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Discussion Starter · #1 ·
Guys - been a while (bikes have been running good :) but I've got a problem with my son's 2012 250XC. Last spring, I pulled it apart and did the top end with a Slaven's kit - higher compression head - and after putting it back together, it ran great great for the summer. Was riding in the fall and after it running for about a half hour, it just quit and we couldn't get it going again. It was late fall so we put it away for the winter and I pulled it back out a couple weeks ago. The starter had not been working so I decided to replace it and while I had that open, I put a new stator in. Also pulled the carb off, cleaned that up and put a new plug in it. Fired it up, it ran for about 15 seconds then quit and we haven't been able to get it going again.

I'm kind of at a loss ... any thoughts on steps to diagnose would be greatly appreciated.
 

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Have you done a compression test? If that checks out you could check the cleanliness of your petcock, and also make sure it can vent at the top of the tank. Sounds like you have all of spark dealt with. If you have a camera on a stick, i don’t remember what the actual name is, but you could look for streaking and grooves in the cylinder through the spark plug. Also i would check and see if your gas still seems good, maybe drain and refill the bike it seems necessary. Did slavens say to change the jetting for the higher compression? That may be an issue


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Discussion Starter · #3 ·
I have not done a compression test. Not sure what the compression should be. It seems very high ... it's a bitch to kick. The Slaven's kit came with two inserts for the head, one for high elevation, one for lower. We never ride above 1,000 feet so we used the lower of course. No mention of jetting. We bought some VP fuel and my son was adding that but I don't know at what ratio. Could that be it?
 

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Just make sure you are running oil in your gas! I use amsoil dominator at 50:1 but vp may use a different ratio. Have you tested for spark just by looking to see if it sparks when you kick it? Also we have an ‘07 250xc that every time we get it out to run it we have to tap outside of the float bowl with an extension to start it, not sure why, but it likes to stick. That may be your problem. Also sometimes a bike with a fresh top end may not need choke to start, so i would try both on and off choke. And last but not least a roll start may be what it needs to get it to fire up that first time


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Does it refuse to start when kicked also? I have some issues with the estart on those. Give the bastard a quick shot of spray ether in spark plug hole and see if she starts.
 

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Discussion Starter · #6 ·
I have confirmed spark, will check again. Have mostly tried to start with choke, no throttle but I'm afraid we're flooding it. Augie, yes, we're using the kick starter (since the E-starter is crappy) and it won't start with it. My bike (2013 250XC) is running great so I'm going to empty his carb bowl and then put my tank on his bike and a try it. I have tried ether (through intake) and no luck. I'll try it through the plug hole when I get the tank switched. My buddy has a compression checker, what should compression be? 150psi or so?
 

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Compression should be higher than 120 psi
If the bastard won't fire with spray of ether in cylinder something is really wrong in there. Best to check for strong spark before chasing fuel troubles. Fuel problems will be verified by motor running on ether.
 
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Discussion Starter · #8 ·
Understand Augie - so your point is that if I have spark, it should run on Ether, at least until the Ether is burned up ... then if it dies, it's fuel. If it won't start on ether, then it's spark or worse. Got it, thanks guys.
 

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Discussion Starter · #9 ·
Understand Augie - so your point is that if I have spark, it should run on Ether, at least until the Ether is burned up ... then if it dies, it's fuel. If it won't start on ether, then it's spark or worse. Got it, thanks guys.
ok - I’m really lost. Have tried everything. I have confirmed spark (got shocked and can see it arc). Put my tank on it (‘13XC running perfectly) shot it full of ether through the plug hole and manages to get it running (very rough) for about 5 seconds. Then quit. Would seem like fuel right? Took carb off and cleaned it and checked reeds. Pipe off and kicked it to try to dry it out. Back together with more ether and now I can’t get it to start with ether either. Has a Slavens high performance piston and head and las lots of compression - it’s a bitch to kick. Took the cylinder head off and looked everything over - pic attached with piston on downstroke. No visible signs of trouble on piston top or cylinder walls. My next step is in for service - the bikes probably only worth $3500 so I really don’t want to pay a mechanic much … any help on next steps of troubleshooting would be greatly appreciate. Also, there was a couple ounces of fluid in the pipe when we took it off - unburnt ether/gas? Are we flooding it? Trying it no choke, no throttle - then a little throttle. Then no throttle with choke. Nothing works. Appreciate the help guys.
 

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Yikes! That bike is a mess! I suspect motor is really loaded with raw fuel if it refuses to start with ether. Do you have compressed air available to blow out cylinder and crankcase? If not maybe you can remove ignition cover and spin motor (with fuel off) with electric drill turning the flywheel bolt(counter clockwise) until you no longer observe fuel vapor spewing from spark plug hole. Once she's cleared out give it a quick 2 second blast of ether into plug opening and try again. Best to loosen air filter also. If filter is soaked it will cause rich running or possible no start. Check back as needed for assistance
 

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I use compressed air into spark plug hole and slowly rotate motor with kickstarter while blowing air into cylinder. That is usually sufficient to clear it well enough to get it to fire up. If crankcase is loaded up she's going to smoke like a freight train until all that metal inside warms up and vaporizes all that premix in there. Best not to let it idle below 3000 rpm for awhile until that burns out. If it loads up and stalls it will be miserable to restart. I'd bring the bastard up my local mountain or hillside road and bump start it if it gave me too much trouble. Once she's cleared out you should be fine. Don't touch jetting or tuning until she's running again. It ran good prior to this problem so no need to try tuning it out. It's not a tuning problem. Check back as needed for assistance
 
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