Thursday, April 28, 2016

Last Stop

I feel that, in time I've gotten to proceed faster and with more self confidence. Wish I were able to be like this at the very beginning, but I believe that was the price to be paid - with a lot of time, reading and trial-and-error. 

Out of the three main systems, the final drive was the first to go. As I sorted out and closed up the engine block, and waiting for the rest of the parts to be painted, it became totally inevitable to move on to the transmission. After all, it has been sitting and waiting for my attention with extreme patience for more than a year now.

I hope you read about my disappointing "special tool" attempt to remove the centre nut of the output shaft. After a few more failures, I decided to go old school. Once again, using plenty of hot air, a hammer and chisel, I made it move. The rest was straightforward.

I had to go ahead and finish this up!

Next stop was the output flange. The engine output is transmitted over the shaft via a rubber "puck" between two identical flanges, this one and the one at the very front of the shaft. The flange sits on the shaft as a tight fit, so I need to find another trick to pull it off.

I tried with my cheapo puller first. Obviously didn't/couldn't work. Then a few more attempts mistreating my high quality bearing puller, which single handedly sorted out the entire engine block. That didn't work either - it was not a proper fit anyway. 

Lesson learned (again and again) - there is just one method and tool to do a job. Without the proper tool, you can't do it. This time, the lesson cost me a decent two armed good quality puller.

Can you notice my brand new "special tool"? The flange is designed for the rotational forces, but it can't bear the pulling. You can find examples of "folded" flanges in the internet. Therefore I supported it with a 22mm and two halves of a 20mm nut to resist bending. It was almost a perfect fit between the two tips.

Having fixed the puller behind the tips, I started rotating the puller bolt. It is an extremely stressful process, especially with all those squeaks and cracks coming out of the parts. It's always possible that another weak point could give up and bend or break instead of the puller breaking loose.

After a few careful turns, with a loud, metallic noise resembling a glass shattering, the flange finally got loose. 

That's it!

I don't expect any big blocking points anymore, but obviously a very thorough cleaning job  is awaiting me. And my brand new bearings and oil seals are ready. 

First, let's get rid of the nuts that are holding the cover. No, not that easy mister!

There are three bearings sitting inside of the cover. In order to get them loose, I needed - guess what - hot air again. At around 70-80C, the aluminum material expands just enough to give way to the steel bearings, which expand less.

No surprises inside. Plenty of dirt and mut leaking through the old seals, remains of old oil and six bearings one of which is shot.

Similarly, the rear (actually front) ends of the three shafts have bearings fitted to the transmission body. Again with enough heat, I got the shafts out of their beds.

There remains the gear shift mechanism. It's a very simple, compact yet very intelligent design. Let me try to explain...

The short shaft extending towards outside is attached to the gear shift pedal there. The circle next to it is for properly positioning the gear selectors.

Unlike cars, the bikes have sequential gearboxes. You can select 1, neutral, 2, 3, 4, etc. from bottom-up. You can only switch to the adjacent gears by strongly pressing the pedal upwards or downwards.

When you press the pedal, a fork rotates the selector circle a few centimeters. You can see the notches below that - they set the proper gear positions by sitting onto a metal tip. Currently it's in neutral. 1st notch is just to its left and 2, 3 and 4 are to the right. Simple, isn't it?

Here are the input and output shafts and the gear pairs for 4th, 3rd, 2nd and 1st from left to right. Output shaft (bottom) gears can rotate freely.

Two railed disks on the output shaft can move along the shaft. They have "dog teeth" pointing outwards on each side, so they can slide and attach to the desired gear and in neutral, both disks rest in the middle. If they ever attach to two gears at a time, you would simply smash the transmission. The gear selector circle avoids that with two properly positioned grooves on it.

The rest was easy... I washed every single part twice, pulled off the old bearings and fitted new ones, renewed the oil seals on the input, output, shift pedal and kickstarter shafts. Again heating up the cover, I then fit all three into their positions (you can't do it one by one) and heated up and closed the cover with the help of my rubber mallet.

While cleaning, I also sanded off the dull and rusty layer outside of the transmission body and treated it with metal polish.

It shouldn't be that difficult to fit the flange back onto the output shaft and attach the awkwardly shaped castle nut.

The rest should come easy...