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2005 Yamaha Big Bear 400 wheel bearings and ....?


mga
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I just brought home a used 2005 Yamaha Big Bear 400 4x4. It needs front wheel bearings, and a new choke cable. I think i can handle those two items. However, when i went to look at it, it ran good, shifted good, brakes all workds great, but at home when i started it, it would idle nice, but when i gave it gas it seemed like it was flooding out and would die. If i just gave it a little throttle it built up RPMs but any more throttle it began dying out again.

any suggestions why it's doing that? 

I'm looking for a service manual, but forum rules say i have to make 10 posts..lol

 

oops...i just realized i posted in the wrong section of the forum!!

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  • Admin changed the title to 2005 Yamaha Big Bear 400 wheel bearings and ....?

Spark plug cable got knocked half off.. 

If you're saying it's got this problem on the trip home on the truck then it must be something simple surely.

Are you sure you got the tap in the right position ? Plenty of gas? No rags stuffed up the exhaust ? (hey I don't know.. but humans do stuff like that ). Hasn't got a tap on the fuel tank breather ? Check anywhere wires might have got pinched by tie-downs.

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44 minutes ago, Mech said:

Spark plug cable got knocked half off.. 

If you're saying it's got this problem on the trip home on the truck then it must be something simple surely.

Are you sure you got the tap in the right position ? Plenty of gas? No rags stuffed up the exhaust ? (hey I don't know.. but humans do stuff like that ). Hasn't got a tap on the fuel tank breather ? Check anywhere wires might have got pinched by tie-downs.

thanks!  i'll check it out in the morning. it has gass in the tank, but i'll drain it and add fresh fuel.

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I believe you have a carburetor issue, my guess is the primary carburetor jet is clogged. I would remove the carburetor bowl and remove the larger jet and clean the tiny hole that runs through the center of this jet as well as the tiny holes on the jets sides. You can buy the professional jet cleansing brushes or to save money find a piece of stranded wire and remove one strand and use that to clean the jet. This clogged jet can be difficult to clean and sometimes you need to buy a new jet, the size of the jet is marked on it (you'll need a magnifying glass to read it). 

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12 minutes ago, Shadow1 said:

You can make the cover for no cost from a piece of plastic and screw it to protect the throttle from dirt! 

ha...never thought of that. thanks

here i was ready to buy a new carb!

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Did you ride it when you went to look at it ? If it was going fine, and you went for a ride at the point of sale, then surely it's something simple, and the carb doesn't need stripping..

If you bought it untested then that new carby is probably the problem, but it's not likely to be as simple as needing a clean.. it probably needs retuning for the bike. I'd contact the old owner and ask if they still had the original carb and could you get it please. It's easier to clean an original carb and get it running right again that retune a new after market carb that might need new jets.

About the only simple adjustments are the idle mixture and speed, and the slide needle height. Your symptoms sound like it could be the slide needle, and the easy test is to take the top cover off and move the slide needle's circlip down one notch and see if that improves things.

Before pulling anything off the bike though you should check the fuel tap and filter's aren't blocked by undoing the drain screw on the bottom of the carby and making sure fuel runs out freely. That checks the tap, filters and that fuel is getting into the carb fast enough. If that's good, try adjusting the slide needle.

Oh.. and that side cover will be availiabe from the dealer. They have a rubber seal and will be much better than a home made one of plastic.

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1 hour ago, Mech said:

Did you ride it when you went to look at it ? If it was going fine, and you went for a ride at the point of sale, then surely it's something simple, and the carb doesn't need stripping..

If you bought it untested then that new carby is probably the problem, but it's not likely to be as simple as needing a clean.. it probably needs retuning for the bike. I'd contact the old owner and ask if they still had the original carb and could you get it please. It's easier to clean an original carb and get it running right again that retune a new after market carb that might need new jets.

About the only simple adjustments are the idle mixture and speed, and the slide needle height. Your symptoms sound like it could be the slide needle, and the easy test is to take the top cover off and move the slide needle's circlip down one notch and see if that improves things.

Before pulling anything off the bike though you should check the fuel tap and filter's aren't blocked by undoing the drain screw on the bottom of the carby and making sure fuel runs out freely. That checks the tap, filters and that fuel is getting into the carb fast enough. If that's good, try adjusting the slide needle.

