Yamaha_Rules69
11-06-2010, 06:22 PM
Hi, I have a nice original 1984 Yamaha Tri moto 200 that I am working on, and was looking for a little input on an idea I had. I got this 3 wheeler from the original owner. He used it for ice fishing, and thats it. About 15 years ago, the pullstart rope broke, and it had been sitting in a shed until I got it. I started working on it, and new right off the bat that the motor was stuck. I went to take the plug out, and it snaped off in the head! I really didnt put excessive force on it, it must have just been really rusted in there. I took the motor out, got the head off, and banged the piston free with a sledge hammer. The bottom end looks really nice, and clean inside. At least it had oil in it, and the oil even looked fresh. The head had a lot of corosion and rust, so I blasted out the inside, and plan on having the valve seats re-cut, and new valves and seals installed, I have an in spec jug, and new piston and rings.
Now for my question - I was wondering if I could drill out and tap the threads that are in there now - for a 12mm plug, to a 14mm plug (install helicoil for 14mm plug). The numbers on the plugs are slightly different - NGK 12mm plug (factory size) is somthing like D8EA and the 14mm I would be using would be a B8ES (you see a lot in 2 strokes). I think they would be the same heat range, and the thread reach is the same, so would I have any issues going this route? I have the helicoil kit for the 14mm - special tap for the helicoil OD and drill bit, seater tool, and everythig to do it correctly. Has anyone done this with good results? Thanks for any thoughts.
Now for my question - I was wondering if I could drill out and tap the threads that are in there now - for a 12mm plug, to a 14mm plug (install helicoil for 14mm plug). The numbers on the plugs are slightly different - NGK 12mm plug (factory size) is somthing like D8EA and the 14mm I would be using would be a B8ES (you see a lot in 2 strokes). I think they would be the same heat range, and the thread reach is the same, so would I have any issues going this route? I have the helicoil kit for the 14mm - special tap for the helicoil OD and drill bit, seater tool, and everythig to do it correctly. Has anyone done this with good results? Thanks for any thoughts.