I spent some time researching for a heavy flywheel for my 250F and ended up buying a Rekluse 2.0 instead which uses the stock clutch basket,pressure plate and inner hub, just have to remove a few plates and slip the Rekluse in there with their springs... Super easy. I spent 6 hours riding locally the first ride, never stalled it once. Then we spent 5 days in Moab, Utah, 4 full days on the 250F and one day on the trials bikes. Then I spent May long weekend (2 full days) in the Canadian Rockies riding the trails. I did run a 18" Dunlop Trials Tire and added two teeth to the rear sprocket along with the Rekluse 2.0. I sound like I have shares in the Rekluse company, endorsing it all the way, a buddy stalls his KTM 250 EXC and I pull up beside him and tell him that would not have happened with a Rekluse, then I pull away... Great product...
I am impressed, the trials tire is well worth the effort too. All this from a 250F motocross bike I have converted to a trail/woods machine. The motor is so smooth and just plain works. It could use a little bit more grunt at lower rpms, but I think I will try the engagement rpm a little higher with the clutch, might cure that. I weight in around 250lbs so a 250F was a tuff choice when I bought it, but seems to be a smart decision. It never gets out of shape and tractors up most anything before starting to wheelie. I don't believe a 450 is needed for trails (for me)... KTM has a 350 which would be nice to try, could be my next bike unless I bigbore the 250F...
Next oil change I think I will tear out the clutch to install the high rpm engagment springs and try it... Check it out for wear also...