BMW R25/2/3

[angusbuchananbmw]

Hi all
l have a BMW R25/3 frame fitted with R25/2 forks and an R25 engine.I am not sure what exhaust pipe i would need for this.Can anyone advise me please as i see that different exhausts are listed for each model.
Regards Ken

[angusbuchananbmw]

[RTwenty7]

Hello there,

the point is that R25 engine is fitted without dampers in engine case and exhaust can be fitted on left frame tube where the engine bolt is fitted. R25/3 engine is fitted with dampers front and rear and exhaust is mounted on a bracket at lower gearbox bolts. So the complete system can shake. the exhaust on 25/3 is 30 mm, on R25 36mm. If you want to put on the R25 engine on  25/3 frame you have to use the distance washer on left side of the frame and exhaust 36mm has to be used.

Or you put on the 25/3 bracket on lower gear box bolts with R26 (36mm) exhaust clamp.

Will say, you have to mix a little bit but it works.

[Borgward]

you should also check what cylinder head is on your engine.
see
https://www.bmw-einzylinder.de/Vergleichstabelle/default.html

if it is an R25/3 head you need the 30mm pipe rather than the 36mm

Hubi

[Taz]

Hello Ken.

Basically, the cylinder head of the engine installed will tell you which exhaust system you will need (diameter of the exit hole), please refer to Hubi's link (it should default to English on your computer, as the page will look for the browser's langauge preferences).

This will also determine which silencer you can use, again pipe diameter being the pivotal point.

On the other hand, as your frame doesn't align with the exhaust system, you will have to do some thinking on how to attach the pipe and the silencer to the frame...let your inner engineer off the leash

If you need help with any specific pounting points, please provide some pictures so we can assess the situation.

Kind regards, Taz