KX500 too slow!

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May 18, 2002
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#1
I just bought a 92kx500 and i rode it yesterday for the first time. I have to say I came away less than impressed.It has a new top end and crank bearings and seals so the motor is totally fresh. I know I couldn't rev it real hard cause it wasn't broken in yet but the mid range seemed really flat and blubbery.It has a pro-circuit pipe and silencer which I've heard is smoother than the FMF but I can't imagine a simple pipe swap making it anywhere near as hard-hitting as my old 86cr500 .I haven't had time to fuss with the jetting but the bike has good snap right off idle and into the lower midrange and then it just seems to load up and not pull as hard as it should.Any help would be appreciated as I really like the rest of the bike.
 
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#2
You might check to see that the powervalve was installed properly.. The punch marks on the gears were not on the correct teeth with my KX250, so when I reinstalled the powervalve (by the manual), it was not opening properly. Just a possibility.

Otherwise, it's most likely a jetting issue..

Another thought, my KX500 would start to get very blubbery on the mid-top, a new spark plug would always take care of it.
 
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#3
I agree with Cam Mitchell, check the power valve. My '91 KX500 is an animal show when it runs clean. I'm running 55 pilot 168 main needle dropped on notch to 4th position @ +/- 3000', +/- 75 degreesF
 
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#4
Also check the gear teeth on the power valves - they can wear quite a bit & not fully open at upper rpm's
 
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#5
Have fun. To check the power valve teeth and timing you have to pull the cylinder! You can allways look up in the exhaust port and actuate the PV from the linkage by the cylinder base to see if it's in the ballpark.
 
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#6
If the jetting and powervalve are correct what other mods make it pull harder in the middle and top.I live on the B.C. coast and don't have any time during the week to test jetting but I guess I could use kmac's jetting as a baseline.Kmac, do you know what the stock jetting is for up here?I've played with the main and pilot in a carb before but I don't know how to change the needle or where to count the position from[top or bottom?]
 

mx547

Ortho doc's wet dream
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#7
this may be the first time in history that someone has said that a kx500 was too slow. :eek:
 

gwcrim

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#8
Well lemme ask this:

When I bought my KX5, it had an FMF Burly pipe & ISDE silencer and an 11 oz. flywheel weight. Obviously, the bike has tons of low end. But it doesn't seem ungodly fast.

Would the add ons have a HUGE effect on the power band?
 
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#9
No, mine was deceptive at times too.. What you have to do is ride a 125 or a 250 for half an hour on a MX track, then go back to your 500.. I scared the crap out of myself at least 10 times on the first lap after doing that.. Those corners come up FAST on a 500!
 
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#10
I have no doubt that it's fast but I expected more especially mid and top.
I have no complaints about the low end power.My friend who has never ridden a kx 500 was not very impressed either.He had exactly the same opinion of the power.It simply doesn't pull cleanly mid to top.It may have been hard to gauge how fast I was going since I was riding in a wide open area with no other bikes around.Also my 92CR250 was much easier to pull the front wheel up in the top two gears.My gearing on the kx is 14/48.
 


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