Featured Tiger 90 Rebuild

Filled the primary cases with about half a pint of ATF.

 

A can of Alaska white paint arrived today. This is for the front mudguard and fuel tank both of which have large patches where the paint is missing.

 

Here is the bottle of Automatic Transmission Fluid that i used. It is a cheap non-branded item, but it does the job of keeping the primary chain lubricated. Many years ago i used to use engine oil, but today modern engine oils are full of anti-friction agents and too slippery to use if they come in to contact with a clutch.

 

Interesting. I’m in the UK so imagine that ATF products would be similar to those in the USA. I have this in the primary case of two other bikes and the clutches are all right with it. Let’s see what the clutch on this bike is like when it is running (soon i hope!).

 

I am working on the front mudguard carrier today. The bolts came apart, but are too rusty to be put back on. The carrier has some extra bends which need straightening.

 

Electrics today. The rectifier is dead (it’s shorted out internally) and the zener diode looks bad but can’t be tested properly until the engine is running. The best option is to replace both with a modern solid state rectifier-regulator.

 

Nearly wired up.

 

Straightened the front mudguard and its carriers. Test fit on the bike to check all is good before painting starts.

 

A picture of the head, with the new valve guides and a home made drift, alongside. Next step was to put the head in the oven and heat to 330 deg C.

 

Picture taken through the oven door, the reflection on the glass window in the door makes for a poor photo. The head is wrapped in tin foil to catch any stray oil drips, and in the top right hand corner is the thermometer. i left it in at 330 deg C for fifteen minutes as that’s how long the engine takes to warm up when running. I found doing it this way doesn’t leave the oven smelling of oil, which keeps the wife happy.

 

The old valve guides. These have a slight bronze colour to them, the new ones don’t.

 

Head with the new valve guides in.

 

Next step grinding the valves in. There is no change in valve angle with the new guides, so a grind with fine paste for the three original valves, and then a leak test. The one valve that was replaced will be ground with coarse then fine paste. None of the seats needed re-cutting.

I am still wondering why one of the valve stems was excessively worn, while the other three were all right. My guess is that there was not enough oil getting to the right hand exhaust valve.

 

I spoke too soon! After the valves were lapped in it was obvious that the two inlet valves were not making full contact with the seat. So out with the cutting tool and dressed the seat to be correct with the new guide.

 

Ready to assemble the head. New valve springs as the old ones were below spec.