Carbs?

[ithebruce77]

BMW R100S 1977 Bike revs fine up to 3000rpm but reluctant to go higher, i think it is a carb problem, but any tips and suggestions would be gratefully received.

[Kurt in S.A.]

Blocked air filter? Torn diaphragms in the carbs?

Kurt

[Ade B]

Hi, having had a similar issue on my 78 R100RS I managed to sort it after much (enjoyable) messing about involving:

Valve clearances.
Checking coils and leads.
New points and ignition timing reset..
New plugs and air filter.
Carb strip, clean and refurb, replacing gaskets, springs, main jets, needles, o rings and diaphragms.
New throttle cables.
Reset mixture and idle.
Balance throttles.

With hindsight assuming fuel is filling the float bowls I'd check the main jet diffuser is clear without disturbing anything else and then take it from there. This can be done with the carbs on the bike, assuming they're Bings which you may not have on your S. No idea for Dellortos...

Let us know how you get on.

Ade

[ithebruce77]

Thanks for the info, will check it out.Ian