250 ETZ gearing

[JawasandMZs]

My 250 ETZ won't rev out in top because to do so would need for it be capable of 85mph! Im considering a front sprocket one tooth smaller? Anyone tried this? What size is the standard front sprocket?

[Blurredman]

19 for the 250.

I have an 18 on my 250, but i'm at 4.5k rpm already at 60mph.


21tooth for the 251.

[JawasandMZs]

Thanks. 4500rpm/60mph sounds about right. 21 tooth on the 251 is clearly due to the 16" wheel.

[breakwellmz]

It should be able to hit 85 i would have thought, unless you are particularly aerodynamically challenged.
My Supa5 was 5000rpm at 70mph, top speed 85ish.

[Kruh]

What sprocket did you have on the supa5?

[DAVID THOMPSON]

all the German made bikes i have had seemed to be on the tall side
in fact the r90s was way too tall but very expensive to change

[Blurredman]

Yes the 251 21 tooth is due to the 16" rear wheel. And I notice in reality that the rpm is quite similar to my 18 tooth 250 anyway. 250 can only go 70 but that's not original spec and I don't really want that to go fast. It's got really nice torque and I like to use it mainly in the country (but atm I'm commuting on it). Anyway... The 251 can't go more than 77ish.... I did caustic soda the exhaust, and did notice a bit of an improvement but unless I'm in a rush or need to go long distance I wouldn't be doing 70 anyway.

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[DAVID THOMPSON]

where i live the traffic is fast and nasty and the risk of getting ran over is getting very high
the fowling distance could be called pushing in place of tailgating
Car drivers seem to have NO manners any more

going at high drive times even in your car is very dangerous

the 2 major 4 lane roads are posted 65 and 70 and to keep up with traffic =85 mph
or get passed about every 20 seconds
Dave

[Kruh]

The fastest I've gone with my TS250/1 (16" wheel), was 110 km/h (indicated on the clock; in reality its less). But thats almost at top revs (~5000 rpm). Don't think there much more in it.
I have a 19 tooth sprocket up front. (Originally it had a 21).
But I prefer the shorter gearing; I live in a hilly area. It doesn't feel stable at those speeds anyways. 100 km/h is top for me. Anything above and I feel like a sail on the bike.

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[Blurredman]

I'm not entirely sure that trying to get to 85 is advised.

After all this, like most manufacture top speed specs take place in perfect conditions and a perfectly working engine etc. We're not even sure whether the testing acheived this..

The redline for this engine is 6000 and top torque is at 5500. Without some serious race engine modification to get it to rev higher, trying to acheive a theoretical top speed of 150km/92.6mph at 7k rpm, I wouldn't advise.

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[breakwellmz]

What sprocket did you have on the supa5?

Hi.

It was a long time ago but 21t rings a bell.
This article reminds me very much of my experiences with mine - http://yewemmgee.blogspot.com/2011/01/m ... upa-5.html

"Top speed turned out to be 87mph. I only found this out when in the company of a friend on a GPz305, as the MZ's speedo comes to a stop at 80mph. It's doubtful if this would be accepted as an excuse if I was ever booked for doing that kind of speed. With the state of the gearbox, it wasn't really worth trying to thrash it through the ratios. The best thing was to stick it into fourth, find a long bit of road, get the throttle to the stop and get my head down in the clocks.

It was then just a question of watching the speedo waver up to 80mph, although it would hit 70 to 75mph with indecent haste. I was quite surprised that such an old motor was able to sustain a 75mph cruising speed with apparent ease"
Perhaps they were built better back then!