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AP or blocked jet? Neither? Off idle stall, suge and backfire...

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Thanks for reading - seeking some advice to cure a recent rideability issue with what seems like fueling.

The bike is an 09, with about 70 hr on the stock motor. Airbox is cut, jets are stock except for a 160 main at 7500ft altitude, and it has a smog block off installed. Well cared for with premium fuel and routine oil changes and filter maintenance. It's a trail and playbike that rarely sees more than 25 mph.

Up until this weekend it has ran very well, and I haven't done any recent mods.

The first thing I noticed was far more frequent and louder decel pop/backfire, any time the throttle was off or trailing. It also surges now at part throttle, low speed, and will not hold a constant throttle setting unless above about 2000 rpm. Finally it requires a lot more throttle than typically necessary to get rolling, if you just crack the gas it will stall when you let the clutch out. Normally this bike will idle uphill.

It starts and idles fine, and still runs pretty good when you're hammering it. Of course, that doesn't help on tight switchbacks.

Any advice is appreciated and thanks in advance!

Edited by xsrdx

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Remove and replace the pilot jet

If there is any corrosion or ethanol poisoning (green) then pull the carb and clean it

 

Also, adjust your fuel screw,  and always treat your gas.

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Few things to check:

 

1.  Hot start is not hung up

2.  Make sure the connector for the hot start is not cracked (usually happens when carb comes out).

3.  Band clamps on the boot between engine and carb are tight.

4.  Check the exhaust is tight at the engine and by the subframe.

 

Does sounds like a plugged slow circuit though.

 

AP by the way only comes into play when you open the throttle suddenly.

 

Jim.

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Thanks guys, :thumbsup: -  parts are on the way and I will check other aspects mentioned. Gives me an opportunity to install the FlexJet fuel screw while I'm at it.

 

I treat the gas with Lucas Ethanol Treatment, but for the past 6mo I've been draining the float bowl to store more than 10 days and I think for the most part it's just better to leave the fuel in the system.

 

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New 48 pilot and ditched the OEM fuel screw for an R&D, after adjustment runs much cleaner from idle and completely eliminated the decel pop / backfire - thanks again for spot on advice!

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Kah Ran Nee, what do mean exactly by treating your gas? Like with stabil, or deadpan?

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Smiley, I'm using an android, but every time R&D fuel screw shows up, smiley...

1419169489033.jpg

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Yeah, I don't use apps for browsing for just that reason.

Especially on any Apple product.

I just use full size Google Chrome.

Impossible for the App developers to keep up with iOS's constant software changes, hence all the glitchyness.

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Yeah, I don't use apps for browsing for just that reason.

Especially on any Apple product.

I just use full size Google Chrome.

Impossible for the App developers to keep up with iOS's constant software changes, hence all the glitchyness.

 

I've actually be pleasantly suprised with the TT app, not perfect, but works fairly well.

 

What are you using to treat your gas?

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Thumper Talk app is awesome... Treating gas, I am unfamiliar with this. I buy 91 octane. Never paid attention to ethanol/no ethanol. I guess I l just learned a lesson here. What should one use?

Edited by xlntdrvr

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Thumper Talk app is awesome... Treating gas, I am unfamiliar with this. I buy 91 octane. Never paid attention to ethanol/no ethanol. I guess I l just learned a lesson here. What should one use?

 

I'll be honest, I've never treated my gas nor have any of my riding buddies and we've, knock on wood, never had any issues. BUt Krannie knows his stuff.

Edited by afcforme
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Thanks Kah Ran Nee! I will note those...I am in the deep end of the pool, it seems. Appreciate the help!

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