17 KTM two stroke throttle question

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10/28/2017 5:36 AM

Im not looking for answers because I know how to fix it but

Has anyone noticed their throttle being far stiffer to turn than the average bike? I lube the throttle cable pretty regularly and that helps but after riding friends bikes and friends riding my bike, I notice how easy everyone else’s throttle is and they notice how stiff mine is

Has anyone else noticed this?

Also, I kind of like it because it keeps the bike from blipping over braking bumps. And I don’t get arm pump. Ever.

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10/28/2017 6:24 AM

No. Might want to double check your cable routing or grit in your throttle tube housing.

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10/28/2017 6:47 AM

Jeff_Crutcher wrote:

Im not looking for answers because I know how to fix it but

Has anyone noticed their throttle being far stiffer to turn than the average bike? I lube the throttle cable pretty regularly and that helps but after riding friends bikes and friends riding my bike, I notice how easy everyone else’s throttle is and they notice how stiff mine is

Has anyone else noticed this?

Also, I kind of like it because it keeps the bike from blipping over braking bumps. And I don’t get arm pump. Ever.

The same has occurred to my '17 250SX as well. I spoke with a friend that works for KTM back in early spring about this, and he said it was a noted minor concern/issue on the new 2 stroke throttle housings. He suggested replacing the OEM housing with a Joker throttle housing/cable to fix the throttle cable wear. Obviously an easy fix by just buying a new throttle cable, which I have done twice now.

Though, I always replace it when it starts to get tougher to twist, as I get more arm pump, and it's harder for me to hammer the bike out of corners.

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My bikes: '73 Honda SL70, '74 Suzuki TM75, '75 Honda CR125, '76 Honda CR125, '76 Suzuki RM100, '76 Honda XR75, '77 Suzuki RM125, '79 Maico Magnum 250, '80 Maico MC 250, '79 Maico Magnum 400, '85 Kawasaki KX250, '93 Honda XR250R, '94 Honda CR250, '01 KTM 300EXC, '04 KTM 300 EXC, '05 KTM 300 EXC, '06 KTM 300 XCW, '08 KTM 300 XCW

10/28/2017 7:30 AM

Mine is harder to twist than my friends 17 450, quite a bit too.

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10/28/2017 8:12 AM
Edited Date/Time: 10/28/2017 8:12 AM

Photo

Realized this issue when I rode a friends 17 250sx. He had gotten use to it being hard to turn but I noticed right away how hard it was compared to my 14 and 15. Best fix is to buy the G2 17 upgrade kit that gives you the better quality domino throttle housing and cable. I've seen 17's wear a hole in the housing after many hours. Do this mod and not have to worry about that ever happening.
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10/28/2017 8:15 AM

I have a 17 300 xc-w. When I raced it the first couple times I could feel how hard that throttle was to twist late in the race. Did some research and in 17 they switched the throttle to a different style. I put the 16 ktm throttle and cable on it and it fixed the issue for me.

Not sure it would have bothered me on a motocross track but late in off road races I got arm pump just turning the throttle lol

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10/28/2017 10:10 AM

Got a ball bearing throttle tube on ebay for 30$. Cut the spring length down 1 coil and stretched the spring a bit. Nice and easy now on my 150.

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10/28/2017 11:33 AM

Just order a 16 SX 250 throttle and cable. We have done this to a lot a our shop. Simple and easy!!

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10/28/2017 2:41 PM

Indian made crap by Baj slowly creeping in I guess on the top models too

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10/28/2017 2:42 PM

I put a Yamaha throttle and cable on mine.

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10/28/2017 3:23 PM

Jeff_Crutcher wrote:

Im not looking for answers because I know how to fix it but

Has anyone noticed their throttle being far stiffer to turn than the average bike? I lube the throttle cable pretty regularly and that helps but after riding friends bikes and friends riding my bike, I notice how easy everyone else’s throttle is and they notice how stiff mine is

Has anyone else noticed this?

Also, I kind of like it because it keeps the bike from blipping over braking bumps. And I don’t get arm pump. Ever.

Man I think It's that new style system on the KTM two strokes, we switched ours back to the old style system and it seems to be a much better operating and fluid system

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10/28/2017 3:24 PM

I just started to notice the last two rides. Weird.

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10/28/2017 4:47 PM

Hmmm, I haven't noticed mine being any harder than my old 2013, I wish I had the old one now to compare.

