For the past 3-4 weeks, every time I would start my enduro I would hear a metallic slapping. Just a few and then it would go away. Couldn’t nail down the exact location before it disappeared. Bike still ran good. More and more though it wouldn’t start with the electric start. I had confirmed the timing and points condition, battery charge, etc. it would start with starter once warm though. Started thinking maybe brushes were starting to wear out already. Since complete rebuild of every component I’ve put about 1600 miles on it. It’s my first motorcycle, restoration, enduro, so it’s all new to me. Started wondering if the noise was the beginning of piston slap already. I don’t know what it sounds like, so it could be. So I go to start it and it doesn’t want to start but I finally get it kicked over. Slap, slap, slap. Huh, more than before. Somethings up, says my experience of one. It wanted to bog when hitting the throttle like it was loaded up or cold or the carb was plugged up. Wouldn’t stay running though, which is new. So I restart it and blip the throttle, which made me think I saw a puff of smoke around the cylinder somewhere. I got down and blipped it again and sure as shit I got a case of head slap! A little puff of exhaust was escaping between the head and cylinder. I was surprised it even ran once I saw that. So I slapped my my head and thought, I guess I should’ve checked the head studs and retorqued them once in a while over the last 18 months! So I did and then went for a good little ride and she really accelerated smooth and quickly now. Once in awhile it would kind of sound flat as the rpms got up there. None of that. Just strong smooth acceleration, well, good for a 125 anyways. I guess I need to bone up on my maintenance practices and wave a few wrenches over it every once in awhile. Lesson learned! So, torque your heads once in awhile!

Good diognosis Dr.! I've got just about (the mirror image) of your tank dent on a newly purchased DT125. Dent in mine has the same crease, how'd yours happen?

It’s a good thing I pay myself on a case by case basis and not hourly, as it took me 4 weeks and assistance from this great resource to get spark after putting it back together
Another time while on my way to work it quit suddenly when the extra spark plug backed out of the head and ended up in the gutter a hundred feet behind me.
The gas tank came off a parts bike and was preformed when I got it. I’d be interested to know what happened also. Actually that tank is only half as bad as before. I’ve succeeded in pulling the dents half way out and will work on it some more when the snow flies. Pin holes on the bottom left side forced me to line it with POR15, which has held up well so far. My plan is to use it on a retitled parts bike as a daily runner once my good 74 tank is done and back from my brother.

P.S, I’m all inclusive when it comes to dent-murals!

Sorry, had to join in on the tank dent hijack...my beloved DT175..Yooper Bike, had a lot of fun on it this fall....
Tried pulling the dent(s) with a Harbor Freight Puller...no go