Trouble w/ idle that works for hot and cold motor

[Barry]

Even cracking the enricher open so it's only on the first fuel hole will cause the engine to die ?   If that's the case then it's obviously flowing too much fuel and not enough air.  Short of blocking off the fuel hole and re-drilling smaller the only other option is to reduce the the amount of fuel flowing by lowering the fuel level in the float bowls. 

How was the fuel level set. Unless the floats are either new or known to weigh close to new i.e. 12 - 12.5 grams, there is no indirect method that will guarantee the correct fuel level.  If the floats are heavy then setting them parallel results in an operational fuel level that's too high. Same goes for measuring the fuel level at 22 mm in a removed bowl. If the floats are heavy you can up to a point compensate by setting them lower than parallel or by targeting a lower fuel level in a removed bowl.  For each gram I'd aim for a 1 mm lower fuel level in the bowl. 


So convinced am I that the enrichers are crudely sized and provide far too much enrichment that when I implemented the service bulletin to drill out the blank in the disc, I drilled it 0.5 mm instead of the suggested 0.6 mm.  That's a huge difference when you take the area into account and yet it still transformed the operation of the enricher. It wouldn't hold the fast idle that you are seeking but at least the engine would now run cleanly with the enrichers partially on. 

[Mucci]

Barry I’m curious why you recommend float level instead of adjusting the mixture screw.

FYI floats are new and set parallel to the gasket surface.

[Barry]

I believe the enricher function is quite sensitive to float levels and might have explained the problem had the floats been very heavy.  Many year back I had one float that was approaching a sinker at 15-16 grams and the idle mixture was affected to such an extent that the mixture screw had to be set 1/4 turn out instead of 1/2 a turn out. Starting with the enrichers at that time was also problematic with the enricher having to be shut off immediately after starting to keep the engine running. 

I think it's generally accepted that float level sensitivity is greatest at idle and at full throttle which can easily be demonstrated by shutting off the fuel 1/2 mile from home. The engine will run well enough on part throttle but when you come to a stop the idle speed will be lower than normal 

If the floats are new and set parallel then I can't think of any other reason why the enrichers are providing such an excessively rich mixture that it stalls the engine at idle. Other than of course that my view is the enrichers are badly calibrated to individual engine sizes from new. I see it in the way they quickly build up carbon deposits on the plugs.  I don't buy that BMW wouldn't have got them wrong as evidenced by a service bulletin being necessary to modify mine. A bit of supporting evidence is that my enrichers seem to work best in really cold weather such at at - 5 Deg C  I can ride off with the enrichers still partially deployed.  They seem to function best when gross enrichment is required but function poorly when only slight enrichment is required.

The mixture screws have no direct impact on the enrichers other than the additive effect which you have already explored.

[Bob_Roller]

The holes in the enricher disc being drilled out is likely place to start .
The enrichment system does not meter fuel, it varies the amount of ' bleed air ' that mixes with the fuel to emulisfy the fuel air mixture before entering the carb throat . If you have larger holes than were originally drilled, more air and less fuel, lean mixture .

[Esa]

Rob, are you sure those holes being air holes? Picture in a previous page would indicate opposite?
 I`m curious because I`m using E85 fuel and I was planning to improve my enricher by drilling those holes bigger. What I need would be richer mixture.
Luckily I haven`t done that yet.

[Barry]

The small holes at the bottom of the disc are fuel holes. Air enters at the right hand side and after mixing with the fuel exits the enricher via the pear shaped slot at the top.

Mike Fishwick produced by far the best drawing I ever seen that explains how fuel and air flow through the enrichers.

[Barry]

At the risk of boring everyone to death, I've just had another thought about explaining the OP's experience.

In understanding how the enrichers works it's universally accepted that as soon as you open the throttle the amount of enrichment reduces significantly due to the lower vacuum in the venturi.  The amount of enrichment required to start an engine is much greater than the amount required to keep it running.  The reduction of venturi vaccuum as soon as the throttle is cracked will automatically reduce the rate of fuel flow through the enricher which meets this requirement.  If the throttle isn't cracked open then there is no reduction in fuel flow so the engine may die at idle through excessive enrichment.  I accept that some bike will fast idle on the enrichers but this effect explains why you are up against it to get an airhead engine fast idling on enrichement.   

[Luca]

Another good indicator of float/fuel level is fuel economy.  A high fuel level will enrichen the mixture across the entire rpm range and reduce fuel economy.

My bike has been a little tricky to start this year.  I'm pretty much starting on half enrichment with some throttle and backing off the enrichener very quickly.  If I don't cut the enrichener it seems to flood.  The fuel economy is not what it used to be, either.  Time to inspect those floats (which I replaced 2 years ago)