Quantcast
Jump to content

  • Do you own an ATV? Join our Forum!

    As a member, you can post in our forums, upload your photos and videos, use and contribute to our downloads, create your own member page, add your ATV events, and even start your own ATV club to host your own club forum and gallery.  Registration is fast and you can even login with social network accounts to sync your profiles and content.

PKR

1989 Yamaha 350 Big Bear Carb problems

Recommended Posts

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

Share this post


Link to post
Share on other sites

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.   

Share this post


Link to post
Share on other sites

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

  • Like 1

Share this post


Link to post
Share on other sites


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

Share this post


Link to post
Share on other sites

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. 

 

Share this post


Link to post
Share on other sites

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.

 

Share this post


Link to post
Share on other sites

This one certainly has been a pain in the ass.

Share this post


Link to post
Share on other sites

Sorry, I thought I had updated this post a while back but obviously I hadn't.

After getting taking this carb apart several times and getting frustrated, I walked away and went fishing for the summer, When I looked at it again I took the carb apart and checked everything, mounted it back on the quad and just hooked up the gas line. Quad fired up right away and throttled up nice and idled nice. I then started hooking everything else up on the carb, vent lines throttle cables air box and filter. Quad ran good until I hooked up the line off the bottom of the carb (overflow line). As soon as I hooked this line up quad started blowing gas out the air intake. I removed the line and it ran great. This line has what Yamaha calls a pipe in it. It looks like it may be a oneway valve of some sort. I removed this "pipe" and the quad ran great. 

I looked at a few other Yamaha quads that have has carb jobs done at dealerships and noticed none of then had this "pipe" on them so I just ran a length of gas line off the bottom of the carb.

Quad has ran great ever since. Owner took it hunter last fall and it didn't miss a beat and is still running great.

Still not a hundred present sure what the purpose of the "pipe" is but that was my problem all along.

Thanks to everyone that responded to this request.

PKR

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Similar Topics

    • By Curtis01
      OK, sooo  I finally did the old skid plate and screen removal to clean out my oil sump during an oil change...  This bike only has a couple thousand miles on it.  Runs like a top still...  Very few issues over the years after buying it used.
      But boy I wasn't expecting to see this!  Piece of a circlip, stuck up in the screen, and a another shard of metal and maybe a piece of gasket material.  Nothing in the oil but that...  Pristine otherwise, and still runs like a top.  Always has.
      Soooo, is it a wrist pin clip?  That's the only thing I can think of like this that could end up in there.  But definitely wanted to throw it out to guys that have seen the innerds of these more than I have.
      The valves on this thing are still within the factory spec even.  Been a really good lil workhorse...
      Any other ideas?

    • By JJ78
      I have a yamaha big bear 400, tested all fuses and relays. When I turn on key I get nothing, no neutral light or headlights. Could it be the key switch bad?
       
    • By billyz57
      New to Quadcrazy, Has any Yamaha owners had similar issue?
      1987 Yamaha YFM 350 Starts on Pull, but just spins on starter, and won't start.
    • By Blenderite
      Hello guys! New to the forum, and fairly new to ATVs. I've driven them, but never owned one. Now I do own one. Just picked it up today. It's a 1999 Yamaha Big Bear 350. It's been through some stuff. The guy I got it from told me the previous owner removed the front diff because he didn't want to replace the half shaft. So it's 2wd, even though it's supposed to be 4x4. Lovely. I can deal with that for now.
       
      More importantly, I need to get it running. The carb needs to be rebuilt. The guy I got it from said he sprayed it all out and it still didn't work. I'm concerned he might have damaged it or not put all the parts back. I was looking at a replacement carb, and the OEM parts is $600. I'd rather not spend $600 if there are any other options. I have seen carbs on Amazon and eBay that are in the $40 - $100 range that say they fit. Anyone have experience with these? I'm going to get a rebuild kit for the current carb just to make sure that won't fix it.
       
      Thats the first thing with it. Secondly, it was completely rewired. I need to find a original wiring diagram so I can put it back how it was, with a key and all. Currently it's wired with just a rocker switch. Any sources for a service manual that would include wiring diagrams?
       
      Thirdly, is the Big Bear 350 a good atv? I picked it up for $700. It does start and run when you spray starting fluid into the air intake, so I am not concerned about the engine being bad. I plan to use it for the farm, running around and carrying things with it like minerals and feed and such. Not really for mudding and things like that. How good is the 99 350?
       
      I am certain I will have more questions as I examine it more, but that's all for now. Thanks in advance for the assistance!
       
      -Blenderite
    • By jolio
      Just got a '98 Yamaha big bear 4x4 in working condition (so far). Looking forward for some good information on this site about how to keep it alive.
  • Recently Browsing   0 members

    No registered users viewing this page.


×
×
  • Create New...