Not so common ETS 250

[Blurredman]

Sounds good! Keep us updated!

[S Barrett]

Hi, I'm new here but I've just completed the restoration of an ES 250/2 and now I've acquired an ETS 250.
I can confirm that the frame and ancillary items are genuine but there is confusion about the engine and I have been informed by some knowledgeable people that the engine is no different to the ES engine despite what it says in the MZ ETS workshop manual supplement.
Are the engines the same or is there someone out there that can confirm the differences in the engine supplement?

I'm puzzled

Thanks

S Barrett

[breakwellmz]

Lovely looking bike that, obviously a very thorough restoration, how do you like it?

I`m no expert but for what it`s worth I thought the engines in the ES and ETS were the same.

[S Barrett]

Hi,
I'm beginning to think the same despite the documented differences in the ETS manual nobody has ever confirmed anything other.
The ES, I've done a comprehensive build, altered 4th gear ratio, blueprinted the engine as closely as possible, balanced the crank to 55%, cerekoted the piston and fitted the Smart Carb (The carb without jets) unfortunately I haven't ridden it due to health issues but I hope to soon.

[S Barrett]

[Blurredman]

Nice bike! I would like to know how that smart carb operates!

I think a lot of people don't realise that the ETS manual has that ES/2 suppliment (?) and just work from the original manual which is not appropriate for ES /2's post 1969/70 which all UK bikes seem to be.

What differences in your ES have you found with the ETS engine?

[S Barrett]

Hi,
The ETS boasts 20 bhp so the first question that springs to mind is how?
What differences are there in the engine to produce that power differential?

As you would imagine the port timing and compression ration are different and the inlet manifold is supposed to be shorter making a shorter inlet tract. That said it also says the inlet port should be Trapezoid shaped but so is the ES?

The Smart Carb, they have cleverly vented the float chamber into the venturi which raises or lowers the fuel level in the float chamber to meet demand. Its more complex than that but that's the principle and it delivers fuel throw one nozzle that you or I would call a main jet. Changes in atmospheric pressure are compensated by adjusting the needle height by a knurled nut at the carb top which takes seconds, likewise you can richen or weaken the same if you fitted an expansion chamber for example.
That's the principle but it is a little more complex but not in operation just build etc.
I sometimes eat biscuits when im bored!

[Guesi]

About the ES/2 and ETS engines:

The first ES/2 models from 1967 on had 17,5 HP.
Later, I think from 1970 or 1971, the engine had 19 HP.

The ETS 250 always hat the engine with 19 HP.

So the late ES/2 and the ETS engines are the same.

The differences are another cylinder and another cylinder head.

The early ES/2 cylinder had an oval inlet from the manifld, the 19 HP had a trapezoid inlet.

[S Barrett]

Hi Guesi,
Thank you but you make no mention of port timing differences with the ES/2 showing 140 inlet, 113 transfer and 160 degrees exhaust whilst the ETS shows 155 inlet, 118 transfer and 170 degrees exhaust and the compression ration differs so the two engines were clearly different.

[Blurredman]

Don't forget carburration, plus exhaust differences!

[S Barrett]

Hi Blurredman,

Thanks for that. The early ETS lists a BVF 28 N 1-1 carb with slight jetting differences whilst the later lists a BVF 28 N1-3 which is identical to the late ES250/2 but again jetted slightly differently.

I am unable to find any reference to exhaust differences if you may enlighten me please.


Thank you

S Barrett.

[Guesi]

Hi Guesi,
Thank you but you make no mention of port timing differences with the ES/2 showing 140 inlet, 113 transfer and 160 degrees exhaust whilst the ETS shows 155 inlet, 118 transfer and 170 degrees exhaust and the compression ration differs so the two engines were clearly different.

I donß t know where your informations are from...
I talked about the 19 hp version of ES/2 and ETS.
The have the same cylinder and the same compressio rate...
Sparer part number for both is: 05-42.072
And they have the same exhaust.