Carburetor Tuning

[Crossrodes]

I have a 79 R65.  The carbs are Bing 64/32 2030 and 64/32 2040.  Recently the idling has gone bad...it barely idles at all and often stalls.

I read the instructions posted by Trolle in another thread and tried the procedure that he says works for him.  

First I tried removing the spark plug on one cylinder so I could set the idle mixture on the other...no joy...she wouldn't run on one cylinder.  So I ran her on both and attempted adjusting the mixture that way.  It is difficult given that there are two carbs on two separate cylinders but I think I did manage to improve it.  It will now run for a minute or two at around 400 RPM without blipping the throttle.

So next I wanted to adjust the idle speed.  Trolle talks about the adjustment but I wasn't sure which was the adjustment screw on the carb.  Is it the screw next to the mixture screw???

I also tried a Bing manual I have and that is just about useless...whoever wrote it should read a Honda manual and then start again.  (That should get some comments).  So next I tried my Clymer manual and there is not much info in that either.

If anyone reads this can you either direct me to a good manual on these carbs or tell me what kind of carb Trolle was referring to in his write up and where the idle speed adjustment is?

[Lucky_Lou]

I have a 79 R65.  The carbs are Bing 64/32 2030 and 64/32 2040.  Recently the idling has gone bad...it barely idles at all and often stalls.
So next I wanted to adjust the idle speed.  Trolle talks about the adjustment but I wasn't sure which was the adjustment screw on the carb.  Is it the screw next to the mixture screw???
If anyone reads this can you either direct me to a good manual on these carbs or tell me what kind of carb Trolle was referring to in his write up and where the idle speed adjustment is?

Correct me if im wrong but these should be the flat top Bing's(mine are 1980)
The two screws underneath the carb one is the vacuum port the other is the air screw(inset) idle speed is affected by the air screw basically the enricher mechanism is a mini carburetor latched onto the main body there are alot of small ports in this bit and its important all the bits are clear i didnt get mine sorted out properly untill i had them ultrasonically cleaned.
check this out its pretty good and in depth
http://bmwmotorcycletech.info/bingcv.htm
follow the link and read page 2 aswell
http://www.gunsmoke.com/motorcycling/r100gs/carb_rebuild/index.html
this one is illustrated
Lou

[Crossrodes]

Thanks Lou.

Yes they are flat top carbs.

It looks like the inset screws are what I'm looking for to adjust the idle speed. I'll play with this and the vacuum port and see where I can go  I don't plan on rebuilding the carbs yet but I don't know their history so it may be in the foreseeable future.  Thanks for the links.

[Bengt_Phorqs]

Hey Crossrodes, did you set the timing before working on the carbs? That is very critical.  Secondly, the bike likes to be nice and warm before tweaking the carbs.  About a 10 mile ride should do it.

Lots of good carb information in the past 90 days on this forum.  Do a 90 search and I'm sure you'll come across some of the threads.

[Crossrodes]

Good point Bengt.  

I set the timing about a month ago but....I could not read the timing marks on the flywheel. So I set it where my gut told me after lots of experimentation.  Now tell me why it is critical to have the timing right on so that the carbs can be set right.  

The bike was warmed up prior to me working on the carbs.

[Bengt_Phorqs]

Now tell me why it is critical to have the timing right on so that the carbs can be set right.

OK, fair question, but before answering, why would you not want to make sure the timing was spot on?  To simplify, there are only three elements that make an engine run, spark, fuel, and air.  If the spark doesn't fire at the precise time you will never achieve a smooth running engine.  You already discovered that "close enough" timing won't get you there.  What kind of timing light are you using?  Make sure that it is bright enough to see the marks.  Most of the mechanical minds on this forum recommend using an alternate battery for the light and hooking up the timing light to the right spark plug.  (Please don't ask me why about that, but it seems to be the optimum method.)  You know to adjust the bean can to advance or retard the spark.  The Clymer manual is pretty straight forward about setting the timing.
Mike, check out this thread:  "Carb rebuild new cables....07/30/09 at 11:23:04"   Lots of good information in there.  Sounds like a carb rebuild may be in order.  Keep us posted.

