Touchy Throttle: What Works?

[esauren]

Hi all. I am hoping someone can help. I have a CRF250X, 2009, stock except for a G2 throttle cam, with less than 50 miles on the bike. I ride mostly tight trails in Virginia at 0 to about 1800 ft elevation, in warmer temperatures (~55 – 80 degrees so far). The bike starts easily and runs well except for the on/off throttle effect just off idle. I have seen many suggestions to solve this problem on both Thumpertalk and CRFSonly, but little feedback as to what actually worked. The G2 throttle cam may have helped a little. But I am interested in treating the problem, not the symptom, so I don't want to change gearing, add a flywheel weight, ride faster, slip the clutch more, or install an auto clutch. Adjusting the pilot screw did not help. I also cleaned and re-oiled the air filter, adjusted the chain tension, adjusted throttle free play, and checked for air leaks (propane test, tightened bolts). I would consider a JD jetting kit if I was reasonably sure that it would work, but the only issue I am trying to solve right now is the on/off throttle effect just off idle. I am interested in knowing how people have solved this problem; what solutions have worked? Any feedback would be appreciated. I am new to this forum and new to working on bikes. I haven't ridden for a long time. Thanks.

[Jaketinaboxer]

based on your description it may be the "bog" Off idle abruptness may be cured by the ap mod.

[esauren]

Thanks for the response. I would not describe the issue as a bog; from coasting with no throttle (in 1st gear, clutch out), I just begin to slightly twist the throttle and the bike instantly lurches forward. After that, acceleration seems relatively linear.

[Jaketinaboxer]

That is weird, usualy the bog is kinda a dead spot in the off idle area.

[99klr250]

I have also been frustrated by what you are experiencing. It makes is difficult in very tight situations and very slippery conditions. In reading old threads I have not found how this can be tuned out of the carb / engine. I gathered it's just a characteristic of the engine. with some practice, slipping the clutch might help. I also think a heavier flywheel would help. Power would come one smoother, less likely to lurch. The trade off is, it would be a little harder to lift the front wheel when you wanted. It would make the engine more tractor-like. I would love to hear other solutions.

[dmac1]

If its too jerky, a mechanical fix can be a throttle cam to make it activate the throttle less. Sounds like you've already tried that approach. You've pretty much got the list of other possibilities, but I wouldn't do them. The better fix is just ride it more and you'll get used to how the bike operates and the problem will go away. When I got mine I too had the same 'complaint'...it went away all by itself long ago.

The bog is fixed via jetting and/or the accelerator pump mod. Some swear by the JD Jetting kit, but at best it is a pricey shortcut to eliminate some effort on your part. I bought it, followed the instructions and mine still bogged. Perhaps my o-ring broke right away...but that doesn't seem likely. I do know that it was broken when I pulled my carb out just a few weeks ago so I have wired it.

I suggest you find a more open area to ride and that you go get in some hours with the bike before you do anything.

Dave

[slaydirt]

+1 to what DMAC says about the JD kit i jetted my bike for like 20$ and doubled the oring when i did the mod...my throttle response is crisp and instant with no bog anywhere in the powerband...seat time will help you get used to the snappy throttle

[Diamond DG]

AP mod does nothing for an 09' bike. It's strange your description of the problem your having. Sounds like your just not used to the power of the newer 4 strokes. Everyone complains of off idle bog which can be fixed with leak and pilot jet.

[renob]

I had the same problem with an '05x that I bought new(still have it). I gradually got used to the jerkiness but it still bugged me. After about 20 hrs I installed the JD jetting kit with the 42 pilot jet and an adjustable fuel screw

and the condition went away. I think it is caused by a lean idle mixture.?

[FORMA MOTO]

Hi all. I am hoping someone can help. I have a CRF250X, 2009, stock except for a G2 throttle cam, with less than 50 miles on the bike. I ride mostly tight trails in Virginia at 0 to about 1800 ft elevation, in warmer temperatures (~55 – 80 degrees so far). The bike starts easily and runs well except for the on/off throttle effect just off idle. I have seen many suggestions to solve this problem on both Thumpertalk and CRFSonly, but little feedback as to what actually worked. The G2 throttle cam may have helped a little. But I am interested in treating the problem, not the symptom, so I don't want to change gearing, add a flywheel weight, ride faster, slip the clutch more, or install an auto clutch. Adjusting the pilot screw did not help. I also cleaned and re-oiled the air filter, adjusted the chain tension, adjusted throttle free play, and checked for air leaks (propane test, tightened bolts). I would consider a JD jetting kit if I was reasonably sure that it would work, but the only issue I am trying to solve right now is the on/off throttle effect just off idle. I am interested in knowing how people have solved this problem; what solutions have worked? Any feedback would be appreciated. I am new to this forum and new to working on bikes. I haven't ridden for a long time. Thanks.

