KX Riders
Maintenance & Technical => KX500 Original => Topic started by: cass on February 09, 2009, 09:50:18 AM
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hi guy`s can you give any ideas why my kx 500 90 wont start? just ran- in ! out last week coughed then died, changed plug fired once then nothing. ive reset floats, checked all wiring with ohm meter within tolerences , mag & stator ok !if you put fuel down the cylinder she still wont start! pull the plug out and its still sparking ! tons off compresion full engine rebuild . surely it sould cough or fart or something? ive never had this problem with a 2 stroke in my 25 year playing with them! not check reeds yet but should still fire with a shot of petrol down the head? fresh fuel in it as well ! woodriff key is perfect and timming bang on! engine has had every seal & bearing done as well !
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Something has to be off. You only need compression, fuel and fire to light up.
How good is the spark? Fat and blue? Stator may be failing.
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I would say your timming is off. Maybe your flywheel had rotated on the crank some how? If you have the three needs for a engine to run then one of the variables are off.
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Have you checked to make sure the flywheel key hasn't sheared?
EDIT!
Sorry, I see you checked the key on the flywheel... :oops:
Will she run if you pull/push start?
There is another post here a fellow had the same set-up whith his 450, after tons of money replacing parts it ended up his flywheel/mag was bad.
I'll look for the thread... See below :-D
Tuck\o/
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sometimes they pop and bang out the zorst like there gonna go when woodruff key has sheared. check here first, then timing, then fuel and filter.have you just oiled filter? sometimes if not left to dry sufficiently they dont allow air flow, hence not running......... :x
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Read through this thread please, Sounds like alot of similar circumstances.
http://www.kxriders.com/forums/index.php/topic,2854.0.html
Tuck\o/
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Cass,
It sounds like the flywheel. Did you remove the flywheel to verfy the key is intact? Let us know. There are also instances where a plug will foul enough so it won't fire under load (in the cyl) but will when removed. Cam.
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cam22, key is perfect ! brand new plug as well ! do you think it could be cdi ? how can i test it ? what ratings should it be kicking out?
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Cass,
It sounds like the flywheel. Did you remove the flywheel to verfy the key is intact? Let us know. There are also instances where a plug will foul enough so it won't fire under load (in the cyl) but will when removed. Cam.
yeah had something similar today,my moped wouldn,t start good for ages..
now it was dark and i was running again :-D
looked down ,saw the spark escape trough a gap in the plugcap
maybe check it like that too??
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definitely check the CDI.
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If you have a friend with a quad, try to pull start it. I submerged a cr250 completely under water. Took about fifty feet of pull starting to get it to fire up.( yes I dried out the air box first.)
The fuel is known good?
The spark is known good?
The compression is known good?
I am sure you are getting tired of the same old questions from everyone, but good compression at the right time, good spark at the right time and the right amount of fuel in the combustion chamber at the right time. IT SHOULD RUN.
John
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My 5 has a 44tron and sometimes the floats stick and floods the cylinder. When this happens it won't start and I have to turn off the fuel, remove the spark plug, put the bike in gear and either just push it around or pull it a bit behind quad -in gear- then put the plug back in and it fires right up. then turn the gas back on.
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cass,
Is your plug wet or dry after you try to start it multiple times? It is possible that it is the CDI. Sometimes they fail weird before they die outright. I once had one go (non KX) under your circumstances - after a rebuild. As I was breaking it in on a slow trail ride the bike began seizing repeatedly. It took about 7 or 8 seizures before I got back to the truck then it wouldn't start, which I attributed to the multiple seizures. In my shop I found no spark then tested the cdi which proved to be bad. Last thing I suspected - I was expecting an air leak.
If you are putting gas down the plug hole and it still doens't fire then there is either, no spark, no compression, or spark at wrong time. Those are the only 3 possibilities. Sounds like you have ruled out the first two so is has to be the third, "spark at wrong time". That can only be sheared flywheel key, damaged impulse pickup, or bad CDI. You have ruled out one of these so it could be, "damaged impulse pickup" or "bad CDI". An ohm meter should verify the pickup (you might have already done this) - you can have heat issues with pickup failures but that is not the case here. Sounds like "bad CD" is the winner.
Heres some suggestions:
1. CDIs arn't cheap. It would be nice to borrow a cdi and try it -but hard to find.
2. Try kicking it over with a timing light on the flywheel to see if it fires at the mark.
Hope this helps. Cam.
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I would still want to check reeds. It seems like it would do something with fuel poured right in there, but might have to be right mixture to kick. Also, another way over obvious suggestion/question, did you swap plug out? Could have been a bad plug that you recently put in. Try not to eliminate things completely, because you already checked. Also, check jets in carb for debris, petcock for flow,
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Check the kill switch.
A buddy of mine replaced many parts including the CDI module just to find out that his kill switch was bad. His was an intermittent problem. Once the bike died the vibration would stop and the bike would usually start again. Sometimes he could ride for hours before the kill switch would act up.
The symptoms you describe don't really point to the kill switch but it may be worth a try and a cheap fix.
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Depending on how bad, the reeds could be the culprit or maybe even a blown crank seal. as all have said, spark (at the right time, compression and fuel and it should start.
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and Air :-D
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HI GUYS CHECKED REEDS TODAY THERE OK ! REPLACED NGK CAP , CLEANED FLY WHEEL AND THE PICK UP`S ON STATOR PLATE! STILL WONT START! WOULD IT DRAW AIR FROM POWER VALVE SEAL WERE THE ROD COMES OUT OF THE SIDE OF CYLINDER AS IT WAS A BIT OILY WHEN I TOOK THE COVER OFF? GOING TO BUY MORE PLUGS MABEE I GOT TWO DUDS FROM MX SHOP! I`LL KEEP YOU POSTED CHEERS
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Cass, this is really a buggar...
