16H misfire

They do get hot...

What ignition timing is it at? The WD manual has it furtherretarded than prewar numbers. Mine was greatly improved by giving it more advance. You can go quite a bit further advanced than the book because you can always retard iton the lever.

But although it's sluggish when retarded, it ought not to misfire. Do you have the wrong leads and/or plug cap? They should not be the resistor type.

Plug cap on a WD 16H, David? Do tell me more. I have all on to get my 18mm plug in, despite the indented dome in the tank. No room for a plug cap, I just have a clip connecting the HT lead to the plug, as per book. (The clips can break, so carry a spare)

Neil - quite right - mine doesn't have one either. But you never know, do you? I'm sure there is room for a plug capon mine. Civilian (pre-war) bikes had alonger front down tube sothey have an extra inch on top of the engine. Hugh has a post war bike.Don't know how long the down tube is.

Has the mag sprocket slipped? It does happen,if you hesitate to over-tighten it onto the taper just in case it won't come back off again when you want it to. And it ends up retarded.

I believe your problem is in the pilot system. If it runs well with open throttle, I think there is no ignition problem or fuel starvation. Do you have standard size main jet ( 170 )?

Today I fitted a brand new float bowl on my 16H (stolen from my Comet). She ran as usual up to 3/4 throttle, then weak. So I guess float level differs. Easy fixed with a bigger main jet.

Mike

My suspicions would be around the carb jet block. Have you removed it for cleaning ? It's not really possble to do it in-situ. The pilot drillings are ever-so finicky and if the main air drillings are cruddy then it will not draw fuel properly.

If you have an 'R' suffix body, make sure that it has an 'R' type jet block with large pilot air inlet - and if no 'R', a block with a flat rear edge and two small drillings...

276/406 is the correct part number for a spare mixing chamber for the 16H.

However, the jet block with the large holes around it is completely incorrect and is intended for the Type 76 (the earlier type with pilot air holes around the outside).

I can't imagine that it is receiving much in the way of pilot air at all (I've not actually tried it though).

Photo below shows the air inlet side of the three types of jet block (l to r - Type 76, 276R and original 276 as fitted to WD Nortons)

This is a very odd story. I have exactly the same mismatch between block and body. The only adverse symptom is that the pilot air screw seems to have no effect whatsoever. But the bike runs fine.

As Richard says - there does not seem to be anywhere for air to enter the pilot gallery. I drilled a small (3mm) hole through the permanent brass plug fitted at the opposite end of the pilot screw hole from the head of the screw so as to provide an air inlet. But is has had no effect whatsoever. Possibly the hole should be much bigger? The air holes on (say) a concentric are perhaps 5mm maybe?

Anyway I've left it now and stopped worrying. But I have no misfire.

So: a) should I drill a bigger hole?

b) can I drill a hole through the block horizontally to match one of the three blocks Richard has show? Has anyone successfully modified n old block?

c) Should I drill holes around the bottom of the body? They'd be difficult to block should it all go horribly wrong.

d) should Hugh do the same - or look elsewhere - bearing in mind I have no misfire?

The blocks are of course unobtainable.

For what it's worth I suspect the mag (or maybe sticking valve) since it sounds like the problems exist long after the carb needle is dominating affairs and the pilot circuit is not doing anything much.

Burlen / Amal told me that they have no intention of making the pre-R suffix mixing chambers or jet blocks. The story behind these is that they were specified for the WD Nortons from 1937 at which point large cannister air filters were being fitted and it was desired to filter the pilot air. Other makes seem to have continued with the Type 76 up until late 1939 at which point the 276/R came into being but the older 276 remained correct for the Norton.

The /R has the advantage that the higher overflow hole above the mixing chamber nut allows excess fuel to drain out whereas on the Norton it either drains into the cylinder (sometimes) or is blown back onto the oil tank (mostly !)

All I can say on the running aspect is that in my experience, blocked air drillings either in the jet block or the tiny bleed in the main venturi make the things horribly rough and lumpy.

It might be worth having a word with Martyn Bratby about blocks. He once told me that he could recondition one for me (they are actually a three-piece soldered assembly). In the event, I found one NOS in Australia.

The very early Norton 276 mixing chambers did not have the gusset under the inlet which is in fact bored out to provide the airway on the /R. If I were modifying, I think that I would use an R type jet block and machine the inlet at 45? down to the rear edge of the jet block.

Sorry to Hugh for hijacking this thread. But thanks Richard. I do get fuel back on the oil tank. My block is the one on the left. My guess is that the pilot circuit would work if I drilled the four holes in the body. But it's a big step to take without having a matching carb as a pattern. But it runs OK so I'll keep it on the road for now.

Pre monoblock carbs were sometimes flow rated to make sure that sufficient fuel was passed by the pilot drillings in the jet block. I am in the process of drilling out the pilot feed in the jet block of a 289 which i am using on a Rudge.. Rudges had larger than std pilot and by pass drillings probably because they suffered from low gas speed with big 4 valve heads and big carbs.