[Crossrodes]

Good question also... I would like to have the timing spot on...The problem is that I spent days attempting to get the flywheel cleaned up so that I could highlight the timing marks.  There is so much crud/rust that I can't remove through the inspection hole that the marks cannot be seen.  The timing light is not the issue (I have two of them...one xenon).  My plan is to take the drive-line apart this winter and get at and clean the flywheel and hopefully find those marks.

I do know how to adjust the bean can.  I have had it and most of the other electrics apart earlier this year.  I have had a little experience setting timing of vehicles (first did this about 50 years ago and have done all my own (and other) vehicles since then....I do understand that the timing has to be right on for the bike to run properly but I believe I have it pretty close at this point (as close as I will get it without getting at that flywheel).  Given all that I still don't understand why it is critical to have the timing right on to set the carbs.  I'm not trying to be a smart ass here.  If I truly do need to get the timing right on I'll wait until I get the flywheel cleaned up and the timing set with the light before I waste any more time on these carbs.

I'll check out that thread tomorrow and see if there is anything else I can learn from it.

Thanks for your input.    

[montmil]

Hey there, BC Mike.   Ol' Bengt Phorqs is giving you the straight dope.

Timing is quite critical to a smooth idle. The bean can plays an important role as the timing advance on the BMW begins a about 1400 rpm. That's barely above the 800-1000 idle revs for a points-ignition engine. !000-1100 for the electronic ignition engines. Both have the old school mechanical advance mechanisms.

It doesn't take many additional idle revs to bring the advance curve into play and mess with your desired BMW idle. Also, your advance weights could be sticking and not freely moving about.

I hope this helps you understand Bengt's point. He is correct with his comments. I also discovered this with my R65's idle issue.

Monte

[Barry]

Mike

Getting back to your original post  "Recently the idling has gone bad"

If it happened just like that without any changes to throttle stops or idle mixture screws and assuming for now you have no significant ignition problems then the most likley reason is a partially blocked idle jet or transfer ports.  You could try cleaning these without carrying out a major carb overhaul.

[Bengt_Phorqs]

Crossrodes, didn't mean to imply you were being flippant, those were fair questions.  It can definitely be frustrating trying to get it sorted out.  Having said that I assume that you do have significant mechanical skills but just need familiarity with the quirks of these little critters.  That's what this board is all about, and these bikes do have some significant quirks.  Monte's comments about the idle arms are good as are Barry's about the simple cleanout.  Come to think of it, it could be that you just have some crud that got stuck as a result of ethanol induced deterioration.  Pull the float bowls and blow out all of the orifii in the carbs with some compressed air.
We'll help you get it sorted out!

[Crossrodes]

Thanks for your input guys.  

I don't think the advance is an issue because the bike accelerates quite well anywhere above idle.  I had the bean can apart a couple of months ago to install new points and condenser and to install a new o-ring seal and all was well in there.  I think it's quite possible that there may be some issue with crud in the carbs though.  I had taken the float bowls off at the same time I had the bean can apart...the bowls were clean but I did not blow out any orifices...I'll try that.

[Lucky_Lou]

Just out of interest does the bike run ok on idle when its warmed up with a 1/4 choke ?? if so you definitely have a blocked jet and not a timing issue. If you do rebuild the carbs dont waste your money on generic diaphragms pay the bit extra for Bing originals a sound investment.
Lou

[Crossrodes]

I don't think so Lou but I'm not sure.  I'll try that.

[R65Singh]

Good point Bengt.  

I set the timing about a month ago but....I could not read the timing marks on the flywheel. So I set it where my gut told me after lots of experimentation.  Now tell me why it is critical to have the timing right on so that the carbs can be set right.  

The bike was warmed up prior to me working on the carbs.

Mike;
When i opened up my drive train, I noticed that the timing marks were not on the flywheel itself but on the little tabs attached to it.  For your reference I am attaching a picture.  So u don't have to clean the whole flywheel, just use a Q-tip with some alcohol on it to clean it and u should be able to see the marks.  
I think in your case the idle jets might be clogged up.  Those have tiny holes around its diameter and idle goes haywire if one or two of those holes gets plugged.  Just my 2cents!!

[Crossrodes]

That's interesting Singh.  I took a look at those tabs when I was cleaning and didn't see the marks.  I'll take another look.  Thanks for the info.

Today I played with the carbs some more and got it to idle much better.  But I'm treating this as an iterative process and I intend to go through the process at least one more time.