Yamaha Grizzly ATV Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
I have just recently put brand new carb on my yfm grizzly 400 and it ran fine when I first put carb on with no airbox and filter on when I put it back together it will idle fine but when I give it gas it dies out, it runs better when the choke is on..Where do I adjust air/fuel mixture?
 

·
Registered
Joined
·
5,544 Posts
You need to go down in the main jet a size or 2.
Adjusting the pilot needle (air/fuel) is not going to fix your issue.

The pilot needle basically only gives fine adjustments of the fuel mixture at idle and very low throttle position. Once above this idle/very low RPM, the main jet circuit takes over.

Basically, you need to re-jet your carburetor.

Why did you replace the carb? What was wrong with the original carburetor?
Did you use a OEM Mikuni or Keihen carb or did you use a Chinese eBay special?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #3
The old carb throttle was seized open as bike haddnt been used for a few years and yea I got my carb off eBay but it came from the USA
 

·
Registered
Joined
·
6 Posts
Have a similar issue with a Chinese carb. Regardless of filter on or off still dies with throttle. It was from zoom zoom. Probably just have to end up rebuilding the OEM Mikuni.
 

·
Registered
Joined
·
24 Posts
Carb

If it was one of the cheap carbs on eBay, then then are hit or miss. I've had a couple that worked great, but I tried the zoom zoom $50 one and it was way off. They responded that it's a "performance" carb, so I would need to adjust the jets. I ended up buying an oem carb, but it sounds like you will need to open yours up to adjust it.
 

·
Registered
Joined
·
5,544 Posts
It came with some more jets do I use thoze?
Yes try those other jets.
These aftermarket carbs are not built bike specific. They are more universal, and that's why some come with multiple jets so you can adjust it to your specific application. But they also rarely work as good as a OEM spec carb.
 

·
Registered
Joined
·
5,544 Posts
Have a similar issue with a Chinese carb. Regardless of filter on or off still dies with throttle. It was from zoom zoom. Probably just have to end up rebuilding the OEM Mikuni.
Rebuilding your OEM Mikuni is the best option.
 

·
Registered
Joined
·
16 Posts
The initial response you posted is a little confusing to me.

“Ran fine at idle with no filter” = rich carb settings. I.e rich air fuel mixture screw which is usually capped with OEM and often uncapped with aftermarket. Around 2 turns out is standard for most carbs.

“Runs better with choke” = lean carb settings. Because choke restricts air allowing greater fuel mixture.

What elevation do you ride at?
Post the stock jet sizes of a 400 and we can go from there.

I have not had an issue with a knock off carb. And from my experience they always have the correct OEM jet sizes and the extras are Incase of MODs or elevation changes.

When you hit the throttle does it backfire at all or bog and dies? I would check if the needle functions correctly and then the float bowl level which is sometimes incorrect.
 
1 - 9 of 9 Posts
Top