1999 Yamaha Big Bear 350 Replaced Carb

[AKMichael 0]

Hello All,

I have a 1999 Yamaha Big Bear 350 4x4 trying to get fixed up so my grandson can go out in the woods with me.

We have owned it over 10 years.  It got harder to start, until it finally would not.  Replaced the carb.  Right afterwards, it started and ran nicely, but after turning it off, would not restart.  Tonight I used starting fluid and ran, then died.  Adjusted the idle up a little, used more starting fluid and ran great.  It idled about 15 minutes.  Turned it off, and restarted.  Ran it around the yard about 5 minutes.  Turned it off, and would not restart.

Any ideas or suggestions would be greatly appreciated!

Thank you. 

[AKMichael 0]

1999 YFM350 Big Bear.  I replaced the carb & intake tube (new spark plug and fuel cock), because it was extremely hard to start, even sometimes with ether.  Same issue.  Then I found out about Valve Clearance.  I attempted to adjust both intake and exhaust, but missed the step of Top Dead Center.  (I now have the Service Manuel)

Started and ran.  Plenty of power, but severe lifter chatter.  I then discovered the step I missed.

Went back and carefully set the clearance, would start and run, but only after a small shot of ether.  I could stop and restart it several times, until it warmed up, (hot exhaust pipe).  After that, It won’t restart.  Today after sitting about 4 hours, I again attempted to start, without ether, it would not.  Choke or no choke, with little to full throttle.  Last time I compression tested it was about 120 psi.  (less than 10 hours ago, running time)

Does someone have a solution to my issue? 

After spending hours reading almost everything slightly related, on this site, I thought about a new plug.  Someone had suggested Iridium.  No one in town had one, but for $7 I found an E3.36 DiamondFire.  I put that in, and change nothing else and fired right up and ran nice.  Ran it over a half hour with many restarts without fail.  I hope and pray the issue is resolved.  Next a new battery, so I can put this one back in my Kodiak.

[MarkinAR 123]

So you say new carb...is that an OEM replacement carb or Chinese clone? I ask because I've had 4 or 5 of the Chinese carbs and even with 30 years of ATV experience, I still struggle to get those to run correctly.  The symptoms you are describing seem to indicate a fueling issue.

[AKMichael 0]

Hello MarkinAR,

My guess it is maybe one from our (WONDERFUL) trading partners over seas, as It was from Amazon.

I've yet to take it out on a along trip, as the temps are hovering close to 0F, but it is running better than it has in years.

The grandson drove while I rode for about 45 minutes around the neighborhood.  No issues.

My one complaint is that it does seem to require some choke to start in a 55F shop, but other than that, I'm happy.

[MarkinAR 123]

Glad to hear it's up and running.  Sometimes close enough with the carb is good enough to go have fun!  I had a clone carb on an old 185s that I never could get to run flawlessly, but it was enough to pop wheelies and rip the gears.