Airbox inlet trumpets

[clouseau]

I was at a shop today picking some parts from an R65 and noticed the air box lid inlets were of 2 different sizes.  Mine aren't. (Mine has 2 identical inlets the same size as the large one in the picture)
I knew the guy had another R65 motor laying around and sure enough the air box inlets were of 2 different sizes as well, so I bought one off of him.  Does anyone know which is the correct one?

[montmil]

Actually, both!  I'll need to see if I can find the internet resource where I tripped across the topic.

That said, one of my R65s has two different length air box "horns". The other R65 has equal length snouts. Both bikes run just fine. Both are correct. Go figure.

Lemme see what I can find. Will post if I get lucky.

And along similar lines... awhile back, I noticed the handlebar brake lever is a different shape than the clutch lever on one (or both, as I forget) of my R65s. Not So Fast Ed Miller -I think it was- said I had w-a-y too much free time.

Monte

[Bob_Roller]

There are different air box covers, for the BMW '81 and later bikes with the square air filters, all of the air box covers are interchangeable, but there were different lengths and diameters of intake tubes, depending on what displacement engine the bike had .

From the best of my memory, both my '81, and '84 bikes, have covers with the same length and diameter intake tubes .

[bruce_launceston]

My '84 has always had 2 slightly different airbox horns (from the factory), from memory the length is similar but the opening size is slightly smaller on one side than the other - as shown in your photo.

[GrimReaper]

My r65 has to different sizes.I think Snowbum explained why?

[Ed Miller]

Snowbum talks about it regarding the R80s but I can't remember if he says anything about why R65s would have different covers.  I have one of each.  My bike came with the same tubes, and later I bought an air box and components off of Ebay that had different snorkles, and I put that cover on my box.  I couldn't tell any difference, and I've since switched back, still no difference.  I didn't have to retune or anything.

Monte, Not-so-fast Ed and Ed Miller are two different people.  But hey, two Eds are better than one.

[montmil]

Monte, Not-so-fast Ed and Ed Miller are two different people.  But hey, two Eds are better than one.

Oh, Lord! Two Eds?

[clouseau]

Very interesting!
I remember a while back when I was chasing down a flat spot between 3K-4K rpm, removing the lid completely almost cured the flat spot,  although it ended up being a timing issue.  Man was it loud but in an annoying way.  I don't have stock mufflers so maybe my bike would benefits from more air.

[raypond]

Yep, mine has two different ones. Exactly the same as in the photo. I can't be 100% certain but I believe they are original. They have different BMW numbers on them: 1 337 501 for the smaller and 1 337 227 for the larger. I would be very interested to find out the reasoning behind it.

[Lucky_Lou]

Invest in some "Clam Shells" they look better anyway..
Lou

[Flash]

Just throwing this out there........

Could they be different sizes so they're not both affected by intake pulsation at the same frequency? Kinda like running double valve springs on some of the high performance motors?

(Sorry... I'm just bored)

[Tv]

I've had an issue with these snorkles.  I had a midrange flat spot problem on my 84 and found the snorkles were both small and the airbox lid on the 81 had big snorkles so I changed them over and the 84 has been running fine ever since. I haven't fired the 81 up yet but I am assuming it'll have a problem with the small snorkles so I'm going to make the two lids identical (One small snorkle and one big)and see if that works OK.  See link below

http://bmwmotorcycletech.info/R80,%201980+,%20Airboxmods.htm

[Semper Gumby]

My R65 has a Snorkel?  No wonder I'm so comfortable in the rain!

However -- My BSA has no snorkle.....

Cleuseau -- That Snorkel picture looks like the top off a Dalek with stereo vision but I digress...