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PKR

1989 Yamaha 350 Big Bear Carb problems

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I rebuilt the carb on a 1989 350 Big Bear. This is a Gen 1 carb ( 2 cables running to throttle).

Quad starts and runs but I have fuel leaking from the air intake.

Is the float set to high / low?

Does the needle for the main jet need adjusting? I have it on the center groove ( 2 groves above and 2 groves below).

All jets are new, float and needle and seat are new.

 

Thanks for your help

PKR

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It’s possible that the float is set to low but that would also result in the overflow also leaking.  The small hose that’s attached to the bottom on the carburetor would have gas coming out. 

If you made any adjustments to the needle my guess would be you need to lower it.  

When you put the slide back in the carburetor did it go in properly? And is it sitting all the way down when the throttle is not pressed ? 

Latlsy did you reassemble the carb properly? I’ve made mistakes. The main jet I didn’t tighten it when I rebuilt one of my carbs.  Shit happens.   Double back and re check everything.   

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Thanks for the tips, I will go through it again and double check everything.

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Check the needle and seat as well. might have a bit of crud in it

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Thanks, I'll check that also

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Took carb apart and reset the float, it was set to high, had to change out the main jet as it wasn't the right one when I compared it to the old one.

Quad starts nice and idles great. Throttles up nice but when reaching higher rpm's it starts to spray a gas mist out of the air intake and does some small backfires through the air intake. When you throttle back down there is a couple of drops of gas comes out the overflow at the bottom of the carb.

Tried adjusting the air / gas screw but didn't seem to make a difference at high rpm's.

Does the needle on the main jet slide need to be lowered some more?

Looking for where to look next.

 

Thanks

PKR

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Did you adjust the float enough? In my last post I said set it was set to low, I meant high.  Is it possable that it still needs a slight adjustment ? It might need a hair more.  Also be careful with the back fires and that fuel in the air box.  A back fire can easily lead to the leftover  gas in the air box to ignite and catch fire.  Have you messed around with main jet needle at all? If anything maybe you can lower the needle one notch but if it was in that position prior to working on it then I would leave  it.

lastly have you pulled the spark plug to see what the color looks like ? It’s a good indicator on how the bike is running. 

 

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Thanks, I will adjust the float a little more. I think I will lower the main jet needle one notch as this carb had been played with before they brought it to me.

 

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It’s going to take a little time but it will get dialed in. Just keep at it.  It’s a pain in the ass! 

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This one certainly has been a pain in the ass.

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Perfectly normal. Just be patient you will get it right and learn a lot while doing it to help the next guy. 

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