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Non Vented Final Drive on my ‘55 R50

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CWRoady
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Non Vented Final Drive on my ‘55 R50

Post by CWRoady »

Wondering if anyone has ever vented the early non vented Final Drive with a vented fill plug? Is a vented fill plug available? If not, I am considering making one by tapping a fill plug out to accept a zerk fitting and removing the spring in the zerk. After a FD rebuild I am still having leakage that I am convinced is related to pressure build up due to the FD being non vented.
Chris
1955 R50 / 1973 R75/5 / 1974 R90/6 Hack / 2015 RT
Yard Art 1968 +/- Hodaka & SACHS

flyingtpot
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Re: Non Vented Final Drive on my ‘55 R50

Post by flyingtpot »

There are EU suppliers that sell an aftermarket vent dome assembly. It is designed such that the cardan housing needs to be drilled and tapped, in the location of the factory venting feature.

The key is to vent as furthest to the top of the final drive as possible. Venting off the fill plug can be problematic if not properly designed.

Also, ensure you're using gear lube in the final drive as opposed to engine oil.

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Re: Non Vented Final Drive on my ‘55 R50

Post by schrader7032 »

There is a service bulletin (#233) that says that the final drive can use Hypoid oil beginning with a specific frame number, unless the older final drive has been refurbished with new seals. That's beginning with frame 641986 for the R50. That's going to be about 1966-ish for the R50/2.
Kurt in S.A.
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gray7252
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Re: Non Vented Final Drive on my ‘55 R50

Post by gray7252 »

I may have what flyingtpot is referring (or it's a custom job). I have a 1956 R69 where the final drive has had a vent added by previous owner. Body of 'vent' is aluminum, and the vent hole is about 1/16" dia. I grabbed a piece of wire and stripped it back about 2.5" and fed it into the hole, and it appears to go all they way straight through.

The main drive casting looks like it had a flat (slight counterbore) machined into it for this to sit flat.
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'56 R69
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'70 R60/5

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CWRoady
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Re: Non Vented Final Drive on my ‘55 R50

Post by CWRoady »

Appreciate the replies. I did find a few European suppliers of different vented fill plugs, with the most promising made for karting, that has a taller dome. I also appreciate the 12 o'clock positioning like on the later vented FD's. I am going to "try" the vented fill plug route first, since my preference is to not alter the stock housing if possible. If it doesn't work, I will have to revisit that position. My FD has new seals and bearings also, so I am using a hypoid gear oil.
Chris
1955 R50 / 1973 R75/5 / 1974 R90/6 Hack / 2015 RT
Yard Art 1968 +/- Hodaka & SACHS

gray7252
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Re: Non Vented Final Drive on my ‘55 R50

Post by gray7252 »

If you are looking at machining a standard fill plug to add vent then also take a look at McMasterCarr.
https://www.mcmaster.com/vent-plugs/
You might be able to get a 1/8" NPT thread into the fill plug.
'56 R69
'57 Lambretta LD150
'70 R60/5

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malmac
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Re: Non Vented Final Drive on my ‘55 R50

Post by malmac »

gray7252 wrote:
Sun Mar 07, 2021 4:55 pm
I may have what flyingtpot is referring (or it's a custom job). I have a 1956 R69 where the final drive has had a vent added by previous owner. Body of 'vent' is aluminum, and the vent hole is about 1/16" dia. I grabbed a piece of wire and stripped it back about 2.5" and fed it into the hole, and it appears to go all they way straight through.

The main drive casting looks like it had a flat (slight counterbore) machined into it for this to sit flat.
What an interesting post. The photos are good and the idea quite achievable.
You have me thinking, as I have a non vented final drive that is ready to be rebuilt with all new bearings and seal.

Thanks.


Mal
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Re: Non Vented Final Drive on my ‘55 R50

Post by jwonder »

Chris,

I just picked up a R50S with a non-vented Final Drive and I am very interested in how yours turns out! Venting the FD in my mind is the way to go!
James Wonder
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Bikesmith01
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Re: Non Vented Final Drive on my ‘55 R50

Post by Bikesmith01 »

I really liked the vented fill plug idea (and I had a few extra since replacing all drain plugs with ones with magnets), so I decided to try it:
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It's a pretty straightforward job. I made a very small (about 1.5mm) hole from the inside of the plug through to the outside, then enlarged it only part of the way through from the outside. So any oil that comes through the 1.5mm hole will hopefully collect in the 'reservoir' inside the plug. Then I brazed in the vent plug.
Once I get the bike back up and running I'll follow up to let you know if it works. If not, I still have undrilled plugs :lol:
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CWRoady
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Re: Non Vented Final Drive on my ‘55 R50

Post by CWRoady »

Very nice! I am using a fitting with some filter element inside and a freeze plug. Havent reassembled yet either but will also report back.
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Chris
1955 R50 / 1973 R75/5 / 1974 R90/6 Hack / 2015 RT
Yard Art 1968 +/- Hodaka & SACHS

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