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Rob's WD16H and Big4 Forum

Dutch army, Johan Herman Fuhler, somewhere between 1945 and 1950

Rob's WD16H and Big4 Forum
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Oil leaking on cylinderhed

I own a WD16H in civil trim since Mai this year, a great bike amazing me every day. After street legalization and fixing a lot of imperfections I'm out for a ride any time weather and family allow.
I noticed that the WD16H is leaking oil on the head. I first checked the head gasket but found it to be proof ( cost me a new gasket ), repaced the copper washer for the inspection plug and made sure it's not the sparking plug. Oil loss is rather cosmetic but sums up to black oil spots thrown on the carburettor.
Can there be oil loss via the headbolts / - is there a need to seal with copper washers?
Any other ideas?


Re: Oil leaking on cylinderhed

Heiko, It's good to see that you're enjoying the 16H. They're ideal for having a bit of fun without breaking too many speed limits.

There should not actually be any lubricating oil up at the top of the 16H engine.

If what you're seeing is unburnt fuel combined with oil from the combustion chamber then the problem must lie with the head gasket. The composition (sandwich) gaskets do need a strict regime of re-tightening and are best fitted with a non-setting gasket compound such as Wellseal. If the leaks are round the studs then it must have crossed the gasket face first to get there.

The 1937 type engines are a bit oily regardless - it's the way they were made, with little proper oil sealing.

Could the oil be coming from behind the tappet cover ? A certain amount of oil will always find its way up with the cam followers. Nortons introduced a drain (for the 1936 model year, I believe) so it's worth checking that it's clear. There should be counter-bores around the brass screw-in follower guides and these are linked by a gallery bored from the rear which is threaded to take a 1/8 BSP connector to which is attached a drainage tube. This ensures that the oil escapes lower down.

These oil drains are frequently blocked with grease and dirt causing the oil to puddle inside the valve cover and then blow out backwards.

If it's not clear and you think this might be the problem, let me know and I can photograph a spare casing for you.