Carbs mounted level, or tilted?

[Slashsevenpig]

Similar problem to jwithers, but I didn't want to hijack his thread. Bike is a 1977 R100/7 that recently developed a stumble while transitioning from the idle circuit to the main jet. Last time this happened (8 years ago,), there was a blockage in the tiny idle transition circuits just behind the throttle plate. I've already checked point gap, timing, and valve clearance. Also, went through the carb sync process. I've narrowed it down to the right carburetor, but I've ordered new idle jet (emulsifier) o-rings, floats, and idle mixture screw o-rings for both sides. The new parts will be installed after I hose down the idle circuit with carb cleaner, followed by compressed air.

Long story leading up to my question: When reinstalling the carburetors on the machine, should they be mounted level to the floor, or should they have a slight inward tilt? I remember there seemed to be two schools of thought on this, and I couldn't find anything using the search function on this forum.

Thanks.

[Kurt in S.A.]

I've always tilted the top in a slight bit on my R100/7. Tom Cutter mentions on another forum that when he inspected bikes in crates from Germany, the carbs were tilted at the top. You might also see where the carb wants to sit by rotating it with the clamps loose on the air tube and the head rubber. Likely you'll find where it wants to settle into alignment.

Kurt in S.A.

[barryh]

I tilt them in slightly to give the throttle cables a straighter run. Limiting factor for me is if tilted too far the dipstick won't unscrew without catching on the choke cable.

[SteveD]

I tilt them in slightly to give the throttle cables a straighter run.

Me too. It's not much.

[Duane Ausherman]

I don't think that it matters at all for how it runs. We always tilted them a bit for the reasons posted.

Your stumble can most likely be fixed without new parts.

[Slashsevenpig]

Thanks everyone, for your input. BarryH makes a compelling point about having a straight throttle cable run. Taking it a bit further, I think a straighter cable run would result in a more accurate sync of the throttle plates from off-idle throughout the full speed range. Tilted inward it is!

[barryh]

I also use heat shrink to give some support at the cable entry to the adjuster.