After years of wanting this project, I purchased a 1979 DT125F today for the grand sum of $100. I know, I know...the $100 money pit, right? Figured I should jump on it while my husband was excited about it too. Anyway, the bike is complete with the exception of mirrors and is in pretty decent shape. The engine is in a box and appears to be all there. The seller bought it to build for his kid, but just never got around to it. Plus I think the kid wanted the shiny new bike that he was sitting on in the garage instead. The bike came with a DT175 top end in addition to the 125. Does anyone know if the 175 top end will work on the 125 bottom end? Any modifications that need to be made? Is it worth the effort? Any common problems with these bikes that we can nip in the bud while it's all apart?

If you have the complete top end, ie piston, rings, head and wrist pin then yes it will go straight on.

There will be some pretty drastic carb mods i'm afraid.......

A 140 main jet and a 5J11 jet needle

The only common problem is people who don't introduce themselves in the new members section , 2 minutes saying hi, from bikesville in bike land 50 kids and a morgage for example, will get a much wider response from the regulars.

Thanks for the info. Will definitely go say hi - crying kid that had a nightmare kinda interrupted last night. Welcome to parenthood, eh?

Yep know your pain our eldest had colic, don't worry the crying and whinging only lasts indefinitely.

... don't worry the crying and whinging only lasts indefinitely.

So say Cynic; so say we all.