Got an old McCulloch chainsaw engine needing a new use
Well here's the adaptor you need to fit a 5/8" Maxtorque type clutch to your Mini Bike
Mac 15 / 250 / 380 etc Clutch adaptor
Note these will not fit tapered shaft engines and are meant to screw on.
The 5/8" clutch and drum is retained by grub screws and located by a keyway
Although i have shown  a McCulloch Kart engine of 100cc
You could use the engine from the 80cc range like a lot of Karters do and often they grab the odd old McCulloch chainsaw to use.

Pictured below is what they call the Standard series of engine from this range of saws take note of the fan housing as these are the ones that will use the adaptor shown above,
The early Kart engines were developed from this range of saw engines.

Strip off the fuel and oil tank along with the bar and chain and the old clutch assy.

Now you can chose a Kart induction system to replace the airbox and 5/8" carby and make your ( new )  mini bike engine look like a Kart engine.
Don't scrap that nice McCulloch chainsaw crankshaft!!!!
Here is a precision custom made shaft extension for McCulloch chainsaw engines with the short threaded stub shaft.
This extension will allow use of a standard 5/8" bore clutch such as the one shown in the photo for go karts and minibikes using a converted chainsaw engine.
The extension is a left hand thread so it tightens as the engine is run with a load.
Features include:
Hi Carbon steel
3/16" keyway
Double flats on the end for installation and removal.

Will fit any McCulloch Chainsaw crankshaft with the short threaded straight shaft.