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10/28/2017 10:32 PM

What is the issue? I have a 2016 150 although I've only ridden it once. I took the throttle housing apart when I replaced the cable after buying it (used) and did notice more dirt in there than I've ever seen on other bikes I own. My dad has a 2015.5 factory edition 250f and that throttle is still great but it is different than the two stroke one of course.

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10/29/2017 12:12 AM

That's funny, I was thinking the exact same thing yesterday. It is really stiff on my 17 300 as well. I like the ODI grips but that throttle design maybe isnt the best.

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10/29/2017 2:53 AM

endurox wrote:

Got a ball bearing throttle tube on ebay for 30$. Cut the spring length down 1 coil and stretched the spring a bit. Nice and easy now on my 150.

Don't cut the spring!

Cutting the spring doesn't make it lighter, but just removes preload. Your 1kg spring (or whatever) is still a 1kg spring, but just shorter. That can mean that the carb slide will bounce and open itself over bumps when closed because there's hardly any pressure on the slide when the throttle is closed and the spring is extended.

Stretching the now-shorter spring to reinstate the pre-load actually leaves you with a stiffer spring. Spring stiffness is determined by wire thickness and number of coils. Thicker wire is obviously harder to bend than thin wire. The more coils there are the less the wire itself actually has to bend for the same amount of spring travel.

Cutting and stretching the spring back out means you now have less coils than before, but the distance the spring has to compress (ie throttle slide travel) is unchanged. That means that for every inch of spring compression the wire now has to move/bend further than before it was cut. That takes more effort. ie stiffer.

The correct way to lighten a throttle spring is to carefully grind the outside of the spring around and along the full length of the spring. This keeps the length (and hence preload) the same but reduces the wire thickness. Thinner wire lessens the force required to compress the spring.

I had a (shit) full time mechanic in GPs for a while, who, without consulting me, cut the spring. The bike (a 500) ran on with a partially open throttle coming into turns. Couldn't figure out what was causing this until I discovered what he had done and realised that the slide was just bouncing open even when the throttle was shut.

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10/29/2017 3:27 AM
Edited Date/Time: 10/29/2017 3:28 AM

That's weird because I have an 18 250 sx and have the exact opposite.. it's so easy to turn, there is almost no resistance. Catches me off guard sometimes.

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*Anyone but Reed or Webb Crew*

10/29/2017 7:08 AM

Fearo wrote:

That's weird because I have an 18 250 sx and have the exact opposite.. it's so easy to turn, there is almost no resistance. Catches me off guard sometimes.

How many hours do you have, mine was very light and easy until about 15-20 hours

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10/29/2017 7:30 AM

25 hours on mine.

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10/29/2017 8:02 AM

Robgvx wrote:

Don't cut the spring!

Cutting the spring doesn't make it lighter, but just removes preload. Your 1kg spring (or whatever) is still a 1kg spring, but just shorter. That can mean that the carb slide will bounce and open itself over bumps when closed because there's hardly any pressure on the slide when the throttle is closed and the spring is extended.

Stretching the now-shorter spring to reinstate the pre-load actually leaves you with a stiffer spring. Spring stiffness is determined by wire thickness and number of coils. Thicker wire is obviously harder to bend than thin wire. The more coils there are the less the wire itself actually has to bend for the same amount of spring travel.

Cutting and stretching the spring back out means you now have less coils than before, but the distance the spring has to compress (ie throttle slide travel) is unchanged. That means that for every inch of spring compression the wire now has to move/bend further than before it was cut. That takes more effort. ie stiffer.

The correct way to lighten a throttle spring is to carefully grind the outside of the spring around and along the full length of the spring. This keeps the length (and hence preload) the same but reduces the wire thickness. Thinner wire lessens the force required to compress the spring.

I had a (shit) full time mechanic in GPs for a while, who, without consulting me, cut the spring. The bike (a 500) ran on with a partially open throttle coming into turns. Couldn't figure out what was causing this until I discovered what he had done and realised that the slide was just bouncing open even when the throttle was shut.

Informative posts like this are the best part of any good forum. Thank you for sharing.

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10/29/2017 10:05 AM

gets rid of the play between the throttle tube and handlebar. Nice smooth ball bearing action. 30$ on ebay


Photo

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10/29/2017 11:01 AM

endurox wrote:

Got a ball bearing throttle tube on ebay for 30$. Cut the spring length down 1 coil and stretched the spring a bit. Nice and easy now on my 150.

Robgvx wrote:

Don't cut the spring!

Cutting the spring doesn't make it lighter, but just removes preload. Your 1kg spring (or whatever) is still a 1kg spring, but just shorter. That can mean that the carb slide will bounce and open itself over bumps when closed because there's hardly any pressure on the slide when the throttle is closed and the spring is extended.

