125-200cc wr 300 rear brake issues! Help

Been riding 2 hr. hare scrambles and lately have had rear brake fade issues. Usually about 45 minutes into race especially when riding hard it seems rear brake fluid boils and I loose my rear brake. Can ride for a few minutes not so hard and can get brake pedal back. Lately I seem to have problem dragging rear brake, that and Im getting faster. Any suggestions on vented rotor or modification to rear brake system, or do I need to change my riding style? Current rear brake is stock with solid rotor. Note: Tried DOT 5 fluid and same result.

DO NOT USE DOT 5 brake fluid, it will eat the seals/orings. Use only 4 or 5.1. I've never had a problem with mine overheating in 1.5 yrs of racing HS and enduros. I run my lever low with about .25" of free play.

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I use Motul 660 brake fluid and EBC carbon X pads. My rotor and pads look like they have been in a fire after a race, but I rarely get brake fade.

Here is what I tried first and it helped rear vented rotor off a older Cr 250 from Halls with motol brake fluid

BUT if you want to get the best here is what I did Had Ty at Zip Ty Racing make a bigger caliper braket
went with a vented rotor off a TE style bike Mounted it solid not free floatting any more

Results great brakes no problem.So why does Husky use a bigger rear brake on ALL there bikes from 125 to 511 except the WR 250/300 gets a small rear brake

Maybe next year we will get a updated 250/300 2 stroke

oops! goes to show how much I know. Good info. Thanks.

+1 on the Motul 600, I've not had rear brake problems but my pumpkin ridin' brake draggin' friends have had to use it to cure theirs.....

Thanks to all for the info.