Oh.. and that side cover will be availiabe from the dealer. They have a rubber seal and will be much better than a home made one of plastic.

yep, i drove it, shifted the gears, etc and i ran nice. However, i never lifted the seat until today and noticed there was no air filter. so, i did order one. I'm not going to try messing with the carb until i put the air filter on. Someone micky moused a throttle spring (You can see it in the picture) and i'm not sure why unless there's an original return spring missing someplace. I'm going to get a service manual and go thru this.

 

As for the cover, i'll see is some one has one. thanks.

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Oh yeah get the filter on there.. That might cure it. They might have warmed the bike up before you arrived to cover up a few small faults..

The carb should have a strong return spring inside that cover.. Perhaps the throttle cable is old and wasn't returning properly.. You should check the kill switch works !!

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You definitely should clean the carb if for no other reason peace of mind, you might try turning your petcock to prime and running it ,sometimes the vacuum petcocks go bad and you can't tell if its getting gas without the engine running.

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unfortunately, my wife wants me to finish putting down the hardwood flooring before i play around with this. 

i appreciate the feedback and when i get into it, i'll let you guys know what i find.

 

thanks again!!

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  • 2 weeks later...

Yeah my wife was probably not thrilled that I have been working on the Kodiak instead of the kitchen but if we get that snow today, she might forgive me........Its really funny that the Honey Do List just keeps growing no matter how many items you knock off of it.......That is how God gave women the power to keep us boys out of trouble..

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ok...back in business!  I replaced the left front wheel bearings. What a pain that was. The drive shaft was rusted to them and i had to use a torch and plenty of penetraating oil to get it out. I ordered new ball joints too. 

I ordered that choke/starter cable from amazon (after market) and it was the wrong size. Sent it back and just ordered the OEM part from Yamaha. Plus that throttle spring. I guess someone was too lazy to remove the broken one and just put that mickey mouse set up i posted above. makes you wonder about people's mechanical abilities. So, that will be here in a day or two. Hopefully with the new "choke" cable it'll start better. And i removed all the old gas.

The carburetor look to be brand new, but i'm not sure if it's an after market or an OEM. in my spare time i'm checking wiring thru out to make sure every this is OK. The cooling fan works but it's noisy...a lot. But, to get it off looks like a big project, so that'll be for another time.

When i get the new ball joints, i'll do the right side bearings as well.

If i change the oil filter, will all the oil drain out from there, or should i just open the drain plug?

And the hardwood floors are done and i also laid hardwood on the staair cases as well. She's happy...happy wife, happy life....or, so they say.

 

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Some of the fan's have a water drain hose, I've filed them up with wd40 through that hose before to shut them up.

Most service manuals tell you exactly what model carb the bike should have.. It will be in a table of specs about the jet sizes and settings.

You should use the drain bung I'd think.. though I don't know yammies.

I think to get the new carb spring in you will have to take the butterfly shaft out.. it's got screws holding it that are splayed out at their ends so they can't come loose. If you try and wind them out it will bugger the threads in the shaft. Try to grind/file the ends back or pinch them into shape before removing, and it's best to have new screws to go back in.. and do re-munt the ends after they are in..

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OEM carb should say Mikuni on it aftermarket no writing at all , some oil may come out from the filter but always drain oil from drain plug on bottom of engine, choke plunger should just pull out of the carb if the threads on the plastic piece are stripped if not unscrew it mine are always stripped. Good job on hardwood floors. Thats next on my agenda. Oh, good job on the bearings ,they can be a bear sometimes.

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On 1/8/2023 at 7:15 PM, Mech said:

Oh yeah get the filter on there.. That might cure it. They might have warmed the bike up before you arrived to cover up a few small faults..

The carb should have a strong return spring inside that cover.. Perhaps the throttle cable is old and wasn't returning properly.. You should check the kill switch works !!

the reason the cover was missing is because the return spring on the throttle lever box(?) on the handle bar was broke. So, someone rigged up a spring into the carb and wire tied the end to the frame to make it act as a return spring. i emailed the guy and he's supposed to send me the cover via mail. I ordered a new return spring to replace the broken one that's in the throttle box on the handle bar (if that's what it's called)

just a lot of neglect and laziness on this atv. next will be all new oils. 

again, i really appreciate everyone's help here. i downloaded some service manuals i found on line, and they kinda help.

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