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First Manx/Inter engine strip

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First Manx/Inter SOHC engine strip

Posted by christian_wyss at Thursday 19:47

Hello,

Going to strip my first Manx/Inter SOHC engine:

- Anything special I should take care of?

- Is there anything easier to do while engine in frame? Like taking valves springs off,

unscrewing crank nut or whatever...

 

- And for rebuild?

Re: First Manx/Inter engine strip

Posted by arne_eftestol at Friday 10:27

Christian

It depends heavily of what facilities you have.

I find it crucial to have a engine stand, if not you might find it easier to perform some operations while the engine is in the frame...

Have you got any literature to guide you ?

Regards

Arne

Re: First Manx/Inter engine strip

Posted by jonathan_newton at Friday 15:36

Crack your big fixings whilst its in the frame, drive sprocket, bevel drive,cam  drive, cam box and head if poss, anything   that may prove tight and its wobbling around on the bench.

I usually leave it intact so you dont have a loose piston or shaft flailing around but its a little heavy.   I have a swivel vice that I stand it in to strip the bits and pieces before parting the casings.   Measure everything, count everything and document it Photos photos photos. 

Shims on the bevel drive, gap in the oldham coupling, turms on you piston oiling bolt.  Keep your head and cam box bolts in their respective locations, cylinder base gasket/ shim(s).

As Arne, said get a book I got one if you need a copy.  Its not complicated but done right you probably not ever need to do it again.  Is it Magnesium casing?   How far you going and why?

 There is a small screw on the right casing lower rear corner, dont forget it.

 Ill help where I can

 

Good luck,  Its a nice motor to work on

 

Jon   

Re: First Manx/Inter engine strip

Posted by christian_wyss at Saturday 18:29

Arne,

Got enough room to do it, and also a few tools. Holding the engine on the bench is of course essential. Am a little poor in literature actually, what I have now is :

- Inter Parts List 46-49

- Don't know how you call it in English, it's a drawing of an open engine from Motor Cycle

- Notes on the assembly of Norton cammy engines by Georges Cohen

- Servicing the Double-o.h.c. "Manx" Nortons by Bruce Main Smith

Last one is a multiple times copied copy and is not that easy to read.

 

 

Jon,

Was thinking of taking valves, cambox, head, barrel and piston off. But now would like to know the compression ratio before taking things off. And correct me if I'm wrong, but an"easy" way is to put the spark plug hole "vertical" and fill up with oil until the first thread with piston TDC.

Could still take the cambox off and crack the big fixings as you said.

 

Where is the piston oiling bolt? And how many turns should it be turned or unturned?

 

Would appreciate your book, and yes it's Magnesium casing, not to be heated with a torch flam!. How far don't know yet but far enough to completely clean it because it had R40 in it and was sleeping more than 23 years with some in the engine.

 

Thank you for your help.

Regards,

Christian

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Re: First Manx/Inter engine strip

Posted by paul_standeven at Sunday 02:46

The engine in your diagram is a long-stroke featherbed Manx, which will have few parts in common with an International engine.

You don't say what engine you have, or what frame it's in.  That does make a difference as to how you go about removing the engine, and how you begin to examine it

I would suggest undoing the engine sprocket nut before dismantling the primary or final drives.  I have a large socket for the engine sprocket nut, a long lever and a foot on the rear brake pedal does the trick.  Put it in top gear first....

The ohc engines were race engines designed to be serviced in the frame.  You can take the cam-box off if you are careful..  Undo the four bolts holding the cam-box to the long head nuts, and the large nut at the base of the vertical shaft.  The cam box will then come off, be careful as you wriggle if out from under the frame top tube.  Just don't let any of the bits fall off, particularly if you have the Hoffman self-aligning ball bearings in the vertical shaft. ...  People were using the SKF EE6 bearing even in the early '50s when the Hoffman bearing was readily available (at a price) due to this problem

The external hairpin valve springs were intended to be accessible so you could replace them during a race, one at a time.  Don't take the valve springs off before removing the head.  You don't want a valve to drop in.

If you take the cylinder head off, the engine will me smaller and much more easily managed.  But don't forget to take a good look at the combustion chamber and joint faces as you do so.

Paul

Re: First Manx/Inter engine strip

Posted by arne_eftestol at Sunday 09:49

Christian

I will be back with a better response to your questions later, but could you please state the year of your bike ?

