Keefer Recommendation: 250 SX-F header on 350 SX-F

I'm noticing this, too.

In the works - stock gearing is 14/51, trying 52 and 53.

OK - got a ~1 hour ride in tonight at the MX track (IMI Motorsports in Dacono, CO) and the track was in decent shape, really good hardpack to test the edge of the tires on as well as instantaneous roll-on power.

Bike configuration details relevant to this discussion:
(1) Vortex ECU mapped by Twisted Development
(2) Full titanium system:  FMF Factory 4.1 RCT muffler with spark arrestor screen in (I can't get it out now!) for 350 SX-F + Megabomb header for 250 SX-F
(3) 14/52 gearing (stock is 14/51)
(4) Thew clutch is stock for maximum grab - but maybe a Rekluse Torque Drive clutch would improve "snap?" Hmmm ... 
(5) FasstCo Flexxbars, 12-degree bend --- Higher and more leverage than OEM Neken bars
(6) 91-octane pump fuel
(7) Rear tire is 100/90-19 --- Yeah, this surprised me. I think tires got mixed up at the dealership when for the previous owner when he had new tires installed.
(8) I am in Denver, CO at ~ 5300 feet (remember you lose ~3% in power for every 1,000 feet of elevation --- I am down ~15% before I even start the bike)

Ride impression:
(1) I wasn't quite as amazed by this setup like I was with the addition of the Vortex ECU by TD or reprogrammed stock ECUs alone (still haven't tried Blais Racing unit). The % change in power delivery was less, which isn't a complaint - just highlights how good the OEM exhaust system is.

(2) The bike really does run crisp --- even crisper than before

(3) I may like the stock 51-tooth rear sprocket better, I seem to carry more speed in most places on the track with 14/51 gearing. Second gear is a tad longer with 14/51 obviously - and enough so that I think I like how it keeps 3rd in play longer, too

(4) The 250 SX-F header was good for a little more throttle response and a very slight amount more torque down low --- but I did notice a small loss of midrange, which was a toss up for me in the end since I do ride this bike in the midrange a lot. I wouldn't buy 250 SX-F header again likely for MX alone, but I probably would for singletrack.

(5) I'd go with a stainless steel aftermarket system on this bike if you go aftermarket, the titanium is quite thin and the Megabomb sticks out in an area I evidently karate kick while riding. I'll try to post weights soon when I have a chance.

(6) Given I am at elevation and I am not running the vented airbox cover or 2-stroke air cage and boot yet, I hope I can put these next mods into play before the snow and get some more oomph as well as play around with additional TD maps on the Vortex as well as the trim switches (low, med, high) which TD gave me some things to try with. I'm 80% confident the bike can be leaned out for a tad more power ... but it sure runs crisp now, so TBD.

(7) I'll also try a 53-tooth rear on my next outing to see if that's the gearing breakthrough I seek to readily loft the front end at any time on the track (can do this with my YZ450F and CRF450R no problem, I also think my YZ250F is better here, too -- -"snappier").

(8) The FasstCo Flexxbars really helped this chassis offroad and on the MX track, too. I've seen this in the past as well, but I think I am definitely highlighting aspects of the AER forks now that aren't for everyone: some harsh landings and slap-downs. I still like the AER forks A LOT for offroad, but I am hesitant to hit big MX jumps currently. Need to bring 2 bikes to the track to compare spring vs. AER on the same day again and play with the air pressure settings and finally write them down. As far as leverage by going to a taller bar, it wasn't as marked as I expected. It helped, for sure, but not night & day. What was awesome was that I could stand and sit with equal comfort and effectiveness - the ergonomics are really dialed now.

(9) I'm an ARC Memlon lever on everything guy --- I actually prefer the KTM levers. I'm learning a thing or two by riding a bike stock first.

(10) Brembo brakes - giddy up!

(11) I am an idiot - I did not heed the "check every fastener on your KTM for tightness" warning and when I recently checked the sprocket bolts with a wrench to be sure things were tight, EVERY sprocket bolt was FINGER LOOSE and 1 bolt was snapped in half. Luckily the wheel hub's sprocket bolt holes weren't ovaled out, but dang. I've literally never had this happen on another bike. Live & learn, I was installing the 52-tooth sprocket to try anyway. I noticed the rear axle nut was slightly loose, too, but not dangerously so. Ironically, my rear spokes have generally been OK near the rim lock.

Summary:
(1) I haven't found "baby bear’s porridge" power-wise yet, but I think I am pretty close --- the bike runs amazing, just doesn't have that low-end snap I am looking for yet to brap it over track litter, whoops in corners, etc. (ironically I am able to do this on my YZ250F though, and all of the Japanese 450s --- but not the 2022 KTM 450 SX-F yet --- see #3 below)

(2) I need to try the Keefer recommended gearing of 14/53 --- maybe 1 more tooth up really is perfect

(3) I tried to swap out my ODI KTM throttle cam for the YZF one, but the YZF one was too thick for the KTM throttle housing --- need to machine it thinner to try. There's something to this "loooong KTM power" that is nice, but a drawback as well. I need more cowbell, dammit!

(4) I need to remember I am at elevation - at sea level I bet I'd be there or at least really close for sure. 15% is a LOT of power! Ironically, I reasoned that maybe a YZ450F with reduced power at elevation = like a 350! Um, no. There's no way getting around 450 engine character with added crank inertia. That is the primary difference between a 350F's flickability vs. a 450F's. I recall Keefer noting that the 350F may be even more flickable than a 250F (maybe on Gypsy Tales?) --- and I think I agree. That is, the rev range I generally ride the 350F in vs. the 250F is lower, lending itself to less crank inertia influence --- and this difference is what makes the 350F most appealing to me a large % of the time.

(5) General KTM chassis observation: I love the handling, but I feel the weight bias & wheelbase may take some getting used to in terms of lofting the front end readily --- need to experiment more here. From a dead stop, it wheelies nicely, has good rear-wheel balance, but there's something about its roll-on power that is ever-so-slightly delayed than the Japanese bikes.

(6) I noticed tonight that I am hesitant to hit the big jumps I can readily hit on my YZ450F. Overall, I may be faster on the YZ450F for the laps I can last still. More to come, but I think it's the unsorted suspension when compared to the YZF. The plushness of the YZF is a big confidence inspirer for me and I didn't realize how much subconsciously until I realized I wasn't attacking certain track sections as aggressively (but others I am much better on the KTM).

I think you're right. It seems the KTM style of throttle feed is simply not what I am used to on Hondas and Yamahas. I'll check this out, for sure.

Either way, KTM has built an amazing platform for a very large audience, and that's impressive - I just need to adapt a bit. What's crazy is how little I've had to adapt to the chassis - it feels like it was built for me personally and has really opened my eyes in a number of handling dimensions.

No complaints, really. Just on a quest - PRAISE MARTY MOOSE!

I still need to try your Akropovic exhaust system, too. I shelved it as soon as I couldn't get a spark arrestor to work after buying a few, but the ease with which these systems go on/off as I've learned shouldn't prevent me from some more experimentation.

With Yamahas I am like ... um, maybe next year.