Intrigued to see in novembers road holder a featurette on Jim Comstocks sump breather for commandos,has anyone this side of the pond produced something similar? Hopefully for under the originals $300 plus &postage. The tiresomeness of wet sumping just weighs on the mind sometimes ,like homework thats due in on a monday .
One off for 850 MK2A but pics on a 750 case.
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Flexible as its going in an…
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Not that I have seen...
I am always on the lookout, but I have not yet come across anything that works quite as well considering how simple it is to install.
The fact it expels air from the crank side means you are not pushing air into the timing side and then out the 1/2” hose (in the case of the 850) - it just works.
For older bikes, you are no longer trying to get air out of the timed breather on the end of the cam - the drillings are small and it’s rather a lot to ask!
The by-product of clearing a wet-sumped crankcase in just a couple of kicks is just a lovely bonus.
There are two things to be aware of:
- A 72 doesn’t have the large sump plug, so it’s not possible to fit.
- The early Commandos have a small bracing bar between the lower frame rails which would stop you from fitting the sump plug breather.
Jim’s sump plug breathers are now available exclusively from Kenny Cummings at NYC Norton.
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Sump Plug Breather
There might be a couple of problems breathing through bottom of the crank case.
The breather could compete with the oil return pump rather than it's primary function of venting the crankcases resulting in poor venting?
Could the breather body get knocked off? it looks a little too low.
However it does look well made as is all of Jim's stuff.
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There is a snorkel that…
There is a snorkel that sticks up a little, so as not to introduce air bubbles into the oil returning via the scavenge side of the oil pump - it is very well thought out.
No problem with positioning on the Commando, obviously the fifteen degree forward slant of the engine helps a little in that respect.
We were initially a little concerned about the Dommie, as the engine is of course bolt upright in the frame, but in reality it hasn’t been an issue.
It hangs down little more than the side stand and centre stand, so not a major issue.
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