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Xr600r Low Rpm Stuttering ???

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Hello, I need help with a low rpm stuttering problem. My specs:

96 XR600R, YOSHIMURA HEADDER AND TAIL PIPE, SNORKLE REMOVED, MIKUNI 41MM NON PUMPER CARB. JETTING: PILOT 22.5, MAIN 240, NEEDLE

4TH FROM TOP, AIR SCREW 1 3/4 TURNS OUT, 500' ELEV.

SYMPTOMS: LOW END IS GOOD AND RESPONSIVE AS IS MID AND WOT. WHEN I TRY TO MAINTAIN A GIVEN SPEED USING APPROX 1/4 THROTTLE, IT STUTTERS AND HESITATES WITH AN EVER SO SLIGHT POPPING SOUND, NOT EXACTLY A BACKFIRE BANG. wHEN GIVEN GAS , IT TAKES OFF STRONG. THE STUTTERING IS SO STRONG THAT IT FEELS LIKE I'M RUNNING OUT OF GAS.

ANY SUGGESTIONS???????

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I failed to mention that the pilot jet that was installed was a 17.5. Was having problems starting and low end hesitation and XRS Only recommended to increase the pilot. The next size I had was a 22.5 so thats whats in it now. It seemed to help with starting and definitely helped the low end hesitation.

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Originally the needle was in the 3rd groove from the top and last week I had moved it to the 2nd from top. It didnt seem to run as well but will have to admit, I didnt run it enough to get to full op temp. I then richened the needle the other way to the 4th from top and it ran good except for the stuttering. Should I go to 1st groove from top to see the difference? or just go back to the 2nd and try again? Thanks for the replies and help Eddie.

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on clip 3 it still stuttered. That was the way it came when I bought the bike.

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I tried clip 2 from top and warmed it up. There is a big hesitation when I hit the throttle, even gradually. I am going to put it back to 3rd clip from top. Could the stuttering be from the air screw in the pilot circut?

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well the needle is back in the 3rd from top and still had stuttering. I turned the air screw out 3 turns from seated and most of the stuttering was gone but now it idles a bit high. I can only increase the idle with the idle screw and cant decrease it, it just darn near comes out. I went from a 17.5 pilot to a 22.5 and do you think I need to go higher?

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its a fuel screw not a air screw.if oyu have to runthe fuel screw out that far it needs a bigger pilot jet.

as far as idle speed goes does the cable have free play?

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My screw is on the left side towards the airbox, wouldn't this be an air screw???? My throttle has about 1/2" of play before feeling any slide tension. I will bump the pilot from a 22.5 to a 25. What brand/type of jet should I get for a Mikuni 41mm flatslide non pumper???

Thanks for all the help as I do realize you keep up on hundreds of these threads in addition to your real job. Hats off to you Eddie.

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the next size smaller pilot I have is a 17.5. Is this too big a jump? If so, what would be the nearest size? what type/brand fits my carb?

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Hello again, I finally installed a size 20 pilot and the bike was hard to start when cold. The stumbling is less significant now. Let the bike cool down completely and could not get it started. I swear I kicked it over 50 times!!! I pulled the plug and it appeared good, sorta black but dry. Remeber that this is a Mikuni non-pumper flatslide. Would turning the air screw out or in help with starting?

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yes I am using the choke when cold starting. I turned the air screw out another 1/2 turn and the bike started on the third kick. When I removed the plug yesterday, I forgot to replace the plug wire and before I realized this, I had kicked it over at least 10 times. Perhaps I flooded it? What would be the best remedy if I flood the bike again in the future? Would really suck if this happened out on a ride. Thanks again Eddie.

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hey bromco,i am considering getting a mikuni non pumper for my warm xr 600. would you recomend them or are they more hassle than they are worth?

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