"had 6 mm more stroke"
The webbing supporting the main bearing saddles needs a little grinding to clear the crank. Nothing significant but a little touch-up in several spots. Just dropping the crank into the upper case half is the go/no go gage. That's the easy part.
The crank ends are opposite the SOHC crank ones. The tapered snout on the 900F crank is where the 750 crank does timing. The snout is cut off (it's soft) to match the 750 crank end length. My machinist spun the crank to cut off the snout. The cut end is then recessed to match the 750 end. Use the casting line to locate the hole for the timing plate pin. After that the stock timing system from the 750 works fine * (IF you use the appropriate 900F crank seals, not the stock 750 ones.)
The other end has a tapped hole in the end. I haven't yet figured out how to attach the kick start gear and or generating system. I just use a bolt with a welded nut on the end to my external starter. Use plenty of Loctite.
I had a 3mm steel spacer made to the bottom of the block sleeves. If everything is flat and square, just a little sealant and everything is sealed up. The thickness of the spacer requires two opposing o-rings where the block normally uses one. When you have everything on the bench, it becomes very logical from just looking at how it was originally sealed. I used aftermarket stock length rods. If you go with DOHC rods, the length varies as does your spacing requirements.
Ok, a little bit of work, but not a lot of $$. Where's the catch? Hi-Vo chain. Not an issue for a Hondamatic, but for a clutch version you need early Goldwing clutch parts. There's one tooth more on the crank, which spins your tranny about 8% faster. The stock tensioner for your primary chain must be cut down to clear the new chain. The challenge is how to put a tensioner that works back into the system. For drag racing, with more frequent maintenance, you may manually adjust the chain tension with rub pads getting shimmed. On the street, well you can't start it, and using any screw adjustment for the primary chain through the bottom of the case is a built in likely oil leak. (aka, not recommended.
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Yes, there's more: the cam chain is different. You have to use the 900F style cam chain. Take the center of a 750 cam sprocket and weld the outer 900F cam sprocket to it. I did it using the stock steel sprockets for better weld strength. Slotted the mounting holes in the resulting hybrid sprocket since you must check the cam timing after reassembling this setup. The cam chain is wider than the stock 750 one. Use the 900f tensioner parts to "rub" the chain the right way.
Yes, everything that swings has clearance. There's actually some more room left. I talked with Big Jay at Valdosta about stroking a 900F crank a little more for my "big" Hondamatic motor. 1200+ cc's can be done.
I haven't used 900F sleeves in a 750. Wouldn't know how much they can be overbored. Suspect that 71mm is out of the question.
Let's not forget the 1100F crank. It uses a heavier cam chain than the 900F does. The extra mass isn't desired for drag racing. People dragging the 1100F went with the 900F crank (same stroke) to get the lighter cam chain. Now you can forget the 1100F
Hope this helps?
Hondamatic