Re jetting the motor is not an option. Besides the fact that you are now so lean you will eventually damage the motor, but you have no idea how much better the bike with run with proper jetting.

It's cheap, it's easy, and it works.

Based on your description, this will reduce the problem substantially.

[TheGrouch]

Ride more. I had the same complaint 2 years ago when I went from my 230 to my 250X. As I got more experienced, my technique improved.

[DJCjr]

Hi Folks. I know this thread is a bit old but it nails my problem exactly so wanted to see if esauren or anyone had any more info. I too have an '09 250X, and the exact same problem, and hoping for a cure. I got a G2 throttle cam a while back and even the super-tame 400 cam doesn't help at all. Santa got me a Rekluse and, while I didn't ask for it to cure the lurching, I now know that it doesn't help at all even set to clutch engagement. As esauren describes, if you're idling along at 0.0001 mph about to fall over (a lot of my riding, tight woods) and just barely ease on about 1/100th of a turn of throttle as slowly and gently as you can, it goes: nothing nothing nothing jump! It's not at all a bog in the engine nor is caused by opening the throttle quickly. I agree with the replies that say "Put in more seat time and it'll go away", my problem is that I only have the opportunity to ride once a month or so, and even then I have right wrist problems and so don't have a lot of hope in developing the required finesse I could have 20 years ago. I'm ready to buy a flywheel weight and a JD kit and anything else that's metallic and sparkly and makes the wife grimace just to keep trying things, cause this bikes behavior and power delivery is great for me in all other ranges. Just that blasted off-idle jumpiness that pulls my wrist of the socket and sends me to the Advil. Thanks.

[jayc250x]

I'm ready to buy a flywheel weight and a JD kit and anything else that's metallic and sparkly and makes the wife grimace just to keep trying things, cause this bikes behavior and power delivery is great for me in all other ranges. Just that blasted off-idle jumpiness that pulls my wrist of the socket and sends me to the Advil. Thanks.

JD "kit" won't do anything - it's just a needle. Put in a 45 pilot jet. That'll solve your problem if it is a bog-burst issue. Otherwise go with 2nd gear like Jake is about to recommend.

JayC

[Jakeblues]

Hi Folks. I know this thread is a bit old but it nails my problem exactly so wanted to see if esauren or anyone had any more info. I too have an '09 250X, and the exact same problem, and hoping for a cure. I got a G2 throttle cam a while back and even the super-tame 400 cam doesn't help at all. Santa got me a Rekluse and, while I didn't ask for it to cure the lurching, I now know that it doesn't help at all even set to clutch engagement. As esauren describes, if you're idling along at 0.0001 mph about to fall over (a lot of my riding, tight woods) and just barely ease on about 1/100th of a turn of throttle as slowly and gently as you can, it goes: nothing nothing nothing jump! It's not at all a bog in the engine nor is caused by opening the throttle quickly. I agree with the replies that say "Put in more seat time and it'll go away", my problem is that I only have the opportunity to ride once a month or so, and even then I have right wrist problems and so don't have a lot of hope in developing the required finesse I could have 20 years ago. I'm ready to buy a flywheel weight and a JD kit and anything else that's metallic and sparkly and makes the wife grimace just to keep trying things, cause this bikes behavior and power delivery is great for me in all other ranges. Just that blasted off-idle jumpiness that pulls my wrist of the socket and sends me to the Advil. Thanks.

Have you tried riding in second gear? As soon as I get rolling I click into second and stay there or higher. So much smoother even at really low speeds.

[papawhiskey1]

You need a richer pilot jet. +1 to 2 sizes from stock. It"s cold out!

[rmoore0852]

Raise your idle a little bit. Not where it is revving high, just a fast idle about 100-200 rpm higher than normal. I found this helped a lot with the jump. At least for me, that was a side effect of getting rid of the bog. Once I eliminated the bog, I was idling along and just trying to crack the throttle, the bike wanted to go RIGHT THEN!!!!

I actually raised the idle at first to lessen the engine braking effect. I came off a two stroke, and while trying to re-adjust my riding style, the engine braking was killing me. So I gave it a fast idle. Less engine braking and the jumpiness disappeared. As you get used to it, lower the idle back down where it needs to be.

