N15CS few questions

trident sam · Dec 3, 2021

I've been looking recently at N15CS Nortons and really fancy one so :-
1/ Do they make a viable road bike ? I'm not expecting a Commando but would want rides of @150 miles to be ok on bike and me (63 yrs old)
2/ I presume they don't have a 'proper' oil filter, is it easy enough to mount a Commando type
3/ What is the spares situation like, I presume engine spares are catered for, but what about the rest
4/ I've never had a magneto bike, are they generally reliable

Other thoughts and opinions on the bike are welcome.

mdt-son · Dec 3, 2021

1/ Member Ludwig should be able to tell you. He has toured all over Europe on one.
2/ If you chose a model built after 02/1966 (serial no. 116372), the oiling system is identical to the Commando, except for oil filter and possibly crankcase venting. Fitting an oil filter should be an easy (and mandatory) task.
3/ The spares situation is very good, apart from primary covers.
4/ 1968 N15CS (I guess from the summer of 1967 onwards) came with points ignition, similar to the P11. For ease of starting, reliability and accurate ignition on both cylinders (!!), I suggest fitting an EI. Timing should be fairly simple even though the points housing is located "behind" the engine and thus a bit inaccessible.

Earlier models with Amal Monoblock carbs run better than the late version with Concentric carbs, but they are also thirstier.
The Achilles heel of the G/N15 series is their primary drive. A simplex chain is simply not up to the job of handling the torque of the Atlas engine. The clutch pack, although nicely designed and uprated for 1962, is fairly stretched and many owners complain about clutch slip and wear. There are options (e.g. convert to a Commando type clutch & fit a Madass rubber cushioned rear hub).

I hope this helps.

- Knut

trident sam · Dec 3, 2021

mdt-son said:
1/ Member Ludwig should be able to tell you. He has toured all over Europe on one.
2/ If you chose a model built after 02/1966 (serial no. 116372), the oiling system is identical to the Commando, except for oil filter and possibly crankcase venting. Fitting an oil filter should be an easy (and mandatory) task.
3/ The spares situation is very good, apart from primary covers.
4/ 1968 N15CS (I guess from the summer of 1967 onwards) came with points ignition, similar to the P11. For ease of starting, reliability and accurate ignition on both cylinders (!!), I suggest fitting an EI. Timing should be fairly simple even though the points housing is located "behind" the engine and thus a bit inaccessible.

Earlier models with Amal Monoblock carbs run better than the late version with Concentric carbs, but they are also thirstier.
The Achilles heel of the G/N15 series is their primary drive. A simplex chain is simply not up to the job of handling the torque of the Atlas engine. The clutch pack, although nicely designed and uprated for 1962, is fairly stretched and many owners complain about clutch slip and wear. There are options (e.g. convert to a Commando type clutch & fit a Madass rubber cushioned rear hub).

I hope this helps.

- Knut

Thanks Knut, I really had no idea about the simplex primary chain and must admit it puts me off, is there any sort of conversion - chain or belt ?
thanks
sam

EstuaryBoy · Dec 3, 2021

Okay, I know P11 is a bit lighter but... I had 'lighter' clutch springs made for my P11, my reasoning being that the Atlas that donated it's clutch was not only a weightier machine, but built for pillion passengers and some had a chair attached too...
Didn't experience slippage, though I tried

But again, single seater only.

mdt-son · Dec 3, 2021

EB, you can't escape clutch plate and clutch centre wear though. I believe part of the clutch slip is due to gear box oil ingress, DynoDave's special center nut should put an end to oil ingress.
Slippage will depend on the applicable torque (and torque resistance) of course. The light P11 will fare better than the rugged G15s and the Atlas.

-Knut

mdt-son · Dec 3, 2021

trident sam said:
Thanks Knut, I really had no idea about the simplex primary chain and must admit it puts me off, is there any sort of conversion - chain or belt ?

Sam, there is no off-the-shelf solution, chain or belt. NEB Engineering and some other companies offer clutches and belt drive kits. NEB Engineering's 30mm belt drive kit will work.
These clutches do not have cushioning (unlike the AMC clutch) and fitment of a cushioned rear hub is recommended, or the gear box will suffer. I have yet to find a belt drive kit offering a cushioned clutch hub.
BTW, I am investigating the applicability of the CNW clutch kit for the G15 series .... as you may now, it's one of the best kits available (for the Commando, that is).

