I did see the photo's, the 77 is a real beast of a saw. I do hope to add one to my collection one day. I did have a chance to run my "new" Super 797 this week and will say it does have a lot of guts, but I still think the SP125 may be a bit faster.
I am going under the assumption that the 103 cc Super 550 has some more aggressive porting than the 99 cc 550, but I don't have anything to back that up. In the case of the 797 I think the biggest difference between the 797 and the Super 797 was thin rings for the 797, and thick rings for the Super; again I am not sure that is so but I believe I have it straight.
Randy Mac, our local Super 250 evangelist is absolutely sure that the Super has a lot more going for it than a mere additional 7 cc's.
I think JJ could set us straight if he every gets back from managing land and fighting fires.
Mark
Reading through a previous post by JJ I thought the Super had the thin rings. While we are on the subject how do you identify thin rings. The 797 I just got looks to have thin rings but I have never seen them to know for sure.
JJ's post
"I got a little time while my lasagna is cooking, so here goes:
The 797 engine was birthed from the 101b yes, but the timing is not quite the same but close to a 101b. If you look at the piston, you'll see it's identical to that in the 101b. Later pistons from other 101 motors can't be easily interchanged without changing the rod as well, since there were minor variations in the crown height of the piston(s). There's a 101 piston with windows that's timed for the boost port blocks that works well in the 797 with the corresponding rod. There's a rod that's proprietary to the 101b, 101d, and 101AA that can be used in the 797 if you have the matching piston.
The 797 is part of the family of "Super Series" engines which include some of the kart engines and saw engines. The 797 blocks have the removable boost port "window" which later became boost ports actually cast into the block, seen on later kart engines and 125 saw motors. The 797 block is not a third-port block like the Mc20 kart engine or D44 saw motor.
Main 797 features: removable boost port window, bridged exhaust, hemispherical combustion chamber, horizontal-mounted coil, DSP-style compression release, right-hand start, moderately aggressive intake and transfer timing, same stuffer as stock 101b motor (w/cut-out for pulse oiling), crank w/bolt-on weights, and kart-mount style exhaust. The 797 Super would have the updated main bearings, different carb (usually SDC?), thin-ring piston.
The CP-125 block has the cast boost ports, slightly smaller combustion chamber, bridged exhaust, less aggressive intake and transfer timing, horizontal-mount coil, kart-mount style exhaust, single-reed intake manifold, and straight compression release. The piston in the CP motors should have cut-outs for the boost ports and came in both thin and thick-ring. The CP rod would use the 1/2" wrist pin with needle rollers in the piston rather than in the rod. The CP blocks are all steel sleeve blocks as are the 797s.
The SP-125 block has the large oval-shaped exhaust port (longest blow-down time of any of the saw blocks) w/different exhaust mounting, larger combustion chamber, lower intake and transfer timing, dual-reed intake manifold, diagonal-mounted ignition, and "hockey-puck" piston w/no cut-outs for boost ports. The rod in the SP motors uses a 9/16" wrist pin with needle bearings in the rod rather than in the piston. The SP pistons were usually thin-ring. The SP block came in both steel sleeve and chrome-lined bore. The SPs used the straight compression release and the funky squared off muffler with its own proprietary cover. These are not compatible on the Cp and 797 blocks. Cranks on the SPs had the welded-on weights."
