Author Topic: 87 KX500 No Start Questions  (Read 13535 times)

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Offline BrantSFGDS

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87 KX500 No Start Questions
« on: April 29, 2014, 11:58:58 AM »
Greetings all! New member from KY here. So, let me bring everyone up to speed on my new "project". An old friend recently gave me an 87 KX500 as payment for getting his Bobcat running. The last time he rode the bike was 4 years ago at which point it ran great and the engine was fresh. He was involved in a serious accident which led to the bike being stored until 2 weeks ago. I brought the bike home and started all the normal maintenance along with rebuilding the carb. So, I got everything ready to go and didn't have any spark. I tested the electronics by the manual and found the ignition coil was toast. I scrounged up a good coil and now I have spark. At this point, the bike should run, or, at least, pop, fart, backfire or something. Nada, nothing! I can't come up with any mechanical reason why this bike shouldn't run. Compression is good, no blowback through the reeds and no obvious air leaks. Here's what I need to know, since I'm not a CDI guru; will a bad CDI box fire the coil, but at the wrong time? I ask because the spark I'm getting doesn't look normal to me. I'm a mechanic, just not a CDI guy, and everything I've ever spark tested before has a single spark across the plug at the appropriate time. This thing looks like a taser across the plug. I'm talking about grounding the plug on the head and pushing the kicker through by hand. Does this sound normal or do I need to start looking for a CDI box? Thoughts?

Offline Foxx4Beaver

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Re: 87 KX500 No Start Questions
« Reply #1 on: April 29, 2014, 12:20:38 PM »
This thing looks like a taser across the plug. I'm talking about grounding the plug on the head and pushing the kicker through by hand. Does this sound normal or do I need to start looking for a CDI box? Thoughts?

1st, welcome to the site!
I'm not totally sure I'm following completely right....but I had a similar experience with a 250, and it ended up being a cracked plug cap.
Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Offline reklessj

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Re: 87 KX500 No Start Questions
« Reply #2 on: April 29, 2014, 02:11:21 PM »
Hey Brant, welcome!! Try reading "having electrical problems on your K5?" By sandblaster. That article had me up and running in no time!! Listen to these guys most everyone knows their sh!t and I've gotten all the help n info from this forum
My rides: 1994 KX500, 1988 T4, 1998, ZXI 1100 JETSKI, 2003 MOUNTAIN CAT 900
WIFES (Baby Fiver) rides: 2004 KTM 105SX,1992 LT250R, 1995 ZXI 900 JETSKI,  2011 RMK 600
SONS ride: 1995 YZ125,2002 RM 250
other rides: 2007 RMZ450 RC Ediition, 2003 RMK700

Offline sandblaster

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Re: 87 KX500 No Start Questions
« Reply #3 on: April 29, 2014, 03:46:26 PM »
It may be a bit simplistic for you but it wouldn't hurt to review it:

http://www.oem-cycle.com/forum/viewtopic.php?f=40&t=163
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline BrantSFGDS

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Re: 87 KX500 No Start Questions
« Reply #4 on: April 29, 2014, 10:34:29 PM »
Thanks for the welcome guys! Sandblaster, I read the entire thread and found it to be very informative. I'm still at a standstill though because I don't know what to check next since I actually have spark. My first instinct is to look for something else since I have spark, but something doesn't look right about it. I checked the timing on the stator and it's fine. There is a procedure in my manual for how to test the CDI box. I had to go buy the required resistors and I hope to give it a go tonight or tomorrow. I wouldn't even be looking at electronics if I was only getting 1 or 2 sparks when I pushed the kicker down but this thing looks like a constant arc.

Offline sandblaster

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Re: 87 KX500 No Start Questions
« Reply #5 on: April 30, 2014, 02:17:11 AM »
Did you test the ohm specs for the stator and coil?
Have you pulled the fly wheel off and checked to see if the key that holds it to the shaft is sheared?
If so, while you had the flywheel off did you inspect the inside carefully for damage?
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline BrantSFGDS

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Re: 87 KX500 No Start Questions
« Reply #6 on: April 30, 2014, 05:05:57 AM »
I did check the stator, trigger and ignition coils with a meter. The ignition coil was bad and has been replaced with a good one. I have not pulled the flywheel yet but it looks like it may have been replaced at some point. There is signs of pitting on the flywheel but no rust, like it's been bead blasted. The inside of the cover is dry. I'll pull the flywheel this weekend and check it out.

Offline sandblaster

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Re: 87 KX500 No Start Questions
« Reply #7 on: April 30, 2014, 07:20:04 AM »
Make sure your flywheel is stamped F3T81171
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline serafin

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Re: 87 KX500 No Start Questions
« Reply #8 on: April 30, 2014, 09:34:53 AM »
I know this sounds real basic, but your using the correct and new spark plug, right?  Kinda like a dead battery may show 12 volts, but when under load it's dead.  Same with a bad plug, when under compression it wont fire.  Just a thought.

S   

Offline BrantSFGDS

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Re: 87 KX500 No Start Questions
« Reply #9 on: April 30, 2014, 12:19:35 PM »
Yep, new correct plug. I had to order it so I got 2. I tested the CDI box according the manual and it tests bad. Anybody got a CDI box for a 1987 500? I'm still going to pull the flywheel but at least I have confirmation that something ain't right, lol. I am surprised that I'm getting spark at all.

Just out of curiosity, will a later model set of electronics work on an 87 if you change the entire system? Will the stator and flywheel bolt on? I'm thinking it may be smart to update the entire system for the sake of parts availability. 

Offline motopunk

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Re: 87 KX500 No Start Questions
« Reply #10 on: April 30, 2014, 03:15:26 PM »
Yep, new correct plug. I had to order it so I got 2. I tested the CDI box according the manual and it tests bad. Anybody got a CDI box for a 1987 500? I'm still going to pull the flywheel but at least I have confirmation that something ain't right, lol. I am surprised that I'm getting spark at all.

Just out of curiosity, will a later model set of electronics work on an 87 if you change the entire system? Will the stator and flywheel bolt on? I'm thinking it may be smart to update the entire system for the sake of parts availability. 
 

yes, if you change the whole ignition system, you can use anyone, that fits to the kx500...
big 2 stroke bikes are weapons for real men, who don´t fear death or devil. ;O)
´83 kx250, ´87 kx250 (with 360 big bore), 87 kx500, ´93 kx500 sfc

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Offline BrantSFGDS

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Re: 87 KX500 No Start Questions
« Reply #11 on: May 06, 2014, 12:20:43 PM »
I pulled the mag today and don't see anything wrong with it. It has the correct number stamped into it and the magnets are tight.

Offline sandblaster

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Re: 87 KX500 No Start Questions
« Reply #12 on: May 06, 2014, 12:35:16 PM »
Did you test the stator with the correct ohm specs?
87-89 KX500 - 21003-1169 -
432-648 OHMS: BLACK/WHITE TO BLACK/YELLOW -
4.0-6.0 OHMS: WHITE/RED TO BLACK/YELLOW
« Last Edit: May 06, 2014, 12:36:47 PM by sandblaster »
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline BrantSFGDS

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Re: 87 KX500 No Start Questions
« Reply #13 on: May 06, 2014, 12:43:33 PM »
Yes, both coils on the stator test good. The cdi box tests bad but I've read somewhere that testing the cdi box may be unreliable.

Offline sandblaster

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Re: 87 KX500 No Start Questions
« Reply #14 on: May 06, 2014, 12:47:43 PM »
Not sure about the 87 but the 89-04 you can't test the CDI other then to make sure everything else works.
If everything else is in spec then the CDI must be bad.
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.