250-500cc WR 300 running hot-really hot

I have a 2012 WR250 that I put the 300 kit on with an FMF Gnarley and standard silencer. After a few rides the mikuni was still not right and after several jetting tries I just called carb warehouse and had them send me the PWK 38. Tried the jetting they sent (I did explain what pipe I had) and it still bogged and sputtered down low and halfway through mid. So, went down to the next set of jets they sent. The sputtering went away about 60% but now the bike seems to run really hot. I'm now running a 170 main and a 48 pilot. They sent a 175 and a 52. The plug still looks a little rich.

Obviously I'm not a jetting genius, and I only ride for an hour to an hour and a half per ride. Just a little worried about what is going on. The only other symptom is it takes about 4 kicks if I stop on the trail. The coolant is up to level, is not steaming or leaking

I will be getting a temp strip this week and finally hocking up my trailtech reader. Just wanted to see if anyone had any thoughts. The wierd thing is I can put my hand on my sons cr85 cylinder and not get burned. Mine would require a trip to the er.

Do you think you might have an air bubble in your cooling system? Seems odd for the plug to indicate rich running, yet the engine is hot.

Yeah i second that. If it was running lean The plug would be dry and tan.

I guess I could drain it and try to fill again. I had this work done at a husky shop because it didn't cost that much. I would have thought they did it right. I'll try to get a picture up here as soon as I can figure out how To do it from an iPhone.

Just pull your radiator cap off and run it for a while. See if you can get some air to bubble out.

Get some of the good stuff from ZipTy.

What elevation are you at? That is an important factor in figuring out your jetting. I run a 38 pilot and a 152-155 main during the Summer depending on temps/elev. Its been super hot here so 152 as of late, elev 6000'-11000'. First kick and never spits coolant. Also, check to see if you have an air leak around your reed cage.. I can't recall if that was a prob in 12. But I do recall it being an issue on the older models, like my 09. I just bought some gasket paper, traced it and cut one out when I bought the bike. Never been an issue.

Here's a pic of a plug after two 1 hour rides.

I'm running the ice coolant but will try to see if I can get the bubble out. I ride in western PA not sure of the elevation.
Thanks for everyone's help.

Here's the bike too......

Realize this is in the wrong section...

But does anyone think this could be a thermostat issue? Can I take it out and replace it with some other type of union?

Thanks.

Could be. Does the radiator feel as hot as the cylinder head?

Radiator is hot, but I can touch it without getting burned. I would lose skin immediately on the cylinder.

I got rid of my thermostat and put the older coolant lines on. Ive run some HS in 90 degree plus for two hours in muddy nasty rock sections, etc and the bike never steamed up on me. I run engine ice as well.

Wrong size piston (too large) in the cylinder causing too much friction maybe? I've had my cooling system apart several times and have yet to have a air bubble. I just fill it up and go.

Or ring gap...?

I sort of remember an issue someone found with their cylinder where the coolant passage was blocked from the factory due to a bad casting or finish job. I searched but can't find it.

Thanks for all of the replies. Marcmo0 hit it on the head. I tightened up the vforce cage bolts as they were not snug enough. I ripped an fx temp strip off my kids bike and fired it up for a 10 minute idle and a few short trips around the yard, then another 5 minutes at 3200 rpm or so. It never got above 177F. I guess it always pays to check the simple stuff first.

I'll put some Zipty in it anyway as soon as I order.

FYI, the JD jet kits that ship in their carbs have a 45 pilot, and I believe some guys find that you be too rich. I have gone to a 42 on mine and I think I am going to go down to 40. Obviously it depends on the setup, needle, location, etc, but just as a point of reference...

i'm from western pa also,above 75 degrees and I need a 40 pilot.42 for spring and fall. imo the jd needles are too rich also. CEL in the middle clip wakes the bottom end up.

I have heard that before about the CEL, and I'd like to try one on my bike. Where did you guys get yours? It looks like PJ Motorsports might have them, but I'm open to other options.

My bike is "sputtery" just off idle with the 42 and the red needle. It doesn't really cause an issue on the trails, but on pavement or dirt roads connecting trails, when I'm going 40 mph steady with very light throttle, it feels like crap. I am going to go down to a 40 pilot, but I think I will try the CEL needle too, since it's so highly recommended.