tech30

A Bike In A Box: Part 1
by Lynn Bennett

Well, not actually “A” box but multiple boxes and some loose pieces.
That’s what I got from a friend. The bike parts were given to him if he
promised to assemble them back to a real bike and to not part it out on
E-Bay. He searched for the missing front fender and landed a new one as
well as a used front hub, and parts manuals for both the motor and the
chassis. What is it you say? A 1971 Rickman 250 cc Montesa Motocrosser.
Sounds good, doesn’t it. My friend found all the dealer hookups: Lynn
Wineland in Apple Valley for new old stock (NOS) Rickman parts
including some engine parts and Southwest Montesa for engine parts. His
plan was to ride AHRMA Classic class but then he found out that the
Rickman Montesa with the 63M motor is excluded from Classic because it
is too fast. That was the end of his interest. So for the $100 he had
expended to date I got it, after he literally pleaded with me to take it
off his hands.

This is the story he got from the other owner. “We bought it in 1971,
raced it for a couple of seasons and then the motor blew up. We then
disassembled it and lost interest.” Good story, huh. It ought to be in
good shape, motor wise, and should only have the problem of years of
storage. My friend didn’t lie to me and why would anyone giving away a
bike lie about its' history.

But here are the facts on the bike. The nickel frame was a little
rusty. The high wear items like the brake pedal show signs of serious
abuse. The rear axle was 15 mm while the rear wheel braking plate was
for a larger axle. The forks are Metal Profile. This model is not
suppose to have Metal Profile forks but since the bikes were
manufactured by Rickman in batches I suppose any combination of parts
is possible. Those forks were not ever on this frame as I had to make
spacers to get them to fit properly. Then there is the engine.

The engine is a 63M 250 cc Montesa. The top end was off it for years
and parts like the cylinder hold down hardware and the head bolts were
missing as was a bunch of other small parts removed years ago. The head
showed signs that a thrust washer on the piston pin shattered and went
through the engine destroying the main and rod bearings in the process.
The engine had been totally disassembled before the blowup and the
sequence of main bearings and spacers was assembled wrong probably
causing the thrust washers on the piston pins to be overloaded, which
probably led to the engine’s demise. The kick-starter was missing but
the shaft’s splines were also destroyed. Since the kick-starter was
probably not usable (or lost) and the return spring is part of it, a
half of a tube of Silicon Elastic RTV was put on the shaft to keep the
internal kick-starter mechanism from engaging. The case wall between
the magneto and the countershaft sprocket areas had a hole in it
probably from a derailed chain. The head pipe from the two piece
exhaust system (separate head pipe from the chamber) was still stuck
onto the loose cylinder because the head pipe retaining nut was cross
threaded into the head and then secured with a hammer and punch to
wedge the cross threaded nut in tight. While the bore was still of
standard dimension and only 1/3 worn out, the cylinder liner was
cracked at the bottom and made unusable.

Parting it out on E-Bay may have been the way to go as the original
giver lied about its' history anyway. One good lie deserves another.
But the challenge was overwhelming so I took out after it, fool that I
am.

The front hub, acquired by my friend, turned out to be a Rickman all
right but it was not off the Montesa motocrosser but the Zundap Enduro
model and has some accommodations for a speedometer. After turning the
drum, cleaning, modifying the backing plate that was part of the
package to fit the fork axle 15 mm size, and polishing the hub, the
front setup was ready for a new rim and stainless spokes. The rear got
exactly the same treatment and was also ready for the rim and spokes.
The engine was disassembled and fed a new crank, thanks to Lynn
Wineland, and all new bearings from my local bearing house. This was
after the hole in the mag/sprocket wall was welded up. The biggie here
was that the transmission shafts and crankshaft had to be shimmed. All
rotating shafts including the shifter drum float in 0.004 to 0.008
inches of endplay. Unlike this Montesa motor, most motors that I have
rebuilt in the past pull one side of each shaft tight up against the
appropriate bearing’s inner race. After a few bad starts and after I
bought a precision depth gauge, the bottom end went back together OK.
The forks were rebuilt with new seals and are probably good enough but
Lynn Wineland had a set of Betor forks that I rebuilt and fitted.
Anyone need a set of Metal Profile forks, recently rebuilt? All the
fiberglass cleaned up except for a few pieces but Lynn Wineland had
those on hand. The kick-starter was found new at Southwest Montesa
along with various bolts, nuts and other small pieces.

