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martinfan30

Anyone ever have this driveability issue..

32 posts in this topic

Just a minor annoyance...

4300 ft., 50 deg F.

WOT, 65-70 mph uphill, halfway up the hill I let off to 3/4 throttle. The bike cuts out... For a split second. Its def. a fuel issue, lack of or maybe too much:excuseme:

I run a FCR 41 pump carb. 158/52, 2 1/2 turns out. Hotcam, E2 slip on...

Any thoughts?

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When you say it cuts out. Is it sputtering, or just cuts out for a second and then continues with no issue? If sputtering I would guess float bowl level.

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When you say it cuts out. Is it sputtering, or just cuts out for a second and then continues with no issue? If sputtering I would guess float bowl level.

Cuts out for just a sec., then it gets back on it. I dont beleive its a float level issue, cuz if you keep it at WOT it motors all the way up.

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Sorry I see it is happening when letting off the throttle after being WO. I would say it is one way or another lean.

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Only when I am under a load, WOT for 5-10 sec. and then let off to slow down to 3/4 throttle.

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Martinfan, did this just start happening after you installed your Clarke tank, or has it been happening since some other mod? (ie; air box/battery mod, etc.) I've found a good way to troubleshoot a problem is to trace it back to when it started happening (it's almost always related to the last mod you've done). :thumbsup:

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Does this carb have the vacuum pulled enricher like the 650r carb?Might try to block it off and try it again.

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I would say it is one way or another lean.

I'm going to say that its running rich actually. I have read and experienced that when the bike is lean and you cut back the throttle from WO, you actually get a quick surge of power.

And when the bike is running too rich, it will "cut out" for a split second.

I have experienced both conditions on my xrr....

this is how I have reasoned through it: When your bike is rich and you quickly close the throttle a little, you are abruptly reducing the amount of air flowing through the carb....and for the first split second the same amount of gas is being delivered, but with a reduced concentration of air....hence for that one split second you are running even richer, and the power abruptly falls.....

The reverse is true for a lean condition....when you abruptly close the throttle a little, you quickly reduce the air flow and thus richen the mixture up just enough to get a surge in power from the more optimal fuel/air mixture.....

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4300 ft., 50 deg F.

I just went back and looked at your first post.....what alt is the carb tuned for? ~2000-2500 of Lost Wages, NV?

I'm sure you know this, but the higher in elevation you go, the less air there is, and the more rich your bike will run. If your bike is set kinda rich @ your base line then a +2000 elevation gain can exacerbate the situation a little...

It kinda makes sense that your experiencing that loss of power from WO....

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I just went back and looked at your first post.....what alt is the carb tuned for? ~2000-2500 of Lost Wages, NV?

I'm sure you know this, but the higher in elevation you go, the less air there is, and the more rich your bike will run. If your bike is set kinda rich @ your base line then a +2000 elevation gain can exacerbate the situation a little...

It kinda makes sense that your experiencing that loss of power from WO....

It was initially tuned for sea level, it came with 170/58 from SUDCO. I knew this wouldnt fly up here at 4300 ft. So i put in the 158/52.

Now I think about it, it didnt do it with the pod filter setup, except when it was hot and dry out. Less dense air=more rich A/F ratio. Now i have gone back to using the airbox and uni filter... With the crf battery plugging up the snorkel intake, I need more airflow. I've already drilled the right side panel with 5 1 1/2" holes and 2 more on the right side of the airbox.

My question is, will a leaner/steeper taper needle compensate? Or maybe drop 1 clip position.

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My question is, will a leaner/steeper taper needle compensate? Or maybe drop 1 clip position.

I would try dropping the needle once clip and see how it work....that should lean things up a bit. If that doesn't do it, maybe kick the main down one notch?

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The needle will have little effect at 1/2 to WO throttle. I would back off on the Accelerator pump duration, or use a bigger leak jet, and try to get more air, somehow. At WO and rich, the bike will just eat gas, at 3/4 and rich, it will hiccup, untill the ap stops squirting, and the main jet is not full in circuit.

