850 MK2 engine mods

click · Jan 5, 2009

Hi,

I have an opportunity to build a Norton 850 from scratch.

The engine is a MK2 850.

Since the engine is being built from the bottom up what mods are worth doing?

I have the following list:

Superblend bearings
Layshaft ball bearing to a roller?
Lip seals for the kickstart and shifter shafts in the tranny cover, and a clutch rod seal on the other side?

Any other mods worth doing?

Is it worth doing any work on the head for running on unleaded?

I’m just trying to end up with as reliable a classic I can, I’m not looking for ultimate performance.

Are there any major engineering differences between the 850 MK2 & MK3 engines?

Can an electric start be retrofitted to a MK2? Any idea of cost & the parts required?

Thanks in advance for any advice.

norbsa48503 · Jan 5, 2009

The Valve seats are the same steel as the valves nothing needed but a really good valve job. A good valve job has tight fitting valve guides made from Amco50 material the holes in these guides must therefore be perfectly concentric with the valve seats. Find someone with the right equipment seen here as an example. http://www.srm-engineering.com/engine-a ... ng-service
Other than that air, fuel, fire. Sky's the limit

mwoo · Jan 5, 2009

Mk2 Mods

There are quite a few differences between the Mk2 and Mk3 engines/trannys. The electric start cannot be fitted to the Mk2 however Old Brits in the States are working on an electric start system for pre Mk3s (looks as though it will be bloody expensive judging by the parts and work involved though!!). One modification I did to my Mk2A was to fit a double-sided gearbox mount (from RGM Motors) - this pulls and holds the gearbox equally from each side of the bike - I've found that chain tension is maintained better since fitting (I have a belt drive fitted).
I've done most of the mods you propose and would agree with all of them.

HtH

bigstu · Jan 6, 2009

Hi Click
I just restored an 850Mk11a
This model has superblend main bearings from new as standard.
These are my recommendations for modifications/rework:-
1) Split the crank and clean the sludge out.
2) Rebuild the engine in the normal manner. (Relpace/recify worn parts)
3) Check your head exaust port threads.
4) Rebuild your oil pump carefully using a surface grinder.
5) Fit Pazon electronic ign.
6) Fit a RGM belt drive with sureflex clutch plates and run it dry in conjuntion with oil seal on clutch pushrod and also double adjuster. Fit a featherlight Tethlon lined clutch cable from Venhill in Surrey.
7) Replace your carbs with new ones. I went for Amals again but some go for a single Mikuni.
8) Fit a crank positive vent valve.
9) All your upgrades are good ideas.
10) If you are replacing your Isolastics go for Norvil version 'vernier' system. No machining required.
Stuart.

bigstu · Jan 6, 2009

Major differences between MK11 and MK111 engine:
Electric 'assist' starter system.
Gearlever on the left.

click · Jan 6, 2009

Hi All,

Many thanks for all your replies, I'm finding this very useful.

RoadScholar · Jan 6, 2009

I am, right now, completing mods and assembly on a '75 MK III engine; I have:

1) Had the head redone (valves, giudes, springs, retainers, mushroom adjusters) I also had the ports cleaned up with the intakes matched to the manifolds; my service opened up the exhaust ports. Also had the head milled to produce a CR about 9.8:1 (give or take).

2) New Hepolite pistions, .020 overbore, with ringes checked for end gap.

3) I have MegaCycle 5600 and a WebCam 12A camshafts, probably going to go wth the WebCam, fully degreed in and checked for deck clearance. The tappets have had a 3 inch radius cut on to accomodate the MegaCycle cam, but will aid in quieting the operation of both.

4) Bottom End: Very important to get this done right or everything else is like burning money: Magnafluxed, cleaned, clearanced and shot peened. Having the flywheel radically cleaned up and having new central fasteners installed. Everything that recriprocates or rotates is balanced.

5) I sent my engine cases to the Colorado Norton Works for cleaning and, most importanly, to have them add their crankcase ventilation system that offers the promise of maintaining a vaccume during operation, adding a few horses and eliminating the Nortons proclivity to extrude oil.

