The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: montmil on September 25, 2015, 01:04:55 PM
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It has been some time since I last stripped the fork innards from the 1981 R65 so before beginning, I reviewed both the Haynes and Clymer manuals, the R65.org FAQs section plus some reference materials I keep in a 3-ring binder.
Removing the fork lowers was made far easier by using a gear puller to depress the upper fork plug and remove that pesky snap ring. After that, everything went smoothly and the little bit of grunge found in the lowers was flushed out.
One of my saved articles is from the February 1997 issue of BMW Owners News titled Rebuilding the R65 Front End written by Paul Burch.That’s also where the use of a puller was discovered. Now here’s where it gets interesting regarding the volume of fork oil for the R65. The article addresses US owners. Paul states:
There are several misprints about oil quantity in the R65 manuals (at least the ones in my possession) that need to be addressed.
The shop manual states that the oil quantity is 190cc per tube, with no mention of whether that’s for an initial fill or an oil change. My owner’s manual (1979) says it’s 190cc for an initial fill (like it would be after disassembly and clean-up) or 235cc for an oil change. The quantities are obviously reversed; it would naturally take more oil to initially fill a totally dry tube than for an oil change.
In addition, the metric to English conversions in the owner’s manual are incorrect. It states that 190cc equals 67 fluid ounces and that 235cc equals 83 fluid ounces. There ar two problems with this. First, they dropped the decimal point. For these numbers to be even close to correct they should be 6.7 and 8.3, respectively. But, as the ads says, “Wait, there’s more!”
They also used the wrong conversion factors; the converted volumes in the manual are British fluid ounces. The factor for British fluid ounces is one ounce equals 28.413cc. For U.S. fluid ounces the conversion is one ounce equals 29.5735cc, so for us the actual converted volumes are 6.4 and 8 (actually 7.95) fluid ounces, respectively. So much for German thoroughness!
I did check both my shop manuals and the figures shown for the R65 are still published using English conversion factors. Our English forum members are spot on for their fork oil volume. Aussies, I dunno but pretty sure they use Fosters.
With dry and clean fork lowers, my ‘81 R65 got eight ounces of Dezron III ATF. Front end performance shows a slight, but noticeable, improvement.
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My BMW workshop manual states 190cc for initial fill or when changing which can't be right. I too found stripped and cleaned forks need a little more than 190cc of oil. In the end though variation in volume impacts on the level and variation in level impacts on how the fork functions so I just bung in 190cc and then measure the level topping up or removing oil to reach the desired level. Haynes gives the level specification as 20 - 50mm above the damper piston top. That range gives scope for adjustment of the "air spring" with lower oil levels giving the most compliant ride and higher levels the least dive. Changing the oil level within that range really does make an easily perceptible difference.
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My 05/1982 repair factory manual (purchased at the time the bike was by the original owner BTW) states that the "Oil volume per fork beam per liter (for oil change) is 190
It makes no mention of different amounts for a change versus a dry fill
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My 05/1982 repair factory manual (purchased at the time the bike was by the original owner BTW) states that the "Oil volume per fork beam per liter (for oil change) is 190
It makes no mention of different amounts for a change versus a dry fill
That's one of the print errors that remains uncorrected in many manuals.
The reason there are different fork oil volumes required for the R65's Type III fork leg is due to the position of the small drain plug on each fork lower. It is some distance above the interior floor of the fork lower. It is not possible to totally drain all the fork oil via that small drain opening unless the fork slider is removed and completely drained.
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so I just bung in 190cc and then measure the level topping up or removing oil to reach the desired level.Haynes gives the level specification as 20 - 50mm above the damper piston top.
Sorry, hope I'm not hijacking the post. Barry, I'm guessing measuring the level of oil above the damper piston involves using a long dipstick from the top of the fork tubes? Can this be measured just by removing the filler bolt while the forks are on the bike?
I've got my forks off at the moment and almost to re-fill them after a rebuild with motobins top out bushes.
Cheers, Dan