Forum

[Martin]

As I just mentioned in a post a moment ago,
intend rebuilding a flawed early Twin with
some later c/cases. On the early sand cast
cases , the chain case is attached with the
universal stud that retains the outer chain
case, besides the three studs around the
c/shaft as all the Twins have. Several parts
books I have here show no evidence of the
later chain cases having anything else to hold
them on. Is that actually all there is? Also,
now notice the c/shaft I did actually use was
from an alternator model, and now wondering
whether the stub's lenghts are the same on all
the Twins? Am sure I checked this before dumping
the other rusted c/shafts I had before selecting
that one. Thanxs!

[Norm]

Sorry Gordon, without looking at it it is too hard to speculate

[Martin]

Thanks, Norm, the part's book illustrations are
somewhat vague with some items, and I only have
a very early chain case set to work with. With
your sundry advicece we did at least get the motor
running sharply 'cept as I mentioned, the oil
pissed out a tad heavily from the wet sump, so
will dismantle same and start again. The plastic
left on the outside of the drive shaft bearing
can't handle c/case pressure, although the oil
shouldn't be up to that level anyway

[Norm]

Gordon, from what I am reading into this there is 2 problems. Are you relying on a sealed bearing outer seal to seal the crank, if so I doubt this would be good enough. I get the inner primary machined and fit a seal in the inner case, the felt bodge setup is just a pita. The poor crank case breather on these early twins will also put pressure on the seal because they just can't breathe. The fact that you think it is wet sumping is another issue that needs to be addressed to find out why it is happening. I have even considered drilling and tapping a plug in the bottom of the crank case on one motor that seems to be wet sumping just so that I can drain the sump just to prove that this is the cause. Haven't got around to it yet

[Colin F]

Gordon,what breather setup did you decide on?With the Alt crank you fitted that would mean
you haven't fitted the flapper valve on the end of the crankshaft so i presume you blocked
the alt bolt hole off.Those early cases don't have the breather hole from the crank to the
timing case either,i added that and all the breathing goes out from the top of the timing case,behind
the generator,fit a duck bill there,or krank vent.You should be able to check flow to the front pump by
removing the 4 screws that the factory used to drill the galleries.
There should be no pressure in the crankcase with a good setup.If you use a "krank vent"you
will find the crank case will draw air into it because they are so efficient.
Bit costly though.
Don't give up on the early case,there's just something amiss,they didn't send them out from
the factory to fill the crankcase with oil.

cheers
colin

[Martin]

Norm, you're spot on, the felt seal is archaic,
and the sealed outer face of the main bearing
is merely a Band-Aid against major hemorrhaging.
Had installed brass elbows at the usual drive
side position , and fitted two automotive flapper
valves, but Colin has just mentioned the timing
side needs to be modified too. Just wish you could
drop the sump pan like a car, and drill this way
and that, but will install a 1/8 gas drain plug
with the motor up on it's nose again

[Martin]

Colin, grateful you responded as previously wrote
out your check list on the early motors. Had assumed
I had fitted the original c/shaft with the end breather'
but turns out I used a alternator c/shaft with stud
hole blocked off. As I just mentioned to Norm, currently
have ersatz automotive tappet cover valves fitted in the
usual drive side position with extra holes drilled down
before I assembled the motor. Will pay more attention
meanwhile to the timing side, and consider the 'krank'
valve despite this word meaning 'sickness' in german as
you probably know! Would like to resolve these issues
before reassembling the primary chain and clutch so I
can kick it over again on it's floor pod, Thanks, Colin
for also reminding that the early motors oil circulation
must have least functioned to some degree when leaving
Redditch originally

[Colin F]

Gordon you can see the hole i'm talking about if you go into used parts,engines,even the '53
Meteor wasn't fitted with it,'54 has it as i have one of those.55 trailblaser doesn't,'56 does.
It's about 1/2" dia directly below the ex Cam.I'm not sure it'll make any difference in your case
and the setup you have could be ok.But yours sounds like it's not scavenging at all.
Problem with those PVC vales is they're usually to heavy to work properly on motorbike motors,but
i'm thinking of the ones with the steel disc,probaly better ones these days admittedly.

[Norm]

Gordon if you do end up splitting the cases then do the mods that has been sorted out for the twins and allow it to breathe out of the oil tank. Have you had this motor running long enough for the scavenge pump to clear the oil from the sump, it can take a while.

[Martin]

Colin, am going over to the garage later in
the week, and will make a beeline for the
spare cases to inspect that 1/2" breather
hole. Am thinking oil tank breathing from
now on. NORM, we had the motor running some
time before an intermittent dribble
came up at the filler cap. even longer before
the tappets got a sniff of oil. Meanwhile,
grew weary of mopping up a quart of my new
Castrol 20/50 that flowed out of the exposed
main bearing. Will feed it this diesel SAE 50
until it stops acting spoilt like that! Eager
now to give it all another shot with your
collective advice.Thank you!