G80TCS 1962

[mervk]

Hi guys. Have just bought a 62 Typhoon, and starting to research it. I need to attend to a few minor things, but basically the bike is in excellent condition. For the experts who may be able to help me with the following questions, the numbers are: Engine 62/G80 4444 TCS, Frame C10518, and Gearbox M35994S.

Only received it today, and first order was to check all fluids, followed by a ride around the block. The two things that were very obvious were:

The front forks are very stiff, with next to no movement. Were they fitted with extra heavy damping/springs for charging across the California desert? And if different specs to standard, what must I do/change to get back to standard?

The gearbox is very close, with low gear feeling normal, but doing about 3000rpm at 40mph in top. Guess this must have been for competition as well, but again, what do I do to get back to something useable on the road? Did they alter the gearbox internals, or is it just a matter of different sprockets?

Will most likely have more questions as we take a good look at it, but answers or suggestions to these two will be a good start.

Cheers

Merv Kroll

[Don Madden]

TCS engines in the North American Registry range from 444x to 445x for 1962 & not many listed, so quite rare. The frame numbers are in the same sequence as other scramblers. The Club Dating Officer may have exact details.

1962 is the year that AMC went to long travel forks, about 8-1/2in, & are very soft & complient. Stiff forks can be from corrosion, wrong parts or too much or wrong grade of oil. Remove wheel & mudguard & drain each leg, catching the fluid in a measuring cup. The service manual did not list the quantity different from other models, which require 6-1/2oz. It should be easy to compress each leg one or two inches by hand.

Typhoons were built as desert scramblers with low gearing, close ratio gearboxes & knarly tires, as other scramblers. Since I no longer wish to destroy my classic AMC bikes in the rough country I now use B*As for that. I have set up my 1960 Typhoon for street by using a 22T engine sprocket & 17T G/B sprockt to calm down the engine. This makes the 1st gear very tall so I rebuilt the gearbox with touring gears, which are wider ratio span. I am using the optional mooblock carb instead of standard GP. The bike is now a Gental Giant, easy to drive in traffic but powerful on the open read.

I am using Avon Road Riders, 3.25x19 & 3.5x19in. I would like a larger rear tire but 19in large tires are scarce here. Mine is fitted with the original 2gal, (imp.), fuel tank, with badges but also have a spare 3gal one to extend the range.

Feel free to ask for advice or suggestions, Cheers, Don.

[mervk]

Don, thanks for replying, and giving me an idea where to start. Knowing the forks should be soft is good news, and I guess I will attempt to do the same as you have, with the gearing. It's always nice to have a 'return to original' path, so maybe swapping the entire gearbox may be my option. Are you aware of what year/model range box is the same externally? Were all the gearbox cases identical from a certain year on, and easily swapped in and out?

When I look at the Roy Bacon book, he lists all the gearbox ratios by type number, however doesn't make reference to if the difference between box types is internal only, or also external. Any advice greatly appreciated.

Cheers

Merv

[mervk]

My gearbox serial number ends with an 'S', does that denote 'Scrambler'? And if so, would I be able to tell what model a box came from by the last character of it's number? And again if so, what are the codes?

Cheers

Merv

Typhoon 002smaller.jpg

[Don Madden]

Hello, again Merv. I notice that your fuel tank has decals as the CS, not badges as TCS, one of the defining characteristics. It is possible that the screw holes have been filled, which I've seen before. The screw anchores were brazed in & if present, can be seen by peering through the filler neck.

I do not have a list of the codes for the gearboxes. I do have the North American registry where members have listed what they believe to be the year & model, frame, engine & gearbox numbers. There are a few errors in the lists but with almost 5,000 bikes listed, most are obvious. For 1957, the first year of the AMC 'box, only two show the "S", both are CS models, one has a number consistant with 1957, the other is later. For 1958 many but not all show "S". For 1959 most CS show the "S". That was the year the adjusters for the primary chain were changed to one on each side, outboard of the mounting plates. The earlier 'boxes had one adujuster inside of the plates & the top of the main case was notched for clearance so that the adjusing bolt bore on the top bolt directly. The later touring boxes continued with the notch but the CS do not have it. We have "T" listed for Trials bikes, "R" on CSR & G15/45, "G" on Norton engined bikes. Only a search of the spares lists will show the ratios fitted. Any of the boxes can be fitted but I recommend the later with the larger kick return spring as the early, shorter spring is prone to break. The notch is only cosmetic & most wont know. The early kick spring can be updated but kick shaft, inner & outer covers are different. I believe a good engineer can machine the early parts to fit the big spring but have not tried it.

Cheers, Don in California, the natural habitat for the Typhoon.

[mervk]

Thanks Don. Think I'll take a day or two to digest what you have written, and see exactly what I have. No doubt I will draw on your knowledge again, and your responses are appreciated.

I'll check for the badge mountings.

Cheers

Merv

[mervk]

Don, I note your comment that the 22 tooth engine sprocket made low gear too high, and that is understandable. However here is where the confusion hits me. I had an early 60's G12 CSR a few years back, and I seem to remember it's gearing was very good. The Bacon book lists both the G80CS and the G12 CSR as having a type 10 gearbox, and then lists the gear ratios etc for that box. So I would assume that all type 10 boxes had the same internal gearing.

It shows for the G12 the engine sprocket to be 23 tooth, and gearbox sprocket to be 17 tooth, with I think clutch and rear sprockets the same as the Typhoon. So my layman's view tells me that changing both those sprockets for the G12 ratios would give me the same gearing as the G12?

Where am I going wrong here, as I'm sure it won't be that simple.

Cheers

Merv

[robcurrie]

Merv, also check what wheel size you have, the G12 had 19" rear.

Rob

[mervk]

Yes Rob, it has 19" both front and rear, complete with Mohave Desert knobbly tyres.......

Cheers

[Don Madden]

I have had two G12CSR(US) bikes, 1960 & 1961. The 1961 was original & I was the second owner. It had the "R" in the number & had close ratio gears, 23T engine & 17T G/B sprockets. I have set up my TCS with the tallest engine sprocket I could find, 22T so almost equal to the CSR. I also replaced the inlet pushrod rocker arm with the 1963 type, giving more lift, as was introduced in 1963 & I fit the "SH" cams. The engine now has the low speed grunt of the touring engine while still revving as the CS. The arm used by the factory is the same as used in lightweigt singles so not difficult to find. I took one out of an old G2 rockerbox. Cheers, Don.