'98 KX500 - Won't Start - Kicks back when kicked over

[manco]

So I had a decent running KX500 that became a "No Start" POS during a group moto trip. Here is the story: The bike was running fine. I took the bike up into the mountains for a few days of horsing around. The night I arrived it started & ran fine though too rich for the elevation. I took it out the next day in the am. Again it started & ran fine except rich. I decided to move the needle from OEM 3rd notch down one notch in before the group ride that day. I did so & took off with the group.

Two miles up the road & the bike is now running for crap. I am starting to think that the needle move F'd things up. I get to a good spot on the trail to wait for behind riders to catch up & look a little into the now crap running bike. The bike dies & refuses to start up via kick start. Luckily I was on a downhill and had the opportunity to push start the bike easily enough. The bike started thankfully though now running crappier then ever. The group went on. I rode back to camp to sort things out. The bike ran even worse on the way back. It was running flat , refused to wind out & was raggedy before dieing as it rolled into camp.

Once back in camp I swapped the needle back to 3rd notch then tried stating the bike. It refused. Long story short after wasting time screwing with the bike in camp I found the pilot jet was clogged & the spark was intermittent. I succeeded kick starting the bike only three times. It never idled. It had to be throttled to run. Also as the messing around proceeded the bike began to kick back once and a while being kicked over. When I say kick back I really mean kick back. It was painful even with riding boots when the lever would kick up. I never got it running. I returned home and brought up another bike to finish out the trip.

The trip is nos over. The POS KX500 darkens my shop. Its been a few days since the bike was messed with. I tried kicking it over today. It doesn't start. It does kick back more frequently when kicked over and yes my foot hurts. I am suspecting multiple air/fuel and ignition issues including possibly timing. I am gonna start by looking into intake, carb, reeds, crank seals, plug wire, coil, CDI, stator, pick up, flywheel key.

If anybody has input on what else to look into or has had similar experiences please post. Thanks.

[Foxx4Beaver]

I'd pull the mag cover, sounds like sheared key...but I could be wrong.

[tecate3]

HAVE A multitester to test the ohms on the stator coils?

[manco]

I pulled the stator cover and found the threaded flywheel weight was hand tight & held with the set screws. I am gonna need to come up with a puller for removing the flywheel. I can't see the crank key slot from the outside with the flywheel on. I still don't know if the flywheel slipped. Considering it was held hand tight it wouldn't suprise me if the key sheered. The key in the flywheel is at 4:00 when the engine is at TDC. I am not sure where the key way would be at TDC. Anyone know?

I do have a multimeter for testing. I will dig out the manual and test components after finishing messing with the flywheel.

[tecate3]

i missed the part where you said it kicked back, i agree with the other guy that the timing sounds off and the key is probably sheared. if you find that then you dont need to test the coil ohms probably.

[manco]

Oh yah. I won't be needing to mess with the coil. I got the flywheel off. Most of the key & some of the crank shaft have sheared been ground to dust collected on the rotor magnets. The crank is junk & the rotor maybe too. 

[manco]

Is this a freak thing? or do fly wheel weights increase the chance of such a thing happening?

[manco]

Can anyone tell me what years of crank will fit in a '98 case?

Update: It looks like 89 to 04 will fit.

[Foxx4Beaver]

I had a feeling ...
that's one of the worst one's I've seen...
it happens periodically...one of those things you really have no control over...

perfect time for COMPLETE rebuild....maybe even a Pinnsonault big bore kit

[Foxx4Beaver]

Can anyone tell me what years of crank will fit in a '98 case?

Update: It looks like 89 to 04 will fit.

that is correct....'89-'04.

[tecate3]

Balls dude, the flywheel weight probably didnt help. Anyway, 89-04 crank is what ya need.

[manco]

...that's one of the worst one's I've seen...

That pic is about 25% of the damage. The whole crank is damaged all the way around in a similar fashion as shown in the pic. Its really messed up.

Its definetely time for a complete rebuild to get at that crank.

[Foxx4Beaver]

just a suggestion....but it's worth every penny to have your new crank balanced....another task Pinnsonault or Crank Works can do for you.

[manco]

Does balancing the crank matter all that much if the bike is ridden primarily at low rpms? I planing an on trailing this bike primarily at low rpms. I looked into crank balancing some. I read up on balancing & weight addition. It seems like balance is to add RPMs to the top and adding weight helps low end torque. One thing I am wondering is how balancing effects reliability of the crank. Does the machining of balancing a crank weaken it structurally so as to be less durable?

If I rebuild I am thinking maybe a compression release would be nice to add. I read somewhere that someone does the mod.

[Foxx4Beaver]

balancing makes it sooo much smoother....it'll also help your crank bearings last longer, and the whole bottom end, since it won't vibrate anywhere near as much.
I had mine done, and it was one of the best things I've ever done...I generally trail ride now a days, with the occasional rip around some tracks, so I do a lot of 2nd and 3rd gear riding.
I know there's several others on here that've gone that route also, and swear by it.

Send Larry a PM...he was doing the compression releases...but I think he said his son is doing them now...
http://www.kxriders.com/forums/index.php?action=profile;u=2245

I think RoostiusMaximus said he was doing compression releases also.