I spotted this nearly new 21mm Delorto on Eblag at Christmas and although it's 1mm bigger internally it's only about half the size externally so with a bit of messing around I can get it pretty much behind the original casing, and luckily it fits straight on the tube where the YB one came off.
There was no way that even with uprated springs and the thinnest oil the clutch was going to hold and luckily 50cctuning has developed a 3 plate conversion which is a real result and works great. Markg is running one to now.
The Dellorto was somewhere near but the power curve was way wrong still so I loaded the ped up and hit the road to doncaster with Jakey as co-pilot, Darrell soon ironed out the bugs and we hit 11.2bhp with the aid of a different pipe which also had the added bonus of flattening out the torque curve and wideninig the powerband. I was really after 12hp but there are a few tweaks I can make and should get there next time.
This pipe known as the V2, here in action
I decided that to ensure the new exhaust was mounted perfectly on the cylinder I would spigot mount it and make some kind of rebate so the tube sat inside the end of the port to aid with this. Having no access to milling machines or the like I looked outside the box and came up with this idea, grinding burr in the Demel and a washer to act as a stop.