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Yamaha TT350 ... what a wierd carb!

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I was hoping for someone to explain some of the rules of tuning a twin barrel tt carb.... with the side accel. pump that squirts to the "primary" slide (thats what the manual calls it, it looks secondary to me.)

the slide is opened by ventury suction from the airbox side. bla bla bla.

well the bike rips and thens sputters, on and off. no popping. like it might be starving for fuel.

I cleaned all jets, replaced all diaphrams, and accel. pump parts. checked float level. I think the guy that had it before me might have opened up the pilot jet, cus it looks like a big hole to me. but everyhthing else looks good.

I'm out of ideas, but I know someone out there knows what I should do :)

thanks!

Adam

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I'll be watching for this too. My understanding is they are really easy to screw up and a bitch to get right if that happens. ;-)

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Check the diaphram in the secondaty carb real close.

A slight pin hole wil cause that.

I get in a dark room with a flashlite and ckeck the diaphram for a hole.

Some time this can be repaired with a small bit of RTV.

Good luck, Corky :):D

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Torn intakes,,

true, I just replaced both of my intakes, one had a noticable crack so I bought both sides and sure enough the right side was bad too, bike now idles very nicely and seems less likely to stall and is more throttle responsive at low speed, actually lost a little power on the high side, total cost was about $90 for both intakes and the O rings. :)

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I have had numerous TT350's, XT350's and XT600's. The problem of the vulcanized rubber separating from the block of the intake manifold is very common.

Also, tuning the dual carb is a real issue. I find this most common in the XT600's about 4500 rpm when the secondary circuit takes over.

The trick I have found is to get the balance of the float level correct, and contrary to common sense, this is driven off the fuel level in the secondary carburetor. You want to make sure the secondary carb is working perfectly before adjusting the primary.

These carbs have go to be the worst things on these fantastic bikes.

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These carbs have go to be the worst things on these fantastic bikes.

Agreed. Without the special YamaTool, the float adjustment on the XT350 is virtually impossible to get right.

Never was a big fan of the shim and bucket valve adjustment on the XT350 either. Without the special YamaTool for holding the valve spring, you have to remove the cams to adjust the valves. Seems like the TT had a simpler head though.

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Thanks for all the ideas!!! I belive that the intake manifolds were changed early last year, but It was not ridden until I got it in the fall. I'll check them since the carb is already out. It is getting gas, but the tank has some "varnish" on the bottom.

I'll get my diaphram and a flashlight, and go to the closet now......

thanks again

adam

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Her diaphram seems tight... and her manifolds are good, n' flexy, still rubbery.

still waiting for the new pilot jet to come in...

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Can i ressurect this thread?

Are you and your tt still around adam? I have 97 model tt350 over in Australia and am trying to sort out the jetting.

Mine also looks like a rediculously large pilot and it is very rich before the second carb starts....

Any ideas? And where do you get jets from for these bikes?

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Digging up an old thread again.

but i have been struggling for a long time trying get my jetting right on my TT350.

Its always been too rich from idle -1/2 throttle. I've changed millions of things with varying degrees of success.

I thought i had narrowed it down to the last possibility: that the needle and needle jet had too much wear. As the needle has a step down in diametre from idle -about the 1/4 throttle mark. So i called yamaha and asked to order in new needle and jet.....AU$86 for needle!!!!after falling off my chair i missed the price for the needle jet, but i'm pretty sure it was close to the same price. The Yamaha parts mechanic then said "is the oring on the needle jet still in tact?" now i dont remember ever seeing one, so I'm going to have a look tonight.

Has anyone else noticed an oring in there? is it placed just above the thread of the needle jet or up where the jet seats into the carb body and the needle feeds in?

Any ideas?

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Does anyone know if there is a better carb that can be used as a direct bolt on replacement? I am thinking about possibly changing the carb on my XT, for better performance really.

I have heard it can be converted to single carb without too much hassle. Also the Keihin dual carbs which are apparently difficult to set up - and expensive, but good.

Anyone done anything like this?

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Torn intakes,,

true, I just replaced both of my intakes, one had a noticable crack so I bought both sides and sure enough the right side was bad too, bike now idles very nicely and seems less likely to stall and is more throttle responsive at low speed, actually lost a little power on the high side, total cost was about $90 for both intakes and the O rings. :thumbsup:

Where did you buy the intakes?

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That is too big to fix. You are going to have to get the whole valve assy.

For some reason, the one for the XT350 is about $50 cheaper. I didn't think there was any differance, but maybe there is, or maybe not.

Maybe someone else knows for sure.

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