Another oil leak question

I know this type of question gets asked all the time and I have searched and read most all the threads concerning it. Also, I am new and admittedly inexperienced working on anything British so please excuse my ignorance as I am learning. I think I have this somewhat figured out as to the source of the leak but though I would post here and see what those with more experience have to say before I go any further.

Picked up this '71 at the beginning of the summer and have been slowly going through it working all the bugs out. It was "redone" years back by the PO but had some less than desirable work done on it and from the looks of it never really got ridden. So far it been electrical (Sparkx replaced with Pazon), new center stand (850 type as the old one was a mess and broken),swing arm bushings and kegler clamps, and getting the front brake working right (thanks to a new master cylinder from Madass). Closest Ive come to the engine was replacing the seals on the primary which seems to have stopped that leak but now a new one has emerged.

Put around 500 miles on in the past week just knocking the cobwebs off and now oil has started leaking from the bolts securing the cylinder head and barrel. Thought it might be the head gasket but there are zero leaks anywhere else around the head, just from those two bolts. Not a gushing leak but one that coats the bottom 3 fins of the head and drips (splatters at speed) all over the front of the engine/primary/and gear cases. Been monitoring the oil level and it seems that now much is being lost but its proving to be annoying as, like I said, it never did in the first 500 miles and just recently started.

My question is, looking at the nuts they seem to be different types. I tried to get an idea for the size and the closest I could come up with is the smaller of the two (right side) is a 13mm and the larger is an 11mm (only tested as an experiment, didn't tighten). I do understand that Metric is not the right too and I should be using Whitworth (I assume) but I wanted to just get an idea, obviously some Whitworth tools are next on my "need to buy" list as I start getting into the engine. Looks like the correct nuts should be 5/16 x 26 according to the OldBritts diagram but I wanted to check with people here before I went any further to see if you have any advice or have seen this before.

Thanks in advance

P.S- The barrel was painted black by the PO, not a combat version

Right Side



Left Side

5/16 studs 3/16 whit socket 20ftlb from memory? These studs can be real wee shits watch what ur doing and don't strip them, it's easy done. I think I used a metric size socket and it fitted well.
J
The middle stud could be 13mm or 1/4 whit 30ftlb from memory. All threads are whitworth. Hope you can make some sense of this.

Looks to me like there is a gap between that LHS "tall" nut and washer, maybe it is just loose.... Pretty sure they are 1/4 whit socket required...

olChris said:

Looks to me like there is a gap between that LHS "tall" nut and washer, maybe it is just loose.... Pretty sure they are 1/4 whit socket required...

Click to expand...

The two nuts at the front are 5/16 whit ,3/16 socket. I stripped the thread in my barrels on one of these had to helicoil it. Just one of my many fuck ups, OlChris . And it won't be my last.

J
Like those exhaust nuts

olChris said:

Looks to me like there is a gap between that LHS "tall" nut and washer, maybe it is just loose.... Pretty sure they are 1/4 whit socket required...

Click to expand...

Looking at the pics I noticed that, just don't want to haul off and put the wrong size (or type) wrench on there and strip the thing. Taking it slow, learning as I go

auldblue said:

olChris said:

Looks to me like there is a gap between that LHS "tall" nut and washer, maybe it is just loose.... Pretty sure they are 1/4 whit socket required...

Click to expand...

The two nuts at the front are 5/16 whit ,3/16 socket. I stripped the thread in my barrels on one of these had to helicoil it. Just one of my many fuck ups, OlChris . And it won't be my last.

J
Like those exhaust nuts

Click to expand...

Thats what Im trying to avoid, in the short time Ive had the bike I'm building my own long list of fuck ups. Good thing it is teaches us what never to do again, bad thing is it costs up downtime and money. Thanks for the advice

Seems to me I remember that sometime around 71 Norton changed from one cylinder nut and stud to another, same with the head I think, but there can be UNC or WW in the engine which makes it sort of exciting. Seems to me I found some information at Walridge or RGM but my bike is early so it wasn't a problem. I think Rocky Point may know the difference too and the different years/numbers. But then you never know what the PO has done. I find it very difficult to tell the difference between some WW and UNC threads, the pitch is the same for some, but the pattern is different. 14MM is close to 1/4WW but not really close enough. Best to have some of all. I found the 3/8 drive 1/4WW from Hemmings a nice tool.

your Norton shop manual has the head bolt tightening sequence.....

the nut at the center rear of the head is a real bugger to both get too and tighten by hand, forget using a torque wrench

from memory I believe I use a 13mm closed end wrench that I ground off a large amount to get it to go around the nut....

looks like you just need to retorque all the head bolts, do you have a Haynes or Clymer workshop manual for the sequence?

after retorquing you should check the valve clearances as they may also need tweaking

blasphemy I know, but I am guilty of not owning any whitworth tools, make do with metric and american standard.......

