Cheapo String Trimmer Running Problem

[primer_bulb]

MTD Remington RM2510 String Trimmer
Model: 41BD110G983

This is a 25cc curved shaft string trimmer with a Walbro carburetor. I bought this trimmer new 1 year ago and have experienced running problems in the last month. The trimmer cold starts with choke and priming like normal. I can use the trimmer up to 5 minutes max before it shuts off (usually while applying throttle). If I pull and pull the recoil starter, choke or no choke, the trimmer WILL NOT restart. I performed a complete ultrasonic cleaning of the carb and checked the plug. I still experienced the same running issues. Today I tried an experiment and removed/reinstalled the fuel cap right after the trimmer shut off. It will immediately start and run the 5 minutes before relapsing. Is this style fuel cap prone to going bad and is it the sole culprit of my running issues? It appears that there is a one-way "duckbill" valve on the inside of the cap. How do these valves work?

Thank you for any help,
Jeff
Duarte, CA

[bgsengine]

MTD Remington RM2510 String Trimmer
Model: 41BD110G983
Today I tried an experiment and removed/reinstalled the fuel cap right after the trimmer shut off. It will immediately start and run the 5 minutes before relapsing. Is this style fuel cap prone to going bad and is it the sole culprit of my running issues? It appears that there is a one-way "duckbill" valve on the inside of the cap. How do these valves work?

Thank you for any help,
Jeff
Duarte, CA

If your trimmer immediately restarts after loosening and re-tightening the gas cap then yes it would be your issue and you may also note run time may vary depending on h ow much fuel is in the tank (on a completely full tank, shorter run time) duckboll valve works much like .. well .. duckface - hold your lips together like some teenage girl doing a facebook duckface and try to blow air out (motorboating) and then try to breathe back in through them.. you should get the idea how a duckbill valve works. they are designed to allow air IN to the tank but not back out - the cap has hidden venting connected to the valve that is more likely plugged up and from the looks of that machine it is probably NOT a recent model (even if it is new to you) 753-06857 I think is the gas cap part number if I remember right (Im quoting that number from memory, yes) - it has a tether now for EPA compliance since 2012 model year (or supposed to)

[creia]

Brian (and others),
Can the vent holes in this cap be cleaned somehow? Maybe by soaking in an ultrasonic? I'm still having a hard time understanding how the cap vent works on this string trimmer, as; in the operating position the tank is always tilted sideways and the cap is submerged under the fuel level in the tank- how does it draw air in this position?
Michael

[KE4AVB]

Think of the duck bill valve as an one way check valve. Tank closes the valve by squeezing it shut and vacuum in the tank will draw in air as it opens the slit by drawing the sides apart. It doesn't need to above the fuel level to do so. The valve can submerged and still operate. Same type is used many fuel caps and even the Echo tank vent is made with a duck bill valve. This the same type valve used the primers of many Walbro and Zama carburetors and they are fully submerged in fuel mix. Many of the Husqvarna chainsaws these tank vents are difficult to get to but they are there.

Cleaning of the fuel cap is just the removal of the surface dirt covering the valve. The fuel cap here has three vent slots in the top. Duck valves do stick close, swell closed, and even stick open (swollen to the point the valve is unable to close). Many of the duck bill I replace are usually stuck open (leaking). Matter of fact I got a Homelite trimmer that I got a new fuel cap ordered for the duck bill is leaking fuel out of the tank. Now some fuel tank caps only have a small hole to draw air through and these do tend to clog easily.

Here I suspect the valve is stuck closed by dried fuel mix and clean gently may open it but I have seen many times once open they don't seal properly leading to fuel leakage. It best to just to replace the cap when you find that venting is problem.

[primer_bulb]

Thank you bgsengine and KE4AVB for the informative replies. I primarily lurk on this forum (look at my post count) and appreciate the free education you provide to myself and many others. I will be ordering a new fuel cap soon; thank you bgsengine for the part number. In the meantime, I may investigate the "duckbill" valve.

Jeff

[creia]

Yes- thank you gents! I learned something NEW today.
Michael