Armac Club
PROJECT
Every man needs a hobby, but when Andy Barefield decided to start a rebuild of his Tiger Cub it turned from hobby into a bit of an obsession. First things first though, we will let Andy tell us why he felt the need to build the Cub and the initial purchase...
Andy: “If we are honest, diets, fitness regimes and finishing the machine project that’s been hanging around for ages will always be dealt with tomorrow; tomorrow will always feature in our calendars and I’m confident that few of us will be on top of all the things that we have put off until that elusive day. Much as retirement has benefits it also means that we have more ‘tomorrows’ to deal with these things and I’ve certainly promised myself to do all of the three mentioned above! It’s thanks to riding buddies like Bob and Heath that I have now stirred my stumps and am ploughing on with my stalled Tiger Cub upgrade.
“I bought my Armac trials Cub from the enthusiastic John McDonald at The Twinshock Shop in October 2012. This is the only Cub that I’ve laid hands on and, much as you can research and read about an unfamiliar machine, you only get to grips with them by using them and chatting to people in the know and building up a network. As with all such things concerning advice the opinions vary greatly, and ultimately you must make your own choices and stand by the results.”
Arrival
Andy’s Tiger Cub originally arrived with a lot of anecdotal history but with few documents; it was already part Armac and the engine specification was high but lacking in provenance. This could have been an issue for some but Andy had confidence in John McDonald at The Twinshock shop, and he just had to do a little digging around, which proved it did indeed seem to have new crank cases; enquiries indicated that these were unused stock and also that the crank was a new unused Serco item with the primary gear porthole in the rear of the case which allows the front sprocket to be changed without major surgery.
It has the trials ratio gears (lower second and higher top), Morgo oil pump, Electrex World self-generating ignition and a Wiseco piston. It also has the Armac clutch lightener which is phenomenal, Armac breather kit (Andy added rocker box breathers as well), a primary chain tensioner kit and an R type cam. For detail aficionados the piston is stamped 4156M06700 and 98240H. The Internet brings this up as a 67mm Wiseco piston with applications for Honda XR/XL 185, 200 and some Honda ATC models. It seems this gives the Cub a capacity of 230cc on the standard stroke. Although Andy has not done any measurements or sums himself he is happy to accept others people’s word on this.
Armac is a small-volume producer of high quality parts, especially for the ‘Tiger Cubs’, and has many items in stock – frames however are done in batches and numbers are limited. Andy had decided that he liked the look of a full-spec Armac and the decision was made to upgrade; of course this was going to involve some open-wallet surgery! Some things just have a nice balance of form and function and for him the Armac has that, and he felt it a project worthy of pursuing.
Having made the decision to go for the full Armac frame-set Andy contacted them to secure a new front unit. He was fortunate, and believes he secured the final one of the proposed batch. When obtaining the Armac frame modifications have to be made to the engine lower mount as the new frame doesn’t have a lower cradle, but Armac offer the mods as part of the package, so the engine was taken from Oxfordshire up to Yorkshire for the work to be undertaken. Once all the frame parts were brought home it went for powder coating.
Head Issues
Cylinder head issues began to show themselves with an innocuous spray of brake cleaner following a trial. All engines have their own character and this one always showed some oil seepage from the front but it was never apparent for sure if it was the head gasket, rocker cover or oil feed. A quick shot of brake cleaner usually removed all traces but this time it was noticed that the shiny pushrod tube was shiny no more; in fact the shine had run off and what remained was a beige coloured steel tube – this became another addition to the shopping list with UPB, where a CNC machined aluminium version was obtained.
With the engine in what was now a full Armac frame and on a workbench it was a good time to remove the cylinder head – the state of it didn’t match the rest of the machine. There were three broken fins which hadn’t been fettled or repaired, it smoked on start up but cleared itself after a short while, and the carburetion needed fettling. The major fin damage around a head stud looked like it had been done when it was tightened down so after a bit of fine tuning to a couple of spanners to enable fitment between the fins it all came off easy enough. What was a portent of doom were the immediate signs of head gasket leakage to the front where it was clear that the previously mentioned oil was coming from. Inexplicably there were no head dowels fitted and the head gasket and head were free to slide forward; tell-tale marks on it showed minimal sealing width and this was the source of the leaks. When taken to the bench and fully examined it was noted that only two of the four head studs bore down onto seating washers, the two that were in evidence were very thin and had distorted considerably.
Andy ran his findings past the guys at UPB who were ever helpful. They had put some of the history of the machine together and knew they had supplied some of the parts for the initial build. It was time to shop once again, and soon new gaskets, head stud washers (thick and thin) and head dowels were in the post. The head was left on the corner of the bench where it could sulk whilst other vital jobs were undertaken.
