N15CS oil tank mounting

Can anyone help with the rear oil tank mounting on an N15?
I didn’t have any of the parts, so am putting it together blind - of course the illustration in the parts book helps no end - haha!
So I’ve worked out that there is a spacer between the frame and the rear mudguard loop, but does the oil tank mount in between the mount and the frame, or on the inside of the spacer, or outside of the mudguard loop ? An image of this area of an original bike would be a miracle

I looked at my 66 G15. The rear oil tank mount is tight to the frame. The bolt that holds the seat down also goes through the rear oil tank ear.
I have a picture, but i'm still trying to post pictures

This how mine is fixed:


Although I own the bike from new (probably the last hybrid ever produced) it is no longer original.
The rear loop has been reinforced, etc..
I may have changed the position of the oil tank, to bring it more in.
You can see that the crease on the oil tank runs parallel with the frame tube.
This will also depend on the front tank mount:
Do you have a straight strap or a later one with an angle to bring the tank more inwards?
(= better, so that the filler cap won't poke in your leg)
Don't worry too much about originality ( they were all different) but try to mount the oil tank as stressfree as possible.
When you tighten the front mount, you get an idea where the rear mount should land.

Thank you Ludwig, this is very interesting and just the info that I needed. My bike is 1965 and the tank does differ slightly in the position and direction of the breather on the top and the direction of the crankcase breather on the back, I will check the mounting against your picture. Thanks again. Andy

franko said:

I looked at my 66 G15. The rear oil tank mount is tight to the frame. The bolt that holds the seat down also goes through the rear oil tank ear.
I have a picture, but i'm still trying to post pictures

Click to expand...

Thank you Franco, that is interesting as if I position the tank naturally, it also rests against the frame. The parts list for mine suggests that there should be the same spacer between the frame and mudguard loop both sides, but then there is no space for the oil tank, so it must go outside, but then it is not aligned! Maybe I turn down a spacer so it fits with the oil tank between the frame and the loop.

Andrew Jago said:

Thank you Franco, that is interesting as if I position the tank naturally, it also rests against the frame. The parts list for mine suggests that there should be the same spacer between the frame and mudguard loop both sides, but then there is no space for the oil tank, so it must go outside, but then it is not aligned! Maybe I turn down a spacer so it fits with the oil tank between the frame and the loop.

Click to expand...

Also interesting you have that type of seat mounting for a 66 bike - I thought that 65 onwards had the single rear mounting to the mudguard - maybe I should rethink that too !

I think I’ve done the image, but not sure ! Also, lots of images I see on N15s show the oil tank in the colour of the machine - is this standard or owner restoration? My tank is black and I can’t see any tell tail signs of another colour below. Obviously the cover would be in the finished colour, but why would the factory use expensive paint on something that was covered?

The Cover does not cover all of the tank. It is more like a heat shield for your leg. I have also seen several where the covers are chromed.
Hopefully, I will be able to post pictures this afternoon of the mounting.

This shows the oil tank mounted. The air filter sits straight along side it, so I believe it is orientated correctly.

It is clear that the front mount makes all the difference:

Andrew: oil tanks were always painted like the fuel tank.
Mostly red for an N15

Thank you both, really useful stuff, I may be back to ask more questions about other bits !

Franko, I have not seen that mudguard bridge before from the top shocker mounts - is it standard? Also I have not seen that air filter arrangement before - I am starting to think that no 2 bikes left the factory the same !

Andrew: I bought this bike last year, so I can't say for sure anything on it is standard. That being said I also bought a 68 N15 about 30 years ago that had been chopped, but it also had the bridge for the rear fender on it. I still have the bike, but it is in parts now, awaiting time and money.
The air filter I had seen on other N/G 15s, but only on internet photos.
I intend to attach a sidecar to the G15, so I will run a single carburetor on it for a bit of better bottom end, I hope.
That air filter is for a single carburetor bike,
The twin carburetor air filters that I have seen is similar to this:
Earlier in this thread, the mounting points for the seat was talked about.
With mine being attached at the same point as the oil tank, was thought of as being earlier in the production run.
The later mount being on the rear fender. I was looking at the bike today and can see where rear mount holes for a bracket were present in the fender. The seat is new, so something just added to help sell the bike and not original. I starting to think so, but I'm not bothered by it.
If you want pictures of other areas, let me know. I will be glad to help now that I think I can post photos.

