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32 mm Bing carb question(s)

K

kjschilling

New member
Greetings,

I recently acquired from a BMW dealership in Roseville CA a 1995 R100R Mystic, 16,000 miles. I'm the 2nd owner of this California bike. The bike started fine and ran fine (fine, but not quite as smooth as I remember a past airhead I had owned; a 1982 R80 RT). The PO had done most of the basic mechanical work and the bike was checked out as good by the dealer before selling it to me,,(no complaints whatsoever regarding the dealership nor the PO).

The less than smooth engine performance was/is most noticeable at RPMs between 3,200 to just under 4,000 and the bike felt just a little anemic throughout just about all throttle settings,,,nothing atrocious just seems a bit anemic from a 1000 cc motor.

I checked the valve clearances, head bolts, timing at idle and at 3,500 RPM,,,,everything checked out good. Both carbs were fairly grimy so I thought what the heck, I'll clean them well and rebuild them, the PO, as far as I could tell had not done that task. I did a full rebuild (new jets, new gaskets, new floats, new pins, new diaphragms, new O-rings,,,,the works) of them closely following the videos on Boxer2valve and Brook's Garage youtube sites (really excellent sites, by the way). Got everything back together and balanced the carbs with a carbtune device. Balancing went fine.

The less than smooth engine performance (which by the way seems to contribute to a pretty noticeable vibration sitting on the seat and looking in the rear view mirrors) still exists in the 3200-4000 RPM range and the anemia still persists as well.

So, after that rather lengthy intro allow me to get to my question(s):

I happened to see a (facebook) post that included a copy of an email exchange between Bing technical support and a guy asking about what the proper jetting should be for a set of 64/32/357 & 358 carbs, which are the same as on my Mystic. (The bing manual calls for the following: main jet 135, needle jet 2.66, idle jet 45 and clip position #3) The Bing tech support guy responded that late model R100s with 32 MM carbs were jetted lean to conform to emissions regs and he recommended the following: main jet 145, needle jet 2.68, idle jet 48 and clip position #3. Has anyone else seen or heard of that different jetting recommendations for that series of 32 mm bings?

I'm wondering if the different jetting recommendations could help with my issue?,,,,,if not, any advice/guidance on what I might do next for the rough/somewhat anemic engine performance?

Thank you in advance for your help.

Cheers and all the best
 
Welcome to the forum! Glad you were able to find some hands-on videos to help with the carbs. While the carbs are relatively simple, nice to see someone do it for learning purposes.

My Bing book suggests that those carb numbers were for R80GS/R100GS models...I don't see the R100R listed. At any rate, since you have anemic conditions at a mid range throttle setting, I'd concentrate on the mid range items which are the needle jet and the needle itself. You could see if the needle position will help immediately by just raising the needle one more position. That is a gross adjustment, but if you notice a difference, then maybe pursue the bigger needle jet and drop the needle back to #3.

As for the vibration, hard to say what that might be. I would think that the carbs need to be synched but you say you've done that. How confident that the carb parts, sizes, etc., are the same side to side? Could there be a difference? I'd say pursue the anemic situation first with the needle and/or jet, and see where you stand with the vibration.
 
Thank you for the speedy response,

20774 said:
Welcome to the forum! Glad you were able to find some hands-on videos to help with the carbs. While the carbs are relatively simple, nice to see someone do it for learning purposes.

My Bing book suggests that those carb numbers were for R80GS/R100GS models...I don't see the R100R listed. At any rate, since you have anemic conditions at a mid range throttle setting, I'd concentrate on the mid range items which are the needle jet and the needle itself. You could see if the needle position will help immediately by just raising the needle one more position. That is a gross adjustment, but if you notice a difference, then maybe pursue the bigger needle jet and drop the needle back to #3.

As for the vibration, hard to say what that might be. I would think that the carbs need to be synched but you say you've done that. How confident that the carb parts, sizes, etc., are the same side to side? Could there be a difference? I'd say pursue the anemic situation first with the needle and/or jet, and see where you stand with the vibration.
Click to expand...

Thank you for the tip(s). Am I correct to understand that raising the needle one more position means moving the clip to position #4? (#4 being the fourth slot down from the top (non-beveled) end of the needle.). That should be easy enough to try,! Thank you

I see that your location is San Antonio. I'm spending the winter in Georgetown,,,escaping the snow-filled South Dakota winters. Can you recommend an airhead friendly shop in the general area? Thanks again
 
Yeah, the clip positions are numbered from the blunt end. So, you'll be making it richer. You might have to recheck the carb balance when done.