The downside of fitting a belt drive kit is that the primary covers no longer fit (the belt is wider and runs further out than the simplex chain). So, a tailored set of primary covers need to be made.
This fact puts most people off. A fabricated spacer approx. 15mm wide may be used - it's a half solution only, and then there's the alternator mounting ....
if you are not a guy who loves to work out one off solutions, or spend two grand on specially milled primary covers, I recommend you stay with the Commando.

-Knut

trident sam · Dec 3, 2021

mdt-son said:
Sam, there is no off-the-shelf solution, chain or belt. NEB Engineering and some other companies offer clutches and belt drive kits. NEB Engineering's 30mm belt drive kit will work.
These clutches do not have cushioning (unlike the AMC clutch) and fitment of a cushioned rear hub is recommended, or the gear box will suffer. I have yet to find a belt drive kit offering a cushioned clutch hub.
BTW, I am investigating the applicability of the CNW clutch kit for the G15 series .... as you may now, it's one of the best kits available (for the Commando, that is).

The downside of fitting a belt drive kit is that the primary covers no longer fit (the belt is wider and runs further out than the simplex chain). So, a tailored set of primary covers need to be made.
This fact puts most people off. A fabricated spacer approx. 15mm wide may be used - it's a half solution only, and then there's the alternator mounting ....
if you are not a guy who loves to work out one off solutions, or spend two grand on specially milled primary covers, I recommend you stay with the Commando.

-Knut

Thanks Knut, your last sentence is probably the most applicable to me, bit dissapointed I must say. Oh well, it'll probably have to be another Rocket 3 (BSA- that is )
Thanks for your time and knowledge.
sam

milfordite · Dec 6, 2021

I recently finished the refurbishment of a derelict N15CS, circa 1968. I was surprised how nice it is to ride, assuming no expressway trips at high speed. IFIRC, I put a 20 tooth sprocket on the gearbox to help with the vibes. A 21 would be better. The engine has plenty of torque and it's a light bike. I needed some parts other than engine and trans, and Walridge Motors in Canada supplied a new rear fender, tail light housing, chainguard, exhaust pipes and seat. The Matchless Owners Club has some stuff as well, since the chassis and bodywork is Matchless. If you are just going to ride it on short runs, I wouldn't worry at all about the clutch and primary chain. Install an aftermarket distributor in place of the mag along with EI, and new carbs. Let's face it, few of us old farts are going to hotrod the old dears like we would when we were kids. Just make sure the parts are in good shape and ride it!

Yorkie · Dec 6, 2021

milfordite said:
I recently finished the refurbishment of a derelict N15CS, circa 1968. I was surprised how nice it is to ride, assuming no expressway trips at high speed. IFIRC, I put a 20 tooth sprocket on the gearbox to help with the vibes. A 21 would be better. The engine has plenty of torque and it's a light bike. I needed some parts other than engine and trans, and Walridge Motors in Canada supplied a new rear fender, tail light housing, chainguard, exhaust pipes and seat. The Matchless Owners Club has some stuff as well, since the chassis and bodywork is Matchless. If you are just going to ride it on short runs, I wouldn't worry at all about the clutch and primary chain. Install an aftermarket distributor in place of the mag along with EI, and new carbs. Let's face it, few of us old farts are going to hotrod the old dears like we would when we were kids. Just make sure the parts are in good shape and ride it!

Who makes an aftermarket distributor for the N15? I'm in the process of restoring an N15 and I would really like to get away from the mag. Thanks.

Gilesy · Dec 6, 2021

It's a lovely bike to ride. I had the mag rebuilt and put a mikuni carb on it and it starts really well. I put a plate under the barrel to drop the compression a bit so it is easy to kick over. I've ridden it for trips of130 miles and it is brilliant. They look great!

ludwig · Dec 8, 2021

Gilesy said:
.l. I put a plate under the barrel to drop the compression a bit ..

Why? std compression ratio is only 7.5

Fast Eddie · Dec 8, 2021

Although a simplex chain ‘seems’ a bit old hat and spindly, realistically unless you’re gonna be dropping the clutch at peak revs for drag starts, or landing back to earth from jumps, I’d have thought it would be fine?

If they survived being ridden as hooligan desert sled machines back in the day, they’ll be up to the task of being a ‘classic bike’ today I reckon.

trident sam · Dec 8, 2021

Fast Eddie said:
Although a simplex chain ‘seems’ a bit old hat and spindly, realistically unless you’re gonna be dropping the clutch at peak revs for drag starts, or landing back to earth from jumps, I’d have thought it would be fine?

If they survived being ridden as hooligan desert sled machines back in the day, they’ll be up to the task of being a ‘classic bike’ today I reckon.

