Featured Tiger 90 Rebuild

Made a stand for the engine. It took all day and the MIG welding wouldn’t go right. I suspect the welding wire has a thin oxide coat. It will be much easier to work on the engine without it rolling all over the bench.

 

Taking the primary drive cover off. Eight of the ten screws came out reluctantly with an impact driver, two had to be drilled out. The adjuster rod on the chain tensioner is snapped. The engine does not turn over with a spanner on the end of the crankshaft.

 

That could be where I find myself tomorrow.

 

Head bolts loosened in the correct order. Front rocker cover off.

 

Rear rocker cover off.

 

Head off. I’ve put some light onto the block so you can see the rust in the bores. Pistons are close to bottom.

 

Looking down the barrels at the piston crowns. There is a lot of muck there.

 

I’ve just noticed something in this picture - the con rods have different profiles where they are cut. They look different sizes as well, but that might be an artefact of the photo.

 

The inside view of the head. Lots of carbon, but the valves don’t appear to be recessed in the seats. I did notice that the top of the valve stems are pocketed (not shown in pic). Remains of a spark plug in the right hand side, needs to be removed. A quick check with a straight edge suggests the face is flat. There is a broken fin on the upper right hand side of the head (not shown). The exhaust collars and inlet manifold will be left in place while the head is rebuilt.

 

Took the points cover off and found that insulating material had been put on the underside. I guess there was a problem with it shorting out at some point.

 

There are eight screws holding the timing cover on. Even using heat and an impact driver only two came out. The other six are stuck and the heads are now chewed up, so I will drill them out. Would a rattle gun screw driver running on compressed air have got them out?
The four screws in the gearbox cover all came out OK.

 

Draining the sump, no nasty surprises came out with the oil. Before I started work on the engine it looked moderately clean, but with hindsight I wish I had degreased and power washed it.

 

Drained the gearbox of oil, removed the kick start lever, disconnected the clutch cable and removed the four screws and two nuts holding on the gearbox outer cover.
The outer cover comes off by holding the gear lever and pulling firmly.
The “inside story” is that the inner screws holding the gearbox together look untouched, so hopefully it’s never been taken apart. The kickstart return spring has jumped off it’s stop.
Before taking the cover off, I managed to move down through the gears to neutral.

 

Close up picture of the points, to serve as a reminder when I’m putting it back together. The left hand wire is black and yellow, the right hand black and white, but with the oil staining and colour fade over time they look the same.

 

Advance retard unit exposed when the points back plate is off. The thin bar sticking out of the centre hole is where I am making a bar to push the unit off the taper when I screw a 5/16 UNF bolt in the end.

 

The advance retard unit popped off without issue using the improvised removal bar and bolt. Now the outer cover can be taken off.