As for Airhead type shops, I'm not aware of anything nearby...mostly Houston and DFW. Lone Start BMW is north Austin, so for parts that would be source. Maybe stop in there and chat them up...see if they have any ideas.

Enjoy the Texas winter!!
 
Following With Interest

I ordered a Bing Manual from Bing Agency and, disappointingly, it does not list 32mm carbs for later R100s. My carb numbers are same as kjshilling's (64/32/357 & 358), and I find those listed in the manual for R80GS/R100GS, but none other. There's a foot note: "Some of the late model R100 carbs were jetted lean to conform with emission standards." Really, it's time for an update to the Bing Manual, or he should disclose it has no info for late R100s other than GS.

At any rate, my 95 R100RT carbs seem jetted perfectly, but I am fighting curiosity and the urge to drop the bowls and see what jets are inside. It never needs full choke to start, and will start harder on full choke, then stumble. It fires right up on half choke, which can be switched off in 10-15 seconds. Of course the lowest temps I've started it up has only been around 40 F, but still. The power is great, with no flat spots, and easily pulled 6000 RPM recently in 5th gear, on level road. MPG is 40-43 when puttering around on secondary roads, and 35-36 on the interstate at around 75 MPH. The lowest MPG so far was when I rode it 225 miles home the first day, at 75-80. On that day it got 31 MPG, but 3 of the 4 valves were all but closed up in the motor. I have not looked at the plugs, but there's no indication of running rich, i.e. black smoke.

Other than curiosity, I should just leave the carbs alone. I could probably squeeze a couple more MPG by leaning it a bit, but it performs very well as is. I'd almost bet this bike has been re-jetted, but impossible to know without looking inside the carbs. The original owner was killed on his Harley, and the second/last owner simply rode it, and had a maintenance guy keep up on regular, scheduled maintenance for him.

So I will be interested to know what kj does in order to get the flat spots out of his.
 
Thank you for the tips,,,I've ordered a different set of main jets and needle jets and also some clips (just in case the ones i remove get damaged). I will also check the diaphragms although I was pretty careful when installing the new ones during the recent rebuild,,,no harm in checking them again. So, first order of business will be to just try moving the clip to position 4,,,seeing how that goes,,,,then perhaps different main and needle jets,,,,changing one variable at a time.

I'll report back as soon as possible,,,,but for now a tour of Texas wine country is in order,,,I never knew there were sooooo many vineyards in this part of Texas.

Cheers
 
Airhead shop

Martindale Motorcycle Works is the closest independent repair shop. (512)-35-2842. He has customers that go there from Dallas/Ft Worth! Good reputation.
 
The guys at Revival in ATX also know airheads very well; not well known they do repairs as well as build bikes, but they do. Shop manager is Nick.
 
kjschilling said:
Greetings,

I recently acquired from a BMW dealership in Roseville CA a 1995 R100R Mystic, 16,000 miles. I'm the 2nd owner of this California bike. The bike started fine and ran fine (fine, but not quite as smooth as I remember a past airhead I had owned; a 1982 R80 RT). The PO had done most of the basic mechanical work and the bike was checked out as good by the dealer before selling it to me,,(no complaints whatsoever regarding the dealership nor the PO).

The less than smooth engine performance was/is most noticeable at RPMs between 3,200 to just under 4,000 and the bike felt just a little anemic throughout just about all throttle settings,,,nothing atrocious just seems a bit anemic from a 1000 cc motor.

I checked the valve clearances, head bolts, timing at idle and at 3,500 RPM,,,,everything checked out good. Both carbs were fairly grimy so I thought what the heck, I'll clean them well and rebuild them, the PO, as far as I could tell had not done that task. I did a full rebuild (new jets, new gaskets, new floats, new pins, new diaphragms, new O-rings,,,,the works) of them closely following the videos on Boxer2valve and Brook's Garage youtube sites (really excellent sites, by the way). Got everything back together and balanced the carbs with a carbtune device. Balancing went fine.

The less than smooth engine performance (which by the way seems to contribute to a pretty noticeable vibration sitting on the seat and looking in the rear view mirrors) still exists in the 3200-4000 RPM range and the anemia still persists as well.

So, after that rather lengthy intro allow me to get to my question(s):

I happened to see a (facebook) post that included a copy of an email exchange between Bing technical support and a guy asking about what the proper jetting should be for a set of 64/32/357 & 358 carbs, which are the same as on my Mystic. (The bing manual calls for the following: main jet 135, needle jet 2.66, idle jet 45 and clip position #3) The Bing tech support guy responded that late model R100s with 32 MM carbs were jetted lean to conform to emissions regs and he recommended the following: main jet 145, needle jet 2.68, idle jet 48 and clip position #3. Has anyone else seen or heard of that different jetting recommendations for that series of 32 mm bings?

