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Is this a jetting problem PALLEEZZ!

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Here's the problem Ive been chasing to no end...

Bike starts fine, runs good off idle. Really no bog to speak of, other than say Im loading it down in say 3rd, without slipping the clutch. But heres where it gets odd, Id say at the top of the rev and 1/2 to 3/4 throttle it starts to "break up". Its a very odd feeling. Its almost like a high frequency miss, or maybe not enough fuel?

I can somewhat fix it by rolling off the gas and then back on. A closed to full throttle roll on works fine until Im near the mid-rane/top of the rev range. No, its not the rev limiter.

172main

70 leak

48pilot

4th from the top on the needle

68what is the other jet:bonk:

needle has no marking that I can see

I have swapped coils and cdi with a known good units and replaced the plug.

I pulled the head and replaced the intake valves, assured the clearances are within spec. No air leaks on the carb boot. Timing is correct.

Whats causing it to break up and sputter up top? Ive tried a 165main and a 180 main, that was before the valve replacement. Ive also had the carb cleaned, no trash in the tank and ran a few ounces of sea foam through the tank. AP wired, not hitting the slide when operated.

HELP:banghead:

Edited by robfromga

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What year is your bike? That 48 pilot seems really big. I thought most people were running a 40-42. Does the problem seem to get worse as the engine warms up?

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What year is your bike? That 48 pilot seems really big. I thought most people were running a 40-42. Does the problem seem to get worse as the engine warms up?

2005

Yes, its slightly there when cold, but there when its run for a while. Also notice very obviously on 4th-5th gear fire roads(great sentence structure)

It running worse when warm sent me in the direction of the coil or the cdi breaking down, but I swapped them both and no dice.

Also the bike had a 165main in it with the needle on the 5th notch, Ive tried both the 3rd and now the 4th notch to no avail.

Ive been chasing this for a month now, since I picked it up.

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I think your pilot jet is way too big. When the engine is cold it can handle the extra fuel but as it gets up to operating temp its too much fuel. Try a 40 or a 42 pilot jet and I bet your problem goes away. Your main jet needs to be about 170-172 and your needle needs to be 3rd from the top. The jetting your describing is way too rich.

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I think your pilot jet is way too big. When the engine is cold it can handle the extra fuel but as it gets up to operating temp its too much fuel. Try a 40 or a 42 pilot jet and I bet your problem goes away.

Not that I doubt that, but I thought the pilot was pretty much done at say 1/2 throttle?

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Not that I doubt that, but I thought the pilot was pretty much done at say 1/2 throttle?

It contributes all the way to wide open. It doesnt just stop feeding fuel when the throttle opens past 1/2.

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Not that I doubt that, but I thought the pilot was pretty much done at say 1/2 throttle?

Pilot is for IDLE ONLY.

Your main and your pilot are way too big.

15-155 and 40-45 is fine.

The issue needs to be determined by THROTTLE POSITION, not RPM.

If you can't get it to replicate at the same throttle position it did that last time, but you can with rpm, then it's not carb, it;s electrical.

Check all your grounds.

Reconnect the plug cap wire with a fresh end.

New plug

There are wires that if they rub through, will arc against the frame and cause your symptom..........

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Sorry for not explaining it correctly, its more obvious when the bikes at a higher rpm, but it only happens at 1/2 to full throttle.

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It contributes all the way to wide open. It doesnt just stop feeding fuel when the throttle opens past 1/2.

So goto what a 42? Will that clean it up?

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So goto what a 42? Will that clean it up?

If your running down fire roads at full throttle or close to it I would go with the 42 pilot and the 172 main to start and the needle clip in the 3rd position from the top. Better to be a little rich and safe.

And check all the things Krannie suggested too.

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All the wiring "looks" ok, no rubs through the loom. I honestly thought the coil was toast. no obvious splices in the harness.

I even unplugged the kill switch thinking it was shorting.

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Took a closer look at the needle. Its not the stock needle, nor is it a jd needle. The bottom of the needle is way smaller than the stock needle. I swapped it, haven't risen it yet. Maybe its the needle? Its certainly richer

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Bumping this for ideas. I'm in the middle of putting it all back together and will ride it shortly.

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I would go back to stock. 42 pilot, 170 main, NCYQ needle in the 3rd or 4th position. You can also change the leak jet to a 40 or 45 even though there probably isn't a bog issue on the 05's for the most part. Go back to the beginning.

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Seems better, maybe. Its hard to get long wide open drags with out p'n off my neighbors.

I'm back on the stock needle, 3rd slot. 172 main 48 pilot and 70 leak. The 55 leak, 42 pilot and a new needle seat are in the mail. I'm getting a little drip from the bowl drain so my float needs to come up. It moves free, but hell at this point it might be worn also.

What's so odd is the bike is clean, cases have no boot rubs. Never would have guessed so many problems from such a clean bike.

That needle was very weird looking, had a serious step at the base. Way smaller than the stock or jd needle. He also had a 165 main...

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Ok...checked my float height as per the link on atm, looks like I was about 13-14mm? 8mm sure isnt much float adjustment, Im getting some fuel smelling oil and was really really hoping it was the float level:banghead:

So I set it a little low, like around 10mm...why, I dont know and may pull it back apart and set it to 8mm. I didnt ride it. Im just paranoid Im not setting the height right. Im holding the carb at a 45* angle, float needle is fully seated and measuring when the tang just contacts the plunger on the needle, correct?

Ive installed a new needle valve seat,55 leak jet and 42 pilot. Im 2 turns out on the AS, 172 main.

8mm huh?:smashpc:

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