Taking A Grinder To Britain's Motorcycling Heritage.
Taking a grinder to Britain's motorcycling heritage. Disclaimer This "Blog" represents the thoughts and actions of the author. It is created for academic interest and entertainment only. It is neither intended or implied that any person reading any article contained within, imitates or recreates any work described.
Think salt and you either think of Fish 'n' Chips or the great white wasteland that is Bonneville Utah USA. Well it ain't always the case, John sent over these pics of his rigid Thunderbird at Lake Gairdner in Oz, Those boys down there in The Great Southern Land have got their own horizon to shoot for.
I'll take the lazy option here and let John tell y'all what's been done.
As you can see its a rigid based bike and I call it a 54 as that was the last year of the rigid frame and first year of the big bearing alt cases for the Thunderbird. I've tried to use as many pre unit bits as possible, though there is certainly a mixture with the frame being a 49, rear wheel, oil tank, guard, gearbox and triple clamps being early fifties, fork sliders are 57, front wheel is duplex type 8" hub. Tank is mid 60's T100? and the tacho bracket is 70's. All other bits are aftermarket or home made.
Engine has big bearing alt cases with a unit crank fitted balanced to 85%. Ball timing side and roller drive side main bearings. R&R billet conrods, 3134 cams with R cam followers. 9.8:1 comp pistons. Standard 5 fin Thunderbird head (58-60 type) with standard thunderbird valves. Lightened and polished rocker gear. Single 30mm Mk1 Concentric, K2FC maggy with manual advance and 1 1/2" pipes with reverse cone meggas.
Managed a best speed of 108 mph at Lake Gairdner earlier this year which I was really pleased with for a first time out on the salt.
Well over the ton on a single carb 650 iron Trumpet, outstanding achievement John, can't wait for further reports on what the twin carb head does for the top end performance.
This is one of the rocker boxes that will be used for the motor in Skankweasel, no point in showing the pair of them as they are pretty similar. The rockers will be lightened around the adjuster boss and ball pin areas only, the rest will be blended where needed and polished in accordance with Dwain Taylor's suggestions. The rocker spindle shown here, is the early type without the "O" ring on the drive side end, it also shows slight mushrooming on that end, so it will be replaced.
Realised, when it was too late, that it would have been easier to slacken the adjuster nuts off while they were still in the boxes. Rather than risk damage by clamping the rockers in the vice, I slipped a 2 metre length of 12 mm tube through the pivot bore, this provided enough leverage to allow the nuts to be loosened without damage or drama.
Seein' as Eric is working his magic on the head, thought it's best to be reading up on a bit of tuning. Also got some really helpful insights from the blokes on The BritBike Forum. there is a rake of real, been there and done it experience on there.
So, anyway, I was looking at inlet tract calculations, and to get the benefit of the tuned length between 3,500 and 5,000 revs, the inlet needs to be 12 1/4" from the center of the inlet valve to the lip of the velocity stack.
As ya can see, it will make for an interesting oil tank!
Had an idea to make up some rubber mounts for a while, and this is as good a time as any.
The holes in the rear mudguard were drilled 8.2 mm as it was known they were going to be pilotting the 1/2" Q Max hole punch. Punching the hole gives a lot cleaner edge to the hole, not like the hexagon a regular drill can give through thin shit.
The grommets are straight forward 1/2" (12.5 mm) wiring grommets, the top hats have been turned to match the bore diameter and thickness less 0.5 mm, just to snug up the fit.
Chris, the builder of that sweet but strangely unsold ( shame on y'all) has just finished his T120 TT rep at least I think it is, it may be pukkah. There's no style suits the big unit motor better that the flat track/desert racer format,
all bollocks and in yer face attitude, a proper British Bruiser!
Rep or not, you may depend Chris scoured the deepest depths of the darkest cellars over the pond to find the original bits.
There's not much available nowadays that is free and still worth having.
This catalogue is just that though, not exactly free as you've got to pay postage, but the book itself is gratis. Containing details on all ranges of post war carbs right up to the Mk II concentric, there's also the standard settings for just about every AMAL equipped bike since 1940. It's just got to be worth owning for the price.
Skankweasel went out for a little trip to Martin's shop yesterday to get a little bit of TIG action going on the rear mudguard mounts. Had these bits water jet cut, nice finish, cleaner than Laser but worth the extra? I'm not so sure.
The brackets were cut with a 10 degree angle to allow for the curve of the guard. The tabs were welded on to the bracket after being bolted to the guard, to get the angle.
The bottom mount bolts to two 3/4" long bosses welded to the frame cross member. Not a thing I'm normally down with, but this rear section has had so much abuse over the years that it's not really heresy to weld extras to it.
The top mount is the same bracketry but picks up on the standard rear guard tapped holes.
There's still the rear loop/stay to sort out, and as it's aluminium a bit of rubber mounting will help.
Decided on the Hal Hall Route, good price and flat and all ya need, barring the thin wall steel tubes that were slotted down the bores of the manifold to seal the potential gaps. On the original factory Tufnol spacers, the nut recesses break through.
Definitely looks the part.
Some say that's Triumph's prettiest ever motor right there, easy to see why.
Meanwhile Bill slipped a pic in the mail.
Notice the tubes.....................................