need help _2007 yamaha big bear 250 carb-air -throttle issues

Reply Subscribe

Thread Tools

Search this Thread

#11

03-11-2016, 12:13 PM

Fasteratv

Pro Rider

Join Date: Jan 2016

Location: Whitesburg, TN

Posts: 591

Likes: 0

Received 0 Likes on 0 Posts

Quote:

Originally Posted by hunter56

all the ideas and help has been great ..update where i am at now ..besides frustration i replaced the fuel petcock ,,and got an oem replacement carb not mikuni original but a good oem exact replacement
put carb on and runs better but still have the problem of the air vent if covered will throttle better .heres the kicker also
we drove it and runs ,,but with choke all off the throttle response is non responsive but if i pull the choke out a little it gets response and shifts well but can get bogged down if the air vent is covered slightly with choke all off runs better
.any help is appreciated ,,,dont what else to do ..could valves need adjusted ? the intake ? it idles starts and runs shifts .runs better with choke out driving but can bog down,,see previous responses and help also here ,,,thanks all !

I'm going to jump in here. I have read the entire thread. I worked on one of these a while back, and what I found was that the 250 would not take throttle ( hesitate and sometimes die ) with the jet needle in the third position ( stock ). What I ended up doing was installing the clip in the 5th position, that is, clip all the way at the bottom, raising the needle as high as it would go. It greatly improved it but it actually needed a washer under the clip as well, but the owner was happy with it. And, are you 100% sure the carb intake does not have a crack in it....these are a terrible design and known to crack.

Have you checked the compression?

Reply Like

#12

03-11-2016, 12:21 PM

hunter56

Trailblazer

Thread Starter

Join Date: Feb 2016

Location: knoxville

Posts: 35

Likes: 0

Received 0 Likes on 0 Posts

thanks for reply ..
the carb is new and factory specs hate taking it apart for needle jet ..being new
..the intake manifold boot boot is a new yamaha part ,,air box is sound w tight lid new lid gasket hoses are clear clamps tight ..u can see my frustration

Reply Like

#13

03-11-2016, 12:25 PM

Fasteratv

Pro Rider

Join Date: Jan 2016

Location: Whitesburg, TN

Posts: 591

Likes: 0

Received 0 Likes on 0 Posts

Quote:

Originally Posted by hunter56

I can understand, and I felt the same way when I rebuilt the customers 250 carb. All you have to do is remove the top of the carb....the float bowl stays on. I'm talking about the "jet needle"

, not the needle jet

.....Also, I recommend a compression test as I mentioned before....low compression can cause a "bog" as well....

Reply Like

#14

03-11-2016, 02:43 PM

hoowahfun

Trailblazer

Join Date: Jan 2016

Location: Georgia

Posts: 36

Likes: 0

Received 0 Likes on 0 Posts

Quote:

Originally Posted by hunter56

Any chance you have an air leak around any of your carb/intake connections? I found one on mine by spraying WD-40 around each joint while it was running to see if I noticed a chance in rpm. An o-ring had shifted during installation so it didn't seal properly.

Reply Like