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Fork dive

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Severe fork dive under hard braking. Can I fix this externally or does it require a revalve? Springs are correct. Thanks.

 

Define "correct" on spring rate?

 

Top professionals often run 3 rates stiffer than "correct" up front.  Allows a fork that holds up better without additional valving.

Maybe you should consider adding a little preload the the spring if you like the fork's performance elsewhere.

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Didn't we have this thread a few months ago ? If it's severe with correct springs something is wrong internally

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Severe fork dive under hard braking. Can I fix this externally or does it require a revalve? Springs are correct. Thanks.

what bike?

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what bike?

XR400 with Pro Action revalve for the previous owner. Set up for C/B rider HS and enduro. He and I are 195-200lbs and same speed. Fork springs are .46 according to spec sheet provided by PA. I use this bike for DS and play riding, no racing. Forks are acceptable, not great but the real problem is the excessive dive. And I do mean excessive, I am a big front brake user. If I need to go internal I will, just hoping for a simple solution. 

Edited by YHGEORGE

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XR400 with Pro Action revalve for the previous owner. Set up for C/B rider HS and enduro. He and I are 195-200lbs and same speed. Fork springs are .46 according to spec sheet provided by PA. I use this bike for DS and play riding, no racing. Forks are acceptable, not great but the real problem is the excessive dive. And I do mean excessive, I am a big front brake user. If I need to go internal I will, just hoping for a simple solution. 

externally you can try adding more compression from the bottom off the fork on this! nothing more really

 

adding preload could help, the XR been heavy requires a bit more around 10-15mm if my memory is correct!  

 

i was happy with my XR400 stock with a bit off HS comp  removed from the base valve! and slightly lower oil level from std!

 

i was around 185 when i had it plus gear and tools stock tank and used .42 springs....only the turning was not as tight turning with 105 sag and forks lowered!

 

maybe heavier springs were needed...but never get to play more with it as it got sold!

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If you are referring to sustained hard front braking and resulting front dive, and your forks are not faulty, then you can either add more oil to firm up the last third of the stroke. Or install stiffer springs to firm up the whole stroke.

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What base valves are in the forks? The stock base valving on those is a goofy orifice damping setup, even though they are cartridge forks. That would definitely make them divey. A "proper" bending-shim valve setup is an improvement.

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after 2000 i believe they had a straight shim stack, all shims same diameter and thickness....i cannot remember dimensions now but i believe around 16-18mm.

 

my 04 had 12 shims which was too much for this fork! removing 3 made it so plush but it was diving so more low speed clicks and high oil level suit me quite nicely for all types off riding!!

 

i even took it to the track occasionally  :jawdrop:, for nothing too serius that is...

Edited by wblake

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They have shims but I don't think it's a bending-shim style like modern forks. It's been a while since I took one apart, but I recall it basically just being a controlled orifice flow, with the shims setting the orifice size?

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Mine has the PA valves and whatever they do. Not really that plush but ok for the DS  I use the bike for. The fork dive is excessive though and sometimes dangerous, it just collapses in am emergency type stop. I'll probably just do a complete revalve with another tuner. My first XR4 with modded stock stuff was perfect, wish my buddy had gone that route. The PA shock is uninspiring also. Thanks guys.

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I assume you guys are talking about the reverse bend style shims.  Same setup the kdx 200 uses?  You can install crf150r base valves super cheap on those.  I assume they're the same as they both have the 43mm showas from the same generation.

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Mine has the PA valves and whatever they do. Not really that plush but ok for the DS  I use the bike for. The fork dive is excessive though and sometimes dangerous, it just collapses in am emergency type stop. I'll probably just do a complete revalve with another tuner. My first XR4 with modded stock stuff was perfect, wish my buddy had gone that route. The PA shock is uninspiring also. Thanks guys.

if you are going to send it away and not go in there your self check out WER he is supposed to be the man for this bikes.

 

 let us know how it goes!

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They have shims but I don't think it's a bending-shim style like modern forks. It's been a while since I took one apart, but I recall it basically just being a controlled orifice flow, with the shims setting the orifice size?

i cant remember clearly how it worked! but it had a piston with the shim stack, a check valve and a needle controlling the orifice!

 

maybe Kan3 is right on the money with the name!

 

it sucked because the needle screw got broke after some use or mine did anyway but could not get the parts to fix it! you had to buy complete assy!

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if you are going to send it away and not go in there your self check out WER he is supposed to be the man for this bikes.

 

 let us know how it goes!

Yep. :thumbsup:

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