Thanks for your input guys, there's nothing like a think tank
The plenum change makes sense , it might even end up being easier to fit,,surely it won't be harder,,,,,
Funnily enough, the original plan was for a "normal" type plenum, but was dropped after trying to think like a pocket of fuel / air mixture, and how it would behave,,best I revert to not overtaxing my last 3 remaining brain cells, and do more research,
EDIT,,,
Space is always a problem, the frame rails do not allow any other intake at the moment, so it's time to reinvent the wheel,,,,,
My co-builder always wanted to build a sidecar,,this engine is a test bed for it,,,I think , with all the input received from you guys , and the gut feeling I've had regarding the plenum appears to be true,
I absolutely HATE working on fiddly things, so the new frame design needs to allow the engine, or parts attached to it to be easily removed when needed . I'm thinking no backbone, maybe a removable one, , structural strength can be designed without the need for a backbone, and the different layout of a sidecar frame will allow for thinking outside the square ?
Although designing a better plenum will be a challenge (I still worry about cylinders #1 + #4 not receiving as much mix as #2 + #3). but if I build a blower / plenum test bench and measure each cylinders flow rates while spinning the blower with a drill or simillar, changes can be made inside the plenum untill I'm happy with the result ?
Long & low is the plan, detachable 3rd wheel on a stick maybe ?
Tiny