasket kit you would not even know its the same bike.
--- End quote ---
Agreed. Leave the head alone unless you plan on running VP fuel. Pipe and Vforce reeds add alot of power to stock cylinder. Power does cost money, but guessing at porting just costs money without the desired results. Its also easy to jet when mostly stock configuration.
Polar-Bus:
--- Quote from: brucegregory on December 25, 2009, 07:37:37 AM ---well i bought the bike last year it is an 2003 for $1700 dollars it had maybe 10 hours on it the first thing i did was put a good clutch in it and changed the reeds just the petals,it is in excellent shape starts first good kick and it really is strong but i want more power i bought another cylinder and i want to port it and mill the head but i still want to run pump gas,i like the bike and it will wheelie in the first 3 gears just rolling the throttle it will in 4th but only if the tire has quit spinning so much but i have a one tooth larger front sprocket on it i didnt like the orignal counter sprocket it was geared too low i thought i weigh 240 so i am not a light weight and i have had a lot of bikes i just thought the kx would hit harder when it got on the pipe i remember my friend had a honda cr450 they only made it one year in 1981 and it would flip over in all 4 gears when it hit but that was years ago when i rode it and i was 100 pounds lighter my bike was running 92 on the gps and it probably could of got a little more if i tucked in but it is hard to do when i was on the street holding my trucks gps in my hand
--- End quote ---
By adding 1 tooth larger on the front sprocket, you are gearing higher, and your acceleration will suffer. It's just the way gearing reacts. The additional fact you weigh 240 is not helping either. Run 14/49 gearing and you will get a great compramise of acceleration and good top end speed. Don't waste your time with high compression porting IMO. Here's my famous words quoted from a long time respected engine builder: "It's far easier to loose 5 hp than it is to gain 3 hp "
jfabmotorsports.com:
I run 15/50 on the AF. It is almost the same as stock gearing for a KX500(14/47) but the larger counter shaft gear is easyer on the chain. I also run 50's on my KX450's so the the bonus is I can swap wheels if I need to. I keep 3 different tires mounted on 4 wheels all with 50 tooth sprockets.
JFAB
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