Posts
1189
Joined
7/8/2016
Location
Belton, MO
US
Edited Date/Time
5/1/2018 8:13am
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.
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.
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.
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.
The Shop
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
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.
Pit Row
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?
Sidenote: my 250exc-f throttle (FI) is almost too easy, it cracks open with zero force.
Post a reply to: 17 KTM two stroke throttle question