Posts
792
Joined
2/6/2009
Location
Altamonte Springs, FL, USA
I have a 2021 KTM 350 SX-F with KYB conversion and a revalved shock with bladder. I’m 190-200 pounds without gear and the bike is spring and valved for Vet A MX. I race hare scrambles with the same setup and it still feels kind of good. A little stiff but good.
These are the issues. Exiting choppy turns or riding over roots coming out of turns, the backend feels harsh. The bike feels like it wants to cram my spine out the top of my helmet. Coming into turns, she’s tracks straight and feels great.
The ass end deflects a lot on rutted jump faces, choppy drop offs (MX) and high speed roots. It bucks pretty hard on roots at 55-60 mph and is chattery harsh over roots at slow speeds (Hare Scarmbles) and is not predictable at all. I’ve set the sag to 105 and have been constantly checking it but the bike still feels sqautty and low in the back. I could be wrong but it just feels low.
The bike tracks pretty well (it goes straight) but at speed on moderately rough to rough tracks the front end feels pretty nervous. It’s a “head shake imminent” feel but never gets head shake. On somewhat sandy/sandy whoop straight aways, it’s smooth and not too nervous. It’s not very confidence inspiring on a wore out MX track. I’ve lived with this since new and just rode the bike. It’s been back to the tuner a few times with the same issue. After spending more time on my old ass 2001 YZ250 that’s been gold valved by the same tuner, this 350 rear end really sucks.
I’ve played with the high speed nut (backed out) and that seems to help but every time I ride this bike, the harshness exiting turns come back and the bike feels different. It’s so harsh, I can’t even really describe it. My back is killing me after just a few laps. The back end feels like it’s skating across the tops of the chatter and amplifying the chatter up my spine.
What say you?
These are the issues. Exiting choppy turns or riding over roots coming out of turns, the backend feels harsh. The bike feels like it wants to cram my spine out the top of my helmet. Coming into turns, she’s tracks straight and feels great.
The ass end deflects a lot on rutted jump faces, choppy drop offs (MX) and high speed roots. It bucks pretty hard on roots at 55-60 mph and is chattery harsh over roots at slow speeds (Hare Scarmbles) and is not predictable at all. I’ve set the sag to 105 and have been constantly checking it but the bike still feels sqautty and low in the back. I could be wrong but it just feels low.
The bike tracks pretty well (it goes straight) but at speed on moderately rough to rough tracks the front end feels pretty nervous. It’s a “head shake imminent” feel but never gets head shake. On somewhat sandy/sandy whoop straight aways, it’s smooth and not too nervous. It’s not very confidence inspiring on a wore out MX track. I’ve lived with this since new and just rode the bike. It’s been back to the tuner a few times with the same issue. After spending more time on my old ass 2001 YZ250 that’s been gold valved by the same tuner, this 350 rear end really sucks.
I’ve played with the high speed nut (backed out) and that seems to help but every time I ride this bike, the harshness exiting turns come back and the bike feels different. It’s so harsh, I can’t even really describe it. My back is killing me after just a few laps. The back end feels like it’s skating across the tops of the chatter and amplifying the chatter up my spine.
What say you?
The deflecting…that’s pretty common and not an occasional thing. It’s pretty much all the time.
If I play with the clickers on the forks, it gets too soft. If I stiffen them up, it works better but it feels like the speed in which the forks move changes. The stiffer I go in on the fork compression, the slower they compress on the initial stroke and then exponentially get slower through the middle to the bottom. I want them to stay the same speed but not blow through the stroke. I rode a buddy’s cone valves with works shock and they were absolutely perfect. Granted, a lot more money but they were insane!
The shock….I’m lost.
Imo for heavier riders, these bikes sit too low in the back under acceleration. Maybe go up a spring rate as well. If your spring rate is correct, spring preload is 7mm. With 105mm sag, if your spring is measuring less than 253mm you might need a stiffer spring.
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DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Stock seat, aftermarket, tall, Do you wash bike with seat on to degrade the foam?
