Exhaust threads

Gary, an expensive job to have helicoiled and you will need to take the head off too. If just a case of one side coming undone there is a cheaper answer: You can buy a pair of rings from most Norton stockists that wedge between the cooling rings on one side and the barrel fins on the other. This stops them turning. It is running with the exhaust loose that causes the threads to become damaged.

The trick is when tightening the exhaust rings is to not tighten too much when cold, a bit more when warm and a final hard tightening when at full working temperature. Unless your threads are so worn the ring justpulls out then that should fix the problem. A bit of copper slip on the threads and perhaps new sealing rings should help too.

A bodge which worked for years is to cut a strip from an aluminiumsoft drinks can and place it between the threads of the head and the exhaust ring. It takes up any slack and ispretty good at stopping the ring loosening when the threads in the head are a bit past their best. Can be done when stopped in any Motorway Services. But otherwise it is heicoil or aluminium welding and a re-cut thread (which I eventually had done) or an insert.

On two of my cylinder heads I went to BLR Engineering who recut the threads and supplied replacement oversize exhaust nuts. This, at the time, was the cheapest and easiest of the options available.

It involved milling out the old threads and then recutting them the next size up. The oversize exhaust nuts came in Brass which could be plated to look like the later Commando type. The big advantage of this mod was that the expansion rate for Aluminium and Brass are similar and consequently once they are tightened do not usually shake loose. The only minor drawback was I had to find new exhaust washers that were slightly larger. This is where the Singles spares list came in handy.

Sounds like it is beyond bodging - was bound to happen sooner or later. A shame it was sooner. Coke cans are made of particularly useful thin shimaluminium - possibly more suitable than a baking tray. I used a strip about 1/2" wide and 3" long for my bodge. The length was adjusted so that there was reasonable resistance when tightening the nut. It held until I got down to doing a proper repair - inevitably quite some time down the line.

GARY, THE CHEAPEST AND QUICKEST WAY ROUND YOUR PROBLEM IS TO BUY A PRODUCT CALLED JB WELD IT COMES IN 2 TUBES MIX EQUAL PARTS TOGETHER SMEAR THE INSIDE OF YOUR THREADS GET A REALY GOOD EXHAST NUT COVER IT IN GREASE SCREW IT IN THE HEAD LEAVE FOR 1/2 HOUR THEN TAKE IT OUT LEAVING A PERFECT THREAD WAIT 24 HOURS THEN FIT YOUR EXHAUST PIPE BACK IN HEAD AND AWAY YOU GO TOTAL COST £6 AND A BIT OF TIME THEN WHEN YOUR HEADS NEEDS TO COME OFF YOU CAN HAVE A PROPER JOB DONE BY R.G.M. IN BEKERMET, CUMBRIA Colin,