250-500cc Is WR300 racing head a good choice?

Measure how much squish you have as standard.
I have mine set at 0.55 thou i took nearly a 0.70 off my head but i had to resess the dome into the cylinder too get the 0.55.
Its simple when you understand it and any engineer worth a bean can turn the head flat
Its reprofiling the head if its needed thats the issue.

The 300 head can not just be milled flat as mentioned earlier in this thread. http://www.cafehusky.com/threads/is-wr300-racing-head-a-good-choice.24946/#post-225053

My WR250 from 2006 gets me to 215 psi... using a compression tester by innova. I kicked it about 10 times until there was no more increase on the measurement:

Eagle freak, thats how my 360 head looks but not as exaggerated my lip sits in my cylinder about half a mill.
That was to get comp up to a satisfactory level.

that was the wrong picture, and a typo. My highest measurement was 210 psi. That one shows 205, not 215. And even with that high compression I still have a hard time starting it when it is cold.

My WR250 has 205 psi. as well, your hard start warm once it's already been started is likely from a lean pilot. If it's a cold start problem it might be the fuel you're using or spark plug.

It starts just fine after it has run for a few seconds. It is the cold start I'm having trouble with. The last time I try it had fuel that was about 4 weeks old, but I never tried with a new spark plug. Hope it is something as simple as that. Thanks for the advice, I really appreciate it.

I had to put a new spark plug in about once a year because a lead coating would build up on it from the vp110. Pump gas doesn't burn a clean especially if it's old so I would guess it would go through more spark plugs from fuel varnish fouling the plug when it sits in the garage.

I think I know the reason for for my hard cold starts. I opened up the carb for the first time since I bought it and I found out that it has a 400 main jet and a 15 pilot jet. I noticed it was hard to start when the temperatures started to drop. I changed the spark plug and put new fuel in, and it was hard to start, but I got it running after a few minutes. I will jump to a 35 pilot and see if there is an improvement. Thanks!