Also, riding in second helps alot. Same as jakeblues said, I usually even start off in second. First is really low. Ride in second or higher as much as possible. Make sure your drive chain is not way too loose, chain lash makes for jumpy throttle too.

[SHOVLE65]

May want to check and adjust the TPS sensor.

If you have been moving the idle speed screw a lot the TPS could be reading too high now.

Possible the the bike is starting its ignition advance too soon.

could even adjust it on the low side to delay the advance from kicking in.

Dont really know it this will work but i do know TPS addjustment too high can cause an idle surge or inconsistent idle speeds. Most TPS problems tend to be idle speed screws set too high.

I would recomend only touching the TPS after the carb is jetted correctly including idle speed and mixture is adjusted right.

[Bturner]

Man never heard of a problem of having to good throttle response. Sounds like you may be a beginner if good performance is to much for you. I wish i had that problem. I didnt knoe this bike was capable of that good of throttle response. But if its a problem for you I understand you want some options. When my bike was geared higher, the throttle respose sucked off idle. When I geared it lower, wow, snappy as hell, front tire didn't wanna stay down. Perfect for my riding style and terrian (woods). I like the bike to react when i twist the throttle, not stop and think about it for a min, then go. IMO, I'd just gear it higher. That simple, taller gearing more strain on the motor and the slower it will start off. I'm wondering if your explaining your issue properly, but that's just my .02......?

[esauren]

Hi all. I have made some progress with this problem. First, I adjusted the pilot screw. Stock setting was about 1 5/8 turns out; it is now out 2 1/2 turns. Some people who responded suggested replacing the stock #42 pilot jet with a #45. I believe this would have a similar effect. I found the following page helpful in explaining carb jetting:

http://www.thumperfaq.com/jetting.htm

Getting some miles on the bike also seems to help; the problem seems to gradually resolve, in conjunction with the pilot screw adjustment. My bike currently has about 300 miles on it, and I noticed improvement much earlier. Before the bike is sufficiently warmed up (engine temp about 125 degrees), it will still lurch, so I warm it up and take it easy at first.

I also installed the G2 (400) throttle cam. It probably helps a little, and it is still on the bike. An adjustable leak jet which I installed did not seem to have an effect. Right now, it is a little hard to compare to the original performance because I put on a smaller front sprocket (1 tooth smaller, 13, I believe) which would probably tend to increase the lurching effect. Even so, when the bike is warmed up, I no longer notice the problem, at least not to the extent that it is bothersome.

I had read on Thumpertalk that these bikes are jetted lean from the factory. Adjusting the pilot screw out or replacing the pilot jet with a larger one would richen the mixture. If I dial the pilot screw back in to its original setting, the lurching returns.

So the following seem to be what helped:

1. Pilot screw adjusted out (richer) or replace #42 pilot jet with #45

2. Put some miles on the bike

3. Warm the bike up before riding or take it easy until engine temp is about 125 degrees

4. G2 400 throttle cam

With the above minor modifications/procedures, the bike seems reasonably suited to tight trails. Thanks to all who responded; any other solutions or suggestions would be welcome.

Edited January 2, 2012 by esauren

[DJCjr]

Wow thanks for all the ideas, now I have several more things to try out that I hadn't before.

Comment to GoonSquad about throttle response just for clarification: I'm definitely closer to a beginner than a pro, but I don't think the problem is what you're referring to. When I want it to go and twist the throttle it goes fine and can get the front wheel up when I want it, it's really just those times when I want to idle along thru some very tight trees or whatever and the slightest quiver of the wrist (i.e. not near enough to kick in the AP) send you from 0.1 mph to 4 mph, instead of 0.2mph like I wanted. I found an old article on some CRF230 mods where they mentioned this same jumpiness, and said it was so annoying they ended up putting a spring on the throttle cable! I'm going to print this and try all the things folks posted next time I can ride - I think I'm at 2 on the pilot screw but I'll go further, up the idle, etc. I too notice it's worse when the bike is cold...

One last thing... I was trying to envision what could physically cause this in the carburetor (me assuming it is the carb) and isn't all that happens at this beginning of throttle is that the slide comes up a hair and the needle cracks off the seat of the main jet? So I thought the the pilot jet wouldn't be changing a whole lot, the AP wouldn't kick in, so maybe it was something with the needle lifting off the main jet too abruptly? Bike only has 130 miles on it and I cleaned the carb & jets...

Thanks again.