KTM 520 Pushing/diving - Suspension/tires/Tclamps?

[Wild Hare]

I'm having trouble with my KTM 520 MXC, I can't keep the front end under it!
There are two major symptoms, fork dive and pushing in corners.

It's diving badly( 3 or 4 inches ) the front anytime there is a transition
that causes a weight shift forward. It is really killing me on steep
technical descents where you have to transition from no braking to braking
based on available traction. I'm talking one finger, ever so slight braking
causing the front to dive, then the it stops suddenly after 3 or 4 inches of
travel. This is not confidence inspiring, to say the least. I thought
maybe it was just me so I let a couple of friends try it (better riders than
I) and they commented on the same thing!

I'm think I'm seeing the same thing in the flats/corners as a "push" in the
front end, it's very vague and pushes badly in the corners.

I've tried slowing the transition by increasing compression in the front, no
help. I dialed in enough compression (over several rides) that I was not
getting to the last 4 inches of travel even in high speed trips through the
whoops. The bike would still dive, even on transitions from climbing to a
ridge with a tight turn at the top. I've tried slowing down the rear rebound
thinking that maybe the shock rebounding too fast was causing it. No luck.
As a "check" I went back and rode some of the same descents on my '02
YZ250(stock valving .46/5.4 springs) just to see if it was a "skills" issue
with me...I didn't have a problem with the descents on the YZ or pushing in
the corners for that matter.

The bike has been revalved by a local shop and has a .45 springs in the fork
and PDS3 in the back. I'm 6'4" and 220 plus gear. Ablity wise, I run with a bunch of
Vet Experts but I'm the "slow" guy in the group. I've placed in the top 5
Sr. open novices in D-37 races.

I'm on the stock rubber M77/78's, ( 16 F/R PSI for desert) They wear well
but I'm starting to think it's part of the problem with the High Speed push.
I've read lots about changing out triple clamps on KTM's - 22's, 18's and 16's! I
guess I can see the 18's and 16's helping bring the front in so there is
more weight on the front to help it hold? I guess I don't understand the
22's at all, wouldn't that make things worse?

Any ideas on sorting this thing out?

 

[Fred T]

Try sag

Have you tried different sag settings? Just a thought.

 

[marcusgunby]

Im not sure of spring weights on your model but the 02 Cr125 comes with 0.44 springs and i can bottom it easily weighing in at 170lb somaybe you need stiffer springs.

 

[zeroo]

You should try some michelins on the front/rear.That should help keep the front tire under you.those stockers are dangerous on KTM'S.Also,are your front brakes to grabby?As far as pushing in corners you can get used to it,I did.But I wasn't switching back and forth from a jap bike.I came off of an RM250 and struggled at first to corner as good but it'll come to ya.I used to(and still do) do figure 8's trying to lay the bike down as low as I can.Good practice anyways.But I think the michelins help the most.Havn't tried the tripple clamps but I plan to in acouple of months when I get an '02.Good luck.

 

[Shaw520]

At 220 pnds, those .45's you put in there are probaly not enough.
I have had 48's,(were'nt enough) and now .50's in mine ( I also have 35 pnds on you) and that made a night/day difference. The .48's were ok for trail junk, but couldnt take any moto. My guess is, if your an aggresive rider, the .48's will suit you, if not then try the .46's
Remember, if the fork is riding mid stroke, they bike will dive and feel harsh, plushness starts at the top of the stroke.

 

[Strick]

It's all of the above. Try heavier fork oil 7.5 or 10wt. Raise the oil hieght 10mm and get a better front tire first. That Bridgestone is dangerous! You also need to address the rear the stock spring, it is too light for you.

Finally that MXC tank carries all of the fuel high and towards the front. This is an issue I believe. Is there any possiblity of you borrowing an EXC or SX tank from someone, and just give it a try?

Good Luck and let us know how it turns out!

 

[cbm4stroke]

Mine did exactly the same thing even with stiffer springs and 18mm offset clamps. The Knifing in was killing me. I send the suspension to Dicks racing in N. Las Vegas and after he revalved both the shock and forks the thing is the best handing bike I have ever owned hands down. My friend has the same bike with stock clamps and heaver springs and we rode the two back to back and the Dicks suspension is night and day different. He is now sending his suspension to Dicks. Im running White Power 0.44s, a Eibach 8.8 straight rate shock spring and set the sag at 100mm (weight 235). My friend is 240 runs 0.46s, a 8.4 spring on the shock and runs 105mm sag. We both are senior expert riders. http://www.dicksracing.com

Dicks has many years of experience with KTM WP suspension.

Clark

 

[zeroo]

Actually,I would try MX-TECH.:)

 

[Shaw520]

cbm, That link is going to some 'e-bussiness site, you got one that works?

 

[trewent]

I just had my '00 400 exc revalved and it made a big difference in exactly what you are describing. I top out at 240 with gear, running .45 springs. stock rear and can't rave enough! When you have the work done have it valved like an MXer when full stiff on Compression, Stock MXC at full soft, that way you get what you want when you want it. I used Mike Weisner in Michigan (Kelly Smith's former wrench).

 

[cbm4stroke]

Shaw520

I edited the URL I had a extra period in the first post. The URL in the post should now work.

Thanks for the find

Clark

 

[Wild Hare]

Thanks for all the feedback. :D

I'll be trashing the tires for starters. I talked to the shop that did the valving and springs today, they want to make it right, so I'm going to give them one more try. If that doesn't work, then it's off to Dick's.... I know MX-Tech does good work, but Dick's is close enough I can drive there and he lives in the terrain I ride:D

 

[motojunkie]

Suspension is probably an issue, but you already got good advice there (MX-Tech), so I'm going to approach the tire issue. I had reasonably good luck with the stock M77/78 combo by running lower tire pressures...For MX on a 520SX I was running 11-12 psi. I didn't have any trouble with pinch flats or anything of the sort. But, I've had fantastic luck with Michelin Starcross MH2 tires front and rear. They're int-hard terrain tires, but work well everywhere, and they wear well also. One of the longest wearing tires I've used.