Rich coming off of WOT

[millerlite]

So first ill explain the problem, then the backstory.

Nomatter the state of tune, the saw dies coming out of a cut. The high is tuned perfect. Low perfect. The only way to have it not die, is to tune the idle lean of highest idle, and give it more air to keep the chain almost turning. Throttle response is non existant like this. I have checked the main check valve, lever height, changed that higher and lower, etc. Always same issue.

The saw is a chainsaw chainsaw g2500 fine china. It has a tube in the muffler and baffle gutted. No porting yet. Worked pretty good with stock carb just slow. I put a chinese cs400 carb on it and opened up the boot to match. Im trying to get it working, because now this set up absolutely rips. The saw is a play toy but I do climb with it also so i wqnt to have it well mannered.

It is definitely flooding itself out. Is this a case of too big of a carb? Any thoughts on modifying the throttle plate notch, or the transition holes in the low? Metering lever spring and height? Im not sure where to go with this.

Edit: Oops, I meant to post this in the general saw section

 

[Mastermind]

Moved it for you. I'm a little biased (ok, a lot biased) towards China saws. So I'm gonna blame that for the issues.

 

[David Young]

the metering lever is hanging up some how. It is also possible that the check valve in the main jet is not sealing well.

 

[EFSM]

Try raising the pop-off pressure, maybe a stronger metering spring or setting the lever lower than it should be.

 

[millerlite]

Thanks guys, the china saw is not the problem, it ran great besides expected power, till i put a wt9×× (whatever cs400) carb on it. Now it has the issue. Other carb back on, fine. Ive checked the impulse, i set the lever lower, then higher. Seemed about the same after tuned. Ive checked for air leaks, swapped diaphrams. I swapped metering levers and spring from another carb. Springs might be the same though. I just tried widening the notch in the throttle plate. No change, might tig weld that back up. Looking at the carb the step after the venturi was pretty sharp and thought maybe puddling fuel. Set it up in the lathe and bored that back at a shallow angle to the main. Picked up more power, no change in tune issue. It seems strange that revving up its lean, and back down it floods.

Since this is an experiment, has anyone put a big carb for the saw size on a saw and had this issue? I am stumped here and wonder if the carb is too big for the saw. Idle wants to tune in at only 0.5 turns out. High needle is 2.5t. Edit: i believe the venturi is 0.53 inches or so. Stock was 0.375 and the main blocked half the venturi.

 

[millerlite]

If the check valve wasnt sealing wouldnt this cause a lean condition and not a rich one? I punched it out of the carb, checked it, and put it back in. Seems fine, but maybe i should get another.

 

[David Young]

it sounds like the main jet with those jet settings.

What is the pop off pressure? does it reseal after pop off?

the carb venturi itself is not too large for that size saw but the idle circuits could be. like any engine a smaller carb/venturi will behave better.
the Husky 335xp was 35cc and came with a 13.49mm walbro WT stock.

 

[millerlite]

Makes sense. Pop pressure i am not sure. I can test it later. For reference, on my mildly ported cs400 my settings are 3t out on high and 1.25t on low. So maybe you are right and the idle circuit is too big? Also, a 35cc saw is still 30+ percent larger than the little 25cc fine china and im sure it doesnt have the best port work. Wonder if there is a better carb option out there.

 

[millerlite]

Pop off at 13 to 14 psi