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Old 11-22-2012, 03:03 AM   #1
patanga OP
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Square top air filter cover types.?????

From time to time I see variations in the intake horn sizes of the Air filter intake horns and am curious if BMW experimented with this for reasons perhaps known here on the forum, or if it was just the various housing manufacturers ideas filtering through. Anyone come up with any answers on this one? See photo below.
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Old 11-22-2012, 03:41 AM   #2
ME 109
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I've seen smaller horns on R65's, could that be it?
Maybe people have played around and mixed horns?
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Old 11-22-2012, 05:50 AM   #3
Rucksta
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A mix of one large and one small horn is said to reduce a flat spot in the midrange of 980cc engines
There was a mod drilling 4 holes around the lip of the horn that addressed the same issue.
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Old 11-22-2012, 06:16 AM   #4
AliBaba
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I think the mix was used for bikes with 32mm carbs and two large horns were used for bikes with 40mm carbs - but there are exceptions.
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Old 11-22-2012, 10:48 AM   #5
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For what I've seen, R65 have 2 small, R80, monolever 1000, 100R and 100G/S one of each, and other R100 two large.
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Old 12-01-2012, 06:56 PM   #6
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All the bikes have one large and one small horn except for the big port models (40mm carbs). A lot of people put the two large horn tops on the models that came with one large/one small but all it does is kill mid range. After camming and carbing my small port R100, two large horns still killed my mid range. Since then I have raised compression, dual plugged, larger intake valves and did a lot of port work. Now my mid range is better with no top whatsoever and shortened stock velocity stacks to just inside the box.
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Old 12-01-2012, 08:03 PM   #7
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The stock airbox in my opinion is best with a stock motor. When you change the carbs, compression, cam, ignition, and exhaust, the standard unmodified airbox is the pimple on the ass of progress.
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Old 12-02-2012, 11:39 AM   #8
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Quote:
Originally Posted by robtg View Post
The stock airbox in my opinion is best with a stock motor. When you change the carbs, compression, cam, ignition, and exhaust, the standard unmodified airbox is the pimple on the ass of progress.
After raising my compression quite a bit, bigger intakes, port work, dual plugging, and remapping my ignition curve, the stock box was a huge pimple on the ass of my progress. With just a cam, sport mufflers, and carbs, my bike ran a LOT better with the stock airbox over setups that now work MUCH better after the above further mods. My advise is to hog things out JUST enough. Too much kills any setup. I have put the stock airbox back on many a stock OR slightly modified bike for a much happier customer many times over. Opened up airboxes and bigger jets are just going to hurt performance unless your engine actually needs them. Hogging stuff out IS the road to better performance but I have seen SO many bikes tuned to a stand still in my life for being hogged out too far here or there for what the setup really calls for. An engine ever so slightly hungry for more works SO much better on SO many levels than one that is getting spooned too much! It's a fine line!
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Old 12-02-2012, 12:06 PM   #9
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2 Small horns on a 1981 R80G/S. Standard.

I think you'll find the size of the horns is related to the amount of maximum air a motor breaths. Simple really.

As always some people thing bigger is better and just like carbs they put things on that are too big and loose performance to gain status.
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Old 12-02-2012, 12:07 PM   #10
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Quote:
Originally Posted by supershaft View Post
After raising my compression quite a bit, bigger intakes, port work, dual plugging, and remapping my ignition curve, the stock box was a huge pimple on the ass of my progress. With just a cam, sport mufflers, and carbs, my bike ran a LOT better with the stock airbox over setups that now work MUCH better after the above further mods. My advise is to hog things out JUST enough. Too much kills any setup. I have put the stock airbox back on many a stock OR slightly modified bike for a much happier customer many times over. Opened up airboxes and bigger jets are just going to hurt performance unless your engine actually needs them. Hogging stuff out IS the road to better performance but I have seen SO many bikes tuned to a stand still in my life for being hogged out too far here or there for what the setup really calls for. An engine ever so slightly hungry for more works SO much better on SO many levels than one that is getting spooned too much! It's a fine line!
Where is the "LIKE" button?
I have the same opinion, but i didn't do much on (engine) tuning this bikes.
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Old 12-02-2012, 02:13 PM   #11
Thickasabrick
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Horn Size

On our 1986 R65 there is a large one on the right side and small one on the left.
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Old 12-03-2012, 06:40 AM   #12
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Same on my 86 R80 G/S.

Quote:
Originally Posted by Thickasabrick View Post
On our 1986 R65 there is a large one on the right side and small one on the left.
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