Installation of New Breather Pipe

[Kurt in S.A.]

My R25/2 came without a breather pipe at the front of the engine.  I bought a new one from Benchmark Works here in the US.  I have a couple of "problems" with installing it:

- the outside diameter of the new pipe is slightly larger than the inside diameter of the opening in the case.  I've thought about griding the new pipe or taking off enough so that there is an interference fit with the case.  Then I could freeze the pipe and quickly fit it in place.  I think I need to be careful with too much interference in case the new pipe might split the case.  Is this a way to go?

- I see from the diagrams that there is supposed to be a pin that holds the pipe in place.  Looking closely on the bike, I do see a small area where is probably the visible portion of the head of that pin.  There isn't enough to grab onto to pull out.  Can it be pushed in?  Or is the pin supposed to go completely through the new pipe onto the other side of the engine case hole?  If that's the case, how can I get the old pin out?

Thanks for any insight.  I appreciate the help you guys have been giving me...I think the single cylinder owners on your side of the pond are much more active than we have over here.  Probably because most of them stayed in Europe??  Certainly don't see many over here.

Kurt in S.A.

[Kurt in S.A.]

[† Knut]

- the outside diameter of the new pipe is slightly larger than the inside diameter of the opening in the case.  I've thought about griding the new pipe or taking off enough so that there is an interference fit with the case.  Then I could freeze the pipe and quickly fit it in place.  I think I need to be careful with too much interference in case the new pipe might split the case. Is this a way to go?

Yes Kurt, that's the way. You can also heat the case up to about 100°C. You won't ever crack the case, don't worry about that.

There is a small conical pin with a diameter of about 2.5mm inside the case, which should normally bar the pipe from moving out of the case. Try to beat it with a mandrel through the hole in that way that the pin falls out.

For correct installation of a new breather pipe stick the pipe with "ice and flame" and adjust it in the right position. Then try to bore a new hole into the pipe through the bore for the pin. It's a bit tricky. Don't be angry with yourself, if it doesn't fit - you're not the first one 

Kurt, there are only a few monos, which found the way across the pond. Most of them in this age were double-monos which were more wanted in the States. However, you've found a proper information-center here

and hopefully I won't be the only one in future, who is answering your questions - Faules Lumpen-Pack!! Kommt raus aus euren Löchern! Misdkerle! 

Best regards to Texas

Knut

[rolf.soler]

Yessir, Knut, Sir,
the pin goes through. If you push it through, the problem is that may be still too long to fall out on the back side...I haven't had this problem, because the pin was lacking - you're probably the only one with a pin in that place... I guess i would shorten or bend it on the back side as it comes, until all is out.
The new pipe came probably without a hole - at least, mine did. It was quite difficult to drill a hole through this rounded surface, and another one exactly on the opposite side, all at the proper height/position, and then put the pin through all 4 holes (2 on casing, 2 in pipe). Exact measuring is the key. But Knuts suggestion to put in the pipe first, and then drill through the hole already there in the casing is more promising. The you just have to stay exactly in the middle to make the second hole in the pipe opposite and come out exactly through the second hole in the casing....With this method, you risk to enlarge the holes in the casing. But then, you can get the pin slightly thicker - 3 mm instead of 2,5 mm, at least the suppliers in Germany deliver this slightly thicker pin. If unavailable, make your own pin from an used drill 2.8 or 3 mm. But the original pin is better, it has a clover-leaf cross section and is compressible, so it holds the pipe nicely. If this all sounds too difficult, warm the casing, put a thin layer of heat-tolerant instant glue (cyanoacrylate) on the freezer-cold pipe, and push it in quickly.
another method would be to make a thread M2,5 or M3 through all 4 holes and put a screw in and fix it with Loctite screw-lock.

[BenW]

Kurt,

When restoring the engine of my R26 some 20 years ago, I was facing the same problem. While I managed to get the breather pipe into the opening of the case, I had no idea how to put the pin back in. In the end, I just forgot about the pin and the breather pipe is stuck in there ever since without it... With the help of the forum, I would have been much smarter.

Cheers,
BenW