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Atlas head overhaul.

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One of my Atlas Exhaust valves  appears too long and the adjuster angle and action on the valve is not good. I expect the seat has recessed a bit although its been nicely angled and appears fine. Am thinking of removing a bit off the valve tip , How much can I remove and still stay within the hardening?. If a problem could fit a hard cap.

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After a closer look I find the errant valve has a longer  stem above the collets. Perhaps its from another model.

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Hell again Robert - there are two different lengths in the sets of valves for the Atlas ( &650SS).  The longer valves came in after engine number 125871 and also the corresponding shorter pushrod to suit.  It is possible that a previous owner may have used an incorrect combination at some time.  It is unusual that one seat should recede by that much but if they were satisfactory before,  then that may be the case.  A follower can also wear and some of the Atlas (and 650SS) camshaft lobes did wear out with little mileage.  I have ground the tops of the valve to remove pitting from the adjuster and on one occasion ground off the extra length (Alpha) to match up an odd pair (0.10 inch).  It was a lengthy procedure because I didn't want to get the valve too hot but the hardening remained ok.  I don't know about the current valve manufacturers depth of hardening but if in doubt use a valve top cap - as you suggested. Regards, Howard

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Its at least a tenth of an inch longer and the adjuster is about that much too far out.  Its got to be worth a try. .I'm going to find a way to test the hardness before and after shortening .

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The drain hole at the rear of the head goes into the case but appears to stop about 15mm down.Is there a cross drilling into the timing cover?, If not should it go down into the case?. Or is this some AMC mod?. 

Hello Rob  Drain hole are at the front and rear  next to the insulating washers  the front ones drain in to the rocker tunnels to lube the tappets , its only the rear ones that drain down the back into the timing chest  via an L shape  drain hole  in the crankcases  that comes out next to the magneto  drive  chain  and this is were it get blocked up  from time to time by the over use of gasket sealant  and when fitting your head gasket do make sure the oil way hole is in line with the head and barrel and your head gasket,  as some are not  and the other thing you get is a blow -by you can get with the head gasket is between the cylinder and the rocker tunnel  , witch then mimics failed piston rings or a worn bore, or worn valve guides    as you get oil being burnt on one or both cylinders,    and drain holes need to be cleaned out with every time you do a  rebuild of your engine    now have fun with your Norton   yours  anna j

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The drains are clear,but I know it is possible to supply more oil than can run away,particularly on the inlet side. I have at present the high pressure feed to the top of the head banjo's and plain spindles without flats that are orientated with holes pointing towards the center of the engine so they line up (roughly) with the rocker oilways to the ball ends. Not sure this is correct ?. But seems logical. 

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Robert,

It seems the logical way that you done it, but I believe it is incorrect, the hole on the spindle must face out of the head with a high speed pump. Many spindles on Commando's move to align the holes and the owners don't notice until the head is stripped. 

Check oilways with oil, especially the RH crankcase return to the pump, if an engine has had a failure the Aluminium usually collects at the junction. Get about one a year who check with wire and then find that once the engine is built they can see no oil returning. The wire stops at the blockage and they wrongly assume it is the junction. 

Using air will do the same but it may disturb some road grime or grit elsewhere on or off the bike in the vicinity and move it to an orifice leading into the engine - not ideal.  

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Not had any failure just a general top end overhaul to solve a smokey cylinder and plug fouling. A re-ring and hone plus 3 new valves and guides recut seats and oil seals on the inlets.

 

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