Sorry for the lengthy post but I'm pretty stumped with this one. If you don't have time to read the details please just read the bold section and tell me what you think.

About three months ago I was riding my 89 to work and after riding maybe a mile at 35 MPH I heard a very loud and prominent clacking noise coming from the motor. I turned around and went home and tried tightening my cam chain tensioner which did nothing, the noise was louder than cam chain noise usually is, but I tried anyway. I took both side covers off and pulled the clutch out and couldn't see anything unusual. Next I pulled the valve cover off and checked and adjusted all of the clearances, nothing off very much there. While I had everything apart, I went ahead and rebuilt the carbs, put it back together, fired it up and the noise is still there. It makes noise in neutral and every gear and gets faster when I rev it, and it sounded like it was coming from the front, lower section of the motor. My stethoscope made me believe it is loudest around the 2nd cylinder. I pulled the oil pan off to see if there was any broken pieces laying in there but I found nothing. I pulled the motor out and pulled off the head. I found that the tip of the splitfire plug for the #2 cylinder had broken off, which caused a lot more carbon build up than the other 3. I found the tip embedded in the carbon, and it doesn't look like it caused damage to the combustion chamber, piston, of cylinder walls. The number 2 spark plug was a little more backed out than the other 3, but I don't remember if I had started pulling out my plugs 3 months ago to check the valves clearances. Could a loose plug cause such a loud noise? I do know that when I started it up after I did the carbs, air was forced up past the number 2 plug boot, but I thought maybe I hadn't aligned the valve cover gasket properly. I pulled the cylinder block off next and all of the rings look good, and there is no play at all in the rod bearings or around the wrist pin. I haven't checked the cylinder clearances yet, the I can still see hone marks on the cylinder walls. The clacking noise doesn't sound like piston slap and doesn't go away after the bike heats up. Any more suggestions? Thanks

 

1. does engine make horrid noise during idle or only at speed?

2. what do the number 2 cylinder valve seats look like? any chips? if sparkplug tip is rattling around cylinder and gets pushed past a valve seat and not clear, the valve as it is closing could catch the little bugger between the valve itself and the valve seat.

3. do all cylinders pass compression test? you can do this instead of checking piston/cylinder clearances.

4. with the head back on and tightened back down, what happens when you hand rotate the engine? in otherwords, how does number 2 feel as you go through it's cycle, does it feel tight as you get to TDC?

5. what do the valves look like? any indentations? any of the valves bent?

6. any non-oem indentations on the piston crown or valve cutouts?

7. does sparkplug rattle when not snugged down? if sparkplug hole is out of round, it could easily back itself out. if so, you may have to put in a helicoil to tighten things up.

8. does sparkplug protrude too far into cylinder? if so, this may explain why tip was broken off.

i can't think of anything else right now, but if i do i'll add to post.

good luck.