Maintenance & Technical > KX500 Original

01-500, eng surges/pulses after run.

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kawdude:
I tried a new carb too and it did help but not totally.  Someone suggested that an airleak or bad slide could cause the surging.

gowen:
It all has to do with jetting. If the jetting is slightly rich down low, the surging will leave or clear up. But, running through two carbs and two KX500's here locally, it is pretty d**n normal. I did get ahold of a 41mm PWK carb from Pro-Flo and it is JUST the same after jetting the low-end to perfection. Nothing has changed even with a new carb, it is just as bad. Which does not bother me now, did though, like hell it did.

jdv500:
hello, it's been 3 months since i posted this surging thing above. i've installed a ton of mods, maint parts and dress-up goodies on my 01. i'm very happy with it but even after the new top end and having the kips valve completely cleaned , mic'd and reinstalled, it still has the same ole' pulsing, right at the end of some hard throttle. i 've jetted, 54/165, response is instant. i see here within the site that roughly 9/10 owners have come to terms with this kind of issue.
**** if i had to make an educated guess at it; i'd say that it's the exhaust gases right out of the flange and the reverbing air flow in the chamber that are trying to get by each other, sending a false signal to the valve actuator in the process- via the last-in-line exhaust air just entering the valve........like an accordian/ ripple, this is just me............i've heard all the other hunches, is in ; case seal leak, carb slide worn, pilot jet too +/-, reed valves or boot cracked, valves out of timing... but even after we've cleared all these up, us and the some new 04 owners are saying the same thing. like you all have said above, we have learned to live with it or grown accustomed to it, i don't even think of it at all now adays when i ride, the bike has tons of great qualities to enjoy, but it did sound a bit odd to hear my bike as i was watching a home video of me on the bike.
 thanks and enjoy...

hughes:
May be hard to compare the two but my 87 500 use to do the same thing. But after 1 size smaller main 1 size smaller pilot and lowering the needle jet one slot. my engine will just wine down to idle as the bike slows or if I roll off to a lower speed it runs fine. I changed the jetting just to clean up the throttle. When I first rode the bike before jetting I can just wine out 3rd and back down off the throttle the bike would surge and seem like it would surge forward. Have you lowered your needle jet :?: How is your idle speed set :?:I have my idle speed set as low as I can get away with. With the throttle rolled back to idle after a high speed run, I think the only air that is going to enter the engine will be under the slide and with the idle mixture screw. I think the only fuel the engine may get is going to be through the pilot jet. There may be a fine line here with the amount of air and fuel vers. piston speed. I think what I am trying to say is the slide hight(idle setting)and air mixture screw turns in or out ,after rolling off the throttle may let to much or not engough air to mix with the fixed amount fuel going through the pilot jet. Man it's getting late going on 1 a.m I hope some of this makes scents.

jdv500:
thats sounds like good stuff there.
my idle is set just enough to keep it running barely, just as yours. my needle is 2nd clip from the top. i have to admit that the surging is alot less then when i first got the bike. and not really an issue now adays. even if it's still present. your right with what your saying there, i thought that with the slide down all the way, just a crack of day-light at the bottom to allow air to mix with the pilot jet then into the reeds. your thinking this may be the source of the problem.?
* up kinda late on a work night there huh.? thanks... joe

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