71 commando seat issue?

Over the last few months I have been getting a 71 750 Commando up and running. As I am nearing a running condition I was finally trying to mount the seat and tank and have ran into a problem. Please forgive me if this a frequently asked question but I have searched both the site and the manuals I have and didn't find the information I needed. It seems according to the 71 parts list I have a Roadster tank and I'm not sure what kind of seat. They meet up fine but the back of the seat sits 1 1/2"-2" above the fender in the back so when you sit too far back or have a passenger the front of the seat lifts. I just assumed I had the wrong seat so to solve the problem I purchased a seat online that looked to be an original roadster seat but when mounted it sit about a foot apart from the tank instead of being flush. My question is is there a part I am missing that the seat rest on or is it just not the correct seat?

Welcome! First stab at it looks like your fender is way too low. Taillight looks to be at a funky angle too, (fender mount under there). Have a look at the fenders front mounts, see if there are extra holes, etc. Some detailed images of the fender mounts, and everything related would help. Underside of the seat pan. The other seat you describe sounds like an Interstate seat, set back to allow the larger tank. Is your seat a steel pan or fiberglass? Does it look bent?

The front of your rear mudguard (fender) is way to low and looks to have had some abuse. Have a look at the parts list on the andover Norton website and decide what bits are missing. In addition the front of your petrol tank looks too high and will probably foul the top yolk on full lock. The tank needs to sit down on the spine with some rubber pads. If the front end of the tank is only supported by the two frame "wings" they will bend and crack. Later coil brackets spanned both the wings and beefed them up a bit. This is more of an issue with a full 5 gallon interstate tank and maybe a tank bag.

Your tank also looks like the front could be dropped down a little, and the back packed up a bit higher ?
Are all the rubber packers up front, and none at the back. ??

There has been previous discussions here on seats - there are more than a few versions, its seems.
Does your seat base look flat underneath, like it was born with, or has it flexed and bowed like some seem to do.
Someone here recently mentioned they straightened theirs, so it would fit....

Look here for a parts diagram that will help you unravel the box-o-parts http://www.oldbritts.com/nor_comm_71.ht ... 2974daf84d

I have been thru this also. Your seat on the bike is correct for a roadster tank, the one on the ground is for an Interstate tank.

Your taillight looks just like mine, The December bike in the calandar. calendar-call-2013-ready-for-download-t15139.html


I would check the bottom of your seat and make sure the frame bumpers are there, if not the front will sag down and the back will have farther to travel before making contact.

I would also double check your fender install. It may not be the correct fender.

Suspect that loose seat you show could be an Interstate seat.
Quite a few inches shorter at the nose than a Roadster seat.
Which is why there would be a large gap behind the tank when fitted....

Anyone know how much shorter ??
Same overall length though, so longer at the back.... ?

I agree with some of the comments above -

The seat you have is the correct seat for that bike. The fender is fine. The seat pan may be bent a little, and you are probably missing the rubber bumpers on the bottom of the seat. If you look at the pan, you should see several holes near the front and back, maybe 1/4" diameter. They're supposed to have rubber bumpers in them. The front ones rest on the frame, the rear rest on the fender under the seat. Without these bumpers, the seat's going to rock back and forth. Original part number for these bumpers is NM21852, item 33 on the seat page of the parts book (p K3)

The spare seat you've got is for an Interstate - that model has a much larger gas tank, and the seat is pushed back several inches because of it.

Hey boxo, don't drop off the map here, any progress report? Pics? :mrgreen: