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Old 04-22-2013, 07:57 AM   #1
ausfahrt OP
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Bing or Mikuni?

I bought my airhead in 2010. I made good progress towards getting the R75/7 running again for the first few months or so and then the project got bogged down due to......life. I am moderately competent with a wrench and I do all the maintenance on my FI hexhead GS but carbs have always frustrated and vexed me.

The main thing left to do on the R75 is the carbs. I have been reading the Mikuni thread with interest and at first I thought that a Mikuni was my answer but I see that there are frustrations there too. I am mostly looking for reliability and a "plug n play" carb and I don't really care about performance. So that brings me back to my original question.

Should I send out the Bings to be rebuilt or should I go with new Mikunis?


BTW here is a link to my original thread if you're interested:
http://advrider.com/forums/showthread.php?t=570173
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Old 04-22-2013, 08:07 AM   #2
Airhead Wrangler
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Quote:
Originally Posted by ausfahrt View Post
Should I send out the Bings to be rebuilt or should I go with new Mikunis?
If you aren't concerned about performance or super snappy throttle response, I'd just rebuild what you have... yourself. Don't bother sending them out, it's REALLY easy to do yourself. Just don't bother with the butterfly shafts, they're a little tougher to do correctly, but the rest is stupidly simple. Just order a couple rebuild kits from bing and a few cans of carb cleaner and you can do it yourself in an afternoon.
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Old 04-22-2013, 08:20 AM   #3
blaine.hale
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Quote:
Originally Posted by Airhead Wrangler View Post
If you aren't concerned about performance or super snappy throttle response, I'd just rebuild what you have... yourself. Don't bother sending them out, it's REALLY easy to do yourself. Just don't bother with the butterfly shafts, they're a little tougher to do correctly, but the rest is stupidly simple.
What he said. Bings are mega easy to clean, tune and maintain. They do sometimes just shit out on you though...
That's what lead me to getting Mikunis. One of my Bings out right failed and I can't chase down the issue to save my life, that's another thread with all kinds of trouble shooting.
Now, I haven't had mikunis on long and I haven't even had time to tune them and ride for more than 2 miles. So my observations are on the negative side, since I haven't gotten to see performance. I know there will be some really great pluses once I'm smoothed out.
-They aren't true left/right side so the idle mixture screw on either carb will be super awkward to adjust, as well as fuel inlet.
-There's no vacuum take off port for my carb balancer
-Unless you buy them from rocky point, rubber connects can be weird. We've found a decent solution in the mikuni thread, that I use...it involves way too many hose clamps, though IMO.
-There STILL isn't a consensus on jetting for each model. Not even a really clear baseline for an all stock bike. Adding more free flowing
-If your engine isn't blasted and clean, they stick out like a sore thumb...but who honestly cares about that, we ride.
-Individual thumb chock paddles...not really a negative, I ditched my pull cable stock bmw choke set up years ago.

I did like the cable set up, really easy to adjust, even while I'm riding (in line adjusters.) They do start up super quick with little throttle.
I'll report back in the mikuni thread when I have them running nicely. Right now, my idle circuit is running so rich that it shits black smoke. Turning the idle mixture screw out about 3 turns kills the smoke, but I should probably rejet that. Balancing is going to be hard for me, I'm not used to ear tuning.
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Old 04-22-2013, 09:09 AM   #4
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Quote:
-There's no vacuum take off port for my carb balancer
I'm drilling my keihins for vacuum ports hopefully this weekend. They have an obvious raised spot for them. Maybe the mikunis do?

@OP: I've ridden several airheads with round slides, flat slides, Dels...they do tend to have a better throttle response in that split second after you crack open the throttle. They should flow more air since there's no butterfly valve blocking the intake track.

However, as performance isn't an issue for you, I'd rebuild the Bings. I think you'd have more luck selling it later if it's stock too.

There's an inmate named Infracaninophile who did a veeeery thorough, photo-heavy explanation of the carb rebuild in his r100gs thread...which I can't find right now. I'd recommend finding that instead of using the book.
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Old 04-22-2013, 09:41 AM   #5
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Just so you know, my VM32 Mikunis came with vacuum ports installed. Since I bought them used I can't identify the original source but the ports are there and they look factory.
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Old 04-22-2013, 10:01 AM   #6
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I can't comment on the Mikunis. I can comment on how easy Bings are to rebuild. I rebuilt mine without trouble or issue. The tricky part is tuning them after.
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Old 04-22-2013, 10:56 AM   #7
Uncle Pollo
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Meh
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Old 04-22-2013, 10:59 AM   #8
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No question. Mikuni's. Indestructable. The diaphram won't split on you. And the 32 round sides are perfect for your application / engine.
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Old 04-22-2013, 03:12 PM   #9
Plaka
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Quote:
Originally Posted by ausfahrt View Post
I bought my airhead in 2010. I made good progress towards getting the R75/7 running again for the first few months or so and then the project got bogged down due to......life. I am moderately competent with a wrench and I do all the maintenance on my FI hexhead GS but carbs have always frustrated and vexed me.

