R26 Exhaust system

[Thorsten Franz]

Meanwhile I could trace a second-hand rocker arm and the bike is running again. Next on the agenda is the exhaust system. The silencer is a made to order piece, most probably more suitable for one of the twins of the same period. The diameter on the side of the exhaust pipe is too large to provide for proper fitting of the pieces. Now I wonder if the exhaust pipe is original. What should be the correct diameter?
How are original pipe and silencer mounted together? Is the pipe inserted into the silencer or vice versa. Is an additional clamp or coupling nut required ?
Does the pipe have a thread on the side where it fits to the cylinder head.
Finally: are clamp ring 18114000-001 and finned nut /-002 alternative parts or do I need both.
The exhaust clamp 18214090-155 that I received doesn't fit tightly around the existing
pipe after tightening the bolt and nut . Should both ends of the clamp come on top of the bracket or below?

Thanks and Bye

Thorsten

[damien clement]

Franz,

First of all, I would says that I've got no «autority» at all to says any thing about technical subjects, excepted that I run a good old R26 since 20 years.

>>> I wonder if the exhaust pipe is original. >> What should be the correct diameter ? >> How are original pipe and silencer mounted together ? Is the pipe inserted into the silencer ? >> Is an additional clamp or coupling nut required ? >> Does the pipe have a thread on the side where it fits to the cylinder head ? >> The silencer ... most probably more suitable for one of the twins >> The diameter on the side of the exhaust pipe is too large to provide for proper fitting of the pieces. <<<
I never had trouble to fit original pipe into flat-twin's silencers, as the silencer's intake is the same diameter. (At less the many ones I used, and freind of mine used too.)

However, there is two kind of troubles :
- One is of an aesthetic point of view. It belong to the silencer's fitting to the frame. According to models, silencer may appear to be lateraly more in-side the bike, or more out-side, then original. (The length of silencer may also differ, but it has never been a trouble.)
- Second, and must important, is of a dynamic mater. That is the silencer's out-put diameter. Original silencer for singles R26-R27 have a 28 mm inside diameter on the out-put. That is smaller then flat-twins.
Best global efficiency (starting, smootness, torque, speed, and so on) was achieved when fiting a washer, or tubular casing, into flat-twin's silencer out put hole, to reduce gaz flow to 28 mm. It provide a better dynamic ballance between engine's intake and exhauste.

Hope it'll help, tell me if you need more data.
Sincerly yours,
damien

[Thorsten Franz]

Hi Damien,

Many thanks for your reply. The silencer on my bike for sure is not original. Most probably it was made by a local backyard workshop. I want to replace it because it does not connect properly with the pipe. What I tried to find out, is if the pipe is original or at least has the correct diameter as otherwise I would need to replace it well.
According to your message the pipe fits into the silencer and not viceversa. So, the only information I still need is the outer diameter of
the pipe.

Thanks a lot again and
Best regards

Thorsten

[damien clement]

Thorsten,

I'm glade it helped you !
The exhaust pipe's outer diameter is 36 mm.

But I'm sorry, when I pasted previous message, some characters seems to have been mis-recognised, so big part of the text was lost. Complet content of previous message follow below. (Hope it'll be OK this time.)

Sincerly yours,
. damien


N.B. : Tell me is Thorsten or Franz the first name ?

_________Previous message re-shaped___________

Franz,

First of all, I would says that I've got no «autority» at all to says any thing about technical subjects, excepted that I run a good old R26 since 20 years.

»» I wonder if the exhaust pipe is original. ««
I couldn't give «cartesian» referances to identify original exhaust pipe. I can just say that original exhaust pipe had a «gracious» shape, with no angles, break of line, and I never came upon rebuilts that was so «gracious» !

»» What should be the correct diameter ? ««
Exhaust pipe's outside diameter is 36 mm.

»» How are original pipe and silencer mounted together ? Is the pipe inserted into the silencer ? ««
Yes, that's the way it is.

»» Is an additional clamp or coupling nut required ? ««
There is a clamp, that the Parts Catalog call «Pipe clamp» (18 21 4090158, might have been repaced by 18 21 4090159). This clamp is suposed to squiz silencer's intake around exhaust pipe, but it's not always needed, nor always usefull.

»» Does the pipe have a thread on the side where it fits to the cylinder head ? ««
No It has no tread of any sort.
On the cylinder head side, the pipe is shaped to form a right angle flange (just made of the pipe material).

»» The silencer ... most probably more suitable for one of the twins ««
As a mater of fact, since 1979 and 'til last year (when I meet Mark and his excelents products), my R26 was always fitted with flat-twin silencers.
During this time, I hade the opportunity to run several second hands flat-twin silencer (original, rebuilt, adaptable and «improuved» or «sport» types).

»» The diameter on the side of the exhaust pipe is too large to provide for proper fitting of the pieces. ««
I never had trouble to fit original pipe into flat-twin's silencers, as the silencer's intake is the same diameter. (At less the many ones I used, and freind of mine used too.)

However, there is two kind of troubles :
- One is of an aesthetic point of view. It belong to the silencer's fitting to the frame. According to models, silencer may appear to be lateraly more in-side the bike, or more out-side, then original. (The length of silencer may also differ, but it has never been a trouble.)
- Second, and must important, is of a dynamic mater. That is the silencer's out-put diameter. Original silencer for singles R26-R27 have a 28 mm inside diameter on the out-put. That is smaller then flat-twins.
Best global efficiency (starting, smootness, torque, speed, and so on) was achieved when fiting a washer, or tubular casing, into flat-twin's silencer out put hole, to reduce gaz flow to 28 mm. It provide a better dynamic ballance between engine's intake and exhauste.

Hope it'll help, tell me if you need more data.
Sincerly yours,
damien

________________End____________________

[Thorsten Franz]

Hi Damien,

This time your message was complete. According to your information the exhaust pipe of my R26 should be original and I just need to order the silencer. Due to lack of access to original parts in the past people here in Manila were forced to develop skills in reproducing parts including such tricky things as the elegant pipe for the R26. Problems usually start when trying to combine them with original components.

By the way, Thorsten is the first name.

Many thanks again

Best regards

Thorsten