Throttle cables to ROTAX 912A2

HI Peter,

If your throttle control mechanism is warn & there is no way of adjusting for this, it is likly you will not achieve consistent carburettor balance throughout the operating rev range. Replacement of cables and or lever system, may be the only option

You can assess this (engine off) by moving the throttle lever, in short increments, from low to max rpm position and back.

Starting from throttle closed, measure/record throttle opening at the carburettors, at each increment. Its important to do the same back, as uneven cable operation anomalies are just as likly in the reducing rpm action. 

You are looking for equal & consistent opening on both carburettors throughout the operating range.

Repeat at least twice, to assess smooth consistent operation or not.

Your "choke" (enriching mechanism) should work okay, assuming when cockpit handle is full on, so is the carburettor choke lever and when  handle off, so is the choke lever.😈

Some throttle systems have play in them so the carbs can't be synced. I've seen this a few times. Their system always causes one side or the other to be slightly different than the other

Hello Peter,

I notice the outer cables are not well supported, this could cause "lost motion". What I mean by that is when operating the control, the outer cable deflects (side to side, up/down) due to spring tension and friction instead of the inner cable simply sliding through the outer. As the cables from the mixer appear to be different lengths, the deflection will be slightly different on each side making it impossible to synchronise their operation. Gently securing the outer cables including between the control levers and the splitter of both throttle and choke, so that all motion of the respective control is the inner sliding in the desired direction and no part of the outer moving at all, may improve things for you. You don't mention if the cables have been renewed, if they have not, they may be binding slightly, perhaps renewing all cables, both inner and outer may help and of course any parts found to be worn, particularly within the splitter, should be repaired or replaced.

I hope this is of some help to you.

Cheers, Des.

Thanks Des, for the feedback.

We are going to exchange the bowden cables, any advice on types ?

Br, Peter

The smaller diameter cables that go through the outside sheathing is far better than thick cables that have too much friction and don't allow the springs on the carb throttle arms to do a good job.