I am investigating using the Command Vtwin 25 hp block to build a stroker direct drive 3200 rpm max and around 35 hp. Looking into what the tractor pullers are doing with performance parts is informative but not really close to what low rpm mission for this engine. One vender is offering forged cranks up to a 3.120 stroke which fits the engine needing some clearance-ing at the bottom of the cylinder and uses the same connecting rods & journal size as stock. I believe the forged crank comes from the ch1000 engine which has a stroke of 3.1" and a bigger rod journal 44 mm, the stock CH750 crank has a rod journal 35.94 mm so you can see that if the 44mm journal size is used it would require more clearance-ing which may not be possible. This stock CH940- CH1000 forged crank is cost around $235 and comes with a 40mm PTO diameter shaft which is nice. The thrust bearing is only spacers on the PTO side of the engine. This may be changed to needle bearings but more investigation needed. Tractor setup only as thrust bearing is only on the PTO side. Comments from the tractor pull engine guy is that the compression ratio should stay under 8.5:1 for 91 octane gas and a 3" stroke crank with(EDIT 4.5") con rods should get us 30-35hp at 3200 rpm. I am not selling anything and everything I investigate will be shared openly. I want affordable 4 stroke power for my ultralight and see the need for affordableaviation. These engines are very easy to work on and many after market parts are available. Parts I plan to use Stock CH750 engine block, heads, stock cam, and stator. CH960-CH1000 crank machined to my specs. Weber light flywheel. Midwest Super Cub ignition. Bosch coils. Mikuni carbs. Planning to have the crank PTO end milled to accept a tapered prop hub which I haven't sourced. Connecting rods need to be 5" and can be from Midwest Super Cub if rod journal in machined down to 35.94 mm but I would like to keep it at 44 mm as this is the weak point in the crank. Further investigation needed to see if I can find 44 mm con rods 5" or slightly under and if the block can be clearanced enough and will it clear the cam??? Target weight 80 Lbs. If I am successful I commit to a tutorial others can follow for free. If you want to help please do.
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