Top overhaul

Well while waiting for the standard size piston purchased from ebay (shipped from the US), I decided to proceed with installing my old cylinder which has now been rebored to +1.75 with matching pistons and rings.

I'll bee needing these ..

Piston, rings, head bolts, piston pin, piston 

bearing, circlips and a gasket set.

Since the cylinder was off the bike, I decided to clean up the crankcase gasket surface, removing the old gasket material. Well this should have been easy but the cylinder studs got in the way... so I removed the studs to enable better access. Bad idea. 

The first three studs came off fairly easily with two nuts locked together but the fourth didn't want to play ball. A bit more force (yeah I should have know better!) and the stud broke off at the base!

Well I stopped for a while to look at my options. The usual course of action would be to drill down the middle of the remaining portion and then use an easy-out. I really dread using this as my success rate is less than 50%. Second option would be to take the engine out and bring it to someone who actually knows what they're doing.

Trying to put off making a decision I looked around the bike and I noticed the Phillips bolts holding the coil mounting plate had butchered heads. Since I had my tools out I tried to remove them with my impact driver.. well I made things worse! The Philips head was totally rounded out even though I was using the correct bit! Well at least this was something I could solve as drilling down Philips screw/bolts is easy as the damaged area will centre the drill bit. This went well and the plate came off and the threaded remnants of the bolts unscrewed easily.

Since I had the drill out I decided to try my luck on the broken stud. Since the break was reasonably flat I had a good chance to get the bit smack in the centre. You don't want to drill off centre as it will damage the threads in the casting! I started by centre-punching the broken-off stud and mounted a 2.5mm drill bit into my trusty Bosch hand-drill. oh-oh.. the front wheel and mudguard was preventing me getting a straight shot at the stud so that had to come off first!

 
The 2.5mm drill bit made a nice hole..centred well too and was followed by a 3.2mm bit. When it got to around 5mm deep I inserted the easy-out. (If you're not familiar with these they resemble a big left-handed screw and the idea is they will screw into the nice hole I just made and reverse the broken bit out. Nice in theory but what can happen is they break inside the broken piece and now you're really screwed as the easy out is made of hardened steel and you cant drill it out). I tried to move the easy out but it was stuck fast. I then heated the crankcase where the stud was mounted to see if that would help (actually this is what I should have done initially when faced with the stuck stud) and with a bit of force the broken stud unscrewed.. Really dodged a bullet there!

I then installed the piston, cylinder and head... damm the gasket set does not fit! I made a new base gasket from gasket paper and re-used the head gasket. One tip when cutting gaskets is to use a hole puncher at the corners. I had one made for leather which has several sizes. Once you've made the holes all thats left is to cut reasonably straight lines. In the picture below it looks weird because the paper is not flat!

When it came to re-install the coil-mount plate I hit another snag, I had bought 2 bolts with a countersunk head but these would not screw in. I then compared new with old and the threads were different! As this was late evening on a Saturday the shops had closed so I put everything away.

To be continued!