Yamaha Big Block Conversion

[Rick2232]

Hi everyone, any chance that anyone has completed a big block conversion on a Yamaha G22 without an aftermarket conversion kit? My G22 is a 2006 with a 4” lift. I have the GX630 engine and a Salisbury 780 clutch already. I don’t want to by a kit just for the cradle and was hoping someone may have some insight or a schematic of one that they may have fabricated. Thanks for your help.

[Dave in VA]

No additional cradle is necessary. Fabricate blocks to set the Honda on. Taller in the rear than the front so the engine will set more level. The mounting holes on one side will need to be enlarged. I enlarged the drivers side. The front of the swing arm can be lowered, but it's not necessary.

[Rick2232]

Thank you! Any other considerations or helpful hints I should be aware of in this process? For example, concerns about the belt tension with engine placement, etc?

[Dave in VA]

Mine's a Briggs Vanguard. You'd have to check the bolt pattern footprint of the Honda and see how it compares with the Yamaha footprint. The Vanguard was almost identical to the Yamaha. You'd have to experiment with the belt.

[sho305]

There are pics here of my build, I used two bars and a stub tube of steel to drop the front under the gen, it was all mig welded together. Did two carts this way, the mount was pretty easy to do. I put a small piece of angle on the back mount to widen it enough. This is a G9 but yours may be similar, or may be able to do it similar with bars. I put the engine on a jack and blocks where I wanted it with clutches mocked up on it and clutch distance/offset I wanted (from stock clutch setup), then made the mount under it. Later I marked and drilled the holes, had to do that again when I changed clutch, and again when I moved to a longer belt. Making it movable would have been nice but really aside from a major changes I got into you should not have to mess with it. The footprint of a clone is not much different than a twin. Make sure you leave a spot for oil to come out, or be aware of the oil drains. My mount did crack the gen plate it must be cheap stuff, I later beefed it up there. The belt side takes more abuse. I used the stock gen and made a tensioner arm out of a lawn mower arm to hold the gen that bolts to the clone behind the clutch. So I had to make sure the gen belt lined up to the engine as well as the drive belt. Later made a solid tensioner cable that yours might not have, in a G9 they are under the gen pulley and holds engine torque under high loads. I built that in 2012 and other one before that both are running great yet, both use the stock mounts and have no vibration.