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So I purchased a 2011 EXC 300, It had been in storage for several years and was in very good shape. It had been put in storage full of fuel.

 

I bring it home clean the carb, tank and replace fuel lines. Fires right up but smoking like a pig, seriously loaded up and drooling like an old man at a strip club.

 

I think ok bad clutch side crank seal so I drain the trans oil and fire it up. It cleans up and runs better jetting seems fat but much better. I then refill the trans with ATF, fire it up and it loads right up again.

 

So I am now sure it is a clutch side crank seal and I freshen the top end and replace the clutch side crank seal.

 

Still loaded up and smoking and drooling.

 

WTF?

 

Bad crank bearing?

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The seal rarely goes bad on it's own. The most likely cause is bad crank bearings. Did you also replace the O ring behind the spacer? Was the spacer badly grooved from the seal?

 

Float height and jetting are your other possibilities if you are not sucking trans oil. Also bad reeds. Post all the jetting in the bike now and your riding conditions. It could be as simple as moving the clip up a notch.

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Jetting is 172 45 needle second from top. Bench tested needle and seat to assure fuel was shutting off and float was floating. I am at 5000 ft purchased from PO at 1000 ft so I am sure it is fat, but not this fat.

 

I did not know there was an o-ring behind the spacer so no I did not replace it. Spacer was not grooved. I believe my next step is to split the cases and go for crank, bearings and seals.

 

Beginning to think this is why PO put in storage, not as good a deal as I thought.

 

Thanks for the reply.

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I was thinking the same as to why it was in storage.

You didn't say what needle, just the clip position.

172 mj seems rich if the carb is the stock 36 MM. The 45 pj is also very rich. I think if the needle is stock OEM [N2ZJ] the pj was 35 and mj 162.

 

Before you split the cases make certain the lower end is loose and that you are burning transmission oil.

A good test is to pull the ignition side cover, grap the FW and push in and out. There should be no movement. If there is only a barely perceptable detection of movement the bearings are beginning to wear but you may still be good.

 

Replace the O ring behind the spacer. The spacer goes in only one way, There is a bevel or groove to accomodate the O ring, do not reverse the spacer. While you have the drive gear off, grab the crankshaft and try and move up / down. There should be no movement, barely perceptable, bearing is wearing but may still be useable for a time. Significant movement means the bottom end is shot and is why the new seal is not working.

 

If your burning transmission oil it should smell like oil and not premix. Maybe drain the oil and refill with an exact amount. Ride for maybe 100 miles, drain the oil and see if you get the same amount you put in. If not and there are no external leaks you know where the oil went.

 

Your jetting could still be at fault so don't tear into the bottom end just yet. 

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I would check the o-ring behind the spacer, if you didn't know there was one. I just went through the same problem on my bike and come to find out the o-ring was missing from behind the spacer, meaning the previous owner must of replaced the seals and forgot the o-ring, causing it to suck in tranny oil.

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Your jetting is waaaay rich, put a 35 or 38 pilot jet in and drop to a 165 main with needle in middle position. It will be better, not perfect but it will stop loading up like it is. You can split the cases and everything else but when you are done with that you will still be pig rich and loading up, unless you are riding at -55 degrees F at sea level....

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OK so I split the cases and found a roasted clutch side crank brg. Blue turns rough and is very noisy but could feel no slop from the crank even with the jug off.

 

Order brgs and gaskets today.

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That sucks, I know your pain though I split cases after second ride on my 250xc when it spit the power valve pin into the primary and sent chunks everywhere.

When you get it buttoned back up try leaning it out a bit from the jetting you posted. it will pull much better!

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