British Transmission Ideas
» Potentially greater range between 1st gear and high gear - better 1st gear acceleration.
» Smaller RPM drop when shifting into high gear - the motor doesn’t “die”.
» More sprocket choices.
» Higher top speed potential.
Here’s some large pictures of a BSA M21 trasmission installation (courtesy of enigmas): .
If you’ve considered doing this, you should read this before you make any plans, or spend any money. By the way - the conversion to a British 4-speed may be cheaper than buying and rebuilding a 45 transmission & clutch assembly. The information applies specifically to Harley-Davidson 45 Model flathead solo 1941-1952, although most of the information is useful for both older model solos (1937-40), and Servi-Car (trike) 1937-1973. An Indian Scout owner will find some interesting ideas here, too (although this conversion is not addressed). This information is not reprinted from other articles, magazines, or factory literature and is not available anywhere else, and not included in any of my other books; click here for other related titles: .
I guarantee that you’ll find information in this product you’ve never seen before, and that will help you plan and complete your transmission conversion.
Consider this: if this product saves you from making even a single mistake or bad purchase, or gives you one new idea, doesn’t that make this purchase worth while? The price is a small fraction of what you will invest in the transmission - plan more intelligently, and get better results. This product is over 19,000 words, including 25 black & white diagrams & illustrations, plus 28 data tables. Subjects covered include:
» Some hints on identifying an unknown transmission, including photos.
» Checking out a used transmission - what to look for, what to bring with you, what questions to ask.
» How to fabricate a motor sprocket compatible with your 45 engine and British primary drive.
» Primary chain types - there are more than you think, how to tell them apart.
» What internal gear ratios (i.e., close, wide, etc.) are available for many British transmissions, includ-
ing the 4, 5 & 6-speed speed factory and aftermarket gearsets.
» How to choose an internal gear ratio set, based on your purpose and engine mods.
» Selecting sprocket sizes for best acceleration or top speed.
» Making an adjustable bracket to mount the transmission.
» What to do about controls (shifter, brake, etc.).
» List of suggested parts for the conversion.
Also included is an update which contains useful information about installing the 5-speed gearset from the 1973-* later Triumph T120V 650 & T140V 750 twins, and T150V, T160 & A75 750 triples into the Triumph pre-unit box.
This latest revision (February 2013) also includes an analysis of the four different 3-speed transmissions used by the 45 since 1934, explains how ratios are determined complete with calculations.
It also includes conjecture on what improvements might be possible (if difficult) for the latest and most common 1941-73 3-speed including:
» Possible conversion to 3-speed + overdrive
» A possible alternate semi-close ratio gearset, moving 2nd and 3rd closer together without using
any factory close-ratio parts.
I guarantee that you’ll find information in this product you’ve never seen before, and that will help you plan and complete your project.
Total price: $9.95. This is not an actual, physical booklet, but an encrypted PDF file which you can read from any computer or lap-top using “Acrobat Reader”.
The PDF format offers advantages over a printed product: the printed text and illustrations may be zoomed much larger permitting close inspection of fine detail. You can read it anywhere (doctor’s office, train station) on your smart phone or tablet.
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