ES250/2 premix

[nibbler]

Hi folks. I've just bought a 1968 250 Trophy and have been researching premix percentages. Some say 33:1, some say 50:1 is best. I'm planning on using fully synthetic 2T oil, and most of the riding I do won't be 'flat out', it'll be brisk (relatively speaking of course, but the motor will get worked a little) acceleration to about 50mph then sauntering along enjoying the countryside. No town work to speak of. What do you exprienced guys and girls think?

[arry_b]

A lot of the documentation you'll find states you need 33:1, but I have a theory that's it's not right for the later bikes.

The major difference between the earlier bikes (throughout the range) is that earlier bikes use a plain small end bush, later bikes use a roller bearing.

I'd be happy to use 50:1 on any bike with a roller small end, especially if you're using decent oil. Note - decent doesn't necessarily mean fully synthetic, but if you want to use that, go for it. The overall cost of oil, whether it's £3 or £15 a litre, makes little overall difference to the cost of running a small bike given that most older MZ's don't do massive mileages each year.

[nibbler]

Thanks arry_b, useful info and appreciated. I will go and see what I can discover about the bottom end on the machine. Cheers.

[Blurredman]

I run my '87 ETZ 250 on a 30:1 pre-mix ratio with the cheapest mineral 2t motorcycle oil I can find.

Been running for several thousands of miles now, no issue, and no plug fouling. Old articles from the height of the 2t days say 20:1 is the best, end of. But there is ofc a balance is needed and costs decided.


The best way to think about it is: Where does the bike originate, and from what time period, mineral two stroke oil the only thing around in affordable means, and if that was too expensive, they used engine motor oil. And to think, that the quality of the mineral 2t oil now, is far superior then they were ever designed to run on in the first place. The engine itself is also extremely understressed by design for reliability (or possibly, fixibility? ). Fully synth is overkill no doubt, but if it gives you peace of mind that's good.


Regardless though, your decision is all your own, it's a rare bike now, and like has been said probably doesn't cover many miles so what you spend on it in running costs is neither here nor there I gather Keep that motor running! I love the old ES's!

[nibbler]

Thanks blurredman, I think the plan is going to be to use the best 2T I can find and go for 33:1 initially and see what occurs. I can always back it down to 40:1 if there is evidence of fouling, seems a sensible compromise. I see no point in trying to save a few pennies on 2T by reducing the percentage if it shortens engine life and brings on an early rebuild! Over the years I saw lots of guys at the drag strip trying to cut unnecessary corners with engines and taking home a pile of bits for their troubles!

[Blurredman]

Good to hear!


By the way, might I suggest an Iridium plug? I use D7HS Iridium and have never had spark plug issues since. When I used to ride my bike less than briskly, offroad in gear and clutch out using some amount of engine breaking, the bike would stall, after a few kicks the engine would come back although with work. That was on a normal D7 plug. Ever since i've had the iridium plug i've not had stalling issues due to fouling, and nor have I ever had to touch the spark plug. It's always perfect in colour, with no deposits and no excess wetness build up!

[nibbler]

Thanks for the tip, I will acquire a couple of iridium plugs soonest . Last night the machine ran out of lights: started up fine, engine ran OK, indicators worked but the headlamp was about as bright as a politician caught where he shouldn't be . Will take a look at it later. Tell me, do you have any experience of the Powerdynamo ignition kit for ES250/2? I have read good things about it. Cheers.

[Blurredman]

I have also heard good things about it, but I haven't purchased one.

I'm still on the stock system for my etz250, and until it breaks catestrophically, I won't be doing anything drastic.
The stock ignition systems aren't really all that bad, after all every car around at that point had distributors and contact breakers so if it doesn't work now, it's not the fault of the design because it's lasted 50 odd years for the MZ's, something has worn or incorrectly been set up if it doesn't work. I still like the system. Easy to work with and fix.


Though, according to many people they find a smoother running and response. I don't know if the contactless system has a built in advance or not? Or perhaps they are under a placebo effect.


In response to your issues, maybe the battery is low? They do need some juice in them, have you checked the fluid level just incase it is dry? Is it charging the battery do you know?


I always have a few plugs with me. I use my Iridium 7 around town and general riding, I have a spare ordinary 7, and I also have an ordinary 8, I switch to the 8 if I know i'm going to be on the motorway for a while.. I would hate detonation. It would take quite a few hundred constant miles though. But I don't do motorway miles for very long, so i've yet to actually put it to practice.

What was the idle like, MZ machines should idle at 1,200 rpm, that most likely extends to the ES. If it is lower, the engine is labouring, and indeed clogs up the plug if under 1,200 too.

[arry_b]

The 6 volt bikes do benefit greatly from putting in fresh earths from headlight earth point, tail light earth and engine direct back to the battery negative terminal.

I use 2.5mm section copper wire with soldered on end connectors.

This usually turns a misfiring, dimly lit bike into something altogether more confidence inspiring. The last one I did changed my brother-in-law's TS125 from something that would only run ten minutes with the (poor) headlight on, or cut out with the brake or indicators on, into something that'll run like clockwork until the tank's empty with all the lights and indicators on.

It's the best £5 upgrade to a 6v bike you can make.

[DAVID THOMPSON]

the ground with good copper wire works excellent
never depend on the frame for ground but do also ground to it...

my sons old trucks work much better with all the lights with a good ground wire all the way to the battery

dave

[vicar]

My etz251 has a power dynamo fitted and its just like a modern bike .Bright lights at tick over I have wired the head light so that the main and dip beams come on with main beam I haven't got a battery fitted.
I get good starting and I can turn the tick over right down /The bike also has a Bing carb fitted and it will ding ding ding until the fuel runs out .I have been running my bike at 50:1 but my Mz book tells me I can go to 100:1 if I use fully synthetic oil.

[DAVID THOMPSON]

the power dynamo units are not cheap but if you use your mz to get to work
its money well spent have 2 friends running them on older BMW
and they love the difference one is an r27 and it runs like a different bike ..excellent
DAVE

[stogadog]

I have an ES250 - owned it since 2010 and had one for a year before that. I run mine at 40:1 and have only ever had one problem when I melted the piston! That was due to ignition timing though. I rode mine back to Zschopau last year and had no issues with it still running at 40:1 . The book does say 33:1 however. I also have fitted a powerdynamo system to it. It has made it easier to start and it does seem to run a bit smoother. Having 12volt lights has made a world of difference too. I have put and adaptor in my headlight so I can use more modern bulbs in - with a 12v halogen it really is much much better!
I don't know how much you have used it yet but have you discovered the joys of the 4 speed box yet? Don't worry they are all like that - you'll get used to it!

[breakwellmz]

My old Supa 5s you to get thrashed on 50:1 without problem,and that was oil technology of 35+ years ago!

Or am i missing something?

Remember,the more oil in the pre-mix,the less fuel there is!

[nibbler]

Thanks for the info folks, once the essential kit for motorcycling here in Oxfordshire reverts back from an aqualung to a crash helmet I will scamper off and put some miles on the bike, at 40:1 after getting the powerdynamo fitted, thanks to stogadog's experiences. I'll report back when I have some news - or further questions!