Rebuilding Yamaha Chassis

After reassembling the front fork I put all the wiring back in place. If you leave this till later is gonna be very fiddly. Before I took the wiring out I made lots of pics but even with those pics it was a bit of a puzzle to connect everything the right way. Actually I still don't know if it's all good; most of it can only be tested with the engine running.

Wiring diagram Yamaha 100 LS3 1972

Part number tag still on the original wiring harness 

Original Wiring head light Yamaha LS3

Next things were the handle bar, rear fender, tail light, indicators, rear wheel and freshly sprayed sprocket. The switch handle also needed some TLC and soldering. The original handle bar was stripped down, sanded and nickel plated and the aftermarket throttle handle was replaced with a NOS one including a new throttle cable and oil pump cable.

Taking the switch handle apart 

Rusty indicator switch

Indicator switch mechanism and horn button

Cleaning indicator switch mechanism

Rebuilding Yamaha LS3 handle bar

Tail light and rear fender Yamaha LS3

Painted original 36 rear sprocket Yamaha LS3 1972

Rear wheel Yamaha LS3

Rear mud guard Yamaha LS3 - Close up

Followed by rear shockers, front fender, front wheel and most cables. 

Night shift: mounting front fender

Left side front wheel Yamaha LS3

Right side front wheel Yamaha LS3

Rear wheel with brake rod and tension bar

Break switch rear

As with most older bikes not all parts are available anymore, so sometimes you have to be creative and make your own stuff. The old dampers for the right side cover mountings were almost perished and I couldn't find them so I made them from an old inner tube. In the middle of the tube is a weld which looks almost the same as the original part but above all it's functional.

Making cover dampers from an old inner tube 

Time to bring back the seventies! Mounting the side covers and a loose fit of the fuel tank, at this moment I'm starting to see why I'm putting all those hours in this once basket case, enough time has passed for the LS3 to be cool again :).

Oil tank with new oil level gauge

Fitting fuel tank

Right side fuel tank, cover and rear shocker

Right side fuel tank, cover and rear shocker

Luckily I took of the original sticker of the oil tank with a razor blade and kept it in a safe spot. Before putting on the clear coat I put it back on the oil tank with some transfer tape. In this pic you can also see the metallic silver shining trough the red dye/clear coats; That's what they call "candy".

Two stroke only !!

Chrome chain guard - Yamaha LS3

Exhaust

The buddy seat was almost ready. I only had to put on the original strap with the chrome button bolts. But because the new buddy seat had the bolts welded on I first had to carefully drill 'm out. The original bolts and chrome "buttons" were stripped of their old chrome, cleaned, sanded and nickel plated.

Welded bolts new buddy seat

Original bolt with pin in place

Yes, it's not in the middle, but that's how it should be

Fixing the front fork

When I took the front fork legs apart there wasn't much oil in them anymore. One of the inner tubes was in good (pit-less) condition but the other one was pitted badly.

Yamaha LS3 rusty front fork

Pitted inner tube front fork Yamaha

I asked around but there wasn't anybody who could repair it.  Luckily the inner tubes of the Yamaha LS3 aren't visible so I decided to fill the pitted parts with JB Weld. It's very strong, smooth and chemical (oil) resistant. If you don't fix the pitted surface your new oil seal will be gone within a couple of days...

Fixing inner tube front fork with JB Weld

It took a while before it was really cured, so I sanded it after a week up to grid 1500.
Another issue which had to be be solved were the old leaky fork seals. They're sitting inside the so called "outer nuts". With a home made tool I took the old ones out, see http://yamaha-ls3.blogspot.com.au/2015/04/removing-front-fork-seals.html Inside the outer nut is also an O-ring hidden in a groove. Don't forget to replace them as well.

One of the outer nuts was too damaged to fix so I bought a new one at www.cmsnl.com . The new fork seal is already fitted in the outer nut, but the O-ring isn't, so make sure you put one in. The rest of the old chrome work was stripped back, sanded and DIY nickel plated.

When I wanted to put all the parts back together the inner tube top bolts both got jammed, but a M10-1.25 tap cleaned the threads out and with some copper grease it was all good.

