I'm working on a buddies LT-Z for him. The bike came to me in pieces. His complaint was-"clutch is slipping". When the bike arrived, the motor would not run. I replaced the clutch, and afterwards wanted to test-drive the bike-but the engine still won't run. It will start, but will only stay running if you keep winging the throttle. When you wing the throttle, it back-fires through the exhaust.. Which indicates to me a fuel mixture problem.

When it got here, the vacuum line from the carb to the pet-**** had been removed and plugged. I don't know if the pet-**** is bad or not. I have no clue why someone removed the vacuum line. I put a new hose on that connects from the carb to the petcock, and the situation is still the same.

What I have found is that if I remove the air cleaner, and hold my hand over the air intake port (blocking off air flow) the bike will actually idle normally. As soon as I remove my hand though, the bike sputters & stalls.

Also, I can rev the bike while holding my hand over the intake port, and the bike will rev like it has power, instead of back-firing through the exhaust like it does when I don't block the intake.

This tells me that the bike is not getting enough fuel, and is running lean. When I block the air going into the carb, the bike runs normally. So, I pulled the carb apart and cleaned everything as best I could with carb cleaner & compressed air, put it back together, and still having the exact same problems! If anyone has any ideas as to what might be wrong.

Based on my testing I am VERY confident that this is a fuel delivery issue.

Please, HELP me before I lose my mind!

 

could you maybe say what the jetting is ,and if any other mods tell what they are

 

Sounds to me like an air leak.

 

No mods to the bike at all. Everything is stock! The air cleaner frame (that goes inside the air filter) is missing, so the foam element was just laying in the bottom of the air cleaner housing when it arrived. Even the sprockets and chain are stock... Owner DOES NOT believe in maintenance, or putting any money in it to keep it running. I'll be lucky if I get paid for helping him fix it.

He is my riding partner though, and my wife would prefer I have someone riding with me in case something happens, so I can't complain too much. Wife WILL NOT ride.. Trust me, I've tried. She just wont' do it!

 

I am sure you messed with it already since you had the carb off and everything else but you didn't mention it, so i will ask

Did you try adjust the fuel mixture screw?

If i recall the Factory setting is 2 1/2 turn out from bottom then adjust it from there until you get a specific rpm (or it sounds good)

 

check your valve clearance.

 

sounds like it is running lean. when you put your hand over the air intake you choke it . start with that info first. richen up the needle on the top of the carb.start by moving the clip down on notch at a time. once it runs without "choking". then adust the carb from there. Seth 03

 

Thanks for the replies everyone. Someone above mentioned adjusting the valves-I already did and they are within specifications.

I have not noticed a fuel screw on the carb anywhere. Can I assume that it is on the underside (float bowl?) and goes upwards into the carb? I have not seen the screw yet, but maybe I have to pull the carb out and flip it over to be able to see it?

I'll start there next to see where it is set at this time.

I forgot to mention in my first post but when the bike came to me originally, the crank-case was full of gasoline. Apparently the needle & seat is not holding pressure and allowing gas to flood the cylinder, and then get past the rings into the crank-case. I found the gas when I drained the crank-case to change the clutch.. More gas than oil. Now that I got the motor back together, and have been trying to start it, when I check the oil it smells strongly of gas.. Don't know if that means I did not get it all out, or if there is now new gas getting past the rings into the crank-case. My first thought was that when it arrived, it had been bouncing around in the bed of truck, and that is what allowed the gas to get past the needle. But since it has been here, and after I cleaned it out, it has only been sitting still in one spot, and gas should not be getting into the motor unless that needle & seat are bad. I pulled the needle out when I cleaned the carb and looked at the tip and it looks to be in perfect condition.

I'll look for the fuel screw first, and go from there.

 

My friend is the one with the ltz 400 so i dont have easy access to it for a picture of where this fuel mixture screw is so I had to find one through google and it amazed me how many people take a picture of the "Passenger" side of their quad lol
The best I could find though is below. The yellow arrow is pointing to the black mixture screw for at least the '03 model, not sure how many others are the same.

Hope it helps

 

[QUOTE=Kawabuggy;2843845]Thanks for the replies everyone. Someone above mentioned adjusting the valves-I already did and they are within specifications.

I have not noticed a fuel screw on the carb anywhere. Can I assume that it is on the underside (float bowl?) and goes upwards into the carb? I have not seen the screw yet, but maybe I have to pull the carb out and flip it over to be able to see it?

I'll start there next to see where it is set at this time.

I forgot to mention in my first post but when the bike came to me originally, the crank-case was full of gasoline. Apparently the needle & seat is not holding pressure and allowing gas to flood the cylinder, and then get past the rings into the crank-case. I found the gas when I drained the crank-case to change the clutch.. More gas than oil. Now that I got the motor back together, and have been trying to start it, when I check the oil it smells strongly of gas.. Don't know if that means I did not get it all out, or if there is now new gas getting past the rings into the crank-case. My first thought was that when it arrived, it had been bouncing around in the bed of truck, and that is what allowed the gas to get past the needle. But since it has been here, and after I cleaned it out, it has only been sitting still in one spot, and gas should not be getting into the motor unless that needle & seat are bad. I pulled the needle out when I cleaned the carb and looked at the tip and it looks to be in perfect condition.

I'll look for the fuel screw first, and go from there.[/QUOTE

sorry its small :bawling: