08 xp 800 154" not holding rpm always.

This 08 xp summit 800 ptek 154 runs great, but one problem. I never have an issue with achieving 8250 rpm, but once it is hot and it will drop rpm on longer climbs in semi deep- deep snow. Belt deflection is good. Using a skidoo 377 belt. Primary clutch internals are good and also clean. Clutches do get pretty warm. Sled is stock other than ggb can. It's like the sled doesnt backshift properly when it should. When rpm start to fade while in a climb I can let off then grab full throttle again and it will hit 8250 but then quickly fades like 500 rpm. Any help would be great. Also, this is my first post so bare with me. Thanks
Premium Features