Front end tuck

lucas51
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lucas51
I have been struggling with front end tuck on my 2018 ktm 350sxf. Will too little sag cause this? I have been running 103 but recently moved the rear axle forward to run my 52 tooth rear sprocket. I know wheelbase might have an effect on it too. I like the gearing so the wheelbase is going to stay. What is the best adjustment for this? More sag, more compression on fork, more air in fork, more rebound in shock? I have been running 160psi in the forks. I'm 220 without gear. The front tuck occurs before "turn in" mainly during braking or as I have finished breaking. I also tried rear brake only it didnt help
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AJ565
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AJ565 9/5/2020 5:24pm
9/5/2020 5:24pm
Mine did it a lot with stock brakes. A floating over sized kit helped me out by making the initial bite less grabby. My bike did it with stock setup suspension, different fork heights, different sag, and even cone valves.
chump6784
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chump6784 9/6/2020 2:40am
9/6/2020 2:40am
You could try sliding your forks down in the triple clamps or get another chain with an extra link or two to move the rear wheel back
CarlinoJoeVideo
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CarlinoJoeVideo 9/6/2020 6:47am
9/6/2020 6:47am
Normally when my front wheel starts tucking in corners it’s because the fork is too soft and dives in. The head angle gets steep when you are deep in the stroke and knifes.

Sounds like since you shorten your wheel base, you moved the weight forward on the bike and it’s make the fork too soft. Try 2-4 clicks stiffer on compression.

103 sag is plenty, maybe go to 105 to take some weight off the front also.
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CarlinoJoeVideo
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CarlinoJoeVideo 9/6/2020 6:47am
9/6/2020 6:47am
I run the 14/52 gearing on my 19 350, but run my axle all the way in the back with an extra link.

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lucas51
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lucas51 9/6/2020 5:44pm
9/6/2020 5:44pm
CarlinoJoeVideo wrote:
I run the 14/52 gearing on my 19 350, but run my axle all the way in the back with an extra link.
I did that for awhile but eventually my axle was all the way back and chain was too loose. I will definitely try some of the changes you suggested and will report back. If I can't get it much better I will try and get a vid of it.
theycallmeebryan 9/7/2020 9:40am
9/7/2020 9:40am
CarlinoJoeVideo wrote:
Normally when my front wheel starts tucking in corners it’s because the fork is too soft and dives in. The head angle gets steep when you...
Normally when my front wheel starts tucking in corners it’s because the fork is too soft and dives in. The head angle gets steep when you are deep in the stroke and knifes.

Sounds like since you shorten your wheel base, you moved the weight forward on the bike and it’s make the fork too soft. Try 2-4 clicks stiffer on compression.

103 sag is plenty, maybe go to 105 to take some weight off the front also.
Moving the rear wheel forward actually takes weight OFF the front end and puts more on the rear, because the rear wheel is moving closer to the center of gravity. Moving the rear wheel backwards puts more weight on the front end.

To answer OP. It's either your forks are diving too much under braking or you have too much rebound damping and it's packing up. Try going like 6 clicks out on your rebound adjuster and see how that feels. If it doesn't make a difference, try going 2-4 clicks stiffer on comp.

160psi should be pretty close for your weight. Remember not to get too caught up chasing air pressures and don't forget that you have comp and rebound clickers.
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27thmx
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27thmx 9/7/2020 1:16pm
9/7/2020 1:16pm
Basically what everyone else has said the wheelbase makes a big difference. I try to run toward the middle of the chain block always to keep consistency. Try sliding your forks down a bit
Leeham
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Leeham 9/15/2020 9:48pm
9/15/2020 9:48pm
Fork compression (either with air or clicker) and more sag will affect the front. If you like how the bike turns now, keep your current sag and just bump up the air 1-2 psi or more compression clicks (or a combo of both but go with compression clickers first) until you get desired ride height on corner entry. Sag and fork height change a lot more with smaller changes, perhaps too much in some cases. To save time, make big adjustments on the clicker at first, then dial it in.
FGR01
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FGR01 9/16/2020 7:55am
9/16/2020 7:55am
Another option, you could try running 13/48 gearing to alter where the axle is placed. It's not quite as low as 14/52 but almost the same. Not sure on chain/sprocket clearances as I've never tried this on my 350.
lucas51
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lucas51 9/16/2020 8:37am
9/16/2020 8:37am
Thanks for all the replies guys! Haven't got a chance to ride and we are in the middle of hurricane Sally right now so this weekend is probably not going to happen either.
FFDan
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FFDan 9/18/2020 11:53am
9/18/2020 11:53am
Lucas,

You said your sag was 103, but what is your static sag? You, like me, are a bigger guy riding, you said you are 220 pounds without gear. I was about that when i bought my KX450 and I had to go to a stiffer spring right away. You have to start with the correct spring rate. Then you begin testing air pressures and clickers.

Personally id start with the factory stock settings after having the correct spring installed. Ride the bike for a couple hours and break in that new spring. It will ride high at first. Then recheck the sag, you will probably have to adjust. I would then make sure the forks are at the recommended height in the triple clamps. Ride again with still stock settings. If I was still getting serious tuck in the corners Id lengthen the forks a mm or 2, but this will alter the sag again so recheck and adjust if needed. Then air pressure to get the front end to hold up and not bottom. From there, fine tune with the clickers.

I had the opposite problem with my Kawasaki. My front end wanted to climb out of the ruts. I shortened the forks to 6mm, set sag at 104, set air pressure to where is was pretty good, then dialed it in with clickers.

Good luck
Paw Paw
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Paw Paw 9/19/2020 5:24pm
9/19/2020 5:24pm
Everyone that I know, whom has the 350, run with a higher gearing than stock to improve the torque and thus help with the steering. This had been done either by reducing the final drive sprocket tooth count by 3 teeth or by reducing the front sprocket by one tooth.

Paw Paw
lucas51
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lucas51 9/20/2020 5:46am
9/20/2020 5:46am
FFDan wrote:
Lucas, You said your sag was 103, but what is your static sag? You, like me, are a bigger guy riding, you said you are 220...
Lucas,

You said your sag was 103, but what is your static sag? You, like me, are a bigger guy riding, you said you are 220 pounds without gear. I was about that when i bought my KX450 and I had to go to a stiffer spring right away. You have to start with the correct spring rate. Then you begin testing air pressures and clickers.

Personally id start with the factory stock settings after having the correct spring installed. Ride the bike for a couple hours and break in that new spring. It will ride high at first. Then recheck the sag, you will probably have to adjust. I would then make sure the forks are at the recommended height in the triple clamps. Ride again with still stock settings. If I was still getting serious tuck in the corners Id lengthen the forks a mm or 2, but this will alter the sag again so recheck and adjust if needed. Then air pressure to get the front end to hold up and not bottom. From there, fine tune with the clickers.

I had the opposite problem with my Kawasaki. My front end wanted to climb out of the ruts. I shortened the forks to 6mm, set sag at 104, set air pressure to where is was pretty good, then dialed it in with clickers.

Good luck
Sorry I forgot to add that I have stiffened the rear spring. I can't remember what I put on it I would have to go to my shop and look. I was thinking I may need to add some rebound possibly to slow down this stiffer spring? Still too wet to ride here guys but can't wait to try these suggestions everyone has and see what works best!

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