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Discussion Starter · #1 ·
I have already had the frustration of my Throttle Position Sensor making my bike have no spark. It just randomly started doing it. I wish you could just overide the TPS system on the KTM like I can on my YFZ. YFZ's struggle with throttle response and Idle becasue of the TPS. But with the Yamaha i Just cut the wires, soder them together and problem solved. with the KTM SX you have to buy a dirtbike CDI if you are gonna do the same procedure. Otherwise i bet you would end up with no spark. Oh well I LOVE MY KTM! Never owned a bike with better fit and finish. SHARE YOUR THOUGHTS.
 

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i already have a fix. what happens when you cut it and attach them together, it will not start. you need the cables unattached to start then connected to rev it up. someone sells a button to do this. i think it is motion pro. what i did is take apart the black blob on the clutch side of the bars, and connect the on-off wires together, and attach the tps wires the the switch.

i then turn on the key and put the switch to "off" then to "on" then i hit the start button. it works perfect.
 

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I just put a bike CDI on, no switches to worry about. Dealer let me have it for $100.
 

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So is the TPS thing a common problem? Its an easy fix, but I was just curious. Jake I like your idea. I wonder if its possible with just the start button. It seams that your black blob is a multi use starter function switch :)

Whats invloved with the bike cdi swap?
 

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So is the TPS thing a common problem? Its an easy fix, but I was just curious. Jake I like your idea. I wonder if its possible with just the start button. It seams that your black blob is a multi use starter function switch :)

Whats invloved with the bike cdi swap?
I got one off an 09 sx-f dirt bike and it plugs right in. no modding necessary, no switches or button to press, also loop my clutch wires together and put a starter button off the bike on ( it plugs right in) you can also get the starter button from the Hard Parts catalog. Bike cdi cost me $100.
 

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Discussion Starter · #7 ·
I got one off an 09 sx-f dirt bike and it plugs right in. no modding necessary, no switches or button to press, also loop my clutch wires together and put a starter button off the bike on ( it plugs right in) you can also get the starter button from the Hard Parts catalog. Bike cdi cost me 0.

so just buying a dirtbike CDI will eliminate the whole TPS system? I hope so. cuz if thats all thats involved i will most likely buy one. Think the sx-f cdi curve is different for the diferent cam profile the dirtbike most likely has? im really new to this whole KTM thing. ive had Yamaha's since 04. I know a guy that just bought a 505sx and before he even left the dealer he had them put on a twist throttle and he had to switch to the dirtbike CDI. But my question i guess is would i have to close the TPS circuit by sodering wires together. just what i assumed.. lol oh a im definately gonna loop my clutch safety switch wires together.just havent got around to it. Ive stripped my yfz's wiring down to the very essentials..
 

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I put a honda throttle on mine. Just unplug the switch on the throttle (do not loop), plug in the bike CDI, loop the clutch switch, and leave the actual TPS on the carb alone (it will still let the bike CDI advance the ign curve with throttle position, it also allows you to up the idle to prevent stalling in corners when you don't quite get the clutch pulled all the way in). I think the cams on the bike are the same as the quad (someone feel free to let me know), but the timing curves (even if they're not the same, they're not different enough to notice a difference).
 

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I put a honda throttle on mine. Just unplug the switch on the throttle (do not loop), plug in the bike CDI, loop the clutch switch, and leave the actual TPS on the carb alone (it will still let the bike CDI advance the ign curve with throttle position, it also allows you to up the idle to prevent stalling in corners when you don't quite get the clutch pulled all the way in). I think the cams on the bike are the same as the quad (someone feel free to let me know), but the timing curves (even if they're not the same, they're not different enough to notice a difference).

So then, all in all, what were the benefits of using the Bike CDI?
 

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It just gets rid of the throttle switch that will not let it start. If the idle is too high it will not start w/ the quad cdi.
 

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Does anyone know if you can switch carbs on these machines? I switched carbs with a fellow member and I cant get my bike to start for nothing. Any ideas??
 

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Well if the TPS is anything like a automotive TPS, you should have a 5volt reference, a ground and a signal wire. The signal should be closer to 0 zero volts at closed throttle and closer to 5 volts at WOT it usually doesnt ever get quite to 0 or quite to 5 volts, grab your DVOM(multimeter) and check these circuits. The carbs should be interchangeable, should be identical TPS.
 

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I finally got it to run. I ended up moving the tps until it started. Weird. Cause then it would start no matter where I had it. LOL I guess it was one of those things.
 

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I finally got it to run. I ended up moving the tps until it started. Weird. Cause then it would start no matter where I had it. LOL I guess it was one of those things.

Sounds like a hard reset kinda thing, just had to move it through its ranges to register maybe?
 

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It could be confusing, I'll try to simplify.

TPS (Throttle Position Sensor), this is used to control the timing advance.

Dirt bikes have 2 throttle cables one to open and one to close the throttle(in case it gets stuck open), Yamaha has thier TORS system which consist of a throttle switch on the carb and one on the thumb throttle. Its design is sepatate from the TPS and is only there the kill the ignition if it sees a difference in the two switches. A separate function to kill spark is not necessary on quads with butterfly throttles(fuel injection), only slide type (FCR).

KTM has both functions in one (TPS is used for timing advance and stuck slide situations), along with a thumb throttle switch. If the idle is too high the TPS thinks the slide is stuck open and will not allow the quad to start. To bypass this you have install a switch and turn key on and press switch every time to start. By changing to the Bike CDI you eliminate the stuck throttle function and the TPS functions normally.

The TORS on my Yamaha was bypassed, and the TPS was bypassed to show WOT all the time and keep the timing at full advance. The TPS on my KTM could be done same now that it has the Bike CDI.

Not sure if this clears up anything, but I hope it helps.
 
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