Zama won't adjust??

[Woodchuckr]

What is the trouble when you can turn the high speed needle all the way in and it still runs full throttle? Should lean out at some point. Low screw is simmilar, a whole turn each way from 1-1/2 and you can barely tell a difference. Ran terrible since new and dealer was useless. Lever is a hair under strait edge, no holes no leaks, carb held preasure and was spotless when pulled apart. Also stalls often when you let off wot. Zama s260 on stihl Bg56 blower.

 

[Tomos770]

You have an air leak somewhere!

Or crank seals....or between carburetor and cylinder!

 

[Woodchuckr]

You have an air leak somewhere!

Or crank seals....or between carburetor and cylinder!

thought of that but if the high speed needle is completly closed and it has an air leak would it even run at full throttle?

 

[PV Hiker]

Also leaning on air leak if low and high screws have no effect. Most likely it idles at high rpm to.

Vacuum and pressure check the case for the leak. Check for any play in the crank bearings too.

 

[Woodchuckr]

Also leaning on air leak if low and high screws have no effect. Most likely it idles at high rpm to.

Vacuum and pressure check the case for the leak. Check for any play in the crank bearings too.

It idles normal speed, you can turn the idle speed down till it dies. It has ran like crap since the first time i started it brand new. Dealer was useless, had every excuse. Turned out it only had 50psi compression. Only had maybe 5-6 tanks of fuel through it. It now has new jug, piston and seals at my expenss.

 

[Old2stroke]

Some confusion here, you say it idles at normal speed but turning the L screw in or out has no affect on idle speed? Does it accelerate normally to high speed and runs at high speed but you think it is running too rich and that's why you are trying to lean it out with the H screw? Also, an engine with a true compression reading of 50 psi should not start, are you using a gauge that is meant for small engines with the valve at the engine end of the gauge extension? Can you be more specific about "runs terrible"?

 

[Woodchuckr]

Some confusion here, you say it idles at normal speed but turning the L screw in or out has no affect on idle speed? Does it accelerate normally to high speed and runs at high speed but you think it is running too rich and that's why you are trying to lean it out with the H screw? Also, an engine with a true compression reading of 50 psi should not start, are you using a gauge that is meant for small engines with the valve at the engine end of the gauge extension? Can you be more specific about "runs terrible"?

Some confusion here, you say it idles at normal speed but turning the L screw in or out has no affect on idle speed?
you turn the L screw a lot and even then you hardly notice an increase/decrease in rpm or a misfire. same with the H screw.


Does it accelerate normally to high speed and runs at high speed
Yes but not cleanly, little boggy and high speed is not crisp, and it's -20c outside. I didn't put a tach on it, it may not be reaching spec rpm but it does rev up.


but you think it is running too rich and that's why you are trying to lean it out with the H screw?
Yes, you can't get to that lean spot where it cleans up.

Also, an engine with a true compression reading of 50 psi should not start, are you using a gauge that is meant for small engines with the valve at the engine end of the gauge extension?
Believe me it ran, I have a video of it running and the compression test, for the dealer. I thought it was the gauge too but I stuck it on my older BG55 and got 137 psi.

Can you be more specific about "runs terrible"?
Rich, poor throttle response, sounds like it always is four stroking. And often it instantly dies when you let off from wot.

 

[Oletrapper]

It idles normal speed, you can turn the idle speed down till it dies. It has ran like crap since the first time i started it brand new. Dealer was useless, had every excuse. Turned out it only had 50psi compression. Only had maybe 5-6 tanks of fuel through it. It now has new jug, piston and seals at my expenss.

Maybe bad rings or jug from the factory?

 

[John Stryker]

Are there limiters on the H and L screws? If so, you could try to remove them for more range of adjustment. Also, the fuel lever arm could be set a bit too high making it prone to running too rich and impossible to set the mixture screws correctly.

 

[Woodchuckr]

Maybe bad rings or jug from the factory?

The first original set or the new ones?

 

[Woodchuckr]

Are there limiters on the H and L screws? If so, you could try to remove them for more range of adjustment. Also, the fuel lever arm could be set a bit too high making it prone to running too rich and impossible to set the mixture screws correctly.

Limiters came off right after warranty was up. Lever was probably .020" down right from the factory, I brought it up to just a hair from flat with the bottom yesterday. It seems better but still seems rich at wot. The zama video said just a hair from level for the lever. It still does not adjust like the BG55 i have where you turn the H+L and the rpms pick up or drop when you turn the screws.

I may go lower than the original .020" with the lever just to try. Lots of complaints on the stihl website on this model.

 

[Old2stroke]

OK, so the little beast is for sure just running too rich overall, limited number of things that can cause this condition. If the fuel control diaphragm is too stiff it can stick in the down (open inlet valve) position the first time it is pulled down by intake vacuum the first time the engine is started. What pressure did you test the carb inlet too? If you tested to less than 7 or 8 psi, there is a possibility that the pressure in the fuel tank might be exceeding the pop-off pressure of the carb when the tank is being shaken when starting. Try going lower still with the control lever. Does this have a primer bulb and is it hooked up right so that it sucks fuel out of the carb and dumps it back into the tank?

 

[Woodchuckr]

OK, so the little beast is for sure just running too rich overall, limited number of things that can cause this condition. If the fuel control diaphragm is too stiff it can stick in the down (open inlet valve) position the first time it is pulled down by intake vacuum the first time the engine is started. What pressure did you test the carb inlet too? If you tested to less than 7 or 8 psi, there is a possibility that the pressure in the fuel tank might be exceeding the pop-off pressure of the carb when the tank is being shaken when starting. Try going lower still with the control lever. Does this have a primer bulb and is it hooked up right so that it sucks fuel out of the carb and dumps it back into the tank?

Tested the inlet to 12 psi. I have cracked the tank lid while running, before starting, just after starting. Primer bulb does dump fuel back into the tank. Haven't had a chance to drop the lever yet. Played a bit with the H L needles and noticed the stalling when you let off WOT happens a lot less with the H screw is richer. maybe have a chance to lower the lever tomorow. Thank's