A while back I fell into a 1975 DT250 project. The bike itself is a real Frankenstein- all sorts of mismatched parts - the motor is from an earlier DT, mystery front end, and various other hodgepodge parts. The silver lining was the bike did come with about three large boxes of parts including the original motor.

I have a personal rule never to start a project until I obtain a title (as I have learned this the hard way) But with these new covid – 19 restrictions and a 12-year-old without school, sports or friends It’s just too good of an opportunity to not start a father/son project! I have rebuilt a few top ends but never a full engine rebuild and its always been something I hoped to tackle one day. And like I said that day now! So my son and I are learning together and will obviously be relying on this forum for help.

Phase 1: Rebuild the original motor


It looks like maybe the piston ring pin got loose? Thoughts?


Can I just sand down this head?


What about the inside of this case, will these be ok to use as is?

What a great way to make lemonade out of lemons! You are building irreplaceable memories with your kiddo!

That's interesting. I've never seen the results of ingesting a broken piston ring. I will follow this thread and learn what I can. I have two 75 DT250s so I will help you along when I can. One is real ruff and the other one is like new. Good luck and hats off to you for doing a father and son project. I did many of those with my two boys and it left us with long lasting memories.

While cleaning the engine case we noticed some damage on the flywheel side next to the clutch actuator. It doesn't seem to affect anything, bolt still has plenty of thread. Is it worth taking a a machine shop and see if they can repair it? What do you guys think!

I know how I'd try fixing it.......
J-B Weld with a bolt threaded into the tapped hole.
Maybe a slight film of soap on the bolt threads so that it will backout without disturbing the J-B patch.

Looks like a job for those aluminum welding rods you melt with a torch... you know the ones in the Facebook videos ?

I agree with schu, JB Weld would work. I once repaired a cracked aluminum oil pan on my wife's BMW after she hit a parking block. She drove it for two year with that repair and it never leaked.

We decided to have it repaired- $60 not bad