Oil Pump Securing Studs or Bolts?

Bolts tend to wear the threads in alloy .Particularly with regular use. studs are also a more accurate positioning .

You need two of 06-7598  STUD  CEI  5/16" x 26  x  1-7/8"

Which is also near enough the same stud as used on the Roadholder Dominator Pinch Bolt - p/n 16664

The nut  torque setting should be no more then 15 ft lb.  This is the problem area as people assume that having 5/16" threads the nuts need 20 - 25ft lb of spannerwork on them and promptly pull the threads out of the cases.

Sorry Philip is wrong, This is a Mk3. Having been round Norton's for years and recently purchasing a project Mk3 I was surprised to see my oil pump was retained by bolts, [having just read The Norton Commando Bible and Mick Duckworth's Commando Book both mention "oil pumps retained by bolts"] as this may be a typo I am going back to studs. as Philip has mentioned I to thought that the thread would be CEI but no the bolts are 18 TPI Whitworth, the replacement studs that I purchased from RGM are threaded 18TPI one end and 24 TPI UNF the other, I have checked this against Andovers excellent website which shows a stud 06-2664 retained by a UNF nut 06-0348.  

Quite correct for a Commando Mk 3 Alan.  The info still stands for any Dominator and probably early 750 Commando. The studs having the same threads at both ends. The Timing Chain Adjuster studs are a bit different still.

The NVT parts book for the Commando 850 Mk3 from 1975 from engine no 325001, and frame number F125001 has the following for the oil pump mounting. 06-2664 oil pump stud. 14-0302, which replaced 27815 oil pump stud nut. there is a * against  06-2664 and 14-0302. At the bottom of the page, is listed the following. 60-2321 which replaced 18316 washer. 06-8109 replaced 27836 bolt. So the later Commando Mk3 models used a bolt and a washer to secure the oil pump to the crankcases. A look in the relevant parts book would have revealed the later updated parts that NVT used.

Watch out for the "oil pimp"

He is going to take the profit out of the conversion.

Mike

'...Oil Pimp...'

I'm just channeling 'Allo, Allo...'

I own 4 E-starts. 328xxx 329xxx, 330xxx, and 333xxx which is NOS (5 miles never registered).

All have helicoils , all have bolts.

As Tony posted Factory parts book shows   *  replaced by

60-2321   18316 washer

06-8109   27839  bolt

Facinating, I wonder why the change to bolts?.A few guesses, The bigger pump and higher speed put too much strain on the thin weak studs?, Daft owners kept stripping out the alloy threads? ,The alloy case getting pulled up and distorting the mounting?, Tolerances getting out of control and gears not meshing well so hole centers needing to be moved ?.Daft owners damaging things trying to lever the pump off studs?, Can't get decent studs made to order so use easy to get bolts?,   Take a guess?.

Robert,

I would agree with:

1. The alloy case getting pulled up and distorting the 26cei mounting?

2.  Daft owners kept stripping out the alloy threads? installing or cross threading wrong thread?

3. Up to 20M3S case threads are 26 CEI... helicoil only on damage repair

200000 series changed to 5/16-18 UNC stud X 5-16-24 UNF nuts Cases all helicoiled

300000 series cases continue  5/16-18 UNC stud X 5-16-24 UNF nuts Cases all helicoiled

325000+ cases helicoiled - 5/16 UNC bolt/washer

The last six engines I've assisted with building , five Mkllls and one Atlas all had the oil pump retained by bolts. On the basis that a number of members have found that their pumps are  retained with bolts, is it likely that Norton decided that this was the way to go. From the point of view of assembly time and cost,  bolts would probably have been cheaper. All the previously mentioned engines had heli coiled threads. It has been mentioned that this was probably to avoid thread wear from regular removal.  I think this to be unlikely as you're not going to be removing the oil pump every weekend. If you've built the engine correctly you shouldn't be seeing the oil pump for 50 or60 thousand miles.                                   I find the remark about daft owners to be offensive ,  I don't think that we have daft owners in the club,  some might not have the mechanical ability, knowledge or tools that older members have.  They might be misled or misguided by some of the answers I've seen on these forums, but this doesn't make them daft.

 Nobody said we have daft owners in the club. If you look at what owners did to bikes in the years gone by you will find astonishing ignorance of basic principals. I worked for many years alongside an MOT station , You would not believe the state of some cars and bikes that were in use and the owners were surprised when an MOT was refused. Now that classic bikes have acquired value and status and there are few repair shops that can be trusted to work on classics we have a new breed of owners that can do it for themselves and take the time to learn to do it well. In the past the opposite was often normal. Bikes that came back from America were either barely used and just neglected or comprehensivley bodged and abused. A throwaway consumable. That's not the case now. An illustration of this is that Commando frames had to be strengthened to cope with the common unloading routine in the main market .Chuck the cased bike off the back of the lorry. then ride it up and down kerbs and use off road as a scrambler. The uk market was just a small sideshow.

... but to my mind, using bolts into an alloy casting is bad practice and it should always be studs with nuts. I take the point that oil pump removal should not be a frequent occurrence. I think that the view that it was done as a production expedient is the right one.

Probably right Ian, but an expensive option, 2 helicoils and the time to fit. Perhaps at this time they were using air tools for assembly and two many slim studs stripped out the alloy.Answer bigger threads in the alloy?. Will we ever know?. I will ask my AMC factory mate when I see him .

Hi Robert, after your two comments about daft owners I could only assume you meant owners of Nortons,               ie: members , I was obviously incorrect, sorry, I wont do it again.                              Regarding modifications to Commando frames,  I recall the pleasure of speaking with Ken Sprayson at the first Cafe Racer event. I'm  sure he mentioned that the alteration to the frame was made to his recommendation after a frame failure caused a serious accident. So, nothing to do with careless unloading.

There were a number of frame failures in the US and I think some Lawsuits. So they looked into the way the bikes were unloaded and the pattern of use. I suspect they thought that there was little chance of a change of behaviour (after all if a Harley Tractor can take it!) . There is film of factory riders leaping the bikes off ramps and  other endurance testing showing that the bikes were ok for "normal" use.  Do you know many "Normal" Americans?. They reinforced the frames anyway, had to satisfy the main customers.

"Normal Americans" ???

What kind of snide comment is that?

I guess that we were normal enough to buy a Norton rather than a certain Milwaukee based unit.

Mike

There has to be a bit of room for humour. Norton expected that new owners would treat a  lightweight (compared to Milwaukee) road machine with respect and use it for the purpose designed for (ride to work,touring,etc.) They soon  learned that what was normal in the UK  was not the norm in the USA.

The later 650 / 750 Dommies had the Junction Block Stud deleted and replaced with a Bolt. I would suggest that over time this bolt is removed and replaced far more often than the Oil Pump Bolts.