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Sooo... Another week another question that's probably super simple for the majority of folks here.
My 350 (an old '17 SXF) has the Race Tech recommended fork air pressure (spring conversion is out for repair) and a bladder kit, revalve and spring for about my weight (spring is for my weight, revalve was for my mate, the previous owner, who's slightly lighter and not so slightly faster, so I figured it'll be in the ballpark for a chunky novice).
With the spring on the brink of dislocating from the collar on the stand, so with almost no preload on it, the best I can get the race sag is 98mm, unladen it's about 33mm, and the spring is about a millimetre short of full length when measuring the spring itself.
High and Low speed compression and rebound very near stock 'standard' setting, linkage and swingarm bearings ok but probably due a regrease, though I can't feel noticeable striction and I've tried to compress the bike and let it settle and measured to reliable points and taken average measurements (although I never get much variance).
To me this seems like a no brainer the spring is too stiff, but it's a 54nm which the few guys I've talked to say is correct and I read similar in the RVanKamp thread.
Any thoughts on if something could be skewing the readings? Tyre pressures good, level ground, gear on, consciously letting the bike settle for stand, unladen and laden measurements.
Anything I may have missed is appreciated as always, Vital Brain Trust 👍
My 350 (an old '17 SXF) has the Race Tech recommended fork air pressure (spring conversion is out for repair) and a bladder kit, revalve and spring for about my weight (spring is for my weight, revalve was for my mate, the previous owner, who's slightly lighter and not so slightly faster, so I figured it'll be in the ballpark for a chunky novice).
With the spring on the brink of dislocating from the collar on the stand, so with almost no preload on it, the best I can get the race sag is 98mm, unladen it's about 33mm, and the spring is about a millimetre short of full length when measuring the spring itself.
High and Low speed compression and rebound very near stock 'standard' setting, linkage and swingarm bearings ok but probably due a regrease, though I can't feel noticeable striction and I've tried to compress the bike and let it settle and measured to reliable points and taken average measurements (although I never get much variance).
To me this seems like a no brainer the spring is too stiff, but it's a 54nm which the few guys I've talked to say is correct and I read similar in the RVanKamp thread.
Any thoughts on if something could be skewing the readings? Tyre pressures good, level ground, gear on, consciously letting the bike settle for stand, unladen and laden measurements.
Anything I may have missed is appreciated as always, Vital Brain Trust 👍
Spring change is easy as you can do it without removing the shock - just split the linkage, lift and chock the back wheel, back the collar off, remove the bottom clip and drop the spring.
54nm is a Japanese bike rate which you can probably use on a ktm if you have a new linkage set up for it and a shock valved for it.
WRC, 54 is what the Race Tech calculator came up with after converting from their kg/mm or whatever they use.
I'm at 250lb, 6'1, lift a little but also still a bit chunky haha, I saw the rate was a big jump from stock but given the above I didn't give it a second though, perhaps I should have 👍
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Free shipping: VITALMX
Luxon 4-Post Bar Mounts
$189.95 - $239.95
* Also apologies to Race Tech if they spot this, I know it's pretty cheeky using their calculator and then buying elsewhere, I'd gladly buy if I were in the US.
I actually wound the collar in a decent bit, straight off the bat after fitting the 54n spring, expecting what you describe yours to be like. It ended up at 84mm race sag as a result and I was super confused. I've ridden on it a couple of times, bike feels a little off kilter due to the sag number but it functions correctly as far as compression, rebound and no play or binding in any components.
I'm using the OE 'sag' molding mark on the rear fender to a marker pen'd point directly vertical from that mark to the hard-edged forging/casting line on the swingarm that the swingarm graphics usually go up to.
I've been getting the wife to measure, so I can make sure the bike settles properly and I can get my full weight on the pegs. She's pretty switched on, did her own piston last time, gapped the rings properly, wired her own racecar, not the usual half-asleep Mrs' measuring job. I've made sure it's measured right from point to point and we've done multiple measurements to make sure they're repeatable.
I've tried to check off any dumb mistakes in measuring / calculating / maintenance issues, however I'm at a bit of a loss now.
Ebay has a lot of 54 and 57 oem springs from older bikes, 260mm
I even had a couple of genuine Deutsch brand wiring connectors, good quality stuff, recently where the pin numbers which are laser etched onto the connector were going clockwise instead of the correct anti-clockwise for that side of the connector, chased that issue for a little while as they had boots on them so wire colours weren't visible haha, shit happens doesn't it.
I'll grab whatever used one seems the most legit and at least then it'll be a definitive answer, good call and appreciate the advice 👍 May even just skip to a 57 from elsewhere as I do like what you said in the other thread.
I've always stuck to genuine wp springs ever since.
mx317, good call and appreciate the heads up, I did convert it at the time before ordering, luckily years of racecars with varying spring measurements in lbs, kg, nm, etc trying to catch me out has taught me that much at least haha 👍
Pit Row
I'll grab another spring and get it in asap.
Fresh one fitted, 2.5 turns of the collar and 105 race sag, 34mm static sag, straight off the bat.
That is measuring correctly per the book, however I tried alternate locations (the theory checks out, wasn't doubting anyone, just wanted to see how significant it was) and if you're in the rough area it's cool, but angle seems to change it significantly and going too far from the axle as said by the wise homies here.
Interestingly, the Pro Circuit sag how-to thing says to make sure you measure to a fixed point and as vertically as possible, but from axle centre to fender line is quite an angle on the KTM.
Always tough when you have a couple of issues compounding each other. Appreciate everyone's help on this, have a good week folks and thanks for giving me a hope at finding some corner speed one day 🤣
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