I have run into a strange anomaly regarding the gear lever seal. I replaced the seal, it was not leaking but very old. Furthermore, I purchased, according to Motobins, the proper seal size 26x7x16. I purchased 2 seals. I use synthetic oil in my gear box. Been using that for 10 years with no issues. I replaced the seal, filled the gearbox with the recommended volume of oil. Seemed to be okay after a short shake down run of 50 km. I went on a longer, harder run. Parked the bike on the side stand. After half an hour, I noticed that the seal was leaking. I replaced the seal with another new one, went for an extended run and low and behold the new seal leaked. I checked for imperfections on the shaft and in the case before installing the seals.
Now the BMW fiche lists the seal only up to R90/6, it does not list the seal for the /7. However, Motobins lists it for the /7.
It is almost like the lip on the seal is not tight enough around the shaft.
Has anyone else run into this, and what did they do? Or is the inner diameter incorrect for the /7 model and beyond?
I am not sure of what bike you have. Looking at the microfiche for a 100/7T the shaft seal is indeed 16x26X7 or part number 23 12 1 338 740.
What shape is the selector lever in? Maybe Richard W will have a clue as to what is happening. I have to think a bit more. St.
Beware! I do not suffer fools gladly! St.
Thanks for the feedback. I have been doing some measuring with the callipers and everything seems to be within spec. However, when I look and feel inside the seal opening, there is very little overlap. I haven't overfilled the gearbox.
I use synthetic oil in my gear box. Been using that for 10 years with no issues. I replaced the seal, filled the gearbox with the recommended volume of oil.
Your problem is probably 1 of several things...
1. Your seal could have worn the OD of the shifter shaft slightly smaller, meaning the seal (even a new one) does not make a good tight fit on the shaft. This is the least likely scenario. Keep reading.
2. Synthetic oil is not the same across the oil market. My brother once changed his final drive oil to Mobil-1 gear oil. Within minutes there was oil splattered all over the rear wheel. We washed the wheel off and changed the final drive oil to Valvoline gear oil and it stopped.... immediately ! Without doing anything else, it stopped.
Synthetic oils are a mixture of several components. Each brand uses these components in a different percentage. One of those additives is "seal softeners" to get the oil seals to be supple enough to actually do their job. I highly suggest you change your gearbox oil to Valvoline 75w/90 and see if that doesn't improve the situation.
3. Oil seals are not the same across the market. They can be made with many different "rubber" compounds, and with single and dual lips. Are you using official BMW certified spare parts, or some "equivalent" 3rd party oil seal that measures the same size ? If the later, then order the official oil seal and install it using a product called "P80 Emulsion" applied to the OD.
The P80 will allow you to PUSH the oil seal into place (using only a deep socket so that you can step over the shaft and apply even thumb pressure). There will be zero need for any hammering or other abusive force that would otherwise distort or hurt the seal.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
If I recall correctly, the depth at which the seal is installed is important. I think it can be driven in too far. According to Snowbum info, the seal should be recessed about 2mm into the bore.
Thank you for your responses, much appreciated. I think I found the problem, I drove the seal in too deep. The gear shift lever bearing does not sit flush with the case. If you drive the seal in too deep, the bearing can damage the seal lip. Should've read Snowbum first. Also, switched to a double lipped seal. We'll see if I solved the problem after a shake down run.
If you'll use P80 to install the seal, then you won't have the issue. P80 allows you to install the seal with thumb pressure, and then you can feel when to stop pushing.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Thanks for the info. However, the bearing not only rotates but pivots. That's why it is imperative that you not push the seal in until it bottoms. When the bearing pivots, it can contact the lip and impact the sealing if you are too close to the bearing.
So I did shake down run today and all is well. No leaks.
Excellent!
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