Yet another "will this fit my bike?" question

[AlfromNH]

Via IBMWR.org I am being offered these 38mm headers and mufflers for $200 shipped. The seller doesn't know what they came off of, but says they'll fit anything from an R65 to an R100 twin shock.


Assuming they're 38mm diameter, will they fit my '79 R65?

Thanks!  

[Rob Valdez 79 R65]

A fairly cheap tool that every airhead owner should have is a pair of digital calipers.  Then you will know very quickly if they will fit or not.

The calipers have an "inside-out" fingers that allow you to measure the inside diameter of a hole.

$20 at Harbor Freight.  You can measure depth, too.  You will need it for your oil filter canister check, which will come in a little while.

[Luca]

Nope, the R65 and R45 had smaller exhaust pipes then their bigger brothers.  I think they are 35mm, but if you've got a set of calipers you could verify with a quick measurement.

Lot's of sellers will say something like "fits all airheads," but with our bikes it's often not the case.  Another example when the "one size fits all" idea fails is with luggage racks, since our bikes have a shorter wheelbase than the contemporary big boys.

With that said, you can usually fit bigger mufflers on stock headers with some adapters (bushings) and hide the cruddy header pipes with exhaust wrap.

[MrRiden]

No they will not fit unless they came off an R65 / 45. The pipe diameter is smaller on our bikes. It is good practice to ignore what a seller is telling you as you well know now. An alternate method of checking parts is logging into motobins and browsing. Here I found that the exhaust nuts are smaller for our bikes and used that tid bit to determine the pipes shown most likely won't fit. No caliper required. Though I do own a caliper.

http://www.motobins.co.uk/bmw-parts.php?model=R%20Series%202%20valve%20Twin

[AlfromNH]

I'm glad I asked. I thought that I had read that R65's had smaller diameter pipes than other airheads. Thanks.

BTW, I have a set of calipers. Unfortunately, the pipes are in Texas, I'm in New Hampshire.  

[Rob Valdez 79 R65]

BTW, I have a set of calipers. Unfortunately, the pipes are in Texas, I'm in New Hampshire.

So, you go to where your engine is, and measure the inside diameter of the exhaust port.
If you measure 35mm and the pipes are 38mm, then you know.

[Barry]

Those are odd looking silencers (mufflers) in the way the reduced diameter section at the front is much longer than usual. Also unusual to see a silencer "blue".  

As has been said R45/65 pipes are definitely 35mm. Other airheads are 38mm and some R100's 40mm.

Still buy a digital caliper. One of my most frequently used tools, don't know how I could live without one.

[Rob Valdez 79 R65]

Those are odd looking silencers (mufflers) in the way the reduced diameter section at the front is much longer than usual. Also unusual to see a silencer "blue".  
 

Odd on both accounts.  Good catch.

[montmil]

The mufflers are most likely one of the EMGO or similer offshore repop, knock offs. When sold new, the muffs come with a brass, multiwrap 'reducers' to allow installation on smaller diameter headers, such as the 35mm R45/65.

Bengt Phorqs "allowed" me to assist him in fitting some aftermarket mufflers on his Hinckley Bonneville. Same reducers came with the Triumph-looking mufflers.

Both my R65s have EMGO Norton Dunstall-style mufflers but they actually fit 35mm headers without the reducers.