Just cleaned up all the oil from the lower 3 fins of the head and ran the bike again for 5 minutes to observe the leak up close. It "appears" that most all the oil is coming from the left (taller) bolt which, as earlier pointed out, seems to be loose anyways though it does not spin freely when I fit an 11mm deep socket to it. I tried the fitting more for reference but am hesitant to put any pressure on it at the risk of breaking something and really putting myself in a bind. I do have a manual with the tightening sequence but don't want to go at it half assed and end up stripping something using standard/metric sockets that I have on hand. Bike is still rideable and not loosing that much oil but it does make a mess and is spattering small drops everywhere when I get above 60mph or so, don't have a problem "marking my spot" when stopped but having oil all over the front of the engine is a bit much. Guess I'll be shopping for a few Whitworth tools in the near future :?

1up3down said:

...the nut at the center rear of the head is a real bugger to both get too and tighten by hand, forget using a torque wrench from memory I believe I use a 13mm closed end wrench that I ground off a large amount to get it to go around the nut...

Click to expand...

I believe that's the nut that I used to use an old (new back in 73 when I had my first 850) Snap-On BW offset box-end wrench that worked very well. It had just the right bend to it and, as with many Snap-On wrenches, there is no need to grind off metal because they're made of strong material and quite thin so they fit into tight places better than most anything else. As an example, Snap-On used to be the only tool maker, to my knowledge, whose wrench would fit on one of the two starter bolts on a mid-70's 4-cyl International Scout without being ground down (International used a Chevy starter for that application and things were very, very tight). No compromise in strength or longevity, just the right tool for the right job.

Just looked at those photos and is it just me or does it look like they have not been tightened down AT ALL ?

You could do what most DPO did and stuff stove wick material in the fins to keep it cleaner, that's what was on the fins on my first commando. Sleazy buggers! Should be given fifty lashes,

J

those 2 bolts definitely look loose. If they don't tighten, pull them out and find out why. They may not be original and too long or there may be shit down the holes. You may be able to work out the gap and put thicker washers under the existing washers etc, and tighten tem up. It may be all you need to do. If you strip the threads, goo, pull the head off and sort it out.
Dereck

Just do it

Witworth sockets /wrenches & a torque wrench coming over tomorrow Josh. I'm worried some dip sh#~|t PO might have put the wrong bolts in. Don't try to tighten them until we can determine they aren't doing damage. Glenn.

Transcon said:

Just cleaned up all the oil from the lower 3 fins of the head and ran the bike again for 5 minutes to observe the leak up close. It "appears" that most all the oil is coming from the left (taller) bolt which, as earlier pointed out, seems to be loose anyways though it does not spin freely when I fit an 11mm deep socket to it. I tried the fitting more for reference but am hesitant to put any pressure on it at the risk of breaking something and really putting myself in a bind. I do have a manual with the tightening sequence but don't want to go at it half assed and end up stripping something using standard/metric sockets that I have on hand. Bike is still rideable and not loosing that much oil but it does make a mess and is spattering small drops everywhere when I get above 60mph or so, don't have a problem "marking my spot" when stopped but having oil all over the front of the engine is a bit much. Guess I'll be shopping for a few Whitworth tools in the near future :?

Click to expand...

That nut could be "gaulled" or cross threaded.. Either way it will eventually need to be removed.... So.... have a poke around in there and see if the washer is loose, if not back the nut off slightly till washer is loose.... If (by the LOOK of it) the washer is freed within a half turn or so then is "just loose" and tightening it will likely cure your leak, but if the washer is loose and the nut is overly tight to back off then you need to stop.. Order some flowers and get a nice card for your wife, just because you a good guy!!! thats prior to buying a full WW spanner set, and necessary replacements for your busted/butchered parts...

Thanks for all the words of advice guys, I look forward to getting to the cause of this and fixing it correctly....which is why I'm being so much of a pussy and double checking myself every step along the way. I'm sure there will be plenty more little "surprises" along the way as I continue to learn more about the bike, thanks for your patience with all my amateur hour questions. Guess I'll see you (and your Whitworth tools) soon Glenn....lunch is on me

auldblue said:

olChris said:

Looks to me like there is a gap between that LHS "tall" nut and washer, maybe it is just loose.... Pretty sure they are 1/4 whit socket required...

Click to expand...

The two nuts at the front are 5/16 whit ,3/16 socket. I stripped the thread in my barrels on one of these had to helicoil it. Just one of my many fuck ups, OlChris . And it won't be my last.

Click to expand...

The nuts/studs are 5/16 Cycle thread (26 TPI) and the correct socket/hexagon size should be 1/4 Whitworth (or 5/16 BSF both of which are 0.525" jaw size).

As the tall nut is "11mm" then I'd guess it's 7/16" AF hexagon so probably isn't the correct thread.

LAB is correct (as usual) about these threads being BSC, however be aware that many of the studs on the commando have a different thread where they go into a casting than on the end that sticks out of the casting for a nut.

dave M said:

LAB is correct (as usual) about these threads being BSC, however be aware that many of the studs on the commando have a different thread where they go into a casting than on the end that sticks out of the casting for a nut.

Click to expand...

True, however not on this particular stud; both ends are 5/16" BSC :wink:

Ta.