With the motor's bottom end back together the next step was to get the
liner installed (takes 800 degree F oven, so one source said), the
ports in the new liner matched to the barrel, and the new liner bored
to standard size to match my new piston. But it turned out that the
cost of the new liner plus the installation cost were only $25 from the
cost of a NOS complete barrel from Lynn Wineland so I went for NOS and
junked the original barrel. The new top end, along with a new standard
sized piston, was put on the completed bottom end and the assembled
motor was air tested (crankcase and top end are pressurized to 7 psi
and the rate of leak down determined to be less than 1 psi per minute).
The test was good and the motor completed.

I decided to do a preliminary chassis/motor assembly in order to make
any frame modifications necessary to add the head steady modification
Lynn Wineland says is really necessary. I have decided to powder coat
the frame rather than re-nickel it. The chemical tank cleaning process
that gets the rust and old nickel off the tubes eats the sift/bronze
weldment holding the tubes together. I just don’t trust a plating shop
to remember to pull the frame before the weldment dissolves. Besides I
have seen some metal powder coat colors that look nearly as good as
nickel and probably protect the metal from rust much better.

So far what have you learned? How about : Don’t ever buy a “Bike in a
box”!

A Bike In A Box : Part 2
by Lynn Bennett

When I went to get new spokes and rims the trouble started. Buchanans,
the manufacturer of the Sun rims, failed to keep up with demand for one
of the few choices for Brit bike wheels with 40 spokes (most others use
36 spokes). They were quoting nearly three months for rims so I chose
to go with the Akront copy made in Spain (or was it Italy??) from Speed
and Sport. Again Buchanans strikes again when they packaged the wrong
spoke set in the package for the Rickman rear wheel but Matt Hilgenberg
at Speed and Sport made it right sending the correct partial set. The
wheel assembly was frustrating as always (I hate wheel truing!) but was
completed. Here’s a hint: Don’t use oversized spokes on a relace job.

The trial assembly went as well as could be expected. Numerous
interference's between the chassis and the fasteners was found and
rectified by making special parts. The welding of the head steady lugs
looks as good as the welding of the rest of the frame. The welder used
a special brasement rod with his TIG machine to protect the chromoly
tubing of the frame from excessive heat (welding chromoly steel can
cause local stress concentrations making chromoly break like glass).
The original mid level pipe (routes above the engine cases but below
the seat level on the left side) was fitted, repaired and modified for
a permanently attached muffler. Next all was disassembled and the parts
to be painted gathered and sent off to the powder coater. The pipe and
header were ceramic coated semi gloss black as well.

The frame and pipe came back from painting. The color chosen doesn’t
exactly look like nickel or chrome (although the color is termed “Near
Chrome” by the manufacturer), but it doesn’t look like paint either. It
looks like a semi polished (light bead blast, maybe) aluminum under a
clear coat but with more metal sparkle. It is totally acceptable (sorry
you resto freaks but performance is more important than originality to
me). All the parts were refitted: Betor forks, rebuilt motor, polished
hubs with new spokes and rims, new tires, new controls, and all the
original fiberglass pieces cleaned up to look good (Resto freaks: not
perfect, its a dirt bike!).

Well, the moment of glory was shattered when the ignition (Motoplat
electronic, often times called MotoSplat) failed to spark. The first
sign of a problem was when the ignition failed simple ohmmeter testing.
Then the kick through test with the plug out and touching the spark
plug to frame ground also failed. A review of the impedances with a
Motoplat Internet Web site confirmed that the Motoplat was toast. I’ll
bet the original lower unit was good and was exchanged for a bad lower
unit, then the bad lower unit was returned to the pile of parts in the
corner (when still a box bike). Matt Hilgenberg set me up with a new
points ignition (commonly called a magneto but is really just a Energy
Transfer Ignition with a six volt AC coil under the tank) as a new
replacement PVL would cost over $500 with the required flywheel
weights. Ain’t points great, at least from a price standpoint?

The bike started within a few kicks after the new ignition was
installed. A ride down the street to test for all gears showed a punchy
little two fifty. The only potential problem revealed in the test ride
is that the clutch seems to drag. It turns out that Montesa clutch
packs can not be shuffled to spread the wear. The replacement clutch
pack is wired together with warning that the plates remain in the
supplied order. Guess what I did with the original clutch: shuffled it.
A new clutch pack fixed the clutch.

Lets review. For the new parts we have: new engine bearings (6), new
wheel bearings (4), new crankshaft and rod, new barrel, new piston and rings, new paint on the frame, new head steady, two new fiberglass pieces, new petcock, new carburetor, new air filter, new rims, new stainless spokes, new rear brake lever, new kick starter lever and shaft, new tires and tubes, new cables, new handlebars, new controls, and new ignition and coil. Not much left on the bike of the pieces that were in the original box. I guess in the end the product was worth the trouble and money but next time I’ll go for a more complete bike, not one in a box!