Rear fender/mudguard should always be bolted at the top , the hole should be slightly larger and not a tight fit, with a penny washer and rubber spacer at each end, a lock nut is preferable for free movement.

Andrew Jago said:

Franko, I have not seen that mudguard bridge before from the top shocker mounts - is it standard? Also I have not seen that air filter arrangement before - I am starting to think that no 2 bikes left the factory the same !

Click to expand...

The air filter depicted was optional equipment for G12 bikes (1963--66). It was never offered for G/N15 models. You will notice this air filter will fit only the non-tucked-in oil tank (i.e., pre-66 design) which goes with the wider touring-style seat. For the G/N15 models, the factory offered the wedge-shaped air filter. There was one version for Amal Monobloc carburettors and another version for Amal Concentric carburettors.

In the absence of "exploded" isometric part images, the fender mounting has always been a little obscure. The mudguard bridge depicted appear to be genuine. N/G15CS model mudguards had 4 fixing points: J-bracket at the lower front (one fixing bolt), a clamp (two fixing bolts), a mudguard support bridge (p/n 030394, two fixing bolts), and the rear loop (two fixing bolts).

The support brigde p/n is left out in the spares list of 1967-68 models. I don't think the design changed from 1964 to 1968.

The following thread discusses all but the support bridge fixings.

As for fairy tales of the hybrids being "parts bin specials", "all were different", etc. these tales are rubbish and unfounded. The factory kept build books for each model and year,and many parts were dedicated a particular model. Model changes mosty occured in Sept. for the coming model year. In some instances there were mid-season updates, the 1967 P11/P11A and the 1967 G15CSR/G15CSR(T) being two of the most significant. Some mechanical upgrades appeared mostly between batches. An overview is given by Norvil m/c here:
(go to "Identify your bike").

-Knut

mdt-son said:

The air filter depicted was optional equipment for G12 bikes (1963--66). It was never offered for G/N15 models. You will notice this air filter will fit only the non-tucked-in oil tank (i.e., pre-66 design) which goes with the wider touring-style seat.
...
As for fairy tales of the hybrids being "parts bin specials", "all were different", etc. these tales are rubbish and unfounded.

-Knut

Click to expand...

I agree. All hybrids where twin carburettor.
Non magneto bikes had 2 12v coils were Franco's air filter is.
Franko:
is your bike magneto or points?

"parts bin specials":
I believe a lot of the confusion comes from the many different variants of hybrids,
and only recently get the attention they deserve.
But I do know that mine, nr 132xxx built summer 1969 (proven by factory records) left the factory with the early version of oil tank and handlebars, so it wàs a parts bin special, so to speak.
It did come with the triangular Atlas air filter.
During the now almost 50 years that I own this bike, I have NEVER seen another N15 on the road, and I have been around.
( I don't frequent club meetings..)
I believe they were never officially exported to continental Europe.

This is how my seat is fixed:

originally by a bolt. Now quick release.
No fender bridge.

Ludwig: My G15 has a magneto. The air filter I bought as I intend to run a sidecar on it with only one carb. I had seen them on internet pictures of N15s. The motor number starts with 108... and the frame number starts 110..., so it is not a numbers matching bike.
It is rough but runs and rides. After I get it sorted a bit better and the sidecar attached, I have a G12 tank and after market ribbed fenders for it.
It is something to work on. I will not cut or damage anything on it that would make hard to put back for the next owner. I found that out with the chopped N15.
MTD-SON: Thanks for posting about the differences. Those are the things that most people would not have noticed.

Franko: Would you please do me the favour of making a sketch of the rear mudguard (fender) bridge, p/n 030394? I have never seen this bridge "loose", let alone advertised anywhere. I will need several samples for my "fleet" of G15CS's. Given your input I will make a proper drawing and post it here.
-Knut

Knut, I found this that is interesting - I know it’s says triumph, but it looks very similar to Franco’s. Not sure if the link has worked!