BIKERS ASSOCIATION OF NORTH DEVON
OF 1972 YAMAHA YR5
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.
The rebuild has been shown here in chronological order, it is possible to jump to any installment by clicking on the links below:
2009 - Part 24
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…
seat holder bracket and rod. These hold the seat up when it is raised.
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…
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.
I must apologise for such a long time before the last update and this one. Events have been moving quite slowly so there has not been a lot to report. Where you are waiting for other people to do things for you then of course the activity level diminishes. The project is drawing to a close actually, and you must come to terms with the inevitability that these reports will cease one day, so this extended interval is actually good practice for you…
Here is the seat that does not fit properly at the rear of the petrol tank as you have seen already.
You can also see here on the right side how uneven is the bottom line of the seat.
…and here a similar situation on the left side.
…and the aluminium trim is very wavy
Here is another photo of this badly made seat showing the uneven seat base line. Overall simply not good enough, so despite not really being comfortable with upholstery as an art, I had no choice but to tackle the issue. I had spent a lot of money buying and/or restoring several seats already - about £600 – so simply buying new seats does not cut the mustard, I had to make this one how I wanted it to be. The seat cover is glued into place and then there are a few 3mm screws clamping it to the seat. You can see two of them here. The screw heads fit inside the aluminium trim.
Undo the 3mm nuts and the trim comes away from the seat with the screws.
Petrol dissolves the glue and then the cover can be lifted away from the seat.
Leaving the foam…
…and the fibreglass base
Now the cause of the uneven line can be seen…
…and fixed with the trusty surform. I can’t believe that Yank charged me £330 for this shoddily made seat.
This is what it should have looked like in the first place.
Nice straight line now.
There was still a problem with the edge of the seat being curved in as I have tried to show in this photo.
I applied some heat…
...and some rapid cooling in water
To give something a little less curved as a result.
Next I had to modify the rear of the seat where there was no place to attach the seat strut bracket, nor any seat base damper which should be in place to sit between the seat base and the rear frame crossover rail.
I wanted to put something in place that would hold a nut captive so that I could bolt the seat strut bracket in place even when the seat had been reassembled with the foam and seat cover, so I drilled these three holes in the fibreglass.
Then a got a 6mm penny washer and cut two ears which could be bent down into the smaller, outer holes to locate the washer.
Then bent an ear upwards which would retain the nut.
...and this is the bracket attached to the underside of the seat.
It works like this to hold the seat up.
I decided to have two dampers on the back of the seat. It is always best to have more of a good thing isn’t it?
Well no! Not when the strut cannot be installed because the damper is in the way!
I had to cut away 900 of the damper as you can see here.
I promise that instalment 27 will not take as long as this one did!
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