MZ/MuZ Riders

My 1972 ETS 250 trophy Sport seems to have an oil leak, this only shows when I ride the bike and the oil runs down on to the casings at the front, I'm unable to find source of said leak?

Can you post a picture? get a better idea of where you mean. Always worth checking you haven't overfilled the gearbox with oil. Also give the oil a sniff. If it smells of petrol it's probable that the crankshaft oil seal on the primary side has gone, and this will pressurise the gearbox and oil will come out of any orifice it can find

I made sure the oil I put in was exact, it seem to be coming from the front near the bolt that joins the cases together, it doesn't smell of petrol and it spots onto the cases both sides.

Chain lube ?
That crap usually gets everywhere.
Cool.
Srinath.

Srinath wrote:Chain lube ?
That crap usually gets everywhere.
Cool.
Srinath.

Deff not chain lube,

My trophy sport does exactly the same,and in the same place,the only place I;ve narrowed it down to is the base gasket which I'm aiming to change when I get a spare weekend,although it doesn't always leak badly it seems messier when I give the bike some welly! ...when its ridden sedately theres hardly any oil visible.

Always worth replacing the base gasket on a 2 stroke, If oily fuel can come out on crankcase compression, air can find its way back in as the piston goes up, and mess up your mixture

philtrophysport wrote:My trophy sport does exactly the same,and in the same place,the only place I;ve narrowed it down to is the base gasket which I'm aiming to change when I get a spare weekend,although it doesn't always leak badly it seems messier when I give the bike some welly! ...when its ridden sedately theres hardly any oil visible.

Thanks for that! it sounds a possibility, I will order a base gasket from the MZ Shop on Monday.

Let us know if it makes a difference if you get round to changing the gasket before I do mine,it should also improve compression and maybe give the bikes a bit more oomph!

philtrophysport wrote:Let us know if it makes a difference if you get round to changing the gasket before I do mine,it should also improve compression and maybe give the bikes a bit more oomph!

Looking at my manual I don't think you can replace just the sump gasket, I rather think it's a full engine split, so a bit more involved than I thought.

Hang on, which gasket are you talking about? ( MZs not having a sump!) The gasket I and I think Phil was talking about is the one between the bottom of the barrel and the crankcase
http://www.themzshop.co.uk/product/cylinder-base-gasket_t3/

Which is a matter of removing the head, removing the cylinder and replacing the gasket (using Stag or a similar jointing compound.)

I think what you are referring to is the gasket between the crankcase halves

http://www.ost2rad.com/MZ-Spare-Parts/Bearings-Sealings-25/Motor-center-seal-MZ-ES-ETS-TS-250.html ( couldn't find it listed at MZshop)

which would entail an engine strip.

Absolutely...the gasket i'm talking about is the cylinder base gasket found between the bottom of the finned barrel and the crankcase,a relatively simple removal of cylinder head and barrel and application of a new gasket and some Hylomar blue or similar compound should sort it...

philtrophysport wrote:Absolutely...the gasket i'm talking about is the cylinder base gasket found between the bottom of the finned barrel and the crankcase,a relatively simple removal of cylinder head and barrel and application of a new gasket and some Hylomar blue or similar compound should sort it...

I have had 3 MZs over the years, my last one was an ETZ250! and have never had this problem before, is this common on the ETS 250s?

Not sure if its a common fault or not,i do know that the youngest Trophy Sport will be about 40 years old and if the gasket is the original part then it cant be blamed for springing the odd leak after all these years..

As I said earlier the job should not be unduly difficult and wont do any harm if its proved not to be the culprit...nothing to lose.

Also some of the replacement gaskets available through the years have been of dubious quality.