Smoke screen MZ ETZ250

Head scratching today, bastarding oil leak from gbox to engine so the smoke is just unreal


Allen Millyard had the same with his Kawasaki off road bike. The seals had gone in the crank. Have a look at his video of him repairing it.

New crank seals already, it’s summat elsewhere

Haven’t got a blocked jet or porous float have you? Is it definitely oil or could it be fuel getting in the crank other than through the carburetor?

It’s gbox oil, I’ve just topped up to see how much has been consumed which is 150ML in the only mile I’ve done on this bike. Also it’s a dry engine on the outside and gbox gets pressure when I send compressed air down the spark plug hole.

1 Like

Time to have your ring inspection done

It’s two stroke!! It has massive holes in the barrel to let stuff through :rofl::rofl::rofl:

1 Like

I just wanted to make a bum joke… :joy:

But you do need to recheck the seals, just because you know they are new, doesn’t mean they haven’t somehow been damaged in installation or just failed after being 30 years sat on a shelf waiting for their moment (and suddenly it’s all a bit much) Can you drizzle a little oil over the penetrating shaft (is there only one?) seal whilst forcing the air in… wouldn’t it bubble if it(they) were leaky.?


I’ve done that with soapy water and unfortunately it didn’t have a fault :disappointed: so it’s a crank case split job now. Oh well it’s another bonding session :rofl::rofl::rofl: I suppose

Made a new gadget!!

Stripped crankcase and built up but before I finish engine I wanted to find a away of testing what I’d done…


Whats happening there then?

Looks a bit ‘steam punk’ I know. It’s to test crank pressure leaks on a two stroke. Tests new seals and any crank case cracks