Throttle position % i.e. Idle.

Those with GP Control what is your Throttle Position percent reading on your bike?

I've been having starting problems and running rich. My starting problems are getting so bad it drains the battery down and it shuts the computer off. I'm pretty sure I have to lower my Injector Offset a tad. Currently, it's at 1.10 with the Injector flow at 2500. Stepper seems fine at 171 when cold.

One thing I have been doing is messing with my Idle to get the bike to even act like it wants to fire. So now I'm not sure where a good starting place is to set the Throttle Position % before I try lowering the Injector Offset. I'm thinking something around 5% seems more logical. What is your reading?


Whats your plug look like at the current injector offset? It seems real high to me. What was your stock injector flow rate? It sounds like you may be running rich to begin with. Adjusting the idle screw will change the TPS reading and dump even more fuel on the start.

My advice would be to increase your injector flow rate 1% above stock to compensate for injector polish and decrease the injector offset until you get a nice burn on the plug.

When I first started with the software they (GP) said not exceed 3.5% throttle at idle. I never was able to get the idel above 1800 rpm usnig the 3.5% I am at 3.7% now and it seems OK.


Flow rate has never been changed. Still at 2500.

My bike is dumping so much fuel into the engine I even have to give it a little throttle to get the thing started. Hence the high Throttle Position Percentage.

Basically I was going to lower my throttle to something, just didn't know what percentage. I think I'll start at 3.5% per your advice then adjust the flow up by 1 or 2%. The I'll start decreasing the offset until she starts better. All the while doing the plug check.

Sound good or should I use a different plan?


If you've been running rich for awhile, chances are your spark arrestor screen is partially clogged, mine was. It is a very fine mesh. With the minor exhaust mods I did, the bike now seems more responsive to tuning changes, and breaths way better. Cut the first cone out, remove the fine screen, and pop rivit a larger mesh over the 2nd cone if the SA is important.


HR's $.05 worth....

your throttle body is going south.

been there....

chased that....

didnt ride for a long time cause of it.



The way I see it that 3.5% is a guideline to set the idle speed screw after a TPS calibration with the screw completely out, just to get the bike to start. Mine ends up about 3.6 - 3.8% after idle adjustment.

I agree with Ron, those settings sound really rich. Mine was a pig at 2550/1.05. I'd re-cal the TPS, go 1% up on the flow rate, and drop the offset 10% (make it 1.00) and see what that does for starters. Mine likes 7-10% leaner on the offset with the exhaust changes. If the TPS sensor is bad, you should be able to see it by slowly turning the throttle or using the idle screw and observing the % position on the screen on the D&M tool. It should be a linear response.


What you mean is the TPS sensor is bad, right? I can't see what could go wrong with the throttle body itself. Can you replace just the TPS sensor?


Glen offered up some good advice on the spark arrestor screen, clean it as part of the project. If you do all that we have recomended and still have problems then start looking elswhere i.e per HR.


Thanks Glen. I'll check into that.

HR - I hope it's not a bad throttle body. I'm still going to try making a few adjustments but what were all the symptoms of your bad part and what went wrong on the throttle body?


yes its the sensor, but it is a sealed/one piece unit after fabrication with the it goes...the TB goes.


Both my dealer and mine went bad (his on his rebuilt mx400 and mine on my E, and oh BTW his E is starting to show the symptoms)...and this is how we chased the fault to the TPS going bad.

get the bike fired up and running good op temp....when the idle races...

push straight in on the center of the throttle cable pulley assembly (TPS is on the other end...) with the bike running.

if the idle setttles back down, there you have it, tps/tb is going bad. Mine got to the point where the idle would not lower, raced all the time (fun in the tight stuff in the corner!!!!!! :) ) and then she just wouldnt start. When I removed my TB there was actual movement laterally of the shaft on the BF valve.

For a while it will settle back down....but once they get going bad....the reduction in the idle speed will only be as long as you apply pressure. You release, the idle goes up. Then she wont start. Its just the beginning.

Have you removed the stepper (by function) from the circuit?




Was your replacement TB/TPS assembly any different (improved) from the OEM part? What about your dealer's bikes? Not very encouraging, and I'll bet that thing is not cheap if you have to pay for it later on. Whats the failure mode? Does the TB wear, allowing play which kills the TPS sensor pot?


We both had the old style throttle body, one of the Tech Bulls at C'Dale shows the new style.

What you described in terms of wear is exactly what happens. The TPS wears ever so slightly, but then the ECU has no idea what the throttle plate position in, vs what it is telling the ECU it is in.... = all goofy in terms of throttle opening vs reality!....bottom line...not a good thing at all.

It either happens early on or never with the old style, but C'Dale knew of the issues, and the reason why they changed TBodys.

My TB is completely different from the old style, identified from the new idle adjustment screw.



OK I set my TP% around 3.5% and got the bike to fire right up. I did have the run away idle thing going but traced it to a loose throttle cable. Hopefully the TB is ok. Didn't have a runaway rpms thing to try the push on the TB thing.

Throttle seems smooth and revs smooth however the idle is slightly rough and my idle rpms skip around a bit from 1900 - 2200. TP% stays around 3.5 to 3.7%. I changed my plug from the "8" to the "9" because it's all I had plus it's starting to cool off a bit hear. 95 degrees today but will be in the 70's by Friday.

I upped my Injector flow to 2525 and dropped my offset to 1.00 and the bike seems to rev a little crisper. Idle still slightly rough. I'll get some fresh fuel tomorrow and take it for a spin and check the plug.

I removed the screws from the exhaust but haven't been able to get the end cap off yet. Any suggestions on the end cap or rough idle?

Thanks for all the help and advice!

Intersting variances in settings. Our throttle percent was/is at around 5.5%. Generally starts and idles fine, 1800-1900. Injector flow was 2630 with an offset of 0.98.

However, according to the air/fuel meter we installed, we are indeed quite rich at idle (12-13). Above about 10% throttle, we are running lean, with the A/F reading around 16. We are running a different intake and exhaust (big K&N cone filter and a SuperTrap straight thru competition "silencer".

Did try to do a universal 10% increase on the fuel map using the ProCAl, but alas, our ECU or wiring harness seemed to develope a sudden onset of Alzheimer's and wouldn't retain maps or calibration files.

For what it is worth, was caught off gaurd by the heat generated by this engine. Radiators which kept our trx250R motor running below 150F resulted in the C'dale running at 220+F. Ended up runing two radiators which brought the temp down to the 170-180 range.


Tap the end cap with a rubber mallet, it will come off, its not RTVed on. You'll be shocked when you see the screen. Ever try breathing through a straw?

Mine never idled smooth until I put the flywheel weight on. Now its a happy motor (with an intermittant high idle).

Took my stepper off tonight, it fell apart in my hand. Its toast. The pintal or valve portion was also carboned up, probably from the coughing and spitting the bike did when it wasn't running right. I designed and built a manual cold start replacement. Its basically a pneumatic toggle valve mounted to the top of the radiator on a bracket, a plate with two small fittings replaces the IACV housing and tubing connects it to the valve. Too late to test, but should work fine. No stepper, no stepper problems!!


Thanks for the throttle body information. All the parts lists say is MC500 and MC1000 versions, not an old and new MC1000 version.

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