I'm wondering if the different jetting recommendations could help with my issue?,,,,,if not, any advice/guidance on what I might do next for the rough/somewhat anemic engine performance?

Thank you in advance for your help.

Cheers and all the best
Click to expand...

I'm not sure of the altitude where you live but this is the jets that I always used for my 1995 R100RT with the 357/358 carbs. Main 135, needle jet 2.66 and idle jet 50, clip position # 3. I used this set up on this bike with a sidecar and found that it worked very well. Over the years that I owned the rig, I tried, various mains & needle jets and found the above set up the best. Worked well for cold starts and good pull through the RPM range. I live just 60 miles east of the Rockies and it worked well at altitudes up to 5000 feet. Where I live it is at 3000 ft, so this mixture is slightly rich according to bing. The airheads don't like to be mixed rich and work much better with a leaner mixture, just not to lean.

All jetting over laps each other so a 50 idle jet is going to slightly richen the rest of the rpm range. The bing book will show you the various overlaps between the jets. The 135 main has had a lot of stuff written on it in the past and was felt to be one of the better setups for the late model R100. Don't get hung up on carb #'s as those carbs where used stock on just about any late model R100 that used the 32mm carbs. In the era of lower compression lower hp of the R100's with the smaller valves the #32 mm carbs seemed to work the best. The earlier R100 with the larger valves did benefit from the 40 mm carbs.

Just change the idle jet and see how it goes. Just change one thing at a time.
 
cycleman2 said:
All jetting over laps each other so a 50 idle jet is going to slightly richen the rest of the rpm range. The bing book will show you the various overlaps between the jets.
Click to expand...

The way I see it, it's not that inclusive according to the book. The needle jet does dip down into the idle jet range and goes up into the main jet range. But according to the diagram, the idle jet is only operating from 0 to 25% throttle while the main jet is only in use from 60% to 100% throttle. So the main jet doesn't appear to overlap into the idle jet.

Given all that, I wonder if I've ever been operating solely on the main jet? :dunno I tend to be pretty easy on the throttle! :whistle
 
20774 said:
The way I see it, it's not that inclusive according to the book. The needle jet does dip down into the idle jet range and goes up into the main jet range. But according to the diagram, the idle jet is only operating from 0 to 25% throttle while the main jet is only in use from 60% to 100% throttle. So the main jet doesn't appear to overlap into the idle jet.

Given all that, I wonder if I've ever been operating solely on the main jet? :dunno I tend to be pretty easy on the throttle! :whistle
Click to expand...
Very strong headwinds will have an Airhead running off the main jet. I recall riding on I-10 West, near Palm Springs and having to use 3rd gear to maintain 50-60 MPH on an RT. That is, supposedly, one of the windiest spots in the nation. I was reminded of that yesterday on I-65 South, about 60 miles south of Louisville, in an unusually strong headwind. In order to stay around 5000 RPM in 5th gear, the throttle was near wide open. Of course later, coming back north, it was just the opposite, only a little throttle was needed.
 
jhall -

Of course you are right! My parents and I had the same experience running I-10 west and into California back in 2007. I don't remember how much the throttle was twisted, but it could have been that much. I was just saying that normally, I don't go that far into the throttle.
 
grcrowell said:
The guys at Revival in ATX also know airheads very well; not well known they do repairs as well as build bikes, but they do. Shop manager is Nick.
Click to expand...

Roger that, I brought the bike to Revival and asked them to check the balancing of the carbs (basically to verify I had done that task properly), they (Alec) made a couple of adjustments and the bike did run a bit better afterwards.

I'm still going to try a different clip position and perhaps different jet combinations to see if the performance in the 3200-4000 RPM range can be better than it is. Vibration is still present.

Revival is a good shop (impressive output for sure) and not too far away from where I'm staying this winter. Nick is no longer with them.
 
cycleman2 said:
I'm not sure of the altitude where you live but this is the jets that I always used for my 1995 R100RT with the 357/358 carbs. Main 135, needle jet 2.66 and idle jet 50, clip position # 3. I used this set up on this bike with a sidecar and found that it worked very well. Over the years that I owned the rig, I tried, various mains & needle jets and found the above set up the best. Worked well for cold starts and good pull through the RPM range. I live just 60 miles east of the Rockies and it worked well at altitudes up to 5000 feet. Where I live it is at 3000 ft, so this mixture is slightly rich according to bing. The airheads don't like to be mixed rich and work much better with a leaner mixture, just not to lean.

