YZ125 L 1984 Basket Case Restore

[Ji Gantor]

Just picked up my Summer burner a Yamaha YZ125 L 1984.
The bike is a basket case and needs just about everything doing, whats new.
This bike has been run on the beach because all the lower nuts and bolts are rusted away.
The chassis has a fair rust problem and will need some hot love via a welder.

Ji

[Ji Gantor]

There was some coolant sitting around the head gasket so I pulled the plug to discover coolant on the plug.
The head gasket must be blown.
This could have been from overheating due to poor coolant circulation.

Ji

[mainline]

make sure you save the "go the rat sticker" during the resto

[Ji Gantor]

With the plug out check the timing.
Insert the timing gauge into the spark plug hole, raise the piston to top dead centre and mark the gauge.
Back the piston back down to timing BTDC.

Ji

[Ji Gantor]

Then check the timing mark on the flywheel. it should line up with another mark on the magneto backing plate.
I do this just to see what the last guy did to the bike. Forensic work on the dead body if you like.

Ji

[Ji Gantor]

Check out the air filter.
If the previous owner was riding it without a filter or a disolving filter then the engine will need a total rebuild.
This filter is clean but oil free.
5 out of 10.

Ji

[Ji Gantor]

The L was the third YZ125 to get a power valve system. This system is very similar to the first generation power valve installed into a YZ. Check to see if the valve has been installed correctly. The hole in the lever arm should line up with the hole in the cylinder. I adjusted this one to get it as close as possible via the slotted hole adjuster. It still does not line up but not to bad. The engine would still start with the valve in its current location.

Ji

[Ji Gantor]

The exuhast pipe on this bike is in very good condition. No dents just a little surface rust.
Nothing a lick of paint will not cure.

Ji

[Ji Gantor]

Lift up the fork skirts to see if there is any rust on the hard chrome sliders.
Nope, these look pretty good.
The seals have a build up of dirt and stuff but are still soft so I will check their oil content and see if the seals are still functional.

Ji

[Ji Gantor]

Check the rubber carburettor boots, front and back for holes or cracks.
These ones look like new.
Best I have seen so far.
Most of the time they are perished.
Yamaha do not have any more of these boots so if needed try Ebay.

Ji

[mainline]

hey Ji, whereabouts did you pick up your Dial Indicator. I'm having trouble finding one that locks into the spark plug hole like that

Cheers

[Ji Gantor]

Hi Paul (AKA Mainline),
The Rat stickers are going to have to go.

The two stroke timing gauges are made in the States.
They come up from time to time on Ebay.
If you need to use it I will come over and time your bike if you would like.

Ji

[Ji Gantor]

Another system on a bike that never seems to get any attention is the linkage system on a mono shock.
Owners just keep on running their bikes through salt water or sandy tracks and never even give the linkage a second thought.
The linkage system has about twenty bearings and seals and should be serviced at least once a year.
All the seals and bearings on my old girl will have to be replaced.
 
Ji

[Ji Gantor]

The shock on the L is rather state of the art for its time.
It had external compression and rebound adjustment.

This shock when tested by pushing down on the seat and releasing has no oil or gas.
It is totally working off the spring.
When we take a closer look we see some oil drops which have leaked out of the seals.

The shocks need a rebuild but the spring is quite stiff and only needs a paint job.

Ji

[Ji Gantor]

If you are going to paint or powder coat the chassis always check to make sure that all the brackets are still attached and in the right place.
This bike has a side number plate bracket broken off.
I will have to mock up a new plate with the number plate, tack weld it to the frame and then TIG it on.

Ji