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RENOVATION PROJECT OF 1972 YAMAHA YR5
BY STEPHAN MORRIS

Part 24-25

The R5 is a complete redesign from the previous R3 model, with very few common parts, and the last model before reed valves and disc brakes were introduced on the RD350A model in 1973. Many R5 design features went through all subsequent air cooled models until the LC in 1980 such as the frame and swing arm design, oil tank as side panel, crankshaft and crankcase design. Even the LC models still used the same base gaskets as the R5 demonstrating similar crankcase design, and it was not until the powervalve (YPVS) models came out in 1983 that 5 cylinder studs were used instead of 4.

August 2009 - Part 24
Well I have not had any emails asking me about the next instalment of this saga. Either my reader is out dodging the puddles on his R5, or his computer has crashed. Obviously I am not yet riding my R5 otherwise you would not be reading about it here! This is partly for the reasons you can read about below and partly because I have not got around to fixing them! I have actually ridden the bike about four miles on the quiet road outside my house. This would be totally illegal of course were it not for the fact that it is my private road and I simply let the cars and trucks use it - oh and there are some other houses along it too...

Disappointingly, the seat that I bought from the States has a few problems. As you can see here it does not meet the rear of the tank properly. Part of the reason is that the tank itself is a little too low at the back. There is a rubber damper on top of the toolbox holder which is under the rear of the tank. I thought that the one I have in place was the correct part, but maybe not. Anyway I will fit a thicker one so that the orange line at the base of the tank is parallel with the frame rail. At the moment you can see it sloping down towards the rear of the bike.

The seat itself also does not look quite right. As you can see here the aluminium trim follows the contour of the bottom part of the seat and is bending in and out. The bottom line of the seat is also not straight.

The seam of the seat is visible from the side, this should be on the corner of the seat in line with the seam of the tank that you can see here.

On the left side, the seam of the seat is better positioned, but this photo shows how far the seat is away from the tank.

This is the underside of the seat. It is made from fibreglass which is one redeeming feature. The rubber pads you can see are riveted to the bosses on the seat. Are they too thick? If I cut them down will the seat then not be level because I can’t alter the position of the hinges of the seat?

This is another seat I have from an RD 350 which fits OK but the foam is too thick and so appears wrong. However it does have the rubber pad at the rear of the seat, and at two o’clock from the pad you can see the 6mm female thread to which fits…

…the seat holder bracket and rod. These hold the seat up when it is raised.
If you look at the underside of the fibreglass seat, both these items are missing!
For all these reasons I think that I will need to take the seat apart to rectify all these problems. Is this something that I can do myself? Should I ask a professional seat restoring business to Do this for me? I have not yet decided…

The four miles I mentioned above was in two lots of two miles. Both times the engine started And ran fine, but both times developed a misfire pretty quickly. The reason is the rust in the tank That you can see above. Small flakes of rust are getting through the petrol filter and blocking the jets in the carbs. I don’t want to put an aftermarket filter in the fuel lines, so the only alternative is to seal the tank with…

…this kit from Frost specially for motorcycle tanks. Well I have now written about what I am going to do.

Now I must summon the enthusiasm to go and do it…

November 2009 - Part 25

Hello Dear Reader

Did you think that I had forgotten about you?

Sorry, I have been so busy at work and on other projects in the garage and the garden that the poor R5 has been neglected.

If you have a long memory you will recall that I had two items left to which to attend, the tank and the seat. I had to seal the inside of the tank because rust particles were blocking jets in the carburetors every time the engine ran, and I had to use a thicker rubber pad to raise the tank at the back to meet the front of the seat in a more aesthetically pleasing way. I have to disassemble the seat to attach missing rubber pads and the seat support rod bracket, and to achieve a better line for the bottom ridge of the seat. It was the tank that needed to be done first…

The chemicals that I need to use to remove rust and prepare the inside tank surface for the sealant would strip paint very quickly. I used masking tape all over the tank surface to guard against this.

I used an old tank cap that you can see in the first photo, and then sealed the petrol tap hole with a piece of appropriately sized rubber that you can see hear top right. I poked some bits of wire up the pipes for the flexible hose that ensures that both sides of the tank drain evenly, so that the sealant would not block them. I then attached the hose that you can see here.

I used a chemical to remove rust and then a chemical to prepare the surface for the sealant. Both chemicals had to be sloshed around the inside of the tank to ensure that all surfaces were treated, and then it had to be dried thoroughly before the sealant itself was employed.

Here is the tanks sealant ready to use. I bought the whole kit off Frost. It is made in quantities suitable for motorcycle tanks. The quantities used for car tanks are much bigger.

It was difficult to photograph the inside of the tank. This shows the surface after derusting and cleaning to prepare it for the sealant.

This is the inside of the tank after the thick sealant has been sloshed all around the inside of the tank and allowed to coat every surface. It dries to a finish impervious to petrol obviously. It now looks as if there are no loose particles in the tank to get through and block the carbs, which was the object of the exercise.

Right there is nothing left to do now except the seat – no excuses. Thanks for reading, and watch this website.