250-500cc WR300 Ignition Troubles

Well, Sunday I had a race I'd been looking forward to all year. Epic dirt, super fun course. Bike was running great all morning in practice, and during pre-race warm up. Come race time, the board dropped, I cleared the first turn, bike stumbled and died by the second turn. Would not start back up. Swapped plugs, tried all kinds of crap, then towed back to the trailer after the AA row lapped me still sitting there.

I pulled the skid plate off and took the ignition cover off, nothing looked a miss, a bit of dust. I couldn't pull the flywheel off to check the stator because my clutch/ignition holder is at my dad's house.

I pulled some more parts off and looked down the spark plug hole with a flashlight, looked rather pitted for being about 10 hours on a new Vertex piston. Pulled the Lectron off, the carb boot, and pulled the reed cage out, they still looked great. I could see and feel scarring on the piston. Not cool.

So, I pulled the head, then the cylinder to get a good view of the damage. The front of the piston was damaged worse. It had a couple spots on the piston about the size of the tip of a ball point pin that were blown out and ended up as deep grooves in the cylinder wall, exhaust valve, and piston and some nice craters in the head.

I've got an '02 CR250 bottom end sitting on the bench, but I hadn't gotten around to finding a cylinder and head for it yet, let alone having the right CDI and coil for it, so I can't just swap that in there.

Pricing up new OEM parts gets up into the $1500-2000 range. Not sure why those cylinders are so expensive. So, I need a plan of action. Love the bike, in 130 hrs I've barely had an issue. But this is a bit hefty considering I still owe on it.

Cylinder - I should be able to get it fixed/plated. I've used Powerseal (thru Cycle Playground) in the past when I had my KTM 200 ported. That should knock the cost of that from $800 for OEM to around $200.

Head - I would think an engine shop would be able to machine this out, but I'm not sure. I might be able to sand/polish out the damage as well, but again not sure.

Exhaust valve - I think the only option is to get an OEM replacement.

CDI/Stator/Coil - Should I dump the Ducati set up and run the stator/flywheel/CDI/Coil from the '02 CR250? Since I already have the flywheel and stator, the rest is around $100 for OEM. I've read some sketchy things about the Ducati ignitions failing. Were the older set up better?


I'm going to pull off the flywheel tonight. It could be that the woodruff key just sheared off and the stator got out of time. But at the cost of the rebuild, I'm not sure what original components I should trust. I'm also thinking that the bottom end should be all gone through at this time as well, so I'll probably add that to the down time/cost -- and look for a craigslist bargain to finish the season on. Hopefully having this back together for the Oct 20 national enduro.

Any thoughts? If I could find a deal on a cylinder, exhaust valve, and head, I would really consider building up the CR250 and putting it in.

wow
a lot going on, go back to basics
why did it not restart? was it ignition related, heard they were weak
why is there piston damage? pre-ignition or hard part damage?
I would recommend looking at each item individually
jumping cc's is ok but why?
lot of questions in one post

I'm at the conclusion that it was ignition related do to the fact that it looks like detonation damage on the piston and head. There was no problem with the gas, 93 octane non-ethanol like I always run, 40:1 with Amsoil Dominator. The bike had no issue prior to clearing the first turn. It ran great that morning and just before the start of the race. So, I'm at it has to be something went bad pretty quick at speed. CDI, stator shearing the woodruf key and spinning enough to get the timing off, or stator otherwise failing.

I'm assuming that the spark was too faint or not timed correctly to start. It did back fire a few times which is not normal. It had no hint of starting. Even with the piston damage, I would think it would have still tried to fire.

I checked the basics when I was trying to get it going, fuel, compression, and spark. It was definitely getting fuel. It had compression, though it apparently was not ideal after the parts of the piston decided to go AWOL. I checked spark by site, it had a spark, it was faint, but I couldn't say if it was strong enough or timed correctly.


Jumping from 300 to 250 would be for quicker revs, and if that meant I could get it back to running sooner. I was planning on finding another frame to put the CR250 in and set it up for a MX/backup bike. So, it's just an option I have.

the weak spark happened on mine mainly when hot
Tim, RideReno on this site took the time to look at my 99 360
he replaced the ignition and it started a lot better but hot still would not relight
the plug cap was the end result of the looking oddly enough seems it was not a good part, who would have guessed