Takes a while to idle down

[thessler]

Hi
I have been fooling with this bike trying to work out some bugs.
Carbs cleaned, valve adjustment, just installed new coil, removed the air system and the popping went with it.
Test rode today and it seems the idle takes a while to come down from 2k to 1,000 rpm, very sluggish returning. Otherwise it's running ok. I do not believe it is cable related.
Any thoughts ?
Thanks  , Tom

[Bob_Roller]

I would perform, or at least check the carb synchronization, if it hasn't been done in a while .

It needs to be accomplished on an engine that is at operating temperature, not a 'cold' engine .

[montmil]

A proper engine warm up on a chilly Long Island may require a 20+ mile ride. You may find the idle mixture screws require a bit of tweaking to get the idle down to where it belongs, ie: 1000-1100 rpm.

Confirm the ignition timing, too.

Tom, please include the model year of your R65 when inquiring. Even better, add the info to a sig line. Different carbs and ignition changes, etc. affect correct/incorrect answers. Help us help you, OK?

[Barry]

Tom

Idle hang up is almost always caused by the throttle plates being too far open.This positions the bottom edge of the throttle plate close to the transfer ports which causes them to flow some mixture. As has been said do an idle tune up on a fully warmed up engine. Basically turning out the throttle stop screws slightly will move the  throttle plates away from the transfer ports and the problem will go away.

[thessler]

ok thanks guys
This is a 1984 R65
It will idle when warm, where i was going with this is even when warm when you let off the throttle it takes longer than usual to return to idle.

This brings me to another question if you don't mind. I am having a very hard time keeping it running while cold. The chokes do work, but my question is do these have a high idle mechanism while on choke ?
I am continually revving this thing until it warms up, other wise it will stall. Pretty sure that is not good for the motor.

this bike sat for a few years so I do expect a few bumps in the road before it's straightened out.

  Thanks for the help, Tom

[nhmaf]

The 'choke' as we call it on these Bing carbs is actually another small carburetor circuit within, and 'enricher' if you will.  IF all is properly setup, you should only need to pull the choke lever to fully "on" position with a cold engine and temps below ~75F to start, and it should rev at around 3K - 4K RPM or so if left that way, I generally slowly move the lever down to its halfway point (it has a detent and will generally stay there) once the engine is running for it to warm up.   After about 30 -60 seconds I can ride the bike away and turn off the choke lever fully.

If you have to continually give it gas to keep it from stalling, I suspect one or both of the enricher circuits is clogged, or partly clogged.   Drop the float bowls from the carbs and look in the frontmost inner corner of the bowl for a small reservoir with a tiny hole machined into it - that is the fuel intake reservoir for the "choke" and is common for it to become clogged.

[thessler]

I did remove both carbs and clean real well when I got into this. I guess i'll re vist them. I think the enrichers are working, just not raising the idle at all.
 Thanks, Tom

[Bob_Roller]

Did you take the carbs apart, like remove the enricher parts ??

They are side specific, even though they appear to be the same .

[Barry]

Operating experience with the choke seems to vary and some will enrich the mixture but not provide a hands off idle. Certainly mine will not  which I put down to it being an early model with less progressive action due to only one fuel orifice in the choker disc where later models have 4 of increasing size.  I would have thought an 84 model has the full complement but it might be worth a check.

For anyone out there that has an early disc with only one orifice I recently came across a service bulletin that recommended enlarging each of the 4 recesses to 2.5mm and drilling through the 4th recess 0.6mm.  This is a European service bulletin so it may not be applicable to other export markets.

Next time anyone has the choke disks out I'd be interested to know how many fuel orifices are drilled through the disc.

[Semper Gumby]

Hi Tom,

The stock Idle Advance setting is 6 degrees.  If it is any more advanced than that at idle then the motor will have a tendency to idle  higher than you want.  This is epecially noticable when coming off a freeway from an extended high speed run.

On the timing inspection hole there should be a gouge mark on the LH side of the hole.  Mine is near the bottom at the 7 o'clock position.  This means my idle advance (set with a timing light) has to be set at the very bottom of the inspection hole.

Other reasons for hi idle are:

1) Exhaust Valves too tight (less than .008")
2) Air leaks between the carbs and the cylinder heads (are there cracks in the rubber hoses??? Replace 'em now)
3) Dried old o-rings on the throttle butterfly shaft in each carb (a royal pain to replace).
4) No freeplay in the throttle cables.

Good luck.   [smiley=bmw_smiley.gif]

PS - What year is this bike and what type of carbs (flat tops or dome)?

Barry - on my March of 1980 Flat top carb bike all the holes on the enrichener disks were drilled though.  I screwed the shoulder on one of the brass shafts and had to get a new one and not all the holes were drilled though.  So I took my old disk and put it on to the new shaft being gentil this time screwing the nut on.

[Barry]

Barry - on my March of 1980 Flat top carb bike all the holes on the enrichener disks were drilled though.I screwed the shoulder on one of the brass shafts and had to get a new one and not all the holes were drilled though.So I took my old disk and put it on to the new shaft being gentle this time screwing the nut on.  

Bill,

Thanks for confirming the differences in enricher discs. I intend to modify mine when I can get hold of a 0.6mm drill.

[georgesgiralt]

0.- mm drill are easy to find in electronic shops and/or small scale model shops (the shops where air plane or boat model builder bought their supplies)

[thessler]

Thanks guys
I took those enrichers out agian last night they are spotless, four progressive holes. I did'n mix them up because I only did one at a time.
1) valves adjusted
2) feel good about rubber hoses
3) butterfly shaft- no idea, when I get this thing running stable I will shoot a little WD around them to check for leaks.
4)throttle cables good
Lastly havn't checked timing yet, I havn't seen my light in years not sure if I still have it  :-?.
 Thanks, Tom

[montmil]

Just to add another brick to your load, Tom...

You mentioned you "cleaned" the carburetors. Does that mean you took them down and cleared all the small fuel and air passages? Replaced all the rubber bits and float needle? If you see a hole, it means there's an outlet somewhere. Blowing air or using the straw on a can of carb cleaner can clear or confirm a clogged passage.

Check the floats. If they are vintage, get new ones. Confirm the floats are set at the correct level and that the small brass 'jet' at the bottom of the enrichener reservoir is clear.

Debris from the fuel tank can easily screw up the carbs. It only takes a tiny bit o' grit to disrupt smooth ops. Install an in-line fuel filter if you have not yet done so.

You're probably going to want one of the famous $4.00 Carb Balancer vacuum sticks.

[Semper Gumby]

<snip> Check the floats. If they are vintage, get new ones. Confirm the floats are set at the correct level and that the small brass 'jet' at the bottom of the enrichener reservoir is clear.

This jet is actually in the bottom corner of the Float Bowl and is often forgotten when cleaning the carbs.  There is a hole which is the same size as the red plastic pipe from favorite can of Carb Cleaner.  Make sure you point the open end of the float bowl away from your face (or any painted surface)    before you press the button on the can.  If it's plugged use some thin copper strands from 10 or 12 gage copper multi strand wire to poke it open.  The jet is pressed in and if it's buggered you have to buy a new float bowl!

Good luck!   [smiley=bmw_smiley.gif]

BTW Monte - My floats are Vintage.  I have no idea why they still float.  Perhaps its all those years of Marvel Mystery Oil and Marine Green Stabil in the Gas.