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The needle will have little effect at 1/2 to WO throttle. I would back off on the Accelerator pump duration, or use a bigger leak jet, and try to get more air, somehow. At WO and rich, the bike will just eat gas, at 3/4 and rich, it will hiccup, untill the ap stops squirting, and the main jet is not full in circuit.

That makes sense. But, when i'm already at WOT throttle holding it there(this all happens after 5- 10 sec. of WOT), the pump is out of the mix. This carb also has an air jet, that should only be for low throttle applications?

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By the sound of things, this all started since you did your last battery mod that blocked off some air flow in your air box ..... ergo; you're not getting the same air volume as you were before. Try doing something to increase the air/fuel mixture. Either make better air flow into the carb or lean out the fuel to air mixture on your carb.

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Theres alot of back and forth on the rich /lean talk

Please consider when closing the slide your dependent on the low speed jetting with a staight pull type carb.

CV carbs will hold there slide up alittle longer alowing a smoother transition.

The feelling of power increase after a slite reduction in throttle position is a

rich condition.

I beleive the cut out you speek of is a lean low speed jet.(Have you increased air flow lately?)

not able to supply enough fuel with the rpm the motor is spinning.

Try turning up your idol up ,if this helps your supplementing the low speed with a little less complete closser of the slide .

If this helps, increase low speed jetting.

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Theres alot of back and forth on the rich /lean talk

Please consider when closing the slide your dependent on the low speed jetting with a staight pull type carb.

CV carbs will hold there slide up alittle longer alowing a smoother transition.

The feelling of power increase after a slite reduction in throttle position is a

rich condition.

I beleive the cut out you speek of is a lean low speed jet.(Have you increased air flow lately?)

not able to supply enough fuel with the rpm the motor is spinning.

Try turning up your idol up ,if this helps your supplementing the low speed with a little less complete closser of the slide .

If this helps, increase low speed jetting.

Throttle up doesnt help. Maybe I'll throw a 55 pilot in. Has a 52 now.

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The needle will have little effect at 1/2 to WO throttle. I would back off on the Accelerator pump duration, or use a bigger leak jet, and try to get more air, somehow. At WO and rich, the bike will just eat gas, at 3/4 and rich, it will hiccup, untill the ap stops squirting, and the main jet is not full in circuit.

needle has every bit of effect at 1/2 throttle, thats the range where you needle does its work! 1/3 to 1/2 range to 2/3 - 3/4 range. It all depends on the taper and what notch its in already. Needle is directly related to mid throttle positions and going from WOT to 3/4 ish range you needle is backed out and letting max fuel from the main come thru, now when you let off to 3/4 ( or close to that) your starting to slow the fuel delivery thru the main.

Throttle up doesnt help. Maybe I'll throw a 55 pilot in. Has a 52 now.

Martin if this is all problems is from wide open and letting off some i dont see how a different pilot will help??? or accelerator pump or anything but air/fuel problem. But 52 seems a bit small for your L since you have a cam. Have you only put the air holes on the left side number plate??? I would say either air or needle may be your culprate for your skip when you let off, i think its rich condition too, like Maroast said. How sure are you about the jetting all across the board after your battery mod?? everything seem good except this sputter your having tearing from the cops trying to outrun them up the hills?

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Only happens when trying to run from the cops.

I want to put a 55 in anyways for the dez ride. I think i'll try a couple more holes in the top of the airbox... The last two seemed to help a little.

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I want to put a 55 in anyways for the dez ride. I think i'll try a couple more holes in the top of the airbox... The last two seemed to help a little.

i agree with that for sure 52 seems pretty small. But your not gonna run from us out there baby!! Me and Splooge got something special for you!!!!!:thumbsup:

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i agree with that for sure 52 seems pretty small. But your not gonna run from us out there baby!! Me and Splooge got something special for you!!!!!:eek:

I told you guys already...

I dont go that way!:thumbsup:

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