All jetting over laps each other so a 50 idle jet is going to slightly richen the rest of the rpm range. The bing book will show you the various overlaps between the jets. The 135 main has had a lot of stuff written on it in the past and was felt to be one of the better setups for the late model R100. Don't get hung up on carb #'s as those carbs where used stock on just about any late model R100 that used the 32mm carbs. In the era of lower compression lower hp of the R100's with the smaller valves the #32 mm carbs seemed to work the best. The earlier R100 with the larger valves did benefit from the 40 mm carbs.

Just change the idle jet and see how it goes. Just change one thing at a time.
Click to expand...

Thank you for your response and input; The bike originally was a Sacramento/San Francisco bike,,,I had it this summer in the Black Hills of South Dakota (altitude riding there varied between 4-6k feet) and this winter am/will be in the Austin/Georgetown area of Texas,,so, with the exception of occasional rides in the Black Hills altitudes below 5k were/are the norm.
It's interesting that your combination of jets is just a bit different from the Bing book recommendations and quite a bit different from the "newer" Bing tech support recommendations. It's good to know your combination works well on a 95 R100RT. I have jets and clips on order (should be here on Monday) and then will start my Sherlock Holmes process of investigation and changes,,,,one variable at a time.
Cheers and thanks again
 
Anemic condition solved

Jets and clips arrived today so I tried various combinations,,first I just changed the clip position (leaving everything else as it was, i.e. stock jets as per Bing book) to slot#4 as recommended earlier; that helped the performance in the 3200-4000 RPM range a bit,,,so it seemed that a richer setting was called for. So, I set the clip back to position # 3 and changed the needle jet to 2.68 as recommended by a "newer" Bing Tech Support recommendation, that helped the performance as well, so just to see what happened if I changed the main jet (also per "newer" Bing Tech Support recommendation) I installed a 145 main jet.,,,very nice performance improvement all across the RPM range with the two new jets (I wanted to try a #48 idle jet but haven't found one online yet, but since the idle circuit seemed fine I don't think it's too big a deal to leave the #45 in there).

Checked the balance and tweaked it each time after a change. now seems to be fine, idles fine, revs fine, no flat spots accelerating etc.

Vibration still exists, though.

I would like to extend my thanks to those that took the time to read and respond with ideas, advice and guidance, it's certainly helped.

Cheers

KJS
 
Glad you narrowed in on the problem. I'd be curious to hear what the miles per gallon performance is as time goes by. I tend to use MPG as another reference point when making carb changes. I hate when there is a big hit on MPG...if it solves a problem maybe it's OK, but still I'd prefer to keep the general MPG when all is said and done.
 
20774 said:
Glad you narrowed in on the problem. I'd be curious to hear what the miles per gallon performance is as time goes by. I tend to use MPG as another reference point when making carb changes. I hate when there is a big hit on MPG...if it solves a problem maybe it's OK, but still I'd prefer to keep the general MPG when all is said and done.
Click to expand...

Roger that, I do plan on keeping track of MPG. Truthfully, the MPG prior to carb rebuild was pretty crappy and initially after rebuild as well. So, like you, I'm curious what these changes will bring.

We shall see !
 
Vibration and RPM.

I bet the vibration you are experiencing is a common trait of airheads that usually occurs between 3800 and 4200 RPM. It’s more noticeable in the liter bikes with those two big 500cc pistons moving about. Recall one side is combusting and the other is exhausting- the ‘bang’ swaps sides every revolution but the vibration only manifests noticeably in that RPM range. Resolve to ride above 4200.
 
Na Cl K9 said:
I bet the vibration you are experiencing is a common trait of airheads that usually occurs between 3800 and 4200 RPM. It’s more noticeable in the liter bikes with those two big 500cc pistons moving about. Recall one side is combusting and the other is exhausting- the ‘bang’ swaps sides every revolution but the vibration only manifests noticeably in that RPM range. Resolve to ride above 4200.
Click to expand...

You're correct; the vibration is quite a bit less below 3200 RPM and above 4000 RPM. I, now, spend very little time in the 3-4k range and that helps. I've had quite a few other brands/models of motorcycles across the years (some Brit, some German and a midsize displacement early 70s Honda) but only one other airhead, a 1982 R80RT. That RT was smooth as silk, it had 20k miles on it when I got it and I put 30k miles on it in a little over two years while living in Madrid; mechanically flawless during the time I owned it. So, perhaps I'm making an unfair comparison between this 95 R100R Mystic and that R80RT.

Thank you for your input, much appreciated.
 
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