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KX100 - No Power?

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Jul 21, 2007
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#1
Just got me a '97 KX100 and its not running right. When I got it, it had some weird spark plug in it and would barely run. So I put in a BR8ES and it runs alot better, starts first kick but it seems like its never in the powerband, wont spin the tire or pull a wheelie even in first. And it seems like there is a rev limiter but its not at that high of an rpm. But there is a probably 500rpm time frame in each gear where the bike pulls pretty hard - slow, fast, and the slow again. for that split second it seems like thats how the bike should always run. Where should I start? Clean the carb, different plug, what?

I was told the bike has been sitting for a month but it has less than 30min since full rebuild -crank and bearings, piston, etc plus it has new stator and clutch. Its in good shape and has some other new parts, Once I get it running right it seems like it would be a really fun bike to screw around on. Should be pretty fast? I topped it out at 55mph today and I could tell it was just about reacing max rpm.

So Im just looking for a place to start, Im sure its something simple. What plug should I be using, and also what mix ratio - 32:1? Any help will be greatly appreciated, would like to go riding tomorow. Thanks!
 
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Jan 3, 2007
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#2
JohnF, it sounds like you need to clean the carb and mabe buy one size bigger and smaller main jets, and pilot jets, and then play with jetting the bike properly. Then the bike should spin the rear tire and catwalk really nice. Also, the spark plug is the right one and 32:1 will work well in the bike after you jet the carb properly. This will help you jet your carb, http://justkdx.dirtrider.net/
Then go to tech tips on the left and then go to engine hop ups and finally to carb tunning. Have fun.
 
Joined
Jul 18, 2007
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#3
yeah man, and dont just go throwing any plug in your bike. Assuming you dont already know this, if that plug is to long the carb. will be the least of your worries. Get a manual or call a shop and get the right plug. That plug is an NGK you got in it, I run B8ES in my rm 125...
 
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Sep 12, 2006
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#5
Run a compression test, check the reeds, make sure the silencer isn't pluged, if this bike has a power valve (not sure if that year had one yet) make sure it isn't broken or stuck.
 
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#6
JohnF, the BR8ES is the right plug. Do all of what griff siad and also clean the air filter by soaking it in gas for a bit and let it dry.
 
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Jun 22, 2007
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#8
i run a BR9ES plug in my kx100... a BR8ES (NGK-R) or B8ES (NGK) are slightly hotter but I'm sure they'd work fine. As for the power issue, I'd fiddle with jetting and see if that helps. While you have the carburetor off undo the reed cage and make sure they aren't all mangled. If that doesn't work I'd check the powervalve... If it was stuck you'd still have good high rpm power but hardly any low end (like a yz80 :P). Oh, and they said it only had 30mins on it? After i rebuild (or even put a top end) in my bike i usually run a tank or two of gas through only riding at about 50% load in order to break it in, that way the rings seat properly. I'm sure that's overkill but according to our local Kawasaki dealer you should always give a bike a "break-in run".
 
Joined
Jul 21, 2007
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#9
ok i cleaned the air filter, checked the reeds and they look brand new, and it has good compression.

the bike really runs like crap, it starts up first kick though ussually. its got no power, no wheelies, no spinning of the tire. but once in a while ill feel it pull good for a split second at high rpm. most of all it sounds horrible, not smooth at all.

oh and also I just found out its a KX80, would that require a different spark plug? Im pretty pissed I know this guy lied to me, he also said it ran perfect and just needed a new spark plug thats why it ran bad when I got it. If I dont get this thing running good without spending alot of money Im gunna have to burn the guys house down

im gunna go take the silencer off and see if its plugged
 

oldguy

Always Broken
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Dec 26, 1999
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#11
I would now be very leery of the 30 minutes on a topend rebuild. If the guy passed off a KX80 as a KX100 he probably saw he had you foolsnagged pretty good and set the hook alll the way.
You are going to need to do a compression test which should tell you if the piston and rings are any good.
The lack of power is either that or the jetting is way off. You also need to pull the carb and be sure every opening is clear of obstructions best bet is to blow each one out.
Good luck and keep in mind if you can do it yourself it won't be a bank breaker- at least you are not repairing a 4 stroke
 
Joined
Jul 21, 2007
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#12
the carb is cleaned for sure, i do think however i need to adjust the float level. i ran out of gas yesterday and leaned it on its side to fill the bowl back up and when i started it, it took off like it should through 1st and second and then went back to ussuall. so i think its not getting enough fuel. but then i was running out of gas again in 5th gear and it ran like a bandit through the top of 6th and then it was out of gas. i know bikes run faster when theyre leaning out (i know its bad) so then i thought maybe its getting too much fuel.

i guess it could be jetted wrong but I think it would have to be way off to run this bad. what size should the jets be? ill check them to see if they are the right ones but i dont think its the problem.

ill take a video of it tommorow and show you all how it runs. its not that its just always slow, its that it runs like crap and then for a second it will move ok. Running rough is the best way I can describe it. I would think if the compression was bad it would be more consistant and just always slow, but its really unpredictable how its gunna run. from kicking it, it feels like the compression is really good but ill check it with the gauge.

so....

carb is clean
air filter is clean
exhaust is not plugged
spark plug is good
reeds look brand new
compression seems really good
fresh gas

possibly the float level needs to be adjusted....how do i do that?
 
Joined
Jul 21, 2007
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#13
and on another subject....would it be possible to fit a kx125 motor in here? it looks like its already pretty cramped, just wondering how much physically bigger the 125 motor is. i can weld and fabricated no prob btw, but i dont want to cut the bottom of the frame out to accomidate a taller motor and then make lower rails
 
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May 5, 2007
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#14
I would think its the clutch.If it had low compression itd be hard to start.If it had bad gas itd be hard to start.If it had a clogged carb it would pick up then bog hard and not pull at all during the bog.But if the clutch is slipping then it would get the rpms but none of the power to the wheel.But im no expert and im not sue if a manual clutch can even slip.But it seems like itd be a clutch issue to me.Unless its bogging and not pulling at all i really would think its a clutch issue.Some one more knowlageable please correct me if im wrong.Hope i helped.
 
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#15
derek the 2 stroke, man your awsome. I never thought about it but that would make a good deal of scence. Take a look at the clutch and see if the basket is grooved abd if so then time for a new one.