The conditions of "Before"

I got this 1971 YAMAHA HX 90 (identical to LS-2, 100cc that soled in the US), 7 years ago. When I got this, I didn't notice to take "before" photos. I regret that I didn't take the pictures now, but this is "It is no use crying over spilt milk". The conditions of the bike was not so serious (I mean it wasn't a real junk but this was a junk for ordinary people), and I thought this is easy project. It was dusty and the chrome plating have some rust but I thought it will be okay if I polished out with steel wool. However, the chrome plating of front mudguard and small parts were heavily pitted. The paint of fuel tank was so-so condition and the inside had no rust. When I was riding RD-LC, the inside of fuel tank rust easily and finally it had a pin-hole. YAMAHA at that era may be using better material than now.

The kick starter worked but the twist grip was stuck. Clutch lever moved and front and rear brake were working. I thought I can start the engine easily.

Fix of Carburetor sliders

The first thing I have to do is fire up the engine. I tried to clean up the carbs at the beginning. However, the throttle grip wasn't move because the sliders were stuck into the carbs body. I removed the ducts of air from the cleaner to the carbs bodies and apply a lot of penetrating oil spray (I'm thinking that most of mechanical things can be fixed with the magic oil). Unfortunately, I had no luck, so I was thinking rough method to remove the sliders (sound dangerous!).

The forced method was;

Step 1: fully loosen the cable adjuster on the carb top cap to make the free play of the cable maximum , then unscrew the carb top cap and apply a penetrating oil splay from the chink between carb body and the top cap.

Step 2: Tighten the carb top cap and adjust the cable again so that there is no free cable play.

Step 3: Loosen the carb top and the slider is pulled forcibly because there is no cable play.

Step 4: If the slider is moved slightly, the penetrating oil help to remove the slider.

Finally, I could remove the sliders with this method but it was funny because the sliders were set the wrong way around. That's why the sliders were stuck hard.

I totally cleaned up the carbs and I installed new main jets because I happen to have the same numbers jets. Rubber packing of the carb bore had broken but I used a rubber ring for waterworks (!), instead.

Fire Up of Engine

I re-installed the cleaned carbs and adjust the ignition timing after I fixed the slightly bent point breaker. I charged the dead battery for long time and I install it. Also, the plugs were replaced to new one. When I kicked the starter, the plugs had spark. I thought that the engine should be fire up soon. I poured pre-mixed fuel into the tank and kick the starter for several times. The engine was fire up without any problems.

The engine was stall, however, when I shift down to the first gear. The friction plate of clutch may be stuck. I sat the bike with the main stand and started the engine again. Shift down the gear to first, open the throttle to turn up the rear wheel strongly and then... I kicked down the rear brake pedal strongly. Hey! It works! The friction plates were apart from the steel plate with the shock. I doubt that this is the correct way of repair but I don't mind because the sticking clutch issue was solved.

Repair of Brakes

The next aim was brakes. I thought this is a peace of cake because both of the brakes are simple drum type. When I opened the rear drum, however, the surface of inner drum was getting black color. I thought "What?" and when I look close, the black surface was shiny. I scratched the surface with a screw driver.... It was carbonized brake shoe layer stuck onto the surface of drum. I spend a long time to remove the carbon layer (it was very hard) with a screw driver. Oh, I'm totally knackered! This may be caused by bad adjusting of brake shoe clearance and the previous owner was running with drugged brake shoe for long time. There was no issue in the front brake.

I replaced the brake shoes to new one but the brake was not so effective. Any way, I'll take the license plate and do the test riding!

Continued......

I can do this level's job easily. I'd go to the other section.