A Basic Guideline to Building a 1955 – 1969 BMW R50-R69S Conversion
Background
I like to restore and work
on motorcycles.
Not only make them like new
but also improve them but keep their original look as much as possible.
Some of the bikes I worked
on before:
For the next project I would
like to restore a BMW slash 2
Looking for modifications I
came across this article from Brock Downey.
A great help if you are
going to do a project like this.
For many years numerous BMW
riders have modified their pre-1970 BMW’s to except post 1969 components.
This involves minor frame
modifications and a transplant of the engine, transmission, electrical
components and various smaller items.
Personal taste influenced by
available …. has prevailed.
When completed correctly,
the finished product is very satisfying and if cared for will give many years
of trouble free service.
The following are a number
of reasons to initiate building a conversion
·
Currently owned
machine is too expensive to repair to regain limited power out put
·
Availability of
parts is greater for post 1989 motorcycles
·
Increased power
for sidecar use or to meet today’s better paved roads with a solo machine
·
The owner simply
wants the reliability of a newer powertrain and electrical system, combined
with the classic vintage appearance
Note: ideally this
modification should not be undertaken with pre 1970 machines with matching
serial numbers, that are affordable candidates for restauration to their
original condition.
These bikes should be sold
or traded to collectors or restorers.
As a point of interest, a
conversion still requires the same level of restauration of a stock bike.
Swingarm, wheel and steering
bearings, shocks and springs, brakes shoes and brake drums, spokes, rims, tires
and tubes all must be in a good to excellent condition.
The idea of building a
conversion is not to build a “bearer” that pogo sticks down the road in a
dangerous fashion and doesn’t stop well just because the builder is trying to
save a few bucks.
Conversions are actually as
expensive as stock restorations.
This is important to know
before starting.
Dreams and drawing board
Before starting it is
important to take time to discuss the following:
·
What do I want
to use the bike for – solo or sidecar
·
How much am I
willing to spend
·
When completed,
will it be a day-to-day rider or am I going to pull out all the stops and start
with a powder coated frame and finish with newly painted body parts
·
Who is a good
contact to talk with that has successfully completed a conversion, or is
mechanically knowledgeable to help and identify to pros and cons of variety of
options available before and during this project
·
Do I have access
to local painters, plating, machine and mechanical shops
·
Should I
advertise to purchase an already completed Conversion
Thinking out loud
In the early 1960’s BMW
upgraded there frames with additional bracing.
This is easily distinguished
by looking to see if the lower steering race is braced.
These frames are arguably
more suited for a conversion, yet earlier frames without the additional bracing
can also be used successfully.
The first items you will
need are obviously a pre-1970 machine and a willing post 1969 donor bike or a
good parts resource.
A complete 1970’s parts
machine may be the least expensive choice.
If you can locate one that
is mechanically sound and inexpensive, it may benefit to purchase it and later
sell off the remaining parts you do not require and off set the initial
purchase price.
Engines from 1978 and prior
are the preferred choice for the Earles fork Conversions, due to the shorter
engine design.
The later boxer engines will
fit the telescopic fork Conversions without the concern for fork clearance.
Good candidates include 750,
900 and 1000cc engines.
The 500 and 600cc engines
will also improve reliability, yet may seem as underpowered as the original
engines.
The 750-1000cc engine share
the same camshaft, therefor you can change/upgrade the cylinders, pistons,
heads and carburetors to gain the larger displacement.
The 500 and 600cc engines
share the same camshaft and can seem a little off in the event the camshaft is
not upgraded to install the 750-1000cc series components.
Staying with the same range
of displacement will allow for a minimal amount of difficulty when
changing/upgrading top end components.
There are a number of
cautions concerning items such as flywheel bolt size and cylinder sleeve to
block clearance when trying to upgrade some of the /5 series engines to later
components.
This article is not intended
to go into that level of detail.
The Project
…………………………. soon, I am still
searching …………….
If you know something just
let me know ……………………..
