B50 Racing Mods By Steve Bacon & Stan Millard
(Legal Disclaimer : This page(s) should not be considered as a definitive guide, nor will I guarantee that anything that appears here will work or improve you bike. For all intents and purposes, it's nothing but unfounded rumors, so don't sue me if you mess up your bike!)
1) Rod breakage.
One rumor: the rod cannot handle the forces and eventually breaks down by the big end.
Another rumor: It's not the rod, it's the crank pin.
My guess: they're both true. Anyways, call Alpha Bearings and get their crank pin set, specifying CCM specification (part B28S).
Then call Carrillo and order a new rod from them (or your favorite supplier). Carrillo also makes a rod that is 1/2"
longer for racing (I'm not sure how it would work for a street machine - can't see why not). The added half inch means
the piston stays near the top longer, which translates to more power after spark. If you use this rod then you've got
to put a 1/2" spacer under the cylinder or else the piston will hit the head. Additionally you'll need longer
push-rods as there will then be an extra half inch between the followers and the tappets.
2) Head work.
Get the head ported and flowed for max. power. (by someone who knows what they're doing of course!)
General consensus for racing seems to be for opening the intake up to accept a 38mm Mikuni or a 40mm DelOrto.
I spoke with one guy who's got a 40mm Mikuni but he felt he was over-carburated.
Note: if you're going to put a really big carb on, have the intake manifold modified or else it won't fit. I believe
the smaller Mikuni's come with adapters (is this right?)
Get the exhaust opened up to put on a 1 3/4" OD pipe.
Max Valve sizes? - I don't know, anyone got some specs? What's best for street, best for racing?
Get a second spark plug hole put in the top of the head. There's some finning up there, so you might need to grind
away some, but once gone there's a nice flat area to work with.
Putting in a second plug will require a dual lead coil - note: it's important to use the right coil with your
ignition system. Points require different coils than Elec. Ignition. Contact your parts supplier.
In terms of elec. ignition (for pro's and con's ad nauseum see Brit-Iron archives ;^) ) the two that you hear
the most about are Lucas/RITA and Boyer.
A problem with the B50 head is that you've got to take the engine out to remove the rocker box. Dumb. A good
mod is to toss the nine retaining studs, heli-coil the head and then use allen bolts to secure the box. Now it
can be removed with the engine in the frame.
What to say here? I don't know of any problems with the stock piston, except don't use it for racing.
I'm using an Arias piston I got through Ed Valiket of E&V Engineering (1-616-937-6515) and I'll let you know
how it held up at the end of the season.
Any other sources for racing or replacement pistons?
Like many other British bikes, these have the clever design of having some of the oil returning from the sump
routed up to oil the head.
This of course means the oil has been heated by the engine, and is also not the best way of guaranteeing a
steady supply of oil.
So, block off the return tube on the underside of the motor (Figure 1-A),
and put a fitting that's been restricted to 0.020" into the oil pressure sending switch hole (Figure 2-E).
Look here also.CCM Mods
This will mean a steady supply of cool oil to the heads.
Now that there's more oil flowing to the head, we want to help more of it get out of there, so we've got to
allow more to drain down to the cases.
Take the two holes in the case that pass oil from the pushrod tunnel (not the cam follower holes! see Figure
3-C for location - sorry about the blurriness), and open them
both up to 13/64" (one should already be that size).
Now chamfer them, and also chamfer the pushrod holes so oil will drain there easier.
Also, take the two holes at the bottom of the case (timing side) which allow oil to drain into the sump and
block them off. (Figure 3-D)
Drill a 3/8" hole (horizontally) which allows oil now trapped on the timing side to pass through to the
primary side and drain down the big hole there.
Cut the tube that feeds the oil pump at a 45 degree angle to assist in scavenging (Figure 1-B above).
The way the return oil feeds into the tank (oil-in-frame models), allows the hot oil to bypass part of the
tank by flowing right through the downtube where the dipstick goes.
The fix here is to machine a tube that allows the dipstick & new oil in, but prevents the return oil from
short-circuiting (Figure 5)
These mods improve the oil flow through the engine, and are apparantly what CCM did to their B50s (If
anyone has the actual CCM specs, it would be nice to put them in here (assuming it's legal))
This engine has extreme crankcase pressure problems which mods will help but not totally solve.
The illustrations show the additional holes to drill / widen out. This will allow additional crankcase
pressure to vent into the cases.
Additionally, a vent-tube connects the two cases so that the timing side additionally vents into the
Now look at the breather hole. Small, puny, weak! By opening this WAY up you'll allow a lot more of
that nasty pressure to escape to the outside world.
This means an easier reving engine and less stress on seals (which means - less chance of oil leakage!)
This pressure is caused by the piston coming down wanting to displace the air that's in the cylinder underneath it.
What happens when the piston goes up? Air wants to flow back INTO the cases of course!
We don't want this for two reasons:
1) air from the outside world has lots of junk in it (dirt, bugs, you-name-it) that we don't want in out nice
engine (there's lots of nice bearings in there)
2) if we can cause a partial vacuum when the piston goes up, it'll get help (less resistance) when it next
comes down (think suction)
This is accomplished by putting a one-way valve on the breather hose
(don't get it backwards or it'll prevent ventillation - my guess is it'll actually pop off the second the motor starts)
Try Ford parts: Flexible hose #E7TZ-9A487-E (this # is on the parts box) and One-way valve #E8TE-9A487-AA
Now you've got to make an adapter to fit the hose onto the primary case where the old one was.
Alpha Bearings Ltd.
P.O. Box 13
Voice: +44 (0) 1384 255151
Fax: +44 (0) 1384 457509
990 Calle Amanecer
San Clemente, CA 92672
Voice: (714) 498-1800
Fax: (714) 498-2355
E & V Engineering (Ed Valiket)
19294 W M46
Howard City, MI 49329
Voice: (616) 937-6515