520 Weak Throttle Return Spring, Stuck Throttle

If my bars are turned to the right, the throttle sticks open. Not a good thing Martha. Took the tank off. Checked the cable routing. Even took the throttle grip off the bar. When there is enough of a bend in the cables, the throttle return spring cannot close the throttle. While I've marveled at the light throttle pull, I'm non-plussed about this discovery. I spent several hours, fiddling with cables, to make sure something wasn't bound up or kinked. It isn't. Proof of this is the very light effort required to twist the throttle open. The problem on mine, is the return spring is simply not strong enough. I suggest you check yours carefully.

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'01 KTM 520 EXC

'95 Suzuki DR350 Dirt

'01 Silverado 2500HD 4x4 Duramax/ZF-6spd

Reroute the cables from the throttle so the cables exit down from the throttle grip.

I've seen pictures and did it to my bike works great!

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Chris in the Mojave

'01 520 MXC

'01 200 MXC

'00 CR250R

'01 KX85

Thanks Chris. Concho gave me a link to an article showing pictures exactly as you describe. Since I was working with the dealer, I wanted to rule out any discrepancies from the as-delieverd cable routing.

Here's an update. Called the dealer I bought from. He's out of state. Though not unpleasant, he was insistent nonetheless that my cable routing was wrong. So I checked the book, routing was correct. Called him back, he gave me direct number to KTM to see if it might be a known problem. Haven't called yet, but on re-examination found an ever-so-slight kink in the area along the frame backbone where it runs under the tank. I carefully massaged this out with the flats on a pair of needle nose pliers. This helped, but throttle still would not return completely if bars turned fully to the right. Against my better judgement, I decided to lube the cables. Disconnected them from the throttle pulley, and checked the mainspring at that time, which was clean and properly installed. Held the cables upright, and used a dropper to drip in some Mobil 1 5W-30. Allowed 10 minutes for the oil to drip down via gravity. Then operated the cable. Reinstalled to the throttle pulley, adjusted the cables, and it seems to be working fine again. These appear to be old style cables, so I don't think there is any harm in lubing them. I had no alternative regardless. A 520 with a sticking throttle is not good.

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'01 KTM 520 EXC

'95 Suzuki DR350 Dirt

'01 Silverado 2500HD 4x4 Duramax/ZF-6spd

Quadrunner500,

Why isn't it good to lube the cables?

One of the first things I did before I even rode my bike for the first time was lube the cable and several other things. The factories sometimes don't lubricate these bikes very well when they're new.

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Joe Bohazi

If In Doubt "Gas It"

'01 520 EXC

'99 640 LC4

'96 KX 250 Gone

'92 RM 125 Gone

'00 ZX-12R

'01 ZRX1200R

Joe, I was trying to remember myself. Then I did. On some Chevy trucks, they've had a few problems with sticky throttles, and GM says NOT to lube the cable. They use some kind of coating inside, teflon I believe. They say not to, that's all.

Only other thought I had about it on a dirt bike, is oil attracting more dirt...

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'01 KTM 520 EXC

'95 Suzuki DR350 Dirt

'01 Silverado 2500HD 4x4 Duramax/ZF-6spd

I use LockEZ or something similar which is a liquid with mostly graphite for lube. My theory is it will not attract the dirt as bad as oil or WD-40. Comes in a nice little bottle which works well for applying to cable ends. Never had a problem with throttle cable on my 520, used to lube the clutch cable on the WR - but the 520 seems to be "permalubed" on the clutch.

Mathew

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