Yes, I've come to that conclusion myself and the way I would use it would probably be ok, so back to plan A

mdt-son · Dec 8, 2021

Yorkie said:
Who makes an aftermarket distributor for the N15? I'm in the process of restoring an N15 and I would really like to get away from the mag. Thanks.

You can buy a new points housing from AN. It has better weather proofing IMO than the "mag replacement" housing sold by Feked (item fkelectign489-A15) and others.

-Knut

milfordite · Dec 8, 2021

ludwig said:
Why? std compression ratio is only 7.5

That's true if you have the original dished piston. Since those are long gone, most engines will have the later pistons which give more compression. A plate will also help a bit with vibes.

EstuaryBoy · Dec 8, 2021

Just to throw another generalisation into the pot: As it's based on the Atlas engine, any head work that includes replacing the valves with Commando items will need the pushrods changing too, IIRC.....

ludwig · Dec 8, 2021

trident sam said:
I've been looking recently at N15CS Nortons and really fancy one so :-
1/ Do they make a viable road bike ? I'm not expecting a Commando but would want rides of @150 miles to be ok on bike and me (63 yrs old)
2/ I presume they don't have a 'proper' oil filter, is it easy enough to mount a Commando type
3/ What is the spares situation like, I presume engine spares are catered for, but what about the rest
4/ I've never had a magneto bike, are they generally reliable

Other thoughts and opinions on the bike are welcome.

I use my N15 almost exclusively for traveling, paved and unpaved roads.
I'm older than you, but 500 -600 km/day is ( still) no problem.
But then, 99% of the parts on the bike are modified to make it a reliable and comfortable tourer.
The engine is basically an 850 Commando, with rebalanced crank, longer rods, lighter pistons ..
If you really want to use the bike over longer distances, you need a larger tank, better brakes, direction indicators, better electronics, better lights ..
The rear loop is too weak to carry luggage, the clutch is not really up to the job, you need an oil filter, maybe a cooler, also address the vibration problem..
The std N15 is not very maintenance friendly : primary case, chain adjusters, seat removal ..
There are solutions for everything.
for ex: under the swing arm spindle, there is a lug that can be used for an oil filter support.
(mount it vertically, not horizontal like a Commando)
A Commando clutch with a double row chain will fit in the original primary case, etc..
Name a part, and I will tell you how to improve it.

trident sam · Dec 8, 2021

ludwig said:
I use my N15 almost exclusively for traveling, paved and unpaved roads.
I'm older than you, but 500 -600 km/day is ( still) no problem.
But then, 99% of the parts on the bike are modified to make it a reliable and comfortable tourer.
The engine is basically an 850 Commando, with rebalanced crank, longer rods, lighter pistons ..
If you really want to use the bike over longer distances, you need a larger tank, better brakes, direction indicators, better electronics, better lights ..
The rear loop is too weak to carry luggage, the clutch is not really up to the job, you need an oil filter, maybe a cooler, also address the vibration problem..
The std N15 is not very maintenance friendly : primary case, chain adjusters, seat removal ..
There are solutions for everything.
for ex: under the swing arm spindle, there is a lug that can be used for an oil filter support.
(mount it vertically, not horizontal like a Commando)
A Commando clutch with a double row chain will fit in the original primary case, etc..
Name a part, and I will tell you how to improve it.

Many thanks Ludwig, I'm sure if I get the bike I will be asking a lot of questions of you. Your bike is beautiful, and I'd certainly be doing some mods that you have listed. thanks again
Sam.

gpzkat · Dec 8, 2021

Nice bike Ludwig, following this as I'm working on getting my '66 N15CS together. A bit of delay as I've been restoring a '69 Airstream Caravel but that's almost done. Cylinders are bored and got new pistons, also valve/guide work and crank journals redone. I have fork sliders and disc brake from a Commando, some improvement there I expect but not miracles. I like the mufflers but with my budget I may just put some baffles in the pipes if possible. Time will tell.

gpzkat · Mar 5, 2022

Threadjacking! Ludwig, especially since you offer real world experience - I'd like to ask about RPM and final drive ratio. I want the bike to move along at around 65 MPH tops at a somewhat 'relaxed' and presumably less vibey RPM. I don't care that it will be slower through the gears than it would be stock. I have looked at the ratios with a calculator such as this one (which is fun, but I need to make sure my gear ratio #s are correctly factored in), but need a target RPM range.

Do you have any info to share regarding a good target RPM to suit what I'm after? Most engines have a sweet spot, generally speaking, and particular to the engine no doubt. Mine will be stock spec with original pistons but .040 over. Any ballpark info will help.

N15CS few questions

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