I'm tempted to send you my flywheel and pick-up to try..
If the plugs don't do it send me a P.M. and if you'll pay to ship them back to me I'll take them off and pay to ship to you.
Tuck\o/
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Is there any chance you somehow got water down in the motor [preasure washed it,left it out in rain] ? I had an older rm250 one time, the powervalve breather came off and water got down in the motor. I had to pull motor, pull the top end and wash the bottomend out with fresh fuel before putting it back together and it fired first kick.
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cheers for the offer friar tuck ! but i have to decline your offer as i stay in the uk , and it would be crazy to send it over to me . the guy`s on this site are so genuine and helpfull . i tried starting it today just wetting the plug all the time, took mag and stator plate off again now theres a small amount of black oily fuel on the crank seal i take it is blown ? i just replaced them when i did the rebuild. including crank case bearings ! bike has only been ran it 1-2 hours puttering around so what caused them to blow? still waiting to get new plugs! tied my jetski plugs in it and still nothing?
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Know this is getting interesting. This is what I think has happened. You replaced everything in the engine, but you may have a blockage in your pipe. You are getting too much back pressure on the engine and developing too much crank case pressure causing the seals to blow out. try starting the bike without the muffler or pipe and see what happens.
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cbxRACER,
Thats a new one for me but a great idea. I know a bike with a soaking wet air filter won't start with all the water vapour drawn in. A puddle in the bottom of the crank case would do much the same. I'll add that one to the memory bank. A plugged exhasut pipe will definitely prevent it from starting but I can't say that I have ever encountered that except when I am an idiot and leave my butt plug thingy in my silencer. Cam.
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butt plug thingy
... that's funny.
-G
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cass,
sounds like you may have a cdi problem to me, you seemed to have checked everythin else, so as i noticed u said ur in uk, try westcountry windings for a replacement. when mine died corby kwak wanted over 200 quid, but westcountry do one for about 115 all in.hth. you can get em on 01279 731172.
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hi guys got new plugs spark today!. spark is still prety s**t! if i earth plug to the pipe, coil and plug spark and it jumps to pipe ok . but if you try and use one of the head bolts the spark is s**t! it still wont start! just took clutch case off. power valve was not engaging into mech so would that stop it from starting? ie; valve ports not moving . im due to torch this f**ker because it should be running ! ive had this baby from 1991/ it`s a 89 uk model so me and this bike has a lot of history . ive just restored it back to new and its doing this to me! should have left it the way it was an old dog that still went! i will post pictures of before and after only when its running the way it used to !
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cass,
when you say you just restored your bike , did you paint the frame ? If you did , you may not have a good ground at the coil. If you did paint it ,the best thing to do is grind the paint off the frame where the coil mounts for a good ground. Also are you sure you have good compression and motor also spin freely with the plug out ? A bad crank bearing will seem like compression. Just some thoughts hope you get it figured out RonM.
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cheers for the advice, have already buffed paint of at coil , also every bearing and seal changed on engine! now fuel is leaking from crank into mag ?. does this mean seal is f**ked because it wont spark right. Ie flooding it self > what causes crank seals to fail when there brand new?
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A little weeping is no big deal. Also, the spark doesn't look bright like a car or truch, IMO. I had a hard time seeing mine also, until I checked in the dark. More often then not, it has spark or no spark. Its not too often that its a weak spark, unless its a deal like that on a loose or bad ground. I'd say you are chasing a cylinder issue or carb problem. If the crank seal was bad, it would still run. I know this is basic, but does fuel poor freely from petcock? How bout when tipped over, does it come out of overflows? Exhaust is definately clear? U tried different throttle positions? Hows the kicker working? I have to get it just right on the sweet spot on top, so I get 2 cycles or it won't start. Especially right after the rings set-in and compression was the highest.
Air leaks or blown gaskets, will usually make it rev high.
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Offtopic:
What does a good spark look like? Is blue and fat good and white is bad?
-J
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hi hillclimer what do you mean by cylinder problem? if i lean bike over fuel comes out of overflows! got reed block out and waiting for fuel to evaporate then ill try her again if it doesent start ill bite the bullet and buy a new cdi !
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At least you are getting fuel to there. Cylinder problem/ compression, is what I mean. A hot plug or lean oroblem can melt a hole in piston. Worse case scenario, but it sounds like you are working out most other possibilities. How cold is it there? Mine had lots of trouble starting in 40 degrees. Does the kick feel like there's plenty of compression? And it kicks free with plug out? Is the kicker worn to where its hard to get the full hard kick?
I have had trouble finding spark, by the sight method, when looking for it with lights on. You can remove plug and put the cap on it, so the engine spins free, but always use a plug, or it may cause damage to ignition. Usually any spark, is a good one. Not always, but thats what makes that kinda problem hard to find.
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You really are having a problem out of this bike. What I would do now is a vacuum and pressure test on the engine. Your seals should not have any gas "even if it is severally flooding" go past them. Crankcase pressure is a two cycle's life line.
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hey guy`s just thought i would let yous know got bike going now! their was a little pin hole in cdi were it bolts to frame and the cdi was full of water, got a hair drier on to it, dryed it out and it started first kick ! back shock is away for rebuild now, then i can go racing! thanks for all the helpfull posts cheer`s
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Jinkies!
Thanks for posting up the fix Cass, something to store in the old memory bank...
Cheers!
Tuck\o/