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YZ 250F beating me up in braking bumps

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I am getting back into motocross after a 7 year hiatus. took my bike to the track and the braking bumps almost fractured my wrists it was so choppy. I am 195 lb w gear and the rear spring is a little too soft, I set the sag and now the free sag is a little tight. However in corners its like the front doesn't even work, like I'm riding a bicycle with no forks. Im not a slower rider and I am heavy for the bike so I don't know why it won't absorb more when in turns. Only went out a couple times with this bike. Stock  fork springs are 4.8 kg. Called enzo and the tech recommended stiffer fork springs?  said I could be riding toward the middle of the stroke creating a tighter more harsh ride since it is more compressed. I honestly don't know if I need stiffer or softer front since I have been out the game for almost a decade. Anyone else getting the same results through braking bumps??

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Forks :   Check your compression and rebound settings and see where in the range its set.  Should be in the middle to start.  Back off the compression first and see if that helps some.  If its just totally stiff no matter what, the best thing you can try that will soften it up is remove oil from each leg.  Back out 10mm of height, and try again.  I would not remove more than 20mm of oil from the forks.  Back off the rebound until it starts to pogo, then crank back in 1-2 clicks, and it should be about right.  I haven't adjusted shocks as much, so someone else will have to chime in on that.

Edited by ronbuell

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Well that's what is confusing I'm heavy enter corners with decent speed idk why I'd have to soften 250f settings. I mean I will if that's the answer but it doesn't add up.

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Since you're just coming back from a long layoff is it possible you're arms are too tense?

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58 minutes ago, 16Yamama said:

Well I got arm pump half a lap into each session so I probably am. Would that make the ride that harsh?

Then part is the answer is technique.  Remember, elbows out, not down.  Elbows loose, allow the bars to come to you and go back out, sort of like an easy pushup.  Grip strong enough to hold on but not a super tight gorilla grip either.  I always find I get arm pump when I forget or get lazy.  YZ forks are much stiffer than WR, so some things you live with.

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1 hour ago, 16Yamama said:

Well that's what is confusing I'm heavy enter corners with decent speed idk why I'd have to soften 250f settings. I mean I will if that's the answer but it doesn't add up.

Also depends on whether you want the wheel to follow the terrain or flow over the top.  I'm about your weight too, and finding a happy medium takes some sorting out.

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What year bike? You need the proper shock spring for sure. Lowering the oil volume in the forks will help take out some initial harshness as well.

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To much preload in the shock is going to make the back end want to kick around and not track straight. If the fork is stock lowering the oil volume will help. At 195lbs you will need a set of .49kg fork springs as well.

 

I run the forks at 4mm and the shock at 106mm on harder tracks and the forks at 2mm and shock at 108mm on softer tracks. 

Edited by c0ncEpT
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I take it you've made sure the forks are in alignment and not binding!!! Put the bike on the stand with front wheel off the ground, loosen axle nut and the pinch bolts on both sides, re tighten one of the left side pinch bolts then tighten the axle nut, loosen the left side pinch bolt again, some guys prefer to take the bike off tge stand push up and down a few times then back off the ground and re tighten, I prefer just to spin the front wheel and jab the front brake a couple times usually does the trick, re tighten every thing starting with the left side pinch bolts, you could also check that the upper fork pinch bolts aren't incorrectly torqued!!

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What I've found on the previous models with similar forks is to install lighter IC springs. They help greatly with smaller braking bumps.

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12 hours ago, 16Yamama said:

Thanks. The guy I bought it from was 290 lb. only had it for a year but maybe he put stifffer springs in. Super harsh

Well dang, he must have re-sprung it...... who would have thought......

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Fork springs are seldom the culprit when it comes to harshness in braking bumps.  It's the valving, most likely.  Like Enzo said, very soft fork springs can give a harsh ride because they allow the fork to travel too fast.  The faster the fork compresses, the more harsh it will feel because the resulting damping force will be higher.  Dyno curves will show what I'm talking about.

For my weight (150 pounds without gear), the ideal fork spring in my 250 is about .42-.44.  But, I've ridden customer's bikes with .48 springs and they still feel plush if the valving is right.

For your weight, .48 springs are about right.  Unless you're really fast, I don't agree that you need stiffer springs.

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