The main thing left to do on the R75 is the carbs. I have been reading the Mikuni thread with interest and at first I thought that a Mikuni was my answer but I see that there are frustrations there too. I am mostly looking for reliability and a "plug n play" carb and I don't really care about performance. So that brings me back to my original question.

Should I send out the Bings to be rebuilt or should I go with new Mikunis?


BTW here is a link to my original thread if you're interested:
http://advrider.com/forums/showthread.php?t=570173
"rebuild" yourself. not much to it, take apart, clean, replace the o-rings, put back together. Don't replace the diaphrams unless they have holes, do have a spare set on the shelf and with you on long trips. if the needles are alloy (non-magnetic) consider replacing them and the needle jets. Early steel needles last a very long time. There are jets in the carb bowl, clean them. The enricher gasket has a narrow spot. Common point of failure. Glue it well there. Put in a stainless top screw kit, totally worthwhile. That's it.

There is a deep well of wisdone on setting these up, tuning, etc. And they are effecient and tough. Takes some REALLY bad gas to make them stumble. A snap to change jets by the side of the road for altitude, the bowls just clip off to give you a quarter cup of gas for starting campfires...just very nice all around.

The Mikunis and Dells have snappier throttle response which is fun. But you tend to use it, which hurts mileage and wears out tires, etc. As the big Mikuni thread reveals, people are doing a lot of fumbling around trying to set them up. Not an issue with the Bings.
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Old 04-22-2013, 03:19 PM   #10
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Originally Posted by Plaka View Post
Not an issue with the Bings.
I have two Bings on the shelf and a bag of Bing jets that suggest otherwise.
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Old 04-22-2013, 04:11 PM   #11
disston
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Mikunis are usually a step up from Bings. If you are ready to make the move, now is the time. It is likely that you will eventually get the Mikunis so don't waste any time on the Bings, if you are ready.
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Old 04-22-2013, 04:19 PM   #12
Plaka
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Originally Posted by oldroadie View Post
I have two Bings on the shelf and a bag of Bing jets that suggest otherwise.
methinksthat's not the fault of the carbs. Try the stock setup on a stock bike. Works good. The manufacturer already sorted it out. Plug and play. There is also a table of altitude corrections in the manual. No guesswork there.

I mean, no offense, but how do you get Bings wrong?
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Old 04-22-2013, 05:15 PM   #13
ausfahrt OP
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See? This is what I'm talking about. There is no real consensus on this board but you guys have me thinking about staying with the Bings.

My history with carb work is not pretty. I own the Bing cd on rebuilds but.....

Thanks for all the replies.
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Old 04-22-2013, 07:30 PM   #14
boxerboy81
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You'll never know if you don't have a go. The BINGs are easy. One at a time though. Disassembly is straightforward, as is reassembly.

If you change the needles, it's also easy, but not intuitive if you've not been there before. Ask back.


* Mixture screw and o-ring.

* Pilot jet and o-ring.

* Main jet/washer/jet stock/needle jet/atomiser.
* Top dome/springs/diaphragms/slide and needle.
* Enrichener circuits.

Do one system at a time. A dental pick is a handy device to help get new o-rings on. Change the dome screws to allen heads.

Ask back when reinstalling the main jet stack as it's vital to place the atomiser correctly.
Soak and clean, including the small holes in the orifice. Blast with air, ream with copper wire or fishing line. Flush and blast with air again.

Reassemble and tune the cables.

You'll get as much help as you need here, at every step. Have a crack.
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Old 04-23-2013, 04:24 AM   #15
oldroadie
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Quote:
Originally Posted by Plaka View Post
methinksthat's not the fault of the carbs. Try the stock setup on a stock bike. Works good. The manufacturer already sorted it out. Plug and play. There is also a table of altitude corrections in the manual. No guesswork there.

I mean, no offense, but how do you get Bings wrong?
Sometimes even a carb as simple as the earliest Bing can't be resurrected even with the $200 rebuild kit. Toss in previous owners ham handed damage. And if you don't have a handy dealership trying to obtain parts is a frustrating, time consuming affair. In my case a meticulous complete rebuild did not solve erratic starting and varying idle...a different rpm at every stop.

On the other hand there's no option for vacuum leaks or torn diaphragms with the Mikuni. Parts are easily sourced from any local Yamahondasuzikawa dealer. Cable drive makes balancing a snap. Totally separate enrichner circuit makes starting a breeze. And then there's the performance.

Feel the same way about Amal carbs, too. Why struggle when you can ride?
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