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OK, raise your
hands if you’ve been guilty of doing this; you pick up a Triumph project,
check the top end out, make sure there’s no untoward play anywhere, put
fresh fluids in and start it up and call it good.
Oh
to be sure many of us have got away with doing just that over the years,
I’ve cobbled engines together with a mystery bottom end and rode the damn
thing for years like that.
I’ve
also paid the price for my lack of foresight.
I
picked up a Triumph 500cc plunger-framed chop from a swap meet for $500, it
looked good, had a big ol’ chrome girder, chrome engine covers and was a
great deal. I had to tinker with it a while to get it running, someone had
put an AMAL 930 carburetor on the engine instead of the 26mm stock carb, and
it wouldn’t run without some unusual choking maneuvers, but I eventually
figured it out. So, being ready to ride this bike all over, I went and
insured it, got plates, came home and bolted the plate on and I was ready!
The bike started first kick and I was off into traffic, it cruised along
quite nicely, I was bopping down main street at about 50mph when that awful
rapid slowing of the engine feeling happened, not the freewheeling
running-out-of-gas feeling, the about-to-lock-the-rear-tire feeling. I
grabbed the clutch and the engine died, it didn’t just die, it was more of
a feeling that it really didn’t want to rotate again anytime soon, that
2x4 through the spokes feeling.
I
pulled the engine apart and found it had spun one of the bottom rod
bearings; it had starved for oil and just let go. The rod was toast also,
but I counted myself pretty lucky the whole assembly didn’t just fly
apart.
The
guilty party here is the archaic sludge trap. It’s name pretty much
describes what it does, as the oil flows through the crankshaft to the rod
journals, it passes through the trap, which accumulates the nasty crap that
non detergent oils in days of yore were wont to deposit there. So once the
trap is full, the oil can no longer get to the rod journals and whammo!
Is
this making you nervous? You’ve had the bottom end apart on that Triumph
you’ve been screaming down the freeway haven’t you?
The
bottom line on this is; if you haven’t checked out the sludge trap on your
Triumph, you are really rolling the dice on how long your bottom end will
hold up. It doesn’t matter if you pulled the whole top end off, checked
rod play, checked crank end play, made sure it was pumping and flowing oil
well, you could be a couple more miles away from a crankshaft meltdown.
It’s
a fairly simple procedure to replace the tube, some people will leave the
tube out altogether, some will clean and replace the old tube, but I like to
put a new one it, with an updated hex-head plug. This is in large part, due
to my tendency to destroy said components while removing them.
First
step (after pulling the crank of course), is removing the slot-head plug
that hides the tube. There will be a punch mark stopping it from unscrewing
itself (hopefully) which you
will have to drill a little to negate it’s effect (don’t get carried
away here).
Then
you have all the fun of trying to turn the big slot, I’m sure there’s
Triumph special tool 155488791987165154896322 for this; some kind of impact
screwdriver is probably the best.
I
used the electric impact with a chisel with the hex shank in a socket.
Be
prepared for the sight of 15lbs of gunk in there; think to yourself that it
is lucky you caught this when you did.
Once
the plug is out, you will want to back out the flywheel bolt that secures
the tube internally.
Now,
to remove the tube, there are several methods, ranging from hooking the
sucker out, to constructing some kind of elaborate slide hammer. I prefer
tapping a big ol’ easy out in there, once the tube is rotating; it’s
fairly easy to get out.
As
you can see, the tube was pretty full of crap, the end of it was plugged
solid and there wasn’t much room for oil to get by. This is a crank from
1971, so imagine what that old 60’s crank looks like that you were
screaming the guts out of last week!
I
shouldn’t have to tell you that it’s very important to get everything
super clean before reassembly, it’s disturbing how much you’ll get out
of there. Make sure all those holes and passages are free of clumps of crap.
It’s amazing how much goop you disturb and shove into every orifice when
you pull the tube out.
Then
it’s just a case of installing the new tube and plug. Make sure the new
tube is oriented so the big hole is facing the flywheel bolt, otherwise when
you screw the flywheel bolt in, it will collapse the tube and you don’t
want that. It’s probably a good idea to red Loctite the plug, and of
course re punch it so it won’t back off.
If
you are going to have the crank journals reground, then remember to pull the
tube before you send it in, so you can make sure everything is super clean
before it all goes back together.
Finally,
if you have access to compressed air, you can put the air into the end of
the crankshaft and feel the flow coming from the rod journals just to be
sure. Paranoia is a good thing here.
With
modern detergent oils and a decent filter, you should get a lot of miles in
before the trap refills. A tube and replacement plug will run you somewhere
in the neighborhood of ten dollars, yeah it will cost more than that for the
gaskets and all that to get to the damn thing, but the peace of mind you get
knowing that the time bomb has been defused, is WELL worth it.
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