Hugh... how hot is too hot? I have one of those Maplin infrared thermometers and a quick reading after stopping after a long hill it gave about 160C on one side if the barrel and 220 on the other side close to the exhaust. Have you measured yours?

Mine is 1937 with cast iron head. Engine same as WD.

Hugh.. that sounds exactly what I should do but have not dared! Do the holes go all the way through? Or just to the centre? And what diameter? Any details will be gratefully received. Any chance of dimensions on a sketch? It sounds like you made educated guesses based on the one photo. I thought about it but was worried that the new holes might join others coming up from below >

Regards

David Cooper

Hugh, I'm really pleased to hear that. It's always nice when half a hunch combines with experience as a compulsive tinkerer.

Although your bike is registered as 1946, it looks considerably earlier to me. From the geometry, the frame looks civilian and not WD. There were no 'open diamond' roadster frames after the war and from 1937 onwards, the civilian bikes had horizontal saddle spring studs.

Based on the enclosed front hub and the pre-doll's head positive stop box, I'd suspect a 1935 bike. These originally had a slightly more squared-off timing cover.

Presumably a previous owner installed the ex-WD engine and perhaps had an NOS carb body and without thinking installed his old jet block.

David, I have a Norton jet block somewhere that has unsoldered itself. I have to dash out in a minute but I'll photograph it for you as soon as I can.

Previously richard_payne wrote:

Hugh, I'm really pleased to hear that. It's always nice when half a hunch combines with experience as a compulsive tinkerer.

Although your bike is registered as 1946, it looks considerably earlier to me. From the geometry, the frame looks civilian and not WD. There were no 'open diamond' roadster frames after the war and from 1937 onwards, the civilian bikes had horizontal saddle spring studs.

Based on the enclosed front hub and the pre-doll's head positive stop box, I'd suspect a 1935 bike. These originally had a slightly more squared-off timing cover.

Presumably a previous owner installed the ex-WD engine and perhaps had an NOS carb body and without thinking installed his old jet block.

David, I have a Norton jet block somewhere that has unsoldered itself. I have to dash out in a minute but I'll photograph it for you as soon as I can.

Hello all. Very good comments about Hugh's 16 H misfire. Just to add a little. I owned this bike before selling to Hugh. I obtained the bike from a gentleman who had owned it since 1952/3. It was all original ,apart from a missing Dynamo. The bike was first registered in Northampton in 1932. It then went to Jersey sometime before WW2. I believe it was then repatriated back to Northampton in 1946. It may then have been fitted with another engine -- I really don't know. After I restored the bike a few years ago she ran perfectly well on the carb that was fitted , right up until Hugh purchased it from me. I was just wondering ----- I always use the very top grade of fuel in all my bikes, could this have caused a problem ? Anyway I have spoken to Hugh and he is so pleased with all the help he has had from Norton owners. Richard , this bike was definitely first registered in 1932. Regards to you all. Russell J Burgess

Just to add a bit more information. The gearbox is also the original . It is a Stumey Archer box -- not a Norton product. These were also fitted to earlier bikes but I believe Norton started fitting their own gearboxes in 1933. I also believe 1931/2 was the last year that inverted levers were fitted. A different type of silencer was also fitted for 1932. This part had to be made especially for me by Armour Products of Bournemouth using the old rotted original parts as a pattern. All in all this is a very special 16 H. And one of the only Nortons that I have owned over the years that I can honestly say is a true piece of good old English engineering. I have owned Commandos, Dominators, Rotaries , lightweights, all good in their own right . But this old 16 H was the best. Russell J Burgess

It's a great looking machine!

I'm curious to see the float chamber is on the right. Mine (1937) is rather inaccessible on the left.

Richard - I'd like to see the pics please - thanks in advance. I can't work out from the pics I have seen so far whether those holes are horizontal or do they slant down. It sounds like Hugh has worked it out.

I see it does have a plug cap...

Hi Hugh/Russell,

I have a 1938 Norton which has the Northamptonshire registration VV 71** so your number looks right for 1946 given the low number of registrations during WW2. If the bike is original it is to 1934 specification which was available from about October 1933 to the following September. The original engine number would be somewherearound 56000 to 59000 and the magneto will run anti-clockwise viewed as your picture. The following year this was changed to clockwise and remained until 1948 when it changed back to anti. I guess it will be best to get a Factory Record certificate from the club to pin it down.

Regards, Richard.

Hugh, no criticism of the bike intended on my part. My interest is in trying to pin down the components in order to make sure that they function well together which is the important thing.

I've had my self-destructing jet block in the untrasonic cleaner trying to make it look presentable enough to photograph for a prestigious forum. It's being stubborn though..

I will photograph it with some dowels or pins in in order to demonstrate the drillings.

Thank you Gentlemen! I'll keep a lookout.

Regards

David

All good stuff about my old 16 H . I really miss her and wish that I had never sold her. Anyway my loss is Hugh and Trevor's gain.

Does anyone out there have another 16 H that needs rescuing form a pile of bits ? I would love to restore another one . I have an up and running ,Mot'd early Navigator if anyone wants a swop. Russell j Burgess member number 101136 email russ@burgessworld.plus.com