The Knowledge - Velocette Owners Club

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#770 On the oil filters, I wouldn't worry too much about a bypass valve. Since it's on the return side the
worst that can happen if the filter plugs is too much oil in the sump. Never seen it happen.
L #774 I plan to modify my "old fashion" oil tank to the more recent standard. The crankcase
having been modified by the previous owner, I would like to "recycle" the oil coming out from the
crankcase breather. My first series oil tank being already fitted with its own breather outlet, coming from
the froth tower down to the outlet tubing coming off the inside face of the tank, if possible, I would like to
know the exact location and dimensional information of the additional tubing to be fitted to receive the
21.375 in. crankcase breather pipe.
#785 Weld in a piece of half inch od tube about 1.5 inches long at the top of the rear of the oil tank.
Make sure it clears the down tube when fitted. For a better pipe run, you can weld the tube in angled
towards the front.
L #783 has anybody converted an engine to the later oil drain from the timing chest to the bottom
of the motor. I think this mod came in about 1964. it looks like an external rib. I believe you can do this
but you have to plug the crankcase in the bottom of the timing chest to stop oil draining into the motor
internally. I was going to this some years ago but hit a problem with clearance between the motor and
the frame, to put a union on the bottom of the motor was going to foul and I decided not to bother, but
having thought about it I could come in at an angle and tap the hole and then screw in a tube much
like the later breather tube under the mag. has anybody tried this ?. it would then be straight forward to
connect to the tube, and then to the bottom of the timing chest. velocette did some tests and
discovered that when the engines were running, oil was backed up to as much as three quarters of the
timing chest as it was unable to drain into the bottom of the motor fast enough due to the flywheels
stopping the oil going down the internal drain hole. this was one of the reasons why they did a revision
of the crankcase. you should end up with a better crankcase than the later ones with this mod because
the earlier cases have the restrictor in the oil passage way to stop debris going into the pump and the
later cases do not have it. any feedback is welcome. Regarding the later breathing arrangement, I read
that people are doing this and breathing into the oil tank, I hope that when they are putting the tube
under the mag into the timing chest that they are also putting a hole from the timing chest into the
crankcase otherwise it is a complete waste of time, because with out the hole from the timing chest to
the crankcase the air cannot be expelled. just my two cents worth. thanks for taking the time to read
this. cheers.
#784 I have added the oil drain line to the timing case. I used two 90 degree 1/8" US pipe fittings, one
tapped in at the bottom of the timing chest and the other at the bottom front of the side of the case
(thinking the oil level would be lowest at that point while running). This is a tight fit in the frame as the
frame curves near the case at that point (swing arm frame). To do over again I would put it further back
where the frame rails are straight as I can't remove the fitting with cases in the bike. A side benefit with
this mod is that with clear tubing I can always see how much oil is in the sump when sitting. I did not
plug the old drain hole figuring it would now function as a breather between the crank case and timing
chest along with several others holes I added. Wet sumping while running has not been a problem
even with pump spinning 50% faster than stock 2 start (1/4 vs. 1/6 crank speed). I'm getting ready to
test pumping additional oil to the exhaust rocker box for cooling which may create a drainback
problem, we'll see.
#899 Having done that, throw the tube away! I did that over 40 years ago, and have never missed it!
Then you have permanent peace of mind, at least as far as a blocked return goes.
#941 Do it that way and you won't be able to take it apart easily to clean it when you do a filter change.
The Velo factory guys weren't stupid, their way is still fairly well thought out most of the time, personally
I would leave it the way they intended or replace with the cartridge filter conversion.
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