A bit late to the ‘partay’ I know but upon reading this topic I thought I’d outline my views.
As an owner of an ’90 etz251, and an ’87 etz250 (and also the new owner of a 250/2 trophy but that’s besides the point perhaps), I can say that I don’t really think too much of the ‘peaky’ performance people say they have.
When I bought my etz250 in 2012, I did have some trouble with the carburettor- it could have been my naivity or something ghostly, but every other week something would occur to make the bike run poorly- too rich one minute, too lean another etc. However one day after a million carb cleans with cleaner. It ran reliably for several weeks, however the bike refused to move off the line unless you slipped the clutch at 3k rpm. I was content with that for a while, and perhaps thought it was what people complained about. A year later it skidded down the road on wet leaves. However- immediately after picking it up and going on again, I noticed the torque it now had under 3k rpm which it didn’t previously have! Strange- yes.
Since then, it is quite easy to rolling start the bike at say 5 mph in 2nd gear and it is quite open to changing to third at 20mph etc. It doesn’t complain doing this (needle position is 4th from top).
2016 I bought a 251, in a very sorry state, but.. With standard carburettor adjustments, I also find that it is perfectly happy to ride at 40mph in top so long as the ground is level. It has a very similar performance than my etz250. Both bikes have their original carburettors (etz250 30n2.5 @ 32k, etz251 30n3 @ 48k), and both run about 30ish:1 premix (and have ever since I purchased them). Both also have nice linear torque curve, with no sudden ‘power bands’, which is actually my preference anyway.
I have also ridden other etz250’s and feel that they are perfectly find below the 3k range.. Sure it isn’t kick your teeth in performance, but the bikes DO have torque if you overgear them when the conditions are right. With the introduction of my es250/2, I finally have the opportunity to compare the different engines with that of the etz’s. Though it is a slow project at the minute so riding far isn’t too much of an option until it gains my trust.