The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: guyom on October 27, 2017, 02:32:26 PM
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well perhaps stupid question, but i have a hole in the junction tube of the pipes you know the small one in front of the alternator... that makes a junction between the two pipes... anyway... i look at it and just wondering what is the use of this pipe ? Can i bend new pipes and remove it ? my guess is it helps the gaz equilibrium.. but not sure...
Thanks for time !
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The balance pipe is intended to tune the exhaust for better torque at low/mid range revs. In theory removing it should reduce torque at those revs but people that have done it generally report that the effect is not significant.
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I would try to find a suitable sized crossover pipe, if necessary, find one that it a little bit overly large in the inner diameter and use some sleeves/shims.
The crossovers do help with tuning for midrange torque, but some higher HP racetrack bikes run single (not cross connected) exhausts. Some folks here have cut the crossovers and welded the holes in the headers closed. Whether you like the results or not is anyone's guess.
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Regarding the finding of suitable cross-over tubes. I have no idea what the "stock" diameter is all of the airheads in our posession having been switched to after market stainless steel systems more than 30 years ago (R65/80 and R100) and a stainless steel system was fitted to the 1984 R65 when I bought it in 1995.
The reason for the long preamble is acknowledge that I know nothing about the measurements of the stock exhaust system.
But, all three of our bikes are fitted with "Staintune" systems, an Australian manufacturer universally regarded as making a 1st class (if hideously expensive) system.
All three bikes use 1" internal diameter tubing for the cross overs - given this uniformity across a fair number of years I am inclined to think that Staintune copied the stock measurement.
The above thought it reinforced by how difficult 1" ID drawn seamless tube is to find, I very much doubt that they would have used it unless they felt they had to.
If in fact you do need 1"ID tube you will find that it is a not a standard "shelf item" at your local steel supplier and that you will probably have to buy a 3 or 4 metre length of it as a special order.
There is however a possibility of avoiding that.
Your local brake rebuilder will likely have 1" ID tube in stock as it was a popular size for brake wheel cylinders and also certain truck master cylinders. They may be willing to sell you an offcut in the length required.
If not, do what I did - buy the 3 metre length and then contact all the brake rebuilders within a reasonable radius and ask them if they would like to buy some from you. I still have 750mm left and am cashflow positive on the whole saga of buying 1" ID stainless steel tube, but id did take a while and I haven't included my time in that of course.
I'd also like to comment on preparing the nice new tube for service on your bike.
Firstly polish the mating surface on both the new pipe and the old "spigots" on your exhaust pipes - you are aiming for a reasonably "easy" slip fit.
Secondly, measure the insertion depth - this is important.
Thirdly, put two brand new blades side-by-side on your hacksaw frame (I used 32 TPI).
Fourthly, clamp the new cross over tube securely and mark a point at least 1/8" less than the insertion depth (otherwise you are going to have "tick, tick, tick" exhaust leaks that will drive you spare - believe me I know.)
Fifthly - stop, go to your local hose shop with your cross over pipe and buy two stainless steel hose clamps of the type that are a full circle and use a bolt to provide tension.
Sixth, go home and carefully and accurately cut two slots in the tube ends using your modified hacksaw and ensuring that you cut no further than the previously marked lines.
Seventh, de-burr the slots you just cut - a dremel or similar tool is a godsend for this.
Eight - Liberally coat the mating surfaces with copper anti-seize and assemble your exhaust.
Ninth - Drink beer and congratulate yourself, unless of course you are a friend of Bill in which event you have a few more steps to follow.
Do not under any circumstances believe the blandishments that may be offered by sellers of exhaust tubing. Stainless steel exhaust pipe is a truly crappy grade of stainless steel and it is also a seamed pipe. You will not be able to polish it and worse, due to the seam it will not fit on the spigots if in fact you are lucky enough to find any in 1" ID (it does exist but according to Bluescope Steel where I buy my steel, it has not been made for many years.
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On the R65RS I actually used a piece of electrical conduit - fit perfectly!
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On my 82 R65LS I deleted the front and rear crossover pipes and cut off and welded over the openings. I did it because I an a cheap sob and it was more economical than trying to replace the crossover pipes. I am not performance oriented (if it runs decent I am happy) and have not noticed a loss of performance by removing them. I have also run a 2-1 exhaust and have the same opinion of it, no noticeable performance loss. But keep in mind I am not riding with a maximum performance output in mind. If it runs good I am happy.
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The conduit (10' stick?) was dirt cheap and I had enough left over to make two painting stands. ;D