Cleaning inner fork tube thread with M10 - 1.25 tap

Cleaning "harvest" after chasing the threads

With a longer bolt I pulled the inner tubes all the way up in the triple tree and tightened the securing bolts. Make sure they are both all the way up otherwise you'll get weird things..

Most parts of a Yamaha LS3 front fork leg

Assembly of the front fork

According to the Service data in the LS3 Manual each leg needs 147 cc Yamaha Gear Oil. I used Castrol 15W fork oil.

Castrol 15W front fork oil

Filling the legs with fork oil

Almost done

Sandy loves the bike

Cleaning carburettor Yamaha LS3

The Yamaha LS3 has a Mikuni VM20 carburetor. It's the same as the Yamaha RS100.  As I couldn't find a repair set for the LS3 I bought the one for the RX100.

Yamaha RX100 with also a Mikuni VM20 carburettor

The only difference was the air-mix-screw being a bit shorter. If it's not working I can easily replace it with the old original one.

Carburettor repair kit Yamaha LS3 - RX100

Exploded view Yamaha LS3 carbie

This carb was in desperate need of some TLC.

Mikuni carb Yamaha LS3 - left

Mikuni carb Yamaha LS3 - right

Before I opened the carbie I cleaned the outside with wax and grease remover and with a couple of steel wool pads.

Carburettor in need of some TLC

The bottom of the bowl was filled with gunk and rust, amazing how the bike ran with all the dirt in the bowl and main jet.

Dirty float bowl Yamaha LS3 100

After cleaning the bowl and taking out the main jet and banjo bolt I took off the floater so I could take out the valve seat and needle.

New and old valve seat and needle Yamaha LS3

Carburettor nozzle

With some compressed air I cleaned all the passages and with a wooden toothpick you can reach and clean all the hard to reach corners. 

Mikuni carburettor with hand choke

Mikuni carburettor with hand choke pulled out

Mikuni carburettor with pushed choke

Original air screw  longer than new one..

As the carburettor set didn't came with a new nozzle (for some reason they almost never do) I just cleaned it and for now I'll keep the original jet needle. When the bike is running again I'll try both needles and see which one is best.

Mikuni main jet and banjo bolt

Float and new gasket Mikuni carb

Mikuni carburettor with Yamaha Reed valve

Mikuni carb attached to reed valve Yamaha LS3

Mikuni carb cleaned and ready to use

Cleaning the Steering bearings

Still had to open and check the two steering bearings. I postponed this for a while because I didn't have a steering nut wrench. That's what I thought... When my pushbike had a flat tire last week I found a combination tool in it's toolkit, including a steering nut wrench :)

The job is pretty straight forward; carefully remove the steering nut while holding the under bracket which can start to drop down. There're two bearings, each existing of two races and 19 steel balls. Over the years the grease in the bearings can become old and hard giving wear and rust a chance.

2 top races with 19 balls partly covered in old grease

Lower race with 44 years old dried out grease

Collecting the steel bearing balls with a magnet

When I took of the ball race (bearing) cover 5 balls fell out and it took me a while to find them all..#@!<" Anyway I soaked them in old petrol for a while and cleaned the 4 races with wax and grease remover.

Cleaned  race - Yamaha LS3

Steel race balls after cleaning -Yamaha LS3

After cleaning I filled the races with high temp bearing grease which I bought once for the rear wheel bearings of my Volvo 122S. All the 38 balls still look like new, no corrosion and no flat spots. Now it was a matter of simply pushing the balls in the grease filled races.

Fresh grease ready for the top race

In the meanwhile the ball race cover and steering nut where nickel-plated for a bit over 3 hours.

Nickel plating the ball race cover and steering nut

When finally tightening the steering nut after reassembly take care not to overtighten  but make sure you got rid of any play. The steering rod must be able to move freely.

Steering head section Yamaha LS3 1972

Steering head section Yamaha after reassembly

I also started the reassembly of the painted frame. Still a long way to go ;)

Reassembling frame - Middle and side stand - Yamaha LS3

Reassembling frame - using old shocker to keep it together