02 DS running lean

[aaron580]

So recently my 02 DS has started to backfire when letting off the throttle, also dying when it gets warm after a couple hours of driving. Spark plug i changed was white, so its lean. I've replaced everything from the pickup to the intake gasket (carb included), adjusted it so the throttle cable closes the butterfly all the way (with barely any slack on cable). Ive done the zip tie on the gov, kept the factory fuel pump and tried a kawasaki pump from a lawn mower engine with pretty much the same result. The fuel filters stay extremely low on fuel, which is why I went with fuel issue. The replacement pump I used is a black plastic pump, engine impulse line doesn't have any leaks that i can find. Vacuum tested both pumps, seems to be the same. Im at a loss. Whos got some ideas?

[FrankenCub]

I'm having a similar problem when ambient temps are high after a long drive. If the temps are below 83 or so, no problems. We've had a heat wave here so it's been a struggle. I put a vacuum gage on the pulse line when it was acting up and found a very poor pulse. Definitely not good enough to operate a fuel pump.

[Fairtax4me]

These engines are jetted to run slightly lean at normal governed speed. Altering the governor/cables to go faster makes it more lean because it's running higher rpm than it's designed. A jet kit for the carb will help with that.

Your governor cable (goes to the carb) should have slack in it. If there is no slack, the throttle lever is going to open too soon causing lean starts, and is not closing all the way while the cart is driving, which will give you the backfire. The throttle lever should not start to pull open until after the engine starter engages. If the throttle lever starts to pull open before the starter starts spinning, you need to loosen the cable adjustment.




The "pulse" that makes the fuel pump operate is a pressure pulse, not vacuum. And it does not have to be very strong to make the pump work.

[FrankenCub]

Originally Posted by Fairtax4me

The "pulse" that makes the fuel pump operate is a pressure pulse, not vacuum. And it does not have to be very strong to make the pump work.

My vacuum guage reads vacuum and pressure. It will show fluctuations in pulse visually, when the outside temps are high making the engine run hotter the fluctuations are almost non existent.
ETA:everything about our DS is stock, nothing changed to increase performance or modified. I suppose we could have a seal starting to wear on ours and only showing a problem when its hot. Just not bad enough to even weep any oil yet?

[aaron580]

Originally Posted by Fairtax4me

These engines are jetted to run slightly lean at normal governed speed. Altering the governor/cables to go faster makes it more lean because it's running higher rpm than it's designed. A jet kit for the carb will help with that.

Your governor cable (goes to the carb) should have slack in it. If there is no slack, the throttle lever is going to open too soon causing lean starts, and is not closing all the way while the cart is driving, which will give you the backfire. The throttle lever should not start to pull open until after the engine starter engages. If the throttle lever starts to pull open before the starter starts spinning, you need to loosen the cable adjustment.




The "pulse" that makes the fuel pump operate is a pressure pulse, not vacuum. And it does not have to be very strong to make the pump work.

Ok, so this makes sense. Tonight, I actually ran the crank case line into the carb intake and the valve cover into the fuel pump. I got a plastic kawi fuel pump from a lawn mower engine testing good. I actually have no lean condition come to find out, I am an idiot. Filters still get drained. About to add an electric fuel pump

[Fairtax4me]

Originally Posted by FrankenCub

My vacuum guage reads vacuum and pressure. It will show fluctuations in pulse visually, when the outside temps are high making the engine run hotter the fluctuations are almost non existent.
ETA:everything about our DS is stock, nothing changed to increase performance or modified. I suppose we could have a seal starting to wear on ours and only showing a problem when its hot. Just not bad enough to even weep any oil yet?

These will blow the front case gasket completely out, blast oil all over the side of the motor, and still make enough pulse to operate the fuel pump just fine.
The hose or port on the crankcase is clogged, or the hose is drooping down and collecting oil. The hose has to go up-hill all the way to the pump. If it's old, it's a good idea to replace it. Make sure the nipple on the engine isn't full of sludge and caked up old oil.

It's possible the pump has a problem, but I've never had to replace one that wasn't leaking fuel.

[FrankenCub]

Originally Posted by Fairtax4me

These will blow the front case gasket completely out, blast oil all over the side of the motor, and still make enough pulse to operate the fuel pump just fine.
The hose or port on the crankcase is clogged, or the hose is drooping down and collecting oil. The hose has to go up-hill all the way to the pump. If it's old, it's a good idea to replace it. Make sure the nipple on the engine isn't full of sludge and caked up old oil.

It's possible the pump has a problem, but I've never had to replace one that wasn't leaking fuel.

I'll reply in my thread, didn't want or mean to hijack Aaron's thread.