Maico Metisse pre 65 update: My Petite Metisse Bultaco frame has finally arrived after it's long and harrowing journey from Flowerpot Ben's house in the UK to Casa del Firko in Sydneys golden west. Today I got around to doing a mock up to see what fits what and my first problem has ALREADY raised its ugly head. All along I'd been dreading that the side exhaust port oval barrel would foul the front downtube so it wasn't a shock when I found my prophecy to be true. The exhaust exits straight into the downtube (
see bottom photo). There's a few different cures to the problem but unfortunately none of them are easy. The first and most obvious is to modify the frame by putting a loop in the downtube. It's a pretty straightforward fabrication exercise but with genuine Rickman built Petite Metisse frames being the rarest of the rare (
it's one of only 102 made) I'm hesitant of doing such a radical change. The next alternative is to move the exhaust port to the centre of the barrel. I've spoken to Frank Stanborough and another good race engineer and they both reckon it's not as big a job as it initially seems. With the exhaust port moved and a later square barrel or radial sleeve used the exhaust clearance problem is solved. Of course, I'll be modifiying a fairly rare 360 oval cylinder but when it's weighed up Maico 360 engines are nowhere as rare as Petite Rickman frames so I don't have any concience issues about doing the barrel mod. Of course, that stupid "
engines must remain externally unchanged" or whatever the wording is
could be used to protest the mod but Frank tells me that "centreporting" was a common modification on all sorts of engines back in the day so if anyone wants to protest the bike using that rule I'll have done my homework and will have to bring their A game to the protest table
.
The third option is to use a single downtube frame that fits the bill....the most obvious being a period Maico frame like Mick De and Rodger Starkey are using. That's a sensible option but by doing that I'm just building another modified Maico, I want to build something different yet legal. I've got a Cotton Cobra frame which is super light but it's twin downtube which would give me the same clearance woes. I've got a period BSA frame but it's too bloody heavy......so, moving the exhaust port to a more convenient location is the way I'm going.
I'm using Rickman Zundapp wheels, Mexican Betor forks from a Cooper 250, the cool ethanol proof glass shown in the photos supplied by Ben and will build an up pipe to suit the flow of the frame. The engine in the photos is a mock up using my 360 barrel on my basket case 250 oval bottom end as the 360 is currently apart getting a 350 crank, Yamaha YZ250 J rod, big end pin and bearing, put together and balanced by Franks Cranks. The head is half welded up and once finished will be shipped off to RK-TEK in the USA for their unique machining
http://www.2strokeheads.com/VintageMX.htm. Frank and I will do the ports using ideas oval barrel guru the late Jim McCabe sent me a few years ago
http://cybermotorcycle.com/archives/maicomadness/early.htm . This is going to be a lengthy build that I hope to have done by this time next year.