Coming Together
The four bearings were pressed into the swinging arm; two each side with an aluminium spacer in-between, this was simply done in the bench vice with jaw plates. The whole assembly was then offered into place and a bit of head scratching was needed to work out how to line up the two subframe holes, four bearings in the swinging arm, their two spacers and the two aluminium bearings in the front frame.
If you’ve ever owned a BMW R100 and changed the engine mountings to stainless steel items, then you’ll have a spare 12mm steel spindle that fits the Armac spindle perfectly and has sufficient excess length to tap it without compromising the powder coating. Luckily Andy had such an item to hand!
With a bright torch and thin screwdriver used to good effect he was able to tap the spindle through the numerous components, it was simple enough to then draw it back out and gently tap the aluminium spindle (coated with Castrol Optimol white paste) through into place. Finally the nut was tightened and a rubber gasket pulled on to the exposed excess thread.
Fitting of the rear wheel needed a couple of spacers turned, and a quick visit by Andy to his old Ariel fanatic friend Dickie resulted in the consumption of coffee, a friendly yarn and the assurance that he’d get on with the task within a few days. A message was received within a very short time to say that the bits were ready and the kettle was on. It’s nice to have friends who are engineers! Some nicely turned spacers for the torque arm were waiting all bagged up, as were a brake rod connector and a wheel spindle spacer turned to fit in the lip seal that Alan Whitton machines into his hubs.
Specialist Work
It was no good – bullets had to bitten and it was time to look at the cylinder head again. The deck height had to be checked as the new pushrod tube could have an impact on how everything lined up. UPB supplies tower-top gaskets in two thicknesses to allow for discrepancies and both were to hand. It was all settled down but it could easily be seen that it wouldn’t work: It was reassembled without the pushrod tube and measured up. With figures to hand and everything written out on the tube in Tipex to avoid confusion Andy trotted through his village to another pal who has a lathe. One quick visit and all was right with the world – and the tube – again!
Time to check the valve seats and related items whilst the top was off and, sadly, the findings could have been predicted: the valve faces were worn hollow where they’d flopped about, valve guides were worn to the point of extinction and the valve stems were worn down considerably on the bearing stroke length. The only way forward was to find another engineer to address the problems with the head. For those of you that have read or indeed are lucky enough to own a copy of ‘The Vintage Motorcyclist’s Workshop’ you’ll appreciate Andy’s admission that he is no ‘Radco’ but he does know who to go to when a problem needs solving. Enter Paul Gardias of Witney.
Those in the area will probably know of GES (Gardias Engineering Services). So far nothing has daunted him. Coincidentally he had been an apprentice with Andy’s aforementioned mate Dickie. If you’re local go to him, if you’re not then look him up and use a courier! He is a specialist engineer who has an astounding level of understanding of both normal and competition engines; the neat piles of projects waiting for his attention attest to his reputation. One of his services is the lining of valve guides with bronze inserts and it was felt that he would be the obvious choice to solve the problem.
All the components were boxed and driven to his location, it only took him an instant of test fitting to confirm that all was not well and that the guides needed lining, new seats were essential as the originals had sunk deeper than the Titanic, and he advised new valves as the stems and heads were past what he’d consider putting back in. A pair of valves from UPB was ordered and was sent directly to Paul.
It turned out the guides were too worn to accept liners so he turned completely new ones out of Colsibro – Copper silicone bronze alloy as favoured by the racing fraternity. These were machined with grooves to accept new valve stem seals (the originals were as loose as a wizard’s sleeve and way beyond salvation). New seats were fitted and cut with triple angles, and the valves dressed to meet the correct facing.
Swift Progress
Progress was then swift and soon the fin damage was dressed up to the point where the loss was not obvious at first glance, and once cleaned off it was time to give the valves a quick fettle with fine grinding paste, as per Paul’s counsel. All that was needed was a good and thorough clean up and everything could go back together using a valve spring compressor and plenty of patience. Assemble the valve in the head, lower spring cap, stem seal, springs both inner and outer and finally top spring cap and compress it all down, grease the inner side of the valve collets, find a small screwdriver and push both into place, then slowly release the compressor and let it all seat gently. It’s also a good point to include the new, slightly oversize, rocker spindles that were purchased as one of the originals proved to be incredibly loose and spun when you tightened up the oil feed nut.
With everything all cleaned off, it was time to anneal the new head gasket (warm to cherry red and quench), tap the two new head dowels into place and paint head jointing surfaces with good old fashioned Wellseal. While carrying out this procedure we were given a few pointers that experienced Cub mechanics will undoubtedly know: firstly run an 8mm drill through the stud holes in the head to remove any burrs as they will drag as you try to put it all together, and second mark the inlet pushrod with Tipex as the pushrods pick up the cam followers at the top of the crankcases but diverge fore an’ aft. With the exhaust pushrod needing to be the closest to the cylinder it’s easy to cross them over, so marking the exhaust pushrod takes away any confusion as it can be easily identified in assembly.