Problem with carb, runs rich when tilted to side.

[banditt007]

Ok so I have one of these carbs, its a chinese knock off of a walbro i believe.

The engine in question passes vac/pressure tests, and i know the problem is the carb itself. The problem is, that the carb runs very rich to the point of stalling or being very close to stalling, lowering the idle, when it is tipped on its side. Its as if the low speed needle is being richened a lot when it is tipped to the side. I have tested the primer bulb function and you can pump the bulb, and watch the psi increase on the gauge, and hold pressure each increment. Also I have tested to 8psi or so on the inlet side, and there is no leak down. I tried reducing the metering lever height (i was chicken and didn't bend it down much) and didn't really see a change in performance. Maybe i should try further but i haven't tried yet. The carb adjusts and tunes just perfect at high rpm.

I can adjust the low speed needle so lean, that it bogs on acceleration, yet when its tipped on its side (either side) or turned upside down, it runs super rich. All fuel lines test good as well as the fuel filter, no cracks in them ext. Also i noticed that its very easy when starting cold, using the choke, to bypass the point where the engine sputters, pops ext, and goes straight to being flooded. Not sure if there are other means of testing the carb than what i have described above.

As a note this is the first time i've had any trouble with these knock off carbs. For the cost sure i could just buy another one but i would like to learn about carbs and what makes them tick. Thanks in advance for any help

 

[cus_deluxe]

what does this carb belong to?

 

[Definitive Dave]

nothing for nothing but did you try the pressure/vac testing with the saw laying on it's side(s), seen a clutch side bearing seal that only leaked on a lying down saw, seems wacky, but replacing it fixed the behavior you describe, worth a check maybe
DDave

 

[banditt007]

cus deluxe, the carb is on a string trimmer, as a chinese replacement for a walbro.

Dave, i did not test it tilted on its side, however, i did pressure and vacuum test it to 10-15 in/hg and 10-15 psi. Also during both pressure and vacuum tests i slowly rotated the crank shaft 360 degrees several times, and when the pressures equalized, i was right back to my original vacuum/pressure. So i'm very confident that isn't the case. I'm wondering if since the engine pulls 130psi that a "lower" compression number is aggravating things. Seems like similar engines are pulling 150psi or a bit more. I believe is just due to worn rings since the piston looks excellent. Some how i don't think that the 130psi is really at fault at all though. seems like it would need to be a good deal lower than that.

As an update i had adjusted the metering lever down, and now when tilted the overly rich running has been reduced a lot. However i still need to run the low speed needle lean. to the point where the engine bogs for the first 15 seconds or so of running before it throttles up correctly. but once warm seems to react well. But even during semi warm restarts where a normal engine would need no choke, this one will need it b/c its set so lean. I'm starting to lean towards the possibility that the spring is an incorrect spring rate for the carb? not really sure.

 

[cus_deluxe]

sounds like youre headed the right direction, hard to say how good quality control is on these things

 

[mikerecike]

Are you sure the twisting is not altering the length of the throttle cable in some way- a mechanical issue.Watch the throttle components carefully as you turn it over. Or, is the air filter or choke somehow moving in the twisting? That would be more consistent with your description but I'd check the cables too.