Low and mid range bog.

[Lemonfresh]

Hey everyone. I just got the '10 250 I purchased a few weeks ago back together. It runs and idles fun, and above around 6k it pulls just fine. Off idle and up to 6k, on hard twists it bogs down.

I just pulled the carburetors and cleaned them out. I completely took them apart including the mixture screws, pilot jets, and main jets. The slide diaphragms were in good shape and are installed correctly. I made sure to put the needle jets in the correct way with the skinny, internally tapered end in first. I let the internals soak in carb cleaner and cleaned all the passages of the body with carb cleaner.

The bike is stock as far as I know with only 3k miles. The gas was a little yellow so I dumped it and got some fresh gas. The bike seemed to be warmed up all the way. When I roll on slow or a slow medium pace, it runs right up without issue. Its only when opened up quickly it bogs. Also if it run it up to around 4 or 5k and open it up, it bogs until around 6.

The foam air cleaner looks pretty clean and paper filter doesn't have a spot on it. The throttle cable is adjusted properly and the choke is not on. I made sure to record the number of turns from closed the mixture screws were set to the 1/8 of a turn. I am at about 300 ft from sea level so I doubt I need to re-jet a stock bike.

Do I need to play around with the mixture screws? If so, richer or leaner? Or try to synch the carbs?

[DaBlue1]

Originally Posted by Lemonfresh

.... It runs and idles fun, and above around 6k it pulls just fine. Off idle and up to 6k, on hard twists it bogs down.

.... The bike seemed to be warmed up all the way. When I roll on slow or a slow medium pace, it runs right up without issue. Its only when opened up quickly it bogs. Also if it run it up to around 4 or 5k and open it up, it bogs until around 6.

The foam air cleaner looks pretty clean and paper filter doesn't have a spot on it. The throttle cable is adjusted properly and the choke is not on. I made sure to record the number of turns from closed the mixture screws were set to the 1/8 of a turn. I am at about 300 ft from sea level so I doubt I need to re-jet a stock bike.

There's not a lot of power below 5k, so whacking open the the throttle is not going to get get you a lot of break neck torque (especially on a cold engine). The bike responds best when it is fully warmed. The bike needs a little time to get completely warmed up and the choke and a little bit of riding is usually needed to help accomplish it.

The carb is designed to work by vacuum, so there is a natural lag when quickly opening the throttle.

What do you mean by paper filter?

When setting the idle mixture screws, they should be opened 2.5 turns out from being fully closed. This is a baseline setting.


How Constant Velocity Carburetors Work
http://www.motorcycleproject.com/mot...bs_work_v3.swf

Motorcycle Carburetor Theory 101
http://www.motorcyclecarbs.com/carbs101.pdf

Carburetor Jet Tech
http://www.motorcycleproject.com/mot...et_tech_v3.swf

[Lemonfresh]

Originally Posted by DaBlue1

There's not a lot of power below 5k, so whacking open the the throttle is not going to get get you a lot of break neck torque (especially on a cold engine). The bike responds best when it is fully warmed. The bike needs a little time to get completely warmed up and the choke and a little bit of riding is usually needed to help accomplish it.

The carb is designed to work by vacuum, so there is a natural lag when quickly opening the throttle.

What do you mean by paper filter?

When setting the idle mixture screws, they should be opened 2.5 turns out from being fully closed. This is a baseline setting.


How Constant Velocity Carburetors Work
http://www.motorcycleproject.com/mot...bs_work_v3.swf

Motorcycle Carburetor Theory 101
http://www.motorcyclecarbs.com/carbs101.pdf

Carburetor Jet Tech
http://www.motorcycleproject.com/mot...et_tech_v3.swf

I am not expecting this thing to launch me back in the seat, but when coming off idle, it stumbles and bogs until 5 or 6k when opened up fully. If I open the throttle slowly it revs up just fine through the whole rpm range.

I thought there were dual air cleaners, I was wrong. I was looking at the flame arrester inside the air box.

The mixture screws were at 2 1/4 and 2 3/8. I put them back there. Ill try running them out to 2 1/2 and see what happens.

Your first and third links are dead.

[alex.s]

is the engine warm when doing this?

[Lemonfresh]

Originally Posted by alex.s

is the engine warm when doing this?

Yes.

[DaBlue1]

Originally Posted by Lemonfresh

I am not expecting this thing to launch me back in the seat, but when coming off idle, it stumbles and bogs until 5 or 6k when opened up fully. If I open the throttle slowly it revs up just fine through the whole rpm range.

I thought there were dual air cleaners, I was wrong. I was looking at the flame arrester inside the air box.


Your first and third links are dead.

See how the bike does without the air filter in it. If it does better without it, replace it with something that breathes better. Kawasaki recommends replacement @ 2 years. The stock filters are a little more restrictive than most aftermarket filters and even worse when too heavily oiled.

Sorry about the links. They are flash pages. Sometimes they work, sometimes they don't. However you can find them and other info on the Motorcycle Project! homepage.


How Constant Velocity Carburetors Work
http://www.motorcycleproject.com/mot...bs_work_v3.swf


Carburetor Jet Tech
http://www.motorcycleproject.com/mot...et_tech_v3.swf

[Lemonfresh]

Well I finally made it back out to the garage tonight and this is what I found.

Removing the air filter made no difference on the low end stumble.

I opened the pilot screws from the factory settings to 2.5 turns out each and the mid range stumble went away. The off idle, full throttle opening stumble is still there although it has gotten much better. It used to die or almost die, it now does a slight, momentary bog and revs up through the whole rpm range.

Should I try opening up the pilots a bit more?

[DaBlue1]

Originally Posted by Lemonfresh

.....I opened the pilot screws from the factory settings to 2.5 turns out each and the mid range stumble went away. The off idle, full throttle opening stumble is still there although it has gotten much better. It used to die or almost die, it now does a slight, momentary bog and revs up through the whole rpm range.

Is the engine cold or completely warmed (ran for 5 miles or more) when it bogs and are you whacking on the throttle and letting it snap shut?

You could try shimming the needles instead of turning the pilot screws anymore.

[genosr1]

Try shimming needle and going one size smaller or bigger on main