250-500cc Cooked my top end on my 2012 WR300

Been out to Kingston South Eastern Australia riding in dunes with a paddle tyre on. Had severe issues with bogging and seeming to run out of fuel. After losing all throttle and locking up the back wheel, I came to a stop and went to kick it over only to have no compression. May be rings, piston or both. I'm blaming my poor tuning skills and or the mikuni carb at this point.

Any suggestions on rebuild kits?

Will probably buy a lectron as well, I hate this temperemental mikuni.

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Just pulled the pipe off and had a look up the exhaust port, piston and rings are fried. There is plenty of piston matter on the bore. Hopefully it can be honed clean and just a fresh piston kit.

What was your jetting? Sorry to hear about your problem.

32.5 pilot 420 main, it just felt like the bike was labouring badly and bottom end and mid range seemed non existent.

You can't ride deep sand dunes with a paddle tire, with the same jetting you trail ride/race at the same temps and elevation. The engine loads increase too much. Even to ride a deep sand MX track, you would usually jet up.

Just pulled the plug, it was dry with remnants of piston material on it. Gone seriously lean.

stock needle? air leak perhaps? those specs sound like a JD kit tho.

Yep jd kit, red needle, second clip

I think that the 2nd clip is way too lean for dune riding. I run 2nd/3rd clip for technical enduro riding where I'm rarely at WOT for more than a couple seconds.

Why are they so temperemental ? I just want a reasonable allround setting. Have never changed a thing on my previous bike and never had an issue.

After I bought my WR250, 2 friends bought 300s, one is a Six Days rider. Both 300s have siezed. My 250 is sold but was reliable as a hammer.

My bike has only done 300km, not sure if I should be doing bottom end as well.

What about upping the oil percentage in your gasoline and leaving the jetting alone?

Been doing a few wide open blast rides recently so I switched to 32:1. Does make it leaner so you hafta jet a lil richer. The added oil definitely provides more lubrication as a safeguard.

Was the V Force reed block sealed up between carb and block? Typical air leak location. Is the intake boot there (from carb to reeds) intact and not cracked at the joint?

I had a look and although the clamp appeared to be seated properly from the shifter side of the engine it was not seated properly after viewing from the other side once i had the exhaust removed not to mention there was a melted breather line that had been making contact with the exhaust. It is possible that's why it was running lean.

I changed my jetting just before a dune trip and placed the carburetor back into the boot. Was in a hurry and also thought same thing that it was seated properly viewed from shifter side. It wasn't. The mis-aligned clamp wore a gaping hole in the boot rim which sucked air all day and made bike run super lean. Completely shocked that it didn't seize. Careful with it now.

I always spray a little WD-40 on the mating surfaces and to make them slide into place better. And then check the mating on both sides of the bike before calling it good.

Will be a very careful rebuild, any factory fitted issues that might require attention whilst apart?

Sorry, double post.