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high speed miss

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yes, i just got through searching, "high speed miss" wasn't very telling. :lol:

Over the last few months my normal 1/2-3/4 throttle steady speed riding has been plagued by a miss. Some would call it a stutter, I suppose. The stator is 3 months old now (I would have to check). Compression is great, since I've just re-ringed it a few weeks ago. Oil is changed every 1000 miles, religiously. Tires are balanced nice and smooth (now). Ignition primary and secondary has been tested (along with stator) several times. It's fine.

Spark ? Yes, fat and blue.

Fuel ? Yes, flows nicely.

3x3, proper jetting.

Today I gassed the intake boots with propane to check for leaks/lean. Nothing.

Idle set to around 12-1500. (guestimate) same as it ever was.

Oil does not smell of gas.

So, where do I start with finding this lean condition and/or miss at highway speeds ?

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Try a new spark plug.

Try taping off part of the 3X3 & run it, the try running it with the air box side cover off, see if either makes a diffrence.

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Try a new spark plug.

Try taping off part of the 3X3 & run it, the try running it with the air box side cover off, see if either makes a diffrence.

the plug is new, and/or there is another waiting on the shelf. i'll give that a go sometime today.

i understand your wanting to diagnose with the 3x3 taped and the cover off, but since i've not changed the jetting, would this only prove the enrichment screw needs adjusting ?

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has it been doing it around the time you fitted the new stator ?

was it doing it BEFORE you fitted the new stator ?

yes, it was doing this before the new stator. i -thought- the new stator had cured it for a couple of rides, but it's very hit/miss as to wether the symptom shows or not. generally, IF it starts the miss on a ride, it will stay at 1/2-3/4 throttle for the rest of the ride.

throttle response from idle to redline is very good. no flat spots or power issues other than the missing at constant speed.

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Try a new spark plug.

Try taping off part of the 3X3 & run it, the try running it with the air box side cover off, see if either makes a diffrence.

i taped off 1/2 the 3x3 and there was a noticeable difference today:

no more miss/stutter, but now a quick rip of the throttle = a bog or 'pack up' feeling so i think you're right, it's leaned out for some reason.

i haven't changed the jets or the filter since this started. any ideas why it would suddenly start a lean condition ?

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the plug is new, and/or there is another waiting on the shelf. i'll give that a go sometime today.

i understand your wanting to diagnose with the 3x3 taped and the cover off, but since i've not changed the jetting, would this only prove the enrichment screw needs adjusting ?

Have you got oem jetting?

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i taped off 1/2 the 3x3 and there was a noticeable difference today:

no more miss/stutter, but now a quick rip of the throttle = a bog or 'pack up' feeling so i think you're right, it's leaned out for some reason.

i haven't changed the jets or the filter since this started. any ideas why it would suddenly start a lean condition ?

1/2 is a lot to tape off, I try taping off maybe 1/4 & see what happens?

What jetting & jet kit are you using?

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I'm thinking that, if the old rings were in bad shape, when you changed rings your compression went up, and now your jetting is off.

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Temperature dropped a good bit around there? May need to raise the needle 1 clip to add more fuel in midrange. For that constant speed miss at a cruise. Do you feel it or just hear the exhaust sputtering a bit? I say this because I just had a similar issue. My issue was a hanging idle. I just turned the tt fuel screw out a tad and it got better. Just added alittle fuel on bottom end. Mine was also kinda sluggish around 1/4 throttle.

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Temperature dropped a good bit around there? May need to raise the needle 1 clip to add more fuel in midrange. For that constant speed miss at a cruise. Do you feel it or just hear the exhaust sputtering a bit? I say this because I just had a similar issue. My issue was a hanging idle. I just turned the tt fuel screw out a tad and it got better. Just added alittle fuel on bottom end. Mine was also kinda sluggish around 1/4 throttle.

ya, the plan was to richen it up a tad. this afternoon's project before the turkey falls :-)

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ya, the plan was to richen it up a tad. this afternoon's project before the turkey falls :-)

the miss/stutter was felt, almost as though spark was cut for a moment, or there was a fuel starvation issue. mucho backfiring on decal before today's fix.

ok, didn't raise the clip but cleaned the carb yet again, and richened the mixture a tad. the miss is gone now, but it hangs for a 1/2 a second or so, so it's still not perfect. i may raise the needle tomorrow if/when family stuff is done.

it's running very nicely, lofted wheel everywhere in 2nd easily, and a good hard pull from 3rd.

back firing is very minimal, only issue now is finding a vacuum leak, if there is one, or rhcening up a little more.

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