ETZ 250 carb screws & gearbox oil seal

[Lone-Wolf]

Wotcha.

O great font of MZ knowledge . . . there are two adjustment screws on my carburettor ( see below )
A large one, and a small one.
I dare say one is a mixture screw for when running on pilot jet - I don't know what the other one could be - I know it isn't a throttle stop screw for adjusting the tick over.

What screw does what ?

Do you screw it in, or out, to richen the mixture ?




Now because the bike has been standing for so long, the oil seal behind the gearbox sprocket seems to be leaking.
Can this seal be changed without splitting the engine ? . . . ( please say yes )



Thanks in advance.

[mr_luke]

Not sure on the screws I'm afraid, as my carb is different. Good news on the oil seal though - behind the sprocket is an aluminium seal carrier held on by 3 screws, and the seal is pressed into this. There may well be a shim behind it. Mine has a leak from this area, but I'm not entirely sure whether it's coming from the seal, from the small plug covered in orange stuff in your picture, or from the neutral switch. Keep on meaning to have a look, but it's only been doing it for 7 months..!

[Lone-Wolf]

Good news on the oil seal though - behind the sprocket is an aluminium seal carrier held on by 3 screws, and the seal is pressed into this. )

Wotcha.

That's what I wanted to hear - many thanks for that information. . . . . . .Now where did I put that socket set ?

[edit]

Just been and looked - and there on the floor was what can only be described as a very small core plug . . . .just small enough to fit in the "orange hole" in the above picture. The orange stuff is silicone sealant. I'm guessing that small core plug should be covering that hole ? I hope it should, 'cos that's where I've put it.

A case of wait and see if the oil leak returns.

[arry_b]

Leaks around the core plug are very common, and yes, you've put it back in the right place.

Carb screws:
The bigger one is used to adjust the tickover. In slows it down, out speeds it up.
Smaller one is a normal mixture screw.

[Lone-Wolf]

Leaks around the core plug are very common, and yes, you've put it back in the right place.

Carb screws:
The bigger one is used to adjust the tickover. In slows it down, out speeds it up.
Smaller one is a normal mixture screw.

Wotcha.

Ah - thanks for that.
I'll try to remember to take a small screwdriver out with me and have a play once everything is up to running temperature.

[Lone-Wolf]

Wotcha.

Well re-fitting that little core plug has stopped my MZ from leaving a small deposit on the floor.

Can't quite get the carb set up correctly though - I might just treat it to a Mikuni VM30 later in the year.

[Tubaman]

Sorry to resurrect an old post, but I've also got myself confused about which of the carb screws is which. My Haynes manual calls them the "Pilot Screw" and the "Bypass Air Screw", but the diagram in there is not clear either about which one is which.

I'd always thought the bigger one (topmost left) was the pilot screw, and the smaller one (lower right) was the bypass air screw. But having just fudged things up following the method in Haynes to adjust things I'm not so sure, and to make things worse the smaller brass adjuster has partially disintegrated on me and won't now unscrew so I can replace it

For reference, here's how how Haynes says to adjust it (paraphrased to avoid getting hassled by copyright bods):

Ensure engine is warm
Unscrew the pilot screw by 3 turns
Start engine and adjust bypass air screw until engine runs smoothly
Slowly screw in pilot screw until idle spped is highest, then back it off by a quarter turn.
If required, reduce the idle speed by backing off the bypass air screw to get 1200rpm.
With things in good condition pilot screw should be 2.5 turns out and bypass air screw 4 turn out.

Will annyoingly have to buy a new carb for mine now i've broken the smaller adjuster, but would be nice to be sure which screw is which!