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TT350 carb bogging on landings

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Hi all, Bike bogs on landings and bumpy terrain, clears up by high

revs(sounds like a flogged wr426).Jetting is fine on smooth roads. Needle and seat or float height? Also when you rock it in the trailer fuel comes in drops out the overflow

thanks

scratch that, found answer in search. needle and seat causing wrong float height

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yep. have got it running well though this is a recent problem, pretty sure worn needle is giving a false float height. btw if you drill the air hole on the secondary a bit it responds a lot quicker.

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The reason I asked is that my XT350 had a factory recall in 1987 about cutting out on jumps and whoops. That was a long time ago, but I am pretty sure they changed the carb venting around. The mechanic that did the recall was a decent guy and used that opportunity to drill out the plug over the air screw and adjust it on Yamaha's dollar. You are right, that is the number one mod on that carb.

Beware the float height adjustment. My XT350 needed a Yamatool to set the float height. And it was done with the float bowl on and the gas on. It was a super PITA job requiring endless trial and error with a lot of spilled gas. The Yamatool is a graduated glass tube that connected to the float bowl drain. And the "engineer" that came up with the idea of setting the float height that way should be made to bath in gasoline.

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Interesting...

My bike is a 1986 but is a tt. The mod I'm referring too isn't the fuel screw because ,mine is already adjustable. the secondary vacuum slide will open quicker if you open up the little hole on the underside of the slide it uses to suck through, makes it more responsive when you wick the throttle. Do you know what they changed when it was recalled? regardless it shouldn't spill fuel just on the trailer when you rock it.

thansk for your help :thumbsup:

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hmm. i have an xt350 2000 and the second carb on mine is totally mechanical. it is operated by a leaver off of the shaft for the primary carb. i currently have mine set to come in at 3000rpm.

be nice if i could figure out the bog at 7000-8500rpm. its annoying when i pass cars on the highway.

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The carb on the early XT350 is also mechanical - to a point. You can change when it starts to open (I had mine adjusted to open at the same time as the primary). But my understanding is that at some point in the throttle range it is controlled by vacuum.

As for spilling fuel, the XT is notorious for that because adjusting the float height is just about impossible. You have to keep installing and removing the float bowl and tweeking the float arm just a bit each time until it stops overflowing but still runs correctly. It is a friggin nightmare even with the special Yamatool.

I ran out of gas on the Shenandoah 500 DS ride despite an oversize Clarke tank because of that issue. It isn't something to let slide. I hope your TT is a different animal. That adjustment is hell.

The TT350 is way different bike than the XT350 though. So maybe you have a better arrangement.

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Aye it is a lever on mine too but if I remember right that activates a butterfly valve which lets piston vacuum activate the slide via a small drill size hole.

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