Stretching the now-shorter spring to reinstate the pre-load actually leaves you with a stiffer spring. Spring stiffness is determined by wire thickness and number of coils. Thicker wire is obviously harder to bend than thin wire. The more coils there are the less the wire itself actually has to bend for the same amount of spring travel.

Cutting and stretching the spring back out means you now have less coils than before, but the distance the spring has to compress (ie throttle slide travel) is unchanged. That means that for every inch of spring compression the wire now has to move/bend further than before it was cut. That takes more effort. ie stiffer.

The correct way to lighten a throttle spring is to carefully grind the outside of the spring around and along the full length of the spring. This keeps the length (and hence preload) the same but reduces the wire thickness. Thinner wire lessens the force required to compress the spring.

I had a (shit) full time mechanic in GPs for a while, who, without consulting me, cut the spring. The bike (a 500) ran on with a partially open throttle coming into turns. Couldn't figure out what was causing this until I discovered what he had done and realised that the slide was just bouncing open even when the throttle was shut.

According to Paul Thede of Race Tech who is a degree qualified engineer, cutting a spring actually makes it stiffer. It's got to do with one less coil pushing back against the others. Force applied in one direction will make like force in other direction? Something like that. He's pretty cluey on that techy side of coil things

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10/29/2017 11:52 AM

endurox wrote:

Got a ball bearing throttle tube on ebay for 30$. Cut the spring length down 1 coil and stretched the spring a bit. Nice and easy now on my 150.

Robgvx wrote:

Don't cut the spring!

Cutting the spring doesn't make it lighter, but just removes preload. Your 1kg spring (or whatever) is still a 1kg spring, but just shorter. That can mean that the carb slide will bounce and open itself over bumps when closed because there's hardly any pressure on the slide when the throttle is closed and the spring is extended.

Stretching the now-shorter spring to reinstate the pre-load actually leaves you with a stiffer spring. Spring stiffness is determined by wire thickness and number of coils. Thicker wire is obviously harder to bend than thin wire. The more coils there are the less the wire itself actually has to bend for the same amount of spring travel.

Cutting and stretching the spring back out means you now have less coils than before, but the distance the spring has to compress (ie throttle slide travel) is unchanged. That means that for every inch of spring compression the wire now has to move/bend further than before it was cut. That takes more effort. ie stiffer.

The correct way to lighten a throttle spring is to carefully grind the outside of the spring around and along the full length of the spring. This keeps the length (and hence preload) the same but reduces the wire thickness. Thinner wire lessens the force required to compress the spring.

I had a (shit) full time mechanic in GPs for a while, who, without consulting me, cut the spring. The bike (a 500) ran on with a partially open throttle coming into turns. Couldn't figure out what was causing this until I discovered what he had done and realised that the slide was just bouncing open even when the throttle was shut.

Underground wrote:

According to Paul Thede of Race Tech who is a degree qualified engineer, cutting a spring actually makes it stiffer. It's got to do with one less coil pushing back against the others. Force applied in one direction will make like force in other direction? Something like that. He's pretty cluey on that techy side of coil things

Exactly.

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10/30/2017 9:17 AM

urbanlift707 wrote:

How many hours do you have, mine was very light and easy until about 15-20 hours

About 10 hours. I hope it stays relatively smooth, although I wouldn't mind if it got a little stiffer..

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*Anyone but Reed or Webb Crew*

5/1/2018 7:39 AM

Having similar issues on my 17 150 at 35 hours and didn't want to make a new thread. I have checked the throttle tube for grit and it is fine. It only seems to be difficult in the first few degrees of motion, and feels like its the tube not the cable. Randomly it wants to stick shut and then moves fine. I have made sure the tube is not too far in on the bar to catch the outside of it. I did just replace the stock ODI's with a newer set of similar lock on grips just the EMIG version.

Considering doing the conversion to the 16 assembly. If I do that do i just need the throttle housing, or do i also need the cable?

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5/1/2018 8:13 AM
Edited Date/Time: 5/1/2018 8:13 AM

In case anyone has the same issue, I had my 250sx throttle get pretty stiff a while back and it ended up being the throttle valve plastic guide that sits on the bottom of the spring (it has a notch that has to fit in or it will bind), it wasn't seated properly in the carb and made it tough to turn the throttle.

Sidenote: my 250exc-f throttle (FI) is almost too easy, it cracks open with zero force.

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