6) I'm a traditionalist, so new 32 mm Amals are fitted, I am starting with 260 mains, .106 needles and a 3.5 cutaways, these will draw air through a K&N filter. The original carbs are on their way to Lund for new slides and to be bushed for when the Norton eats these new carbs.

7) a Pazon will fire the mixture and get it's juice from a 220 watt Sparx with soild state regulator.

I am hoping for an honest 65 RWHP, but even with all the attention to increasing reliability you dance with this as you would your grandmother; and that is to imply that Granny can tango, just not all night. God knows it would be as difficult to replace one or the other...

My primary advice to you would be to pay particular attention to your bottom end: Clean it, magnaflux it, shot peen rods, check for concentricity of rods/journals, check for proper clearance adjust as necessary, balance everything, replace ALL the fasteners--never use bottom end fasteners twice unless you want to redo the bottom end twices as well. New Super Blends on both sides properly checked and adusted for end play

Best wishes,

RS

click · Jan 6, 2009

Hi,

Wow!!, there's the wrong way, the right way & the RS way!!

That is an extremely comprehensive list, I really appreciate your advise. Best of luck with the rest of the rebuild, sounds like it will be of world class standard.

Many Thanks

RoadScholar said:
I am, right now, completing mods and assembly on a '75 MK III engine; I have:

1) Had the head redone (valves, giudes, springs, retainers, mushroom adjusters) I also had the ports cleaned up with the intakes matched to the manifolds; my service opened up the exhaust ports. Also had the head milled to produce a CR about 9.8:1 (give or take).

2) New Hepolite pistions, .020 overbore, with ringes checked for end gap.

3) I have MegaCycle 5600 and a WebCam 12A camshafts, probably going to go wth the WebCam, fully degreed in and checked for deck clearance. The tappets have had a 3 inch radius cut on to accomodate the MegaCycle cam, but will aid in quieting the operation of both.

4) Bottom End: Very important to get this done right or everything else is like burning money: Magnafluxed, cleaned, clearanced and shot peened. Having the flywheel radically cleaned up and having new central fasteners installed. Everything that recriprocates or rotates is balanced.

5) I sent my engine cases to the Colorado Norton Works for cleaning and, most importanly, to have them add their crankcase ventilation system that offers the promise of maintaining a vaccume during operation, adding a few horses and eliminating the Nortons proclivity to extrude oil.

6) I'm a traditionalist, so new 32 mm Amals are fitted, I am starting with 260 mains, .106 needles and a 3.5 cutaways, these will draw air through a K&N filter. The original carbs are on their way to Lund for new slides and to be bushed for when the Norton eats these new carbs.

7) a Pazon will fire the mixture and get it's juice from a 220 watt Sparx with soild state regulator.

I am hoping for an honest 65 RWHP, but even with all the attention to increasing reliability you dance with this as you would your grandmother; and that is to imply that Granny can tango, just not all night. God knows it would be as difficult to replace one or the other...

My primary advice to you would be to pay particular attention to your bottom end: Clean it, magnaflux it, shot peen rods, check for concentricity of rods/journals, check for proper clearance adjust as necessary, balance everything, replace ALL the fasteners--never use bottom end fasteners twice unless you want to redo the bottom end twices as well. New Super Blends on both sides properly checked and adusted for end play

Best wishes,

RS

Coco · Jan 6, 2009

As many say, the sky is the limit. My 1 year MKIII project is now officially on year 2+ but it is drawing to a close. I just got word my engine is coming back from the rebuilder so my dream will turn into reality soon.

I'll gave a bigger grin than this guy here -

Just what ever you do, make sure it is done right so you will not be let down by shoddy work. Always budget extra cash for problems that may pop up out of nowhere.

click · Jan 6, 2009

Hi,

I know I need to make my own mind up but I'm just seeking other's opinion.

All things being equal, would I be better building up a bike with a MK3 engine rather than a MK2?

I'm aware of the electric start & rear disc differences between the MK2 & 3 but are there other more subtle engine & frame differences which are worth considering?

My simplistic thinking is that the last generation(MK3) should? benefit from lessons learnt from various design weaknesses from previous models? or is this fuzzy logic!!!

