Repaired the clutch cable (as mentioned in a previous thread) and found the one I had was about 15mm longer (or more accurately has more travel) than stock so I sorted that out while I was about it. Now the clutch activation is in a good spot with the adjusters only half way out whereas before I had them almost entirely wound out.

Anyhoo, in between this I've been dialling in the carb. I was getting rev hangs at >4k so tried a bigger main jet. It was fine for a while but it's doing it again. Pretty sure it's going to be (at least) the magneto side crank seal. Thankfully I already have an impact wrench and magneto puller on hand so doesn't seem like a big job.

A few questions: which way round does the seal go? Spring side in or out? Black gasket sealer, worth applying to the outside of the seal? Should I be doing the clutch side at the same time? Or for that matter, all the engine seals? (I can get a kit of the whole lot for £20 + P&P from Yambits.) Finally, I'm sure I read on another thread about SD & SW type seals. Something I need to look at?

If it's a 125 or 175 use the IT175 dual lip seal.

Thanks, Mark, it's my DT175 (UK, '76)