Aftermarket exhaust for etz 250

[JawasandMZs]

I see unbranded replacement exhausts on ebay for an extremely reasonable hundred quid delivered. Anyone able to comment on thd quality of these items? Personally I'm doubtful they're gonna match the original.

[Puffs]

There is not 1 maker of aftermarket exhausts, there are probably many, from the EU, Turkey, India, China, Taiwan, and maybe even more. Hence it is a bit difficult to give a blanket reply to your question (certainly wrt the total harmonic distortion of their quality).

While original (from Zschopau) will be difficult to find, and traders may disagree, IMO there is not necessarily a strict correlation between quality and price.

[nice2day]

When it comes to exhaust systems particularly the silencer part there are many aspects that require evaluation. I'll list them starting from the outside to inside and comparing them to the factory originals:
1) The basic shape...is it made in exactly the same shape? (length angles and curvatures)
2) The general fabrication...is the welding good and is the surface undented?
3) The chrome plated finish...has the steel been polished well and does the chrome plate have the same quality?
4) Is the steel the same gauge or thickness?
5) Are the internal baffles identical to the original design? This is nearly impossible to see although one could try shining a torch into the outlet to see some detail.

Point 5 above is probably the most important as regards 2 stroke performance, economy and sound output level. A 2 stroke relies so much on resonances within the exhaust system so changing the baffle design is guaranteed to change the performance in some part of the power spectrum. Often 4 stroke replica silencers have less baffles and so are often louder (too loud?)

On my etz 250 rebuild I bought a silencer from a well known Ebay seller and I have to say the quality looked excellent with good chrome, excellent welding and not a blemish or even a small dink anywhere. Unfortunately I could not compare weights to the original as it was thrown away earlier but I would have to have made some deduction from its weight as the carbon build up would have added several grams to it but it felt decently weighty. The sound of the exhaust seems to have the correct volume and tone but a direct comparison with an original is not available to me. However only full bore maximum performance test will reveal if the exhaust affects the performance negatively. The only way this silencer looks different is the absence of the stamped writing on the outlet plate at the end which is something I like on the originals....Addendum: after checking I note that the end plate does have a series of numbers stamped on it so not completely bare.
Even though I have praised this aftermarket replica silencer I have to remember beauty is only skin deep and it would be nice to hear from other owners how similar their engine performs comparatively when fitted with the same item.

Les

[nice2day]

When you study the factory diagram of the the complexity of the original baffle system shown below, one gets a worrying feeling that the aftermarket copies aren't going to be anywhere near the same inside. It's very clever how the various length internal tubes are arranged. Each one will have a different resonant frequency and also different path lengths to the exit hole. This will blur the bang of the exhaust pulse after it has passed through the front and middle section of the silencer*, yet at the same time there is not really any barrier or restriction to impede the gas flow. The vertical bars are actually steel discs with a series of holes by the way.

*NOTE: This complex baffle is fitted right at the END of the complete silencer very much like a tail pipe muffler on racing bike expansion chambers but much wider. Indeed, the long front taper and midsection of the silencer are completely open/empty and unrestricted so what you have is a tuned expansion pipe system but disguised as a normal looking silencer....Ingenious as most things are with MZ design...

Les

[Puffs]

Ta for that Les!
Exhausts and their tuning are a very important, particularly for 2T's. Resonance-wise, normally (tuned) expansion exhausts, but those do not damp the noise very well, so baffles & tuned pipe lengths is what you find inside road-approved silencers. And yes, details matter.

Also, while the engines of the ETZ251 and the ETZ250 are largely identical, there are some differences in the port timings and the header pipe, hence also the silencer. In aftermarket silencers this may be ignored - one size fits all. Of course at a price you can buy a dedicated silencer.

When I cleaned up my 251 a few years back, one of things it got was a new exhaust. The original one had taken badly to the salty Scottish roads in wintertime, and I had filled the holes by covering it in fibreglass:

Original in fibreglass.jpg (6.67 KiB) Viewed 63 times

Of course all the fibreglass prevents a meaningful weight comparison. Here's the end cap of the original:

Original end cap.jpg (36.64 KiB) Viewed 63 times

I forgot what I paid for my aftermarket replacement silencer, this is the end cap:

Aftermarket end cap.jpg (34.83 KiB) Viewed 63 times

It still looks fine, and no problems have appeared. Performance-wise I cannot remember any significant difference with the original. But if you want fast, best take another bike anyway, IMO. Or at least tune it properly, like they do for the race track, but that's not why I have an MZ.

[nice2day]

Thanks Puffs for posting that aftermarket end-cap photo. I have just checked my one and it has the same numbers stamped on it. You say it performs well so that's reassuring.

So we have a reasonably good consensus that the silencer with NH10023693 stamped on the end is of decent quality.

Les

PS Puffs...Your frequent mentioning of Scotland makes me think you are indeed Scottish and not Belgian? ( not being nosey)

Les

[Puffs]

It's where I did most of the miles on the 251 Les.

[JawasandMZs]

The enigmatic Puff is NOT British. He informed me that in his (unspecified) native language "MZ's" is correct.
BTW I'm perfectly happy to tell you all what MY native is (as well as my name & phone number) and that's Welsh.

[Puffs]

And your point is?

Please try to contribute positively. Telling everybody your name, address & **** size is hardly helpful on an MZ forum.

[nice2day]

I have to say JawasandMZs, that I was surprised you could come back on this thread but not give any acknowledgement or thanks to Puffs or myself when we tried to help by giving you some information which you asked for. We obviously wasted our time as well then?

Les