Tank question - highrider versus roadster

Hello! This is my first post here, looks like a lot of knowledgeable folks. I've got a few older bikes, including a 74 Commando sporting a highrider tank. I finally decided to get a roadster tank for her and picked one up off of eBay. I looked at the bottom of the roadster tank and the bottom of my highrider tank and they mount differently. Does the roadster tank actually fit back further on the bike? Does that interfere with the seat? Do some tanks only fit certain years? Sorry for the newbie questions. Yes, I can (and will) pull the highrider tank off and try and fit it, but thought I would ask first before going to the trouble if I've clearly got a tank that isn't going to fit (wrong year or ??).

I'll post pics of the bike once I figure out how that works on this board.
All replies appreciated.

Jeffrey

Jeffrey, the Commando was sold in a number of different model styles throughout it's production life, differences in tanks seats and exhausts were the most obvious changes from model to model, there were also fibreglass and steel tanks available for the same models depending on the year and the regulations in some countries. I expect that your high rider and roadster tanks should be virtually interchangeable, they are about the same length and the front mounts should be very similar if not identical, although there may be slight differences in the rear mounting arrangements. All Commando tanks will fit on your frame although the Interstate for example being longer requires a different seat.

The Roadster tank will require a different strap on the rear that goes under the frame rail . That's the only difference I remember from when I replaced my Highrider tank with a roadster one .

It depends on whether the Roadster tank is metal or fibreglass what the mounting arrangement is. The steel Roadster tank has 4 metalastic mounts fitted and is bolted onto the frame bracket at the front and has its own separate insulated strap that goes under the frame backbone at the rear of the tank. The fibreglass tank is similarly mounted with 2 metalastic mounts or two long studs with thick rubber washers on the front, however the rear is mounted with a large rubber band going around the main tube and onto a couple of bobbins on the rear face of the tank.

Are the metalastic mounts the same part # as the muffler mounts? I got a steel Roadster tank of unknown year (black with gold pinstripes) and it had them on the rear only. I just thought someone had done this - The parts books just show the studs and rubber washers. Seems easier to do it with the one piece.

Russ

Believe they should be individual washers but mine are the same as exhasut head steady mounts and work fine.....

Different tank mounting assemblies ('73-'74 shown): http://www.oldbritts.com/1973_g28.html

Parts list: http://www.oldbritts.com/nor_comm_73_28.html

Looks like all studs and rubber washers in 1973.... Except for the Interstate tank it shows an unidentified metalastic mount at the rear that is also not on the parts list.

The one drawback I found with the "muffler" mount was that one of them on my ebay tank was rusted in and was a bear to remove. After soaking for days in Aerokroil it still wouldn't budge so I had to cut off the rubber and then grab the remains with the visegrips. It finally came out and the tank was OK. If I do decide to go that route I will load it up with anti-seize. With the studs the double nut method works fine.

Russ

Both my '73 Roadsters (including the purchased new MkV) had rubber wasters over the front studs and muffler mount bushes at the rear. It makes it easer to adjust the front height of the tank for clearance of the handlebars and wiring underneath to use the washers. At the rear you don't have washers falling off studs as you try to slip the rear bracket on with the muffler mounts.

Just my $0.02.

Heck Ron, you make it sound as if they thought about it !

I actually just use plain nuts on the front Roadster tank mounts. The 'staytites' always took the stud with them. The compression of the rubber washers seems adequate to hold the nuts on. I've never lost one.

Heck Ron, you make it sound as if they thought about it !

Click to expand...

Not sure if it was Norton or the dealer! :wink: I imagine after chasing those rubber washers a few times, the mechanic might have grabbed the muffler mounts!

I ran plain nuts once. They lasted a month! Just my luck! I find that after the nylocks are run on a time or two they get "adjusted" to the threads and don't try to take the stud with them. A dollop of Loc-tite on the stud at the tank end helps, too.

OK I'm sold on the rear rubber biscuits. I still have my original 1972 nylocks on the front of my fiberglass tank. Once loose I can now take them off with my fingers but they do not spin off for sure.

Just got word today from the paint shop that my metal tank will be done later this week (signal orange). So now I'll need to pick up a rear bracket, studs, rubbers, and another set of petcocks. Wooo hooo! Riding season here we come.

Russ