Regards

Arne

PS. Mine is a 1948 manx

Re: First Manx/Inter engine strip

Posted by ian_soady at Sunday 10:45

Previously paul_standeven wrote:

The engine in your diagram is a long-stroke featherbed Manx, which will have few parts in common with an International engine.

I would suggest undoing the engine sprocket nut before dismantling the primary or final drives.  I have a large socket for the engine sprocket nut, a long lever and a foot on the rear brake pedal does the trick.  Put it in top gear first....

Paul

 

 

I always use a sprag for engine sprocket nuts as I think it's kinder to the power train - and never wedge things between the back wheel spokes as some barbarians do!

Any old bit of alloy or mild steel will do provided it's strong enough to take the compressive force. The pic shows it in position for tightening.

 

Ian

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Re: First Manx/Inter engine strip

Posted by ian_allen at Sunday 17:08

Hi.

I thought some of you might be interested in a jig that I built to enable me to torque up (and undo) the two nuts on the SOHC camshaft.

Using nothing more than an angle grinder, a pillar drill and various taps and dies, it’s made from a piece of right-angled 3” high grade stainless – the type used in the construction industry – mine came from an offcut I found in a skip at work. It’s tough stuff and I haven’t found a need to harden the metal to cope with the torque involved. You’ll need a piece about 8” long.

Cut a suitable size piece on which to mount the cam-box. Start by drilling and tapping two holes for the long bolts (it’s ¼” thick so it has plenty of ‘meat’ to take the bolts) that hold the cam-box. Grind a cut-away for the top bevel housing. Drill two larger holes to clear the pad adjusters if required.

From what’s left of the steel, cut two plates 1½” X 3¾”. Mark out an 11mm or 7/16” square the centre of which should be ¾” down from the top (narrow) edge on one of the plates. Mark the centre of the square. Now get the other plate, align and clamp the two together and drill through both using a 10mm drill. Take the first plate and open this out to 11mm or 7/16” using a square file to neatly fit the square end of the camshaft.

Take the second plate and using the 10mm hole as a guide, drill it out (using a ‘blacksmith’s drill) to 7/8”. Place the L/H threaded camshaft nut over this hole and mark around it – I used insulating tape – and file it out to shape. All this is bloody laborious but worth it in the end!

Mount the cambox including the shaft, spacers, cams and bearing, horizontally on the jig. Put the L/H threaded nut on and then place the second plate on the nut - check to see if a spacer plate or washers are required to enable it to sit true over the nut.

Once this is done acquire two suitable studs. I used two old Roadholder bottom yoke studs and cut the thread further on the ‘long’ side. Then take the first ‘square hole’ plate and drill two ¼” holes 3” down from the top edge and about 7/8” apart. Going back to the cam-box on the jig with the spacers and the second ‘hexagonal hole’ plate over the nut, place and align the first ‘square hole’ plate and using the ¼” drill bit mark the second plate. Drill the second plate and repeat the above procedure to mark and drill the spacer plate and the main body of the jig.

Finally drill the two plates out to the require stud size. Then drill and tap the main body of the jig to take the studs. Remember to use the pillar drill to start the taps off ‘square’.

All that’s needed then are some nuts for the studs and an 11mm or 7/16” square section socket to torque up the L/H threaded nut  – these are available from http://www.davidharriesstore.co.uk/ or through http://www.impactsocket.co.uk/ who will tell you who your local stockist is.

Quite a bit of effort to make, but, it means your not risking levering on the bearing behind the large bevel gear nor are you relying on one bevel tooth to take the strain when undoing the nuts!

Cheers.

Ian (1948 350 Manx).

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Re: First Manx/Inter engine strip

Posted by ian_allen at Sunday 17:10

Here it is set up to undo the nut holding the large bevel or for undoing the left-hand camshaft nut.......

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Re: First Manx/Inter engine strip

Posted by ian_allen at Sunday 17:12

......and again for doing up the nut...

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Re: First Manx/Inter engine strip

Posted by ian_allen at Sunday 17:13

....finally setting the torque. For some reason this site wouldn't let me load 4 photos on one post!!!!

Cheers.

Ian.

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Re: First Manx/Inter engine strip

Posted by Michael Rettie at Sunday 18:33

More on this issue of nut tightening:

http://www.vintagenorton.com/search?q=camshaft+nut

and my version of Ian's jig. Meant for stabilizing camshaft to tighten LH nut after torquing opposite RH nut.

http://www.vintagenorton.com/2017/12/mikes-take-on-oz-cambox-jig.html

Great minds.............in spite of what my domestic supervisor may think.

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