The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: URon on June 19, 2013, 02:16:59 PM
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Anyone know if the later model bikes with plastic air boxes can be retrofitted to the older (and much cooler looking) metal air box?
URon
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The "Clam Shell" air filter box looks much better than the "after thought" plastic box, i am sure you could get the bits of eBay only mod may be the engine breather.
Lou
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Anyone know if the later model bikes with plastic air boxes can be retrofitted to the older (and much cooler looking) metal air box?
URon
Another Texas member.................... Yeee Haww
Lou
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Hello !
One of the reason to switch from metal air box to square metal air box (it is metal too...) was to improve the breathing of the engine, and it helps achieve the increased output power of the engine.
Remember that when switching...
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You have to consider what else happened at the same times as the plastic airbox. As Georges said better breathing came from the combination of a tuned air intake system and bigger valves which also impacted on carb jetting.
If you added the tuned air intake without any of the other changes I think there is a high probability that it would impact on the mixture to some extent and likely not evenly across the rev range.
If you compare power and torque curves for the 2 engine specs the 50HP model has pushed peak torque up the rev range and yet the curve is still fairly flat perhaps the mid range is helped by the tuned intake system.
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It can be done and is an easy swap (I did it on mine) but there are a number of parts that are needed. A different starter cover, a different airbox (obvious), a metal spring plate that attaches to the top of the transmission to hold the clamshell halves, a locating tab that goes on the left side of the back of the engine, a different crankcase breather tube and a different airbox to carburetor intake manifold. The cylinders are staggered. On the flat airbox so are the intake manifolds. Not so on the clamshell airbox, there is a definite left and right side.
Sounds like a lot but most of the parts are very inexpensive. Even the chamshell airbox and starter cover can be found inexpensive if you just look and wait until you find a good price (that means a lot of cleaning and touch-up paint) Duplicolor makes a spray can engine enamel called cast aluminum that works great.
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YeeHaw indeed Lucky Lou and thanks to All for your input. Great pictures Marc: very helpful. I felt sure that it could be done but .....
I appreciate the comments on airflow but IMHO believe that might be more of an issue for the bigger engines that also used the LX194 filter .
URon
R65/K75S/R90
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Well, the new air box WAS designed on the R45/R65. Then transferred to the other bikes... so my bet is that it is useful for us too :)
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mind you the old ones do look better.