Valve lengths

Steve - hello. There are many different valve lengths for the Dominator range of bikes.  Just a few ground rules first. Your 99SS would have had the fastest camshaft available at that time and it's usually marked X1 to define the depth of hardness.  It is paired with flat footed cam followers and has the hollow-blown pushrods which are quite a bit wider in the central region than standard Dommie types.  Because of the wider pushrods the cylinder barrel pushrod passages are also wider to give the clearance.   The cylinder head is the big-finned, big-valve type that usually wears the twin carb manifold with the large vertical mounting holes ( 1 and 5/8 inch centres).  All of these things effect the rocker clearances to the valve besides the actual valve length.  Can you confirm any or all of this first for your engine,  please ?  regards, howard

Me again - If your engine is still as built in the factory,  the inlet valve for the 1961/2 99SS is listed as p/n 17221 and the exhaust valve as T2204.  The dealers are able to look up these numbers and convert them to their current stock lists.  The valve springs are listed as inner p/n 22839 and outer p/n 22838.  The pushrods for the 99SS are the same as those for the 650SS of the same year.   Cheers, Howard

Shorter pushrods were also fitted to the Commando engine  to go with the longer valves, I have just solved a similar problem with our Atlas that somehow got fitted with a longer Commando valve , after changing for a correct valve one of my spare 99 pushrods  has put the adjuster back to where it should be. I'm hoping that it will be strong enough as the Atlas is not revved up much and is running tired springs too.

In the search box (top right) type in the following.  

Atlas / Dominator exhaust valve correct length?

That will take you to a similar thread to this one. Read all the postings as some contain useful lists that will help you ID the various valve train related items.

Only if you are buying new ones ,I think at some stage they widened the spindle supports in the head and narrowed the rockers.

Robert is quite correct, Steve.  At engine number 114870 the rocker bearing bosses were reduced in width by 1/4 inch to give more aluminium support for the rocker shafts at the outside end of each side of the head.  By the way at engine number 125871 was when the valve stem lengths were lengthened by 0.1 inch and the pushrods were shortened by a similar amount.  Of course any of these changes can be made by owners on earlier versions - so long as consequential changes are made as well, accordingly.   Cheers, Howard

Norton used two valve lengths in the life of the Commando, as Steve has found above. The change was to add stellite tip, but instead of reducing the length by the thickness of the tip to be added they seemed to have mis-calculated and cocked it right up. If I remember rightly, the thickness of the tip to be added was 0.036'' so how the hell they ended up over 3mm longer is anyones guess. 

All other parameters remained the same, so it seems really strange to lengthen the valves in the later life of the engine

Evident by the valve gap adjuster running close to the edge of the valve.