YZ125 L 1984 Basket Case Restore

[Ji Gantor]

The power valve is not indexed via the holes lining up.
The holes should line up.
As previously stated when removing or installing the power valve you must place a pin through the holes to hold the linkage system while tightening or undoing the retaining nut. If this is not done the linkage arms are bent and the power valve system is no longer timed with the engine.
My linkage arms are bent and will have to be replaced.

Ji

[DJRacing]

Usually there is allot of wear in the linkage arms and its good to clean that up. The governor gear can be altered by removing one of the washers(if I remember correctly). For aligning of the powervalve in the correct position there was usually a DOT mark and that was to be at the top, and then the linkages tighten up. A good trick to do on the rebuild is to check that the powervalve opens completely and that can be done by lifting the linkage arm and checking the valve up the exhaust port. Put a small mark(line) on the mating surface of the powervalve gasket surface where the slot for the pin is pointing to when the powervalve is fully open. When you start the motor and rev it make sure that the slot for the pin goes all the way down to the mark(line) that you made. Also check that the powervalve cover doesnt foul with that slot, as I have heard of it happening.
Another thing to keep an eye out for is port timing.

[Ji Gantor]

Hi DJ,
Yes I agree that the linkage arms and joints get sloppy and need a tighten up.
The power valve should be checked to see that they have full movement prior to starting and that the indicator arm does not foul on the cover.
The linkage also has a plate that is attached to it via 2 screws inside the clutch cover. If someone has not used a pin to prevent the valve rotating while undoing the fixture nut this plate can become bent and throw out the alignment.
The linkage boss a small rectangular plate with a slotted hole that fits onto the power valve prior to the linkage is supposted to have a punch mark on it that should point straight up. This places the the valve in the correct position. Unfortunately mine does not have the mark. This does not matter as long as it points straight up, which mine does not.
So as DJ suggests it could be the linkage arms, it could also be a bent plate inside the clutch cover. If the engine has had a hard life the power valve itself may be the problem. seized engines cause damage to the power valve. If the cylinder was bored out with the power valve in place this could create a problem.
The power valve holders one on each side of the cylinder are bearings or bushes. These also wear and can throw the indexing out a small amount.

I will be stripping down the top end this week end so we should have a better idea what is wrong come Monday.

Thanks DJ great add to this topic.

Ji 

[Lozza]

There is a few good tricks with these type PV's

[Ji Gantor]

On Saturday we dismantled the rest of the bike.
The engine came out of the frame carb and all.

Ji

[Ji Gantor]

In the afternoon we removed the head and cylinder and discovered all this engines darkest secrets.


Ji

[Ji Gantor]

For all you that have not replaced your swingarm bearings and seals and for those that have not used the following product I present the All Balls Swingarm Kit.
If purchased on Ebay they don't cost much and arrive from the States in 2 weeks.

Ji

[Ji Gantor]

The kit has all the seals, bushes and bearings required.
Normally I just take all the old bearings and seals down to the bearing shop and pick up a set but this is even easier.

Ji

[Ji Gantor]

When ever performing an engine rebuild always replace all the seals.
They don't cost much and are usually easy to remove/install.
It can save heaps of time and money later when they do go wrong.

The first to be looked at with a water cooled engine should be the impellor seal in the clutch cover.
If this leaks you will have oil in the coolant and coolant in the gear box oil.

This seal was had it.
The aluminium housing is corroded so i heated the rubber up with a little gas.

Ji

[Ji Gantor]

The way to remove this seal is by placing a small pin punch through the access holes provided in the back of the cover and tapping with a hammer. Fully support the cover when doing this or you may have to buy another cover.
I am sick of seeing housings destroyed by fools that try and remove a seal by bashing a screw driver down between the seal and the housing. This does not work and it will never seal again. Please if you don't know how to do it please ask and save the next guy that buys your bike the problems.

Ji

[Ji Gantor]

When you have the clutch cover off always check the impellor, it is the heart of your engine. If it stops working the engine will blow.
This impellor has stopped working.
The plastic propellors have seperated from the steel shaft.
The shaft turns but no water is being pumped.
The unit is one piece when new. This unit is still one piece and may give the impression that it still works. Grab the plastic bit and the steel bit and twist, they should both turn at the same time.

Ji

[Ji Gantor]

I needed a flywheel puller so I ordered one from my Yami dealer.
When I went to pick it up it was for a modern Yami so I decided to make my own.

I purchased a 40mm long M18 1.5 bolt and a 50mm long M8 1.0 bolt.
When I got home I placed the M18 into the lathe and started turning.

Ji

[Ji Gantor]

Once all the work was done I had a new flywheel puller.
It cost $10 for the bolts and took half an hour to turn up.

The tricks to removing a flywheel are,
First soak the unit in WD40 for a while,
Tap with a pin punch and a hammer the woodruff key to make sure it is not binding on the flywheel,
Screw the puller on and tighten the end bolt to place force onto the crankshaft. Only use a small spanner for this or you may damage the end of your crankshaft,
If the flywheel still is not off, with a steel hammer tap the end bolt of the puller to jar it. Don't whack it just tap it.

Ji

[DJRacing]

Ji, the other bearing that will need replacing is the one where the clutch actuator arm goes into the cases. Its usually a stubborn little roller bearing that requires a slide hammer. The oil seal that protects that bearing always seems to let a little water in over the years.

[Ji Gantor]

Hi DJ,
Your to quick, but very right.
I am slowly getting to all the bearings and seals.
Just not enough time in the day to get them all done and posted here.

Great add mate, keep it coming.

Ji