Heat Seize at High Speed? CHT Sensor Leak?

[dresearch]

Re read the post and a 45 pilot is huge on stock pb carburetor, unless....there is no air filter in the air box. Or it is not oiled properly. Did you positively cap off the pulse-port under the oil pump area? If it's leaking there then you have symptoms like you described earlier.
I would do a 6-7 psi crankcase pressure test for leaks. Only test to 6-7 psi and monitor the gauge. Use a 0-30 psi gauge if you can get a gauge that small. 0-100 or higher is not going to be near as accurate. Just 6-7 psi watch for leaks in the area I mentioned and use soapy water in a spray bottle. Remove carburetor, air box, exhaust pipe and spark plug and seal off those openings first. Resolve any leaks and re test compression before riding. The 38 pilot is sufficient to use and if everything else is bone stock, the 80 main jet is plenty big or the 78 and raise the needle one notch. BR8 plug is what I use also.

Thanks so much for the info Bones, it helps to know what jets you're running.

I pulled the fan shroud off a few nights ago and found that the headgasket didn't seal properly and there was a small leak again. Is there a cure time for the copper spray? It doesn't help that I'm working outside in near freezing temps, I'm sure it doesn't help the copper spray to seal properly. I may have made the mistake last time of running the motor 30 minutes after installing the headgasket with copper spray. It may have blew out the coating before it could seal.

Anyway, I used another gasket and sprayed it with copper spray again and let it sit for 2-days, and now the head seems to be sealed because my idle races with the huge pilot jet installed. Carb tuning is difficult, the throttle sputters and the idle doesn't settle until a few seconds after coming to a stop, probably from all the excess fuel dumping from the larger pilot. Engine temps run a lot cooler though, I can barely get it to spike 300F. Will need to downjet the pilot and retune. I'm just hoping I don't blowout the headgasket again. It just might be my calling to get a Polini kit already..

[Wheelman-111]

Greetings:

All the copper-containing Goo in the world won't help a head gasket leak if it's caused by non-flat surfaces or a nick somewhere.
Consider this: Get a sheet of glass. Tape a full sheet of 220-grit wet-dry sandpaper to it. Then Ouija-board the head and the cylinder jug on it until all the high and low spots are gone. Then just wash well and install the top end with a new gasket and torque to spec.

[Meloshameless]

U could be getting an air leak from either crank seal as well, did u happen to check those?

[dresearch]

U could be getting an air leak from either crank seal as well, did u happen to check those?

The seals were replaced prior to the swap. I don't see any blowby near the seals.

[dresearch]

I ended up downjetting back to the original 38 pilot and throttle response and idle is a lot better. I maybe potentially have a small leak at the airbox neck as there's a lot of wiggle room between the neck and the connection into the airbox.

Also, I've come across a new issue where the idle speed screw is completely screwed in with the air screw at 1.5 turns out. Turning the air screw clockwise raises the idle speed, but I'm unable to turn the speed back down to the baseline 1,800 rpm since the idle speed screw is completely shut. Has anyone experienced this issue?

[Wheelman-111]

Greetings:

Check for a bent needle jet or something keeping the throttle slide from resting on the stop screw.