Echo cs490 dies in the cut

[benartm80]

Working on this saw for a friend. Awhile back I removed the exhaust tube, modded the muffler and removed limiters. the saw was running great for a couple months but now I can’t seem to adjust the high side to get enough fuel at wot (more than 4 turns out from seated) Stumbles and dies in the cut unless you ease off the throttle. Saw has 130psi compression, cleaned air filter out and cleaned the screen inside the carb.

Looking for help with why it might be dying. I don’t have a tach so I just tune by ear listening for 4 stroking. I think it is leaning out so maybe a pressure/vac test to find air? Or maybe something simpler like a fuel filter?

thanks, Ben

 

[Jasonrkba]

Sure your not flooding it?

 

[Big_6]

Air leak?

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[RED-85-Z51]

Its possible the carb can't keep up, maybe raise the lever a couple thousandths?

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[benartm80]

I don't think I'm flooding it as I had started off with the high needle at 1 turn and worked my way out from there. It was starving until I got the needle opened up more.

When I have had air leaks in other saws & equipment they seemed to show up while idling or accelerating. Not ruling it out, but only seems to be in the cut when pulling hard.

If the metering lever is too low (or in stock height), it's possible to adjust the high needle to where the fuel can't refill the bowl fast enough and lean it at WOT?

 

[cscltd]

Fuel filter and or carb inlet screen plugged, or carb diaphragms stiff

 

[Old2stroke]

Could be the fuel pump diaphragm has become too stiff to supply enough fuel for full power operation. Leaning out in the cut can mean a fuel restriction somewhere, fuel filter, pin hole in the impulse line if it has one, clogged input screen in the carb, sharp bend in the fuel supply line, nozzle check valve that isn't opening properly or some mysterious dirt in the high speed circuit.

 

[benartm80]

Thanks for all the replies, will try a couple of those suggestions