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mailman1

96 Yamaha Big Bear Replacing carburetor jets

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I have a 96 Yamaha Big Bear 2x4 with a 350 engine and have replaced the original carburetor with a Zoom  Zoom version twice to no avail. I am thinking about rebuilding my original carb. and was wondering if the same mikiuni jets that you would use  for a snowmobile will work in the ATV or are they different? Thanks

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If the  jets are the same size  and thread as the originals   they should work.  If the motor  is   not modified, or  the quad is nor  being regularly  driven  in very  high altitude  areas,  why  change the  jets? They  don't wear  out. All  the  carb should need  is a  good cleaning. If there  is damage to the  floats or obvious wear  on the float needle  and seat ,  they   could be replaced as well as gaskets  and any  diaphragm  the  carb  might   use. Don't  change the  jet sizes .  I'm  sure the engineers that   made the selection  for that  motor  knew  what they  were doing  choosing  jet sizes. The  only reason  to    change  size  would be   for a modified  motor that would demand  more  fuel as a result.  I think  more people  have carb problems  when  they  start  fiddling  with  jet  sizes than   those  that  stay  with  stock  on their  machines.

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Thanks for the reply. One other question that I forgot was do you know if the jets, etc. from the Mikiuni will fit in the Zoom Zoom carb. or do they have their own specks.?

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Sorry ,  I have no  idea  what  parts  are interchangeable  between  carbs.

 

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Is your fueling issue a tendency to stall at idle?  That's the problem I've had for years, and I've considered swapping in one of those carbs that you see all over eBay for $35.  And yes, I have tried cleaning the carb, but to no avail.

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I'm in the process of cleaning my original carb right now as like I've said before  I have had two Zoom Zoom  carburetor's and nether one would work. They seem to stall out when you try to give it gas, pops, bangs, stutters, etc. and then if you keep feathering it,  it  might finally take off. I'm not a fan of Zoom  Zoom to say the least.  I didn't have any problem with the Co. in replacing the carburetor it's just that they don't work the way they should.

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So it sounds like replacing the carb with a cheap after-market unit isn't a good idea.  It seems to me that if there's a jet which is used at idle which I could step up one notch, that could be a resolution.  But I really don't know enough about how this carb works to know if that's feasible.  Anyone know better?

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23 hours ago, mailman1 said:

There should be a thumb screw on the carb to adjust your idle, might try that and see if it helps.

Yea, I tried messing with that some a few years back and it didn't seem to yield good results. I forget exactly now so it might be worth messing with again.

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Also there is a brass slotted head screw I believe on the bottom of the carb., try turning it all the way in (keep track of how many turns) and then back it out 2 3/8-2 1/2 turns out for starters.

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On 3/13/2018 at 1:17 PM, mailman1 said:

Also there is a brass slotted head screw I believe on the bottom of the carb., try turning it all the way in (keep track of how many turns) and then back it out 2 3/8-2 1/2 turns out for starters.

I just went out and quickly looked for this but didn't find it.  But it's kinda hard to see the bottom-side with the carb installed, so maybe it's just hiding? 

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Well it's been several day and I finally had a chance to get the original carb back on after I cleaned it. It starts right up better than before but now I get what sounds like a misfire on one cylinder and I know there's only one cylinder to start with so does or has anyone ever had this problem and is there a way to take care of the problem? By the way I did take the plug out and clean it and also when I had the other carburetor on it wouldn't miss just buck, cough, and spit when I tried to add power.

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1 hour ago, mailman1 said:

Well it's been several day and I finally had a chance to get the original carb back on after I cleaned it. It starts right up better than before but now I get what sounds like a misfire on one cylinder and I know there's only one cylinder to start with so does or has anyone ever had this problem and is there a way to take care of the problem? By the way I did take the plug out and clean it and also when I had the other carburetor on it wouldn't miss just buck, cough, and spit when I tried to add power.

Have you checked your timing? If you have it running and idling around the correct RPM, that would be the next thing I looked at. When you cleaned the carburetor did you verify that everything was in spec? Did you put a carburetor rebuild kit in, when you cleaned it? Pay very close attention to the float height measurement, especially if you are having any starvation or flooding issues. Also, if you didn't put a carb kit in you might want to. If the gaskets and O-rings or needle seat are not 100%, it can cause a lot of grief. A kit for my Suzuki is worth about 15$, and if I remember the last time I bought one for a Yamaha it was about the same. 

Clean-up or replace your plug, if your bike hasn't been running properly. Also make sure that the gap is close to what is recommended in your manual.

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