Honda tiller will not start

[Rekusu]

What ho one and all,

I have a well maintained Honda FG110 (mini tiller) with a GX25 engine. It has become increasingly difficult to start, but recently, it will not start at all. When it is running, it runs well.

Since the carb is the most likely cause, I bought a carb repair kit and everything has been cleaned and replaced. Nothing. Bought a complete replacement carb and still nothing.

New spark plug and ignition coil and still nothing. Checked the timing and seems perfect but that is not adjustable. Good spark, valve clearances are as the book, valves not stuck open. Dismantled and cleaned again the original, refurbed and new carbs in case drying fuel has blocked the tiny holes. Nothing.

Do not have a compression tester but with finger over the spark plug hole, there is compression but I really don't know if it is sufficient; I almost think there is insufficient compression, but what do I know?

It does occur to me that perhaps the off switch is working too well and is preventing the engine starting. I know that off switch sorta shorts the ignition pulse but does it actually stop the spark at the plug? Certainly in the run position, there is a good spark.

If it is a compression issue and the valves are closing fully, presumably the problem can be with the piston rings and /or piston itself. Can I check this without dismantling and without a compression tester?

Thanks and toodle pip

 

[Burnerman]

Don't expect a huge amount of compression with the GX25 - it's a tiny motor but there should be enough to push your thumb off the spark plug hole when you pull it over.
If there is a spark at the plug then all is well there.
Does the carb primer bulb fill with fuel, and return it to the tank? Next, just in case the engine is flooded, turn it upside down and pull the starter - if raw fuel comes out, then it's flooded.
If its not flooded, try some petrol direct into the carb venturi and see if the motor fires a couple of times.
John

 

[Rekusu]

Thanks for your reply. This is not rocket science and i am determined to get it running myself rather than take it to an 'expert' who will do more o less, what I have done.

Yes, bulb fills with fuel and when refurbing the carb, certainly was coming out the carb return port. There is compression with finger over the spark hole, but seems to be less than I would have thought.

Tried some WD40 into the card but probably squirting it in the wrong place. May be I will give the valve stems some carb cleaner jsut to be on the safe side. Pretty sure the valves are working correctly, but .....

 

[Burnerman]

Does the compression actually blow your finger off, or at least allow air to escape - or can you stop the compression completely?
These engines don't like to have any throttle when starting - just full choke.
Try raw fuel down the carb intake - it's probably more reliable than WD.
Do you have a compression tester?
John

 

[Rekusu]

No, the compression does not blow my finger off but I can feel something, just not as great as I would have thought. And I think I can stop the compression.

Never used the throttle when starting; it would be difficult as it is just a lever on the top of the handle; right handed lever, right handed pull!

Don't have a compression tester.

Removed the carb again and while still connected to the tank, primed the bulb to see if there is any fuel going to the inlet side. Don't know how much fuel should appear on my finger, but it is virtually nothing. So once again, dismantled and squirted every hole, jet, filter with carb cleaner, little bit of wire through any micro hole. Still nothing.

Checked the stop/start switch; no continuity in the run position, continuity in the stop so assume all is fine. Gave the valve stems a shot of carb cleaner but they were not sticking before and at still not sticking.

Put my endoscope into the plug hole and the piston has some blackish areas but nothing that I think is out of the ordinary and the bore appears OK. But may be it is worn but only a compression test will reveal that.

After all this effort, will open a celebratory bottle when I get it running again!

 

[Burnerman]

At this stage - if the engine won’t fire when neat fuel is poured into the carb venturi- I have to say that compression does seem to be an issue.
When you prime the carb it does not flush fuel into the motor, rather it primes what is known as the metering chamber, ready for you to pull the recoil starter.
As you have replaced the carb as well as cleaning it, maybe its time to assume that is good and its time to look elsewhere.
Now, you need to decide what to do next. The piston size is 32mm and you can get one for around a tenner ( pattern). Of course you don’t know what state the bore is in, but it could be worth a look see.
Over to you!
John

 

[lostinthelight]

pour a teaspoon of oil in the plughole and see if that increases compression, are you testing with throttle and choke open

 

[Rekusu]

As I have an ultra-sonic cleaner, am considering dismantling the carb and giving it a blast of ultra-sonic vibration. But what would be a recommended liquid? White spirit? Petrol? uPVC cleaner?

 

[Burnerman]

I’d use an appropriate ultrasonic cleaner that is aluminium friendly.
However, you have cleaned the original carb to no joy, and bought a replacement still to no effect.....maybe its something else that is the problem?
John

 

[Rekusu]

Th choke has been closed when I have done a finger compression test and there is no throttle adjustment until the engine is warm and the tine ' engage' lever can be activated.

Not too concerned as to whether the ultrasonic cleaner is ali friendly. It is a smallish device used for cleaning spectacle and jewellery, etc. Just wonder what would be a good liquid to dissolve any 'c**p' that has blocked the micro bores

 

[lostinthelight]

Engine needs to suck air to compress it so if the choke and throttle butterfly are closed your not giving it a fair chance

 

[Rekusu]

My understanding is that the air intake has a start and run position. The start blocks the intake port with the exception of a very small hole. Once warmed up, the choke can be opened to the run position.

The throttle is by default in the 'no hand on the lever position for starting and in this position, the butterfly (actually a tube with a hole through it) is in an approximate 10% (or less) open position. When the engine is up to running warmth, a button has to be engaged to pull the throttle cable back. Without engaging the button, the throttle lever does not move the cable.

These things are pretty much the default setting with little to no adjustment.

 

[lostinthelight]

Engine needs to suck air to compress it so if the choke and throttle butterfly are closed your not giving it a fair chance

This is for a compression test