The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: jep129 on January 09, 2014, 10:18:06 PM
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I have searched and not found exactly what I am looking for so I will open the question to the group.
Will a pair of velocity stacks allow the stock bing carbs to operate properly?
by this I mean, will the engine run well? Will they make tuning very difficult?
I have found information for airhead owners using pods and reporting numerous problems and although aesthetics are important to me, I want to delete the airbox and elbows, proper engine performance trumps eye appeal.
I have also looked at the mikuni carbs which seem to work well with the velocity stacks, and I could always sell my stock bings and buy the mikuni.
Thank you
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Changing from the stock airbox to anything will require jetting changes of the Bings to have them work anywhere near correct. Those German boys actually spent alot of time tuning the airbox volume, plenum lengths, etc. to the exhaust capacity and pumping throughput of the engine pretty well to the jet sizes and needle positions - if you try to change the airflow, especially on a CV carb like the Bings, you'll have to compensate in other places along the line of the system.
The slide Mikunis are possibly less "interactive" in their operation with changing the wavelength/impedance of the input airflow, but they do come with their own quirks in the airhead application. Usually they are used by guys/gals who are looking for increasing peak HP at high RPMs. Many people find that they have difficulty balancing out having them running too lean at the high RPMs (which can be both HP limiting and contribute to cylinder overheating) or running too rich in the midrange (which can actually make throttle response more sluggish where you spend more of your time on the street), though changing jets, slides, and usually exhaust systems can eventually be worked out.
I ride my airheads on tours and encounter dirt roads, rain, snow, dust, etc. The pods filters don't do nearly as good a job at keeping crude out of the carb and engine as the stock filter box does, and if you're caught in a heavy rain with pods or stacks you're liable to suck a bunch of water in and stall the engine, so I keep my air/carb setup stock (though I would play with jet/needles positions of the bing carbs if changing exhaust systems).
So, depending on what you plan to do with the bike, I'd consider it carefully as it can be a tedious process to work out.
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I agree - with the removal of the airbox, the bike will become a sunny-day-only ride. And no dust, either, especially with velocity stacks.
Velocity stacks are for guys that rebuild their engines between races.
Either VS or pod filters also lose the 2nd half of the carburator mount.
It is quite possible one could come loose.
One of our regular contributors ran pod filters for as long as I've known him. I'm not sure if he took it out in the rain much, and apparently he never dropped a carb, either.
If you keep the Bings, you WILL want to get their book. It is cheap and has much information.
http://www.bingcarburetor.com/manual.html
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I ran pod air filters for many years on my café Racer with standard jetting. Never had a real issue. Top end performance might well have been slightly compromised if they are restrictive. However I did not run a standard exhaust either. Although the headers were standard.
I did not run the round pod filters, I went for the oval ones with more surface area.
I have always found that Velocity Stacks seem very expensive and difficult to get a hold of. I also prefer to have at least some filtering. depends on your climate as well - hot and dusty? oval pod filters at the very minimum for a road bike.
As already alluded to above, it is important to have new rubber for the carb mount to the heads, or the carbs will fall off. Old rubber is stiff and does not grip to well. New inlet rubbers, and you should not have a problem - or at least I did not after replacing them.
I am about to fit the same filters to my R100.......
Rev. light
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Thank ya'll for the quick response. Funny you mention being a sunny day only bike, while I am a sunny day only rider. Some may be embarrassed to admit that but not me. I just want to be honest. My airhead and I are the opposite of the post office, wind - rain - snow - no go.
I found some stacks that looked really good, http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-carburetor-parts-machine-finished-mikuni-vm30-vm32-vm34-velocity-stacks-sd-vm32-mwl.html
but I don't know about fitment or anything else.
Sounds to me like I need to try out Steve's pod set up and see how it works for my application. Should be inexpensive enough to not matter if it doesn't work for me.
Thanks again
Adam
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You want your velocity stacks?
Here they are, right here:
http://www.bonhams.com/auctions/21389/lot/328/