450 for slow, lazy vet?

I like to use everything an engine has.  Sounds like you can control that .  91 cr250 low to top engine the hit isn’t violent, chassis has excellent balance . Noleen did a great revalve to get the funky forks to work. 

Any 450 will be better and with more torque, higher gear no need to rev and throttle control no clutching you will be happy. You might even consider putting in a no clutch kit in it. 450 I bought already had the clutch and it’s storage not needed to grab the lever all the time. Works Great slowly going up the leading ramp

I commented on how easy my recently bought 24 KX450 is to ride.  Any of the late model YZ250F’s are also easy to ride and with the phone app tamed down if need be.

 If a guy can live with Kickstart, a 250 RMZ would be a good vet ride also.  But most old guys don’t like kickstart 4 strokes.  

Nearly any four stroke motorcycle will be easier to ride at a less "intense" pace than a 125/144.  Aside from a 250f, maybe look at a woods version of something.  The Austrian XC's are super smooth engines as well at Beta's.  And if you say you won't be getting that much air time, an XC type bike might be the ticket.  Even the Beta two strokes I've ridden, some on an mx track,  were incredibly smooth and easy to ride.

Reading through this MPJC, maybe you need an XC350 with a recluse. We have owned them, the newer ones are torquey enough and have speed when you need it. Guys that use them exclusively swear by them.

If you feel good about that ‘17 KTM then go for it. I’m sure thought about all the ins and outs of it, and I assume you’ve ridden it.

Any bike can be tamed with gearing changes, a Rekluse (if one is made for the model), and ECU tune if it applies. 

Given all responses above, I'd tend to agree with 2020-2023 YZ250F recommendation.

I am an idiot, so let's get that out of the way, but I went and purchased a modern 250F, a 350F, and three 450F models and the YZ250F is the most impressive to me with respect to the application you have in mind. It is the bike I would say friends and I have the most fun on overall as a group (but my 350F is close now with suspension and engine mods).

After having purchased all the bikes mentioned above, what really stood out to me about the YZ250F was the handling and lightweight FEEL (none of the other bikes can come close to this - truly - and you can only appreciate this by trying all bikes back-to-back), the suspension is AMAZING stock, and the low-end is GREAT (better than the 350F IMHO). Honestly just an incredible bike overall. I am always surprised when I ride it.

I just don't think the Austrian bikes have the comfort you seek - without major investment.

Those late-model KX450s look like an outstanding option, too, and for a bargain. 

Happy to explain my multi-bike experiment on the phone in detail. Just message me and I'll throw out my cell # and we can find a time to discuss.

Most of the Beta 4 strokes (350, 390, 430) have a lot of torque but only make about 40hp so your chance of getting in trouble due to whiskey throttle is reduced quite a bit. I would also look at 250/300 KTM TBI bikes. They have a lot of torque but don't rev out as much as a 450 race bike so they are also a little safer I think in case of whiskey throttle. 

KTM also has 350 and 450f (and 500) trail bikes, but you have to watch as they really started cranking up the power on the 450 XCF-w the last couple of years. The 350 XW-F or EXC-F could be an option. It has a lower rev limit than the SX/XC models, but only makes hp in the mid 30s stock so it might not be enough or it might be perfect. There are also Husky and possibly Gasgas versions of the KTM trail bikes that have linkage instead of PDS. If you aren't launching jumps to flat the stock suspension might even be better for what you are doing. They will be way more fun to ride off track too if you do that.

Have you tried a modern 250F? They are plenty fast. I would think even a 350 would good for you.

YZ 250F is god’s gift to vet riders. 

That’s as good as you’re gonna get right there 👍

KTM’s heyday

Good luck, nice bike! Hope you have many great rides on it!

The 350 excf is made for you. Map it slow and save it to position 1 on the switch and then stock to 2. It will have more power than you ever need but have little to no weight penalty. 
Another thought, maybe a Renthal auto clutch so you don’t have to worry about pulling it in in emergency situations just hammer the brakes on and the bike will stay running. 
Such a predictable tame bike that has plenty of speed. 
Golden oldies ride them everywhere around me and swear by them. 
I’ve owned one too and it was amazing 

I have had the itch for a new bike and to try something else, just because I'm conditioned to be that way (unfortunately.) I really want to get the new YZ450F even though I'm not a 450 guy. I almost caved to some of the deal we had over the winter, around here on '24s. That being said, a 21-23 YZ250F, is still an amazing buy for a Vet rider. That's what I'm currently on, with some nice mods (including a TD dual injector.) It's honestly pretty flawless. But even stock they are tough to beat, they just run out of steam up top, compared to a 350. But I think the power is easier to ride than a 350 because it's always in the sweet spot. My thing with 450s is I don't like the slow rev feeling because I think it makes the chassis feel heavy and not reactive. But I get worn out / in trouble with something like a YZ450F that is super lively. So that's what has always been my issue as a Vet guy and 450s. Had a 350 and it was ok but so far the YZ250Fs have been great to me. Still want to try a 450 again at some point though.

Nice! Those are my favorite KTM models. 

Loosen the throttle cable so it doesn’t give it as much throttle.

1-2 tooth larger on counter sprocket works wonders, too. 450s have no problem pulling + calms chassis, too.

Mellow mapping and the heaviest flywheel weight available. 

I'll get the haters for that.