Something different.

You could buy a Indian made Royal Enfield with a Robin diesel .....good milage,terrible vibration..............If I was going to do one,Id use the 3 cyl 750cc Kubota engine .........they seem to run smoothly

A diesel Matchless
 

 A Howard V twin fitted to late 30's BSA cycle parts. It looked fantastic but as the max. RPM is 3000 it's probably better back in a rotary hoe. 

 
 

I started building something like this a bit over 25 years ago after seeing one in Brisbane (in an Ariel frame). I collected a few engines, a donor Jampot frame and various other parts. Then I met the missus......
Still have all of it scattered about.

Jarrod.

Here is the Royal Enfield

 

This one including the frame was made out of odd bits by a chap named Powell and is powered by a lawnmower engine
 
 
 

The Howard is heavy with a cast iron crankcase and double flywheels ,but its a clever design in parts .......some of the earlier ones the cylinders were in 3 pieces,with the valves separate to the barrel,and a single lengthways camshaft ...which was copied from a US made Deluxe motorcycle engine .....the weird flywheel was copied too..............the single cylinder Howard was clever too,the only sidevalve Ive seen with thru studs from crankcase to head..............Incidentally<if you see a rotary hoe with a 600CC JAP engine ,the engines are worth money .....around $1500 for a good one ,and at least $1000 for a complete one that turns over.

Looks like  Villiers Mkll 98cc.

Yes John, it certainly is heavy!

I recently picked up a JAP 350. What I would call a "motorcycle pattern" engine, but thought to be from a reel mower.
Probably a much better candidate than the Howard.

The bike I mentioned went to England, along with its owner about 20 years ago.

Jarrod.