5-7,
Were you ever able to get the GP460 to mate up with this tranny? I remember you were changing clutch springs at one time. Was thinking about getting a GP460 or a PF-4000. What are your opinions/ideas? Thanks
Sorry I missed this query. I'm taking almost three years to respond.
Yes, the GP460 bolted directly to the pb tranny. It is extremely important NOT to overtighten the clutch bolts. The engine case at the mounting points is VERY thin. If you overtighten and damage the case, you're SOL. Also, the original clutch springs were designed for high-rpm engagement. I replaced the springs with aftermarket lower-rpm springs. Engagement slightly above high-idle worked well, although one of the three springs always tended to break. I also tried the pocket-bike clutch. It had very light springs and engaged slightly above high-idle. The pb clutch seemed to fit perfectly onto the GP460's tapered crankshaft, once you shaved the mounting crankshaft nut about 1/8".
The GP460 is an awesome, very powerful engine. I installed one on friction drive. It performed well on flat ground. However, no matter what size roller I used, it always ran out of power when climbing steep hills, especially long ones (It also had a habit of gouging divots into literally every inch of the rear tire). HOWEVER, when I bolted it onto a shift kit and proper gearing, it became a powerful hill-climber. It was VERY loud with stock muffler or even the Dominator pipe. Then I bolted on the SBP pipe designed for Happy Time engine. Although the exhaust port and head pipe were mismatched (rectangular port and round head pipe), the exhaust flange sealed very well. And lo and behold, the GP460 purred and screamed from idle to 8000rpm+ like a quiet little motorcycle. I swear I could hear the piston rings scraping the cylinder wall at idle speed. Notwithstanding the fact that the clutch springs were undependable, power was smooth and more abundant than my Tanaka 47R engine. Disappointedly, I broke a few clutch springs on my rides. The spring hook would slip out of its hole, break up and lodge itself between the clutch shoe and the drum. When this first happened, I'd call to have someone pick me and the bike up. Then I remembered how I'd driven my car home with a broken clutch, so I'd hobbled home on the bike the same way. Jack the rear wheel off the ground, start the bike, then roll the bike off the stand and hop on. When I came to a stop, the engine would lug down and die, and I'd repeat the rolling start. When I acquired the Tanaka 47R engines, I got rid of the GP460 engines. Voila, absolute dependability albeit a little more noise and less hp. Being a glutton for punishment, I MIGHT scrounge up a spare 460 engine. If I can find a way to keep the clutch springs from falling off their mounts, the 460 would be powerful AND dependable for my bike.