Strimmer won’t start

[Superdave]

Hey everyone 👋

Usual thing with an older 2T strimmer....

It's a Flymo Maxitrim

Stuff I have tried:

New plug.
Full carb strip, ultrasonic clean and rebuild using all new seals, gaskets, needle, gauzes and diaphragm.
New fuel lines.
New weighted filter in tank.

Starting on easy start but only for a second.

I'm a keen motorcycle enthusiast and have owned several two smokers....

Engine has good compression
Reed valve is doing the business
No reason to suspect crank seals
Spark is strong

I've tried 25:1 mix as recommended by the handbook, and 40:1 as I think 25 is a little oil heavy but still nothing.

Plug gap is 0.8 standard, I've tried 0.7 (advance timing) as this usually gives easier starting, and 0.9 but still nothing....

Any advice appreciated, I'm embarrassed to say I am stumped here....

Runs for a second as stated so points at fuel, but the plug is wet when removed.

I've triple checked carb and settings.

🤔🤪

[Kevin]

Hi SuperDave,

Have you considered the possibility that your strimmer might have a vacuum lock in the fuel tank. When it has run briefly undo the fuel tank cap and see if you hear a hissing sound. Some strimmers have a venting system in the cap or a separate vent diaphragm.Usually the trimmers with a separate system will have three pipes coming out of the fuel tank.

I had a recent case of poor starting with a Ryobi multi-tool motor and this turned out to be a dirty fuel tank cap filter.

Kevin

[Mick]

Not sure what carb that machine has on it, but as you mentioned it runs for a second and the plug is wet when you remove it, there's a possibility one of the welch plugs has fallen out, and the engine is choking on excess fuel.  Check that all the welch (blanking plugs) are in lace, and not sitting in your sonic tank. 

Going to be brutally honest, the cheapy half crank machines with the carb bolted on the crankcase backplate will never be super reliable, they never were to be honest.

[Superdave]

Hi Kevin, many thanks for your message.

Yes I've tried starting it with the cap fully removed, still no dice.

It has to be said that I have quite literally tried everything Along with the bikes I am also Mariner OBM certified, from 4hp up to 300 non conventional 2T "Optimax" so I know my way around these things, it's almost like an impossible situation that shouldn't be....

Professionally I am a diesel engineer, with OEM service certification for CAT, MTU and Volvo Penta, plus the outboards too....

I've even considered a faulty kill switch but have tested it with a multimeter while trying to start the strimmer to see if the vibration is causing an intermittent open circuit, but all is fine.

This is a professional pride swallowing cry for fresh ideas, and I appreciate your input 👍🏻

Anything I can do just let me know.

Many thanks

Dave

[Superdave]

Not sure what carb that machine has on it, but as you mentioned it runs for a second and the plug is wet when you remove it, there's a possibility one of the welch plugs has fallen out, and the engine is choking on excess fuel.  Check that all the welch (blanking plugs) are in lace, and not sitting in your sonic tank. 

Going to be brutally honest, the cheapy half crank machines with the carb bolted on the crankcase backplate will never be super reliable, they never were to be honest.

Thanks Mick,

Definitely still in tact and correct, I've checked it through three times.

I've set the low speed screw at 1 a 1/2 out (as it was originally set before the sonic tank)

Points at flooding for sure, but it's all together correctly.

I tried 1 turn out, and 1 and 3/4 and 2....

Tried different angles, tried warming the plug 🤪 did I mention the phrase
'professional pride'

It's almost a joke this thing, yes they're not the most well built thing, but my sons Chinese 47cc quad is by far less quality than the strimmer, and it goes second pull....

I use ethanol stabiliser and 97 Ron in everything, and never let stuff sit for too long.

Appreciate your help mate, I'll put my thinking cap back on and see where we get to 👍🏻🥃

[Superdave]

Just some whiskey guided thoughts:

It's old and was previously owned by my folks neighbour, who was also old.

I'm thinking about taking the exhaust off and soaking it overnight in diesel as it's quite mucky and probably has never been de-coked.....

Possible exhaust restriction?

I'll start with that, then back to fuelling;

I'm going to set the idle fuel (low speed) screw at 3/4 and give it 10 pulls, remove the plug and see if it is wet.

If it is then I'll go in a bit maybe.... if not then I'll set it to 1 and repeat.

I'll use 40:1 as that's what I've currently got in the mixing bottle.

Easy start will stay in the garage.

I'll update you soon 👍🏻

Thanks for the help people, I'm going back over it all again if this doesn't work 😣

[Mick]

Blocked exhaust, or even the exhaust port is always a possibility and definitely worth checking.

Fingers crossed. 

[Superdave]

Here's an IPC (Illustrated Parts Catalog) image of the carb.

It's not exactly what is fitted, but 99% the same.

Made by Walbro and fitted in several forms to lots of different machinery.

As you can see there's no primer bulb so it's not the easiest thing to get going at the best of times....

[Mick]

Thanks for the pic Dave.  Just another thought.  Make sure the diaphragms haven't gone hard, especially the metering diaphragm, they can do especially with age and these modern fuels. 

[Superdave]

Hi Mick, glad you're liking the media 👍🏻

The carb has everything new in it including the diaphragm.

Still not had a chance to look at it since yesterday, I'll update when I can.

Have a good one ✌️

[Superdave]

Oh and on the subject of modern fuels.....

Remind me as I have a lot to say about this 👍🏻

Good night and god bless

[GardenKit]

Hi Dave.
If its flooding instantly as it seems it may be, I would firstly be checking the diaphragms again to ensure that the metering diaphragm is fitted the right side of the gasket. Also ensuring that it is the correct diaphragm and a genuine Walbro too.
If the diaphragm is fitted too low it will be opening the metering valve too soon.
Also important to set he height of the metering arm (needle lever), if its too high it will flood easily.
Good luck

[Superdave]

Hello Gardenkit,

Thanks for the message 👍🏻

The kit is a genuine spare from Walbro, although it was from eBay it was from a uk based garden machinery service business.

I have fitted the diaphragm as per the picture I posted on here (gasket first, then the diaphragm on top, cover plate on top of the lot and nipped up in a good old fashioned opposites type way 😉

The only thing is the little hole in the cover plate, I'm not 100% which way it should face, but as it's only there to allow movement of the diaphragm, while offering it protection (and obviously securing it to the carb!) I cannot see it makes much difference...

Still not had a chance to fiddle, update soon.

Dave

[Superdave]

Oh yes and the metering valve pivot thingy.

On this carb this doesn't have any adjustment as it's just a pressed metal two pronged flap with a rolled section for the pivot pin.

I replaced it with the one supplied with the kit, but (and like every other component) I put it side by side with the replacement and there was no noticeable difference....

I'm used to setting float heights in carbs so the thought did cross my mind, maybe I'll tweak one with a pair of pliers and see🤔

Anyway, bye for now 👋

[GardenKit]

The metering lever should be about 1.5mm below the face of the carb. I say 'about' because I always use a gauge rather than a measuring stick, but its about 1.5mm.
With the still fitted, push down on the needle end and lever the long end up or down to set the height.