14CS Piston questions

[mattward]

Hi Folks,

For some silly reason, I have decided to try and construct my basket case 1960 14CS, it may be having finally caught Covid19 for the first time...

So the stocklist has begun and immediately I am wondering about a few things. I have just cleaned the 48 years of storage muck off its piston and am not sure whether it is useable, what do you think? Hopefully, pictures show my main concern which is the pitting in the piston's outer surface only, this is from being stored in water for some time at some stage. If the piston by consensus seems useable, would the rings available from the club stock fit? they are Gandini brand, the piston I have appears to be BHB. If the piston is not salvageable would the pistons available from the club do the job? or are there better options? I have noted that JP pistons only have model 14 sapphire specs available.

The barrel is in great nick but the piston seems very loose in my experience, especially compared to the Model 8 I recently restored. Does anyone know what the clearance tolerance should be, I have searched all the manuals I have, to no avail.

(late note) I have just looked closer at the details on the top of the piston, and the part number and 'C61' possibly suggest the bike may actually be a 1961 model, anything else I should look for? The engine is stamped 60-14CS, but it may be late that year possibly?

Many thanks in advance.

Cheers
Matt[/img]

[Groily]

I wouldn't put that BHB piston in Matt - it's really quite moth-eaten, especially on the lands in the rings area where the larvae have been hungry. Not sure what the options are, let alone the best one, but I reckon anything would be better than what you have and would ensure your good cylinder bore stays good for a while.

[SPRIDDLER]

I wouldn't re-use that piston either.

I'm no L/W expert but I believe that sexy names were given to all export machines (they were standard U.K. models) as a marketing exercise to promote export sales.

As far as non wire-wound piston to cylinder clearance is concerned I use a rule of thumb for reboring of 1.5 thou inches per inch of bore diameter (plus an extra 0.5 thou for luck).

You may find this thread from March of interest re. L/W pistons and rings

viewtopic.php?f=15&t=28716

[Red Gauntlet]

Definitely don't use that piston, the corrosion will be far deeper than the eye can see and it may shatter under highish revs undoing all your hard work. Get a new one from the club spares and give the machine a fresh rebore, the Gandini ones are good, I would also check to make sure you have the steel flywheels, not cast ones, (someone may have changed parts in the past) you will hardly notice the compression difference and the engine will be happier for it in the long run. Spriddler is correct, 'Sapphire' was just a name for the model 14 AJS or 'Monitor' for the G2 Matchless, all the same engines apart from a few subtle differences, of course the CS is different externally but almost the same internally.

[mattward]

Thank you very much for the feedback Gents,

I was thinking the piston would make the box of original but knackered parts. Thankfully my flywheels are the steel ones, possibly replaced early on along with the 'c61' March 1961 piston. Thanks for the recommendation of the other thread very helpful.

The steel flywheels are also able to take the large crankpin and bearing as per the Model 8 arrangement so that's an improvement too. I will purchase a bottom-end bearing assembly and piston/rings from the parts scheme along with some washers from AMC Classics, and then hopefully the conrod I purchased locally will set me up to get started on the motor. Phew...

For some reason, whoever imported this bike got it with a lighting setup, which seems a bit weird (possibly wanted it road worthy), why I say that is that this includes a rather large boxy looking tail-light number plate arrangement which fixes to the frame extension behind the seat not on the rear guard...

I'm sure i will be in touch with more puzzle in time it seems like this marque is an unusual and rare beast with little info available (compared to Model 8's).

Tusind tak
Matt