Ever consider on of these linkages that gets you back to a true-to-weight shock spring?
https://www.procircuit.com/ktm-husqvarna-linkage-system-16-20.html
I rode Croom today and went in three clicks on the shock compression and opened up the high speed about an 1/8 of a turn. The rear end feels like it was riding higher in the stroke and the bike turned really well. Not many roots or chop to judge it from but I’m pretty sure it was better. I need some choppy chop chop acceleration bumps to confirm.
The Austrians have a very "unique" OEM spec. on their machines
Always on the light side, even for the heavier bikes and it seems their rate/rider weight recommendations rarely match what all suspension companies end up with.
OEM valving can accommodate date some rate change above/under stock, up to a certain extent
Regardless , suspension setup must start with the correct spring
KTM sure likes to keep suspension companies busy
Pit Row
I am getting 37mm of static, 105mm rider sag and 12mm preload on the shock on my fc250 2023. Is the 12mm preload bad for the performance of the shock, should i change spring?
Any sign of coil bind?
https://www.keeferinctesting.com/2020-6-1-rep-knuckle-for-20155-up-ktm-…
Seems pretty standard numbers. I wouldn’t be worried about 37mm static. I think 35mm is the dream.
so if you can get your hands on a spring rate above, could be fun to try. Orrrr drop 10-15 pounds before riding and back off your preload. J/k just playing.
We need to know if it is packing or too slow on rebound. on the mx track, open you high speed all th way up and ride an area thats choppy and square edged, then turn it all the way in, do it again, then start moving it out. once the back feels more stable, work the fork, but start in the middle of the clickers and for every 2 clicks on compression, slow down rebound by 1.
I am an old vet guy, once a fast young A rider, the taller you are the less rider sag you may need, and your transitions have a greater affect on these bikes. I have the wp conversion and revalve on the shock. run spring for my weight. I did notice my I have very little spring preload, I am 6'4 225 Ish, run a 5.4 rear. I have a motool sag thing coming, as I dont have a person who can seem to read a tape measure,lol My wife is tired of dealing with me.
I have JB do my suspension and I am amazed at how well it works, so I may not be the person giving advice as I can only fast for 1 lap, then i am rubber noodle. Maybe by end of the year will get my endurance back.
Buddy I know this is old. But I’m going through the same thing on my 250sxf at the moment. The shock is one of the worst I’ve ever ridden. I’ve realized people hate the air fork, but a ton of issues with that fork are caused from the shock being so bad. The bike just isn’t balanced well. I can hit the same bump at the same speed, every lap, and the bike react completely different each time. The only jump faces I can jump have to be perfectly groomed or I’m getting kicked. I just sent my shock to Factory Connection for a rebuild, revalve, and bladder conversion. I suggest giving them a call.
I have since done the bladder kit for my shock , it was ok but not great . I run the REP knuckle and it is way better now . I did take it off once and it was noticably worse so I put it right back on
I agree that the shock is not good. Factory Connection revalved everything and put in the bladder kit. It's better but still the weak link imo.
I have since sold this bike, got a 23 and sold that bike. I loved the 350 but I love the 300 two stroke more. The 21 350 was an ok bike but pretty overrated compared to the 23. The 21 felt like it was 20 years old compared to the 23 frame and ergos. I have since installed cone valves an had the shock redone on the 300 and it is a totally different bike. Not sure if I will get another 350 in the future but for what I do, the 300 is amazing.
I have family who are the regional managers of the local Honda dealerships, and that triumph is looking enticing. I bought the KTM because I grew up on steel frames when I was on minis. Figured it would feel similar. It doesn’t. At all. My buddy’s new YZ 250F feels way more comfortable. As a smaller guy, the KTM cockpit seems a bit too open for me. Like I’m sitting down inside the bike, and I like to feel like I’m on top of everything. I’m waiting on getting the suspension back right now from Factory Connection to see if they can make a difference. I see a lot of people who rave about having their suspension done, and I had TZR do the air fork last year. I could only tell a difference before the fork broke in again. Then it felt exactly the same.
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