R80ST

[marcmax]

Anyone familiar with an R80ST? I have an R65LS that I bought as a spare parts bike. missing the fuel tank, fenders and some small parts. I didn't use enough to justify parting it out so I am going to build a "frankenbike" out it. I found an R80ST tank recently for a great price (just cleaned and relined but bad paint) and bought it. Any ideas on if it will fit? It will be going on an R65LS bike (frame, etc.)?

[Tony Smith]

Will fit straight on.

I thought it was the same tank actually.

[BPT]

Are all of the R80's of the same era interchangeable with the R65's?
I saw a thing on Facebook recently with a guy asking about an R100 tank.  I knew that wouldn't fit but wasn't sure which ones were a guarantee.
From my limited knowledge I think the main things are that the R65 tanks are offset underneath, to match the electricals, and they have that loop that latches the seat end to the frame tube.  Am I correct there?
Just curious.........

[Barry]

The R80st tank is definitively a slightly different style and size to the R65 tank but I've heard that it fits albeit with a different height where it meets up with the seat.  I never heard that anything else will fit except perhaps an R80g/s.

[marcmax]

My biggest concern was that the R80ST is a monoshock frame and I know there are differences between it and a dual shock. Didn't know if the top tube length is longer. The tank itself has a offset tunnel like an R65, it has the rubber bumpers and wire bail for attachment. It appears to have a larger, rounder front portion with a top that slopes downward from the filler to the seat. I guess I'll see once it gets here.

[Justin B.]

Many moons ago seems I remember reading that the tank and seat won't match up perfectly.  Can't remember if it was a length issue, or what.

[mrclubike]

My biggest concern was that the R80ST is a monoshock frame and I know there are differences between it and a dual shock. Didn't know if the top tube length is longer. The tank itself has a offset tunnel like an R65, it has the rubber bumpers and wire bail for attachment. It appears to have a larger, rounder front portion with a top that slopes downward from the filler to the seat. I guess I'll see once it gets here.

Have you had a chance to fit the R80 tank yet

[marcmax]

I did get it on the frame. It has the same offset tunnel to clear the electronics and went right into place. The fastening hoop even snapped securely. I don't have a seat yet so I can't say how that will line up but I think it can be made to fit. The R65 tank is more rectangular being approx the same height at the front as at the rear. The R80ST tank has a definite slope to a shorter rear section of the tank. It also has a nice "knee" area on each side that is inset a bit.

[marcmax]

Pics

[Tony Smith]

Looks good.

Our now departed local member Peter with the R65LS cafe racer had a /7 tank on his bike. Aside from having to relocate the electrics he reported that fitting it was a "piece of cake"  requiring only the fabrication of a rear mount, iirc he used a couple of worm drive clamps to hold his tank rear mount to the frame.

[Tony Smith]

Didn't know if the top tube length is longer.

I wish you had asked because unlike some answers which are "best guesses" that is one I can answer definitively.

From /7 to end of days the top tube length is identical. There are very minor variations of steering head angle, which in my view you would never fall foul of no matter how much you mixed and matched components.

The only change to the main frame in honour of single sided swing arms is the mount for the top of the shock and different rear sub-frame lug position. I have supervised the cutting out of part of the RHS rear frame loop and the welding in of the same section from a monolever frame to convert a 1976 R75 frame to rebuild a 1986 damaged (front end accident) R80. A few hours with an angle grinder and a MIG transferred all the lugs and mounts.

The only thing that was not replicated were the small additional rear braces on the later frame (introduced in 1981 iirc).

The project was undertaken by the owner because he needed a new frame and the R75 frame was free, as opposed to the cost in excess of $AU1,000 for a suitable monolever frame.

After watching my recent experience he is about to put a K100 front end on it as the straightened original fork legs have not proved satisfactory.