OK guys, I'm looking for educated comments about a project I'm considering for my current XS650 chop build, relating to making my own custom billet inlet manifolds.
As you'll know, Mike's XS make a pair that take VM34s. They have a 16mm flange and a manifold spigot that is perpendicular to this flange. Makes for easy machining. The downside is that it tilts the carbs at an angle of approx 5 degrees, due to the cyl head mating surface being this angle from vertical. I'm not sure whether VM34s tilting forward is problematic or not. All I know is that I have these manifolds on my 750 big bore 270 rephased motor and it doesn't upset performance.
So my real question is: will this 5 degree tilt upset performance if BS38s are used, as in, on my stock 650 chop engine? Yamaha compensated for this tilt in their rubber boots, so the carbs sat level. Has anyone fitted BM38s to manifolds that follow the simple profile of Mike's XS manifolds (carbs tilting forwards) and if so was it a problem?
I ask because I've modelled a handed pair of manifolds that also compensate for this tilt angle but obviously this will involve a greater amount of machining trickery to achieve the result. I'm debating whether it's actually necessary. Would prefer to just machine a set like MikesXS ones for my BS38s.
As I say, educated comments would be very welcomed.
As you'll know, Mike's XS make a pair that take VM34s. They have a 16mm flange and a manifold spigot that is perpendicular to this flange. Makes for easy machining. The downside is that it tilts the carbs at an angle of approx 5 degrees, due to the cyl head mating surface being this angle from vertical. I'm not sure whether VM34s tilting forward is problematic or not. All I know is that I have these manifolds on my 750 big bore 270 rephased motor and it doesn't upset performance.
So my real question is: will this 5 degree tilt upset performance if BS38s are used, as in, on my stock 650 chop engine? Yamaha compensated for this tilt in their rubber boots, so the carbs sat level. Has anyone fitted BM38s to manifolds that follow the simple profile of Mike's XS manifolds (carbs tilting forwards) and if so was it a problem?
I ask because I've modelled a handed pair of manifolds that also compensate for this tilt angle but obviously this will involve a greater amount of machining trickery to achieve the result. I'm debating whether it's actually necessary. Would prefer to just machine a set like MikesXS ones for my BS38s.
As I say, educated comments would be very welcomed.
I think the biggest reason Yamaha changed to a tilt was to keep floatbowl fuel overflows from dumping into the engine.
