balance pipe

schrader7032 · Post by **schrader7032** » Fri Jan 16, 2009 9:21 am

I'm not sure about that. On the one hand, you have one cylinder, one carb, one exhaust on each side...there's no connection between them except for the rods on the crankshaft. Seems like that's pretty close to being isolated and that carb balance ought to be easy.

However, it might have some effect as it modifies the backpressure or resonant volume that is produced during the exhaust stroke. As time went by, BMW added crossovers to help with sound abatement, mid-range power (I think) and other subtle requirements. My /2 has a single cross-over, while I believe my /7 has two.

I would think that your troubles are more carb related than exhaust related, though.

Kurt in S.A.

Bruce Frey · Post by **Bruce Frey** » Fri Jan 16, 2009 4:52 pm

You might post this query at the R90SWorldnet Group on Yahoo.

http://autos.groups.yahoo.com/group/R90 ... d=25164877

I recently jumped from prewar bikes to an R90S. I have not had it long enough to get familiar with it, but I agree with Kurt that it is more likely to be a carb related issue of some sort.

Bruce

cone · Post by **cone** » Wed Jan 21, 2009 7:06 am

thanks for the replies and also the address of 90S website. I spoke to an old BMW mechanic and he is of the opinion that the balance pipes are very important. I would like to bring the bike back to standard and will get the correct pipes made up.

VBMWMO · Post by **VBMWMO** » Mon Feb 15, 2010 2:52 pm

Hi, the exhaust pipes on my 90S were replaced with mild steel ones without a balance pipe by the previous owner. I cant seem to get the carbs syncronised despite rebuilding the Dellorto,s. How important is a balance pipe? My 100RS had two balance pipes if i remember correctly but I have seen other BMW,s without these.