Discussion in 'Norton Motorcycle Rebuilds' started by Fast Eddie, Feb 11, 2019.
Looking good, will it be ready for the festival?
That’s the plan Ralph.
All hinges on how much shed time I can find / make.
And of course, how the ‘one step forward / two steps backwards’ pans out !
Following Storm42’s thread regarding his breather body coming loose, here’s my idea for retaining the screws.
I filed a notch in the Allen head, then centre punched the alloy inside the notch when the screws were tight.
I centre punched the alloy up against the flats of the outer retainer bolts too.
AHRMA offers much more variety in vintage racing...
Whilst I’m well aware that there is still a ton of work to do, it’s always nice to reach this milestone in a rebuild:
Well bugger, like I said, one step forward - two steps backwards...
Here’s a view, from above, of the space (or in my case, lack of) between the crank case and gearbox.
Clearly, Maney case and Maney belt drive with TTI box do not go well with a cNw breather.
I’ve got a Comnoz sump plug breather on the shelf, guess what I’ll be doing tomorrow!
@Fast Eddie Nigel - there is room (just) to countersink the four 1/4” holes.
Countersink until it breaks out, then face off four countersink 1/4” UNC bolts in the lathe.
I have just done exactly this on a Dommie i’m building to make room for the centre stand spring that runs between engine and gearbox - it worked out really well.
That’s absolutely beautiful. Like the ‘NYCNorton’
I caught myself staring at the photos... must have been the angelic music.
You did put the photos to music, right?
Yes, that would work... perhaps that’s how it should be supplied... but I’m done with it and I’m gonna use the sump type breather.
That’s what I had on the 850 and it worked perfectly. It was a toss of a coin as to which to fit on the 920. I’ll take this as ‘a sign’ that I shudda stuck with the sump type!
I think the fixation of the breather body could be further simplified providing clearance to your TTI gearbox.
Why not provide four thread inserts in the crankcase which appear to have sufficient thickness, slim down the inner housing, enlarge the 4 bores and affix the outher breather housing using longer screws. I haven't done this mod myself but I believe it will resolve some shortcomings in the design. Maybe Jim will chime in here.
Knut, if the engine were not yet assembled I venture to suggest it could be simplified further still.
As standard, the breather comes with an adapter plate that mounts on the standard Combat style fixing points. The reed valve and outer housing then mount onto this adapter plate.
This adapter plate adds 1/4” to the depth / thickness of the breather unit. Without this, I’d have no space issue.
The simplest method would simply be to dispense with the adapter plate altogether and simply drill and tap 4 new holes into the (plenty thick enough) crank cases and mount the reed valve outer body directly onto the crank case. If this was combined with the countersunk screws idea as suggested by gtiller, there would be enough space to hold a party in there!
My mistake was doing none of this! I thought about it, but then thought “lots of people use these, so why fix a problem that doesn’t exist”.
But that’s the power of hindsight I guess!
Irrespective, I ain’t investing any time in re designing / re machining this breather, I’ll be making up a simple blanking plate and using the Comnoz sump type breather.
For those who aren’t familiar with the Comnoz sump breather, it’s a fabulous bit of design, easy to install, no machining etc required, works perfectly at breathing AND at emptying a sump full of oil when the bikes been stood a while.
You can see it, and buy it, here:
If anyone who is NOT running a motor with Maney cases, Maney belt drive and TTI box requires a brand new, unused, cNw breather, PM me.
Is there enough gearbox adjustment to fit a longer belt?
Yes, a longer belt would have done it Ralph, although that’s not the way I wanted to go. Anyway, it’s all done now, fortunately I managed to do it without removing the engine.
Blanking plate in place:
Sump breather in situ. A neat and functional solution. Well done Sir Comstock...
You have my sympathy, Nigel. I did the same thing on my MK3 restomod. I built a similar breather at the back of the engine, and after installing engine and gearbox I couldn't adjust the gearbox enough. I pulled the engine and shortened the breather, solving the adjustment problem, but now I can't remove the gearbox unless I pull the engine first! I should have done what you did, and gone with a different breather. Oh well. Anyway, yours is really starting to look good.
Your 1007 hot rod build progress is ahead of mine, but I’m on a roll now Ken, might beatcha to it...!
Superb really enjoyed the thread whats the idea behind the sump breather Eddie is it to do with crankcase pressure?
Yes, it’s a one way reed valve that allows crankcase gasses out, but does not allow air back in, thus preventing the build up of positive pressure in the crank cases.
Thanks Eddie guessing that'd hit the frame rail on the 68' Just been reading up about positive pressure very interesting
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