New member intro and TS250 fuel tank size question.

[Guesi]

To check for "flase air" simply take a brake cleaner spray and spray all parts around the carb with this spray while the engine is running. If the revs change during this, then you know where the false air comes in

[Puffs]

Excellent suggestion (without trying to be political). The overflow ports might also be leaking at the cylinder base gasket. Any signs?

The factory recommended ignition settings (lift height & timing) should work well, assuming cam & points are OK. And what you describe does remind me of 'lean @ idle'.

[R1100purist]

Okay copy all puffs and Guesi. I won’t rule an air lease until I do the old butane leak detection trick. I’ll also fatten the mixture at idle (mixture screw out right) to see if I can achieve the high idle again. Otherwise I’ll check ignition settings. The reason I suspected ignition is on some of my old Bmws when the ignition advance got stuck it would idle high after a sustained high speed cruise on the interstate.

[Blurredman]

When I reconditioned a carb from a non-working (Seized actually) mz, it was evident that the carb was just completely blocked.

After boiling the carb in lemon juice for a while, I had to constantly clean out the idle circuit in the carb itself with pressurised air and brake cleaner and eventually after a while I got it clear..

[R1100purist]

The previous owner actually rebuilt the carb fairly recently. And it actually performs well. The only issue I have it after sustained high speed running in 4th it doesn’t come down from its high idle at a stop.

[Blurredman]

But when you're riding around town and in lower speeds it's fine?


I've had that with my bikes sometimes after a few miles at sustained 50+mph, I can come to a stop and sometimes it'll idle higher by 2,3,400rpm.. Either it will eventually go down by the time the lights go green, or i'll ride off and the next time I stop everything will be normal... Is that what you're experiencing?

[R1100purist]

Yep, that’s about what it’s like for me except it doesn’t really come back down until I ride around at lower speeds and come to the next stop. Although it could be that’s because I adjusted the carb to idle higher when cold and then it was set too high for when warmed up.

I don’t have a tachometer because I have a /1 but, seat of the pants is about 4/500 rpm increase!

Either way we’ll test ride again soon and find out

[Puffs]

Adjustments to the carb are best done with the engine warm.
Also have a look at P. 63 & beyond from "MZ_TS250-1977-Official_Service_Manual.pdf" (Blurredmanswebsite).

[R1100purist]

Puffs (and by extension blurredman for putting it together) thanks for the guide. I think my printed out copy is missing those pages so this is helpful. I’ll start there and report back.

Oh yeah another thing. I heard drilling out the idle jet to .5mm helps with idling smoothly? Has anyone done this with good results?

And one last thing, does the “air mixture screw” control the ingress of fuel or air at idle...ie screwed out means richer?

[Puffs]

Well, Blurredman gets our gratitude for making those documents available publicly!
FYI, if you can handle German (you yourself, or your browser), you'll find more complete & more original documentation on miraculis.de.

I don't know about drilling pilot jets and while I do have precision drills down to 0.80 or so, I do not have a 0.50 drill. And if I had it I probably wouldn't have a chuck that can hold it. If you need a different pilot jet (but do you really?), I'd just buy one.

I think opening up screw #11 (P.64) makes the mixture richer, but I'm not sure. On my 251 (different carb) I just adjust it till it runs to my liking.

[Blurredman]

You'll find a lot of myths and untruths about MZ's..
And also things that sound plausable and even true, but potentially unfounded..


I've got a 30n2.5 and 30n3 carb and I have not drilled out the pilot yet.


If your idle is running a bit high after a speed run, it's possible that you need to enrichen the fuel screw- you do this by turning the screw anti-clockwise (to let more petrol through). Your model of carb will have two screws- one being the pilot jet adjustment screw, and the other being the slide screw (which controls the air flow) you're probably thinking about that, which indeed can change the idle speed, by increasing the air intake (clockwise) of the screw as you're raising the main slide. For idle mixture, you'd want the pilot/idle/fuel screw.

[R1100purist]

Went on another ride yesterday. No air leaks that I can descent with the butane torch but still surges at stop lights at “idle” starts and idles from cold real well so I’m a little reluctant to change too much.

However I find that if I just barely touch the enricher lever it decreases the idle back to normal...haha really strange.

[breakwellmz]

It must be running a bit weak then.

[R1100purist]

So unscrew (anti-clockwise) the mixture screw to richen it up. I just had a nice idle so I was reluctant to do so, but we’ll give it a shot.

[breakwellmz]

I was doing the same enrichener fiddling the other day on my Beta.
Whilst the engine was idling from cold, the revs would go up if the enrichener was pulled (which makes sense) but when the enrichener was pulled once the engine was hot it would kill the engine.
If it is a fuel screw (I can`t remember) then yes that`s correct.