I'm in a quandary here, and I seriously need some help with this issue. I have exhausted all ideas at this point. I will do my best to go through everything I've done to try to correct this problem so far. This is a 2001 Craftsman chassis, G/P class, 700 transmission. EC engine and transmission pulleys. EC clutch assembly. Fully welded/frame, EC tranny plate with support bushing as well. 68" drive belt.
This chassis was originally raced as a C/P and the belt drive system was flawless. No thrown belts, no seized bearings, nothing. I always tried to take the time to repack the bearings and replace the belt every three months whether it needed it or not. Then last September I converted it to a G/P. That's when stuff started wearing out. I had never experienced a worn engine pulley, and after 3 years of racing it finally gave up the ghost. Belts were "wearing out" in 30 laps, and just flat wouldn't pull. Anyway, I tried to compensate with shorter belts before I realized the engine pulley was severely grooved and wouldn't let the belt seat properly, (I was in the middle of figuring out the right gearing for G/P class, swapping sprockets back and forth with different 4" and 5" tranny pulley combinations before I found what worked.) at which time I replaced the engine pulley, and finally went back to the 8" and 5" pulley setup with the original 68" belt.
But the problem changed. No longer am I replacing belts every 30 laps, but when I press in on the clutch, and then shift into gear, the whole mower bucks and jerks from the belt acting like it is not fully disengaging. I have blown up two transmissions so far because of this, and I'm getting pretty frustrated. It doesn't take long to ruin a good 700 when you are experiencing this issue. I verified the correct belt length using George's trick, all is well (as far as I can tell). I lengthened the clutch pushrod to allow for more adjustment. I can literally pull the belt off in any direction I please, it is so loose. I noticed the v-groove clutch pulley was worn as well, so I replaced it. I verified the pulleys are on the level from front to rear, clutch included. Afterwards I replaced the transmission pulley just to see if that would make any difference. No change. I tried running without belt guides at the transmission and the v-groove clutch pulley, no change, however I noticed the belt didn't fall off when I disengaged the clutch, and it jumps around a TON, not simply slowing or stopping like it should. Without using a measuring tape, I visually looked at the crankshaft in relation to the hole in the frame, and it appears centered. I've flipped the mower before, but I never noticed any belt related issues after that.
The only thing left that I can think of is possibly the crankshaft position has changed when I went from the flathead twin to the G/P engine, but you would think that issue would have been revealed long beforehand, by verifying the proper belt length. The only thing I haven't tried yet is a 69" belt, but I'm afraid it will be TOO loose. Would too loose of a belt cause this issue as well, when it is trapped inside the belt guides? The guide bolts are the same ones, and in the same original locations, so I don't think that's the issue.
I know I have given a bunch of information, but I believe it will help to a good diagnosis. I hate making stupid mistakes, and overlooking the simple stuff, but maybe you have run into the same issue and might have an idea. You can poke fun if you want, that's not as expensive as a new EC transmission.
Thanks for your help as always,