1962 Model 88; previously 1957 basket case value?

[Kiwi]

Correct in theory as you say and by that definition you agree that the gear pump will pump more flow with more rpm and therefore with this particular engine there will occur some more pressure however slight?

[wetdog]

"I remain of the belief that increasing the speed of the pump will increase volume and pressure as there are already restrictions in the system so adding more flow will affect pressure from the original setup to what degree is the debatable element."

if the restrictions remain the same this is true

[R]

Posted at about the same time.

Have you checked what pressure your pressure relief valve is actually set for ?
And how the pressure stands up in its present setup.
Simply shimming the relief valve to a higher pressure will push more oil through the motor, rather than dumping in back into the timing cover - and potentially superheating the oil if it does a lot of simply recirculating.

The Commando (later ones) altered the way the oil was dumped out of the relief valve.
This helped prevent churning and superheating.

While there may be no harm in upping the oil pump speed/output, there may be no benefit either- if it all simply goes out the relief valve.
Nortons weren't known for bottom end oiling problems - in fact they were considered one of the strongest of the times ??
If it ain't broke...

[Kiwi]

Yes good point, I do not know what pressure I can expect in the first place as I have not been able to check a running engine

[Kiwi]

Moving on.

Was the original Speedo drive on the back hub 2:1 ratio?

[R]

Yes good point, I do not know what pressure I can expect in the first place as I have not been able to check a running engine

The workshop manual should give that vital number.

Earlier dommies were 40 psi (I think, without rustling up the handbook).
It was upped a bit by the time of the Commando = 50 or 55 psi ??

Since its all external to the motor itself, can all be attended to later if necessary.

[R]

Was the original Speedo drive on the back hub 2:1 ratio?

What does the parts book say - and what speedo do you have. ?
Doing it by the book is the only way, unless you are improvising

22888  is Nortons/Smiths number for early 1960s, but has a few more later type numbers ?
It is listed as 2:1 Norton triumph BSA fitment.

[Kiwi]

Its a Smith's chronometric SC 3303/17. 1548

[R]

Someone on the NOC states that thats a 120 mph chrono, correct for  1961 Nortons and thereabouts
(SS and 650 had 150 mph !).

[Kiwi]

Great news! (for me)  I have found a well regarded 45 year veteran Norton Mechanic who has started to reassemble my engine! When you can be shown first hand by someone it helps join the dots big time! not so much the reassembly but the little things, minor modifications here and there that one would never think of.

Interestingly he regularly puts the six start gears on the early oil pumps as normal practice and enlarges the oil gallery specifically for feeding about twice the oil to the top end, allowing us to utilise the scrolled rocker shafts. He also said it was quite common to put the 3 start gears on the later pump with a similar outcome.

He commented that putting a late model/Commando 6 start geared pump on the pre 1963 engine causes excess oil consumption from flooding the crank case among other things.

Paul Dunstall's Norton Tuning book chapter 5, sheds some light on this also. (should have read this before starting the war of the oil pumps! ) Notably Dunstall refers to the 6 start gears being made for the older pumps as a special modification before becoming standard fixtures on the later pumps. It seems my question about putting six start gears on an early pump was asked by someone over 54 years ago!!!

The plan now is to go 60 oversize with the pistons and repair the other barrel with the broken fins as it will clean up at 20 oversize leaving me with a good spare.

wetdog and a couple of other people a few pages back recommended staying with the 60 oversize, when I was contemplating sacrilege and cutting up my original barrel (thanks for the good advice). When I commented about my original plan to the Norton mechanic he banished me to the naughty corner of his workshop for a few minutes to contemplate my own stupidity!

FYI I understand there is someone in the UK I think, who has had a number of (50)thou over pistons made and there may be some still available for a model 88, I am not able to use them, I will ask for details if anyone needs them?

[R]

Unless he assesses how much oil the pressure relief valve is bypassing, all this may be for nought though ?
The scavenge side of the pump has more capacity than the feed side, so the sump should never be overfull, no matter which pump is fitted ?

Its unclear too from those words how he is getting twice the oil to the top end ?
Pressure fed, or off the scavenge side. ?
Flooding the top end with oil is where many attempts to 'upgrade' the oil pump come unstuck.

??

[R]

The really important bit we should ask (again) is if the crank has been split, to check if the sludge trap is clean ot not. ?

Nortons without oil filters have a sludge trap in the crank, that can fill up and block off oil flow to the big ends if not cleaned out. Not good....

[chaterlea25]

Hi All,
I think it should be the other way round with plain rocker spindles for a pressure fed top end?
The scrollled spindles will allow too much oil to the head if fed under pressure
This floods the head with oil and much smoke ensues 
I have had a lot of these problems when building a 99 from parts, it had a six start oil pump gear fitted
I dont know if the oilways were modified but doubt it
It also spews oil out the crankcase breather
I now have the original 3 start gears and am going to fit those when time  permits
I believe the final Commando set up was to divert the oil from the PRV back to the feed side of the pump ??
as this lessened the excess amount of oil thrashing around in the crankcase

Regards
John

[Kiwi]

Hi John

Thanks for your comments

I have now fitted a Commando oil pump with 3 start gears, my old small pump had too much lash meaning it would allow oil to run out of the tank into the crankcase when not running.

My situation is:  Commando pump. 3 start gears, return fed rockers, oil feed galley to the pump enlarged to 1/4in, by pass valve set to 60psi, scrolled rocker shafts, standard dominator valve guides, barrels honed with 360-400 grit.

The oiling system with the above setup keeps equilibrium up to 4500 RPM I am told.

The enlarged oil feed galley prevents cavitation usually caused by installing a higher volume pump.

Pressure fed top end in a dominator requires Commando guides with seals and plain spindles to prevent excess oil burning as you say.

Cylinder honing with 360-400 grit is important as a courser hone will cause excess oil burn during running in and beyond most likely.

I should have my motor re=assembled this week and hope to have the bike running within the Month

[Kiwi]

Question.....

In the attached photo you can see a swage in the frame on the right hand side top bar oposite to the tank rubber, the bloke who is doing my engine saw the frame for the first time yesterday and commented that it was there for the Manx engine as a rule and we pondered why it would be used in the Dominator.

Any history on it out there?