First post from a long time lurker. I haven't seen much about putting a Tyga 300 kit on the MC18 so figured I should share my experience.
It all started out with seizing the rear piston. That was caused by a floppy loose exhaust valve petal hammering on the bottom of the port, displacing metal into the bore and making a tight spot. SQUEEK!!! I was hoping to get the cylinder re plated but the exhaust port bridge is cracked. The idea of the 300 kit being new and available parts was a real incentive to go that way.
The pistons, cylinders and heads bolted on as advertised. I did it with the engine in the frame, so it was a little more of a challenge than when I had previously built it on the dining room table.
The first problem I ran into was getting the coolant hose on from the rear cylinder head to the thermostat housing. There isn't much room for my fat fingers in there and the hose doen't have quite the right bend. I did eventually get it on. It doesn't look all that good but is on securely and not leaking.
Next there was a problem fitting the chambers. The upper one went on OK but the lower one was too far back for the mounting bolt (by the foot peg) to line up. I had to machine about 1/16" (1.5mm for you technically advanced folks!) off the adapter spigot to get it to fit. Of course there isn't room for the gasket so I made one of .01" copper. That seems to be working.
The other problem was the HT leads from the coils were too short. This is because the new heads have the plug in the center and the original ones were offset. I had a friend X-ray them to see how they are put together. Turns out it is a fairly standard arrangement, a little screw in the middle the lead gets screwed onto. The only problem was getting the old leads off and preparing the coil for the new lead. They were glued in and took quite a bit of digging and scraping to clean out.
Yesterday I put the body work back on the bike. The center piece in the lower needed a little carving out to clear the lower spark plug.
It started up and runs! I have put it through a few heat cycles and am about to take it for a short ride. The jetting is currently set a little richer than the Tyga base line. I expect to get some practice taking the carbs on and off in the coming weeks!
Peter
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