Many Thanks

Seeley920 · Jan 6, 2009

Hi Click,

You could give Cormac at Redline in Rathdrum a call too. I know he used to race commandos so he might have a few bits still lying around too. Also be careful who you get to do your head......a certain business who were in Wexford and have now moved back to England aren't really recommended......ask how many heads of mine he ruined for starters!! Don't forget that the isolastics will soak up most of the vibes from the motor, jsut get it nice and free. A higher balance factor is really only necessary if the engine is rigidly mounted e.g. Seeley or Featherbed frame.

Cheers

daveh · Jan 6, 2009

Hi Click and Seeley 920. Including myself, that makes at least three members of this forum who are in Ireland.

Click, welcome to the forum. I hope your rebuild goes well. This forum taps into a large knowledge base, so you will get some excellent advice. As you are in Dublin, you're probably not that far away from me. If I can be of assistance, email me from the members' list.

Dave

click · Jan 6, 2009

Hi Seeley920 & Daveh,

It's a small world!!

I've dealth with Cormac before from Redline but not about Norton's. I'll give him a shout, thanks for the info.

Dave thanks for the offer when I perform my first FUBAR I'll head in your direction

Do you have a Norton at the moment?

Many Thanks

Click

daveh · Jan 6, 2009

Hi Click, yes, I have an 850 Mark 1 that I bought in England in November '07 and rode 250 miles back to Ireland. Initially, it looked to be in quite good nick but, as I delved into it, I discovered a long list of things that needed sorting. It took a lot of work and some expense to get the machine to the stage where it is now a pleasure to ride. And of course that work continues...!

bill · Jan 6, 2009

click
a MK3 bottom end WILL NOT interchange to any earlier years. the crank and cases are wider along with a diffrent bolt pattern where the primary case bolts on.

windy

click · Jan 6, 2009

Hi windy!,

You must have taken me up wrong I was not suggesting that I would perform any brain surgery with a MK2 & 3!!

I'm just trying to figure out is it worth holding out for a MK3 over a MK2, is there enough of a difference to make a difference!!

The bottom line; I'm trying to figure out, from a pure engineering point of view, is that MK3 far better than the MK2??

Thanks for your comments.

Click

bill said:
click
a MK3 bottom end WILL NOT interchange to any earlier years. the crank and cases are wider along with a diffrent bolt pattern where the primary case bolts on.

windy

BillT · Jan 6, 2009

I think a MkIII is more different than better. Many of the changes were made in order to bring the bike into compliance with the new norm.

click · Jan 6, 2009

Hi BillT,

Interesting. Another way of asking my question is:

Is the 850 MK3 just an 850 MK2 with a rear disc, electric start & gear lever on the 'wrong' side

OR are there other mods made to the MK3 which are worth thinking about.

I know these type of questions are somewhat pointless, ever chasing the nirvana Commando! Ultimately I'm sure the best Commando ever will be the one I own

Once again thanks for your reply.

Click

BillT said:
I think a MkIII is more different than better. Many of the changes were made in order to bring the bike into compliance with the new norm.

RennieK · Jan 6, 2009

bill said:
click
a MK3 bottom end WILL NOT interchange to any earlier years. the crank and cases are wider along with a diffrent bolt pattern where the primary case bolts on.

windy

This is interesting and should have a bearing on your main question click. I wonder why the crank and cases were wider. Maybe be to withstand extra forces from the electric start or was there some other reason that could be an "improvement" over previous years.

BillT · Jan 6, 2009

click said:
Hi BillT,

Interesting. Another way of asking my question is:

Is the 850 MK3 just an 850 MK2 with a rear disc, electric start & gear lever on the 'wrong' side

OR are there other mods made to the MK3 which are worth thinking about.

I know these type of questions are somewhat pointless, ever chasing the nirvana Commando! Ultimately I'm sure the best Commando ever will be the one I own

Once again thanks for your reply.

Click

For many, those differences are enough. Another change is the redesigned engine mounts, called isolastics, were were dramatically improved and simplified for the MkIII. I fit them on my '73. Rear disc isn't a major thing for me, as I rarely use the rear brake, anyway, and I like the shift on the right - gives my right foot something to do for a change!

If I were offered a MkIII, I'd snap it up in a minute.

I'd also jump at a '68 Fastback.

850 MK2 engine mods

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