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KX500 too slow!

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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

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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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#11
There is likely something wrong then, you'll probably find that one of the previous suggestions will be the cause.

I had a thicker head gasket, which makes a slight difference of less bottom, more top end.. But mine would make your eyes bleed at high RPM if you could stand the vibration! Any KX500 should have good top end power unless it has been modified.
 

RVL

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#12
The Pro-Circuit pipe is the problem. I bought my 1989 KX500 used and it had a Pro-Circuit pipe on it. When I took it to Race Tech to get revalved, Paul Thede (the owner of Race Tech) asked me if I had the stock pipe. I said that I did. He said he would not bad mouth any competitor's product, but strongly suggested I try the stock pipe.
I did, and it scared the **** out of me. I loved the power, but the 1989 models had a much lighter flywheel than later 500s, and it was too crazy, even in the Mohave Desert. I wanted the huge power, so I added a flywheel weight to it, and lived happily ever after. I didn't even keep the Pro-Circuit pipe for a spare. It went right in the dumpster.
Later on that year, I spoke with Mich Payton, the owner of Pro-Circuit, about the pipe making the bike so slow. He made sort of a pained look, and gave an excuse that you needed his porting to make the pipe work.
If you really want that bike to fly, put a stock pipe on it. If you want even more power, run avgas in it. (I know usually it is bad stuff, but it made both my KX250 and KX 500 very frisky. My Hondas were the opposite. They got sluggish with avgas.) An engine tuner said the combustion chamber shapes of the Kawasakis made avgas work well.
 

gwcrim

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#13
I think I might try a stock pipe, I already have the FWW. But what about the silencer? Is the Turbine Core ISDE too restrictive? Should I get a stock silencer as well?
 
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#14
My 91' KX 500 flies. I have the stock pipe and silencer on it. I haven't ridden it since I bought my CRF450, but I miss the crazy speed every once in a while. The stock silencer is a cannon with a sparky on it, but there is virtually no restriction.
 
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#15
I changed the pilot from a 60 to a 58 and moved the clip one notch to the top position [n82r].It made it run a little cleaner.before the plug was wet but now it's dry and dark with carbon deposits so I'm not sure if I should go leaner still maybe to a 55 pilot or a leaner needle.The powervalve was checked by the mechanic.It still doesn't rev as hard as I wanted but I went to Destry Abbott's website and watched some of his video clip's with kx500's and his bike sound's similar to mine so maybe that's just the way they run since I don't have another one to compare it to.The 98 I rode about a year ago ran very similar to mine as well and it had a fmf pipe and silencer.I don't want to go and buy a stock pipe and silencer since they supposedly crack alot easier.However the old factory KX500 that larocco and kiedrowski rode sure looked alot like stock.
 

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