Help! Bike suddenly stopped....

[simon43]

Right, let me check this...

[vogie]

Found this on fault finding for your bike.

 

http://hondacg125.awardspace.com/basic_fault_finding.htm

[SteveK]

Surely a genuine Honda dealer can fix it? If the engine has been started, there can't be anything major wrong. I had exactly the same problem with my Triumph in the UK after being serviced by a generic garage, and traced the problem back to a kinked fuel pipe where the fuel tank had been put on heavy handedly. Problem solved in about 20 minutes.

I'm fairly sure your bike has a tap to switch to reserve, try that because it's a different pipe.

Edited September 23, 2018 by pr9spk

[Vacuum]

24 minutes ago, Daffy D said:

Just as another thought are you getting any intake suction when placing your hand over the carb.

Nah, in that case there would be a hole in the piston or if it's a 4 stroke, a valve would be stuck in open position. Possible but not likely.

Edited September 23, 2018 by Vacuum

[SteveK]

1 minute ago, Vacuum said:

Nah, in that case there would be a hole in the piston or if it's a 4 stroke, a valve would be stuck in open position. Possible but not likely.

If the valve was stuck, the dealer would not have been able to start the engine.

[Daffy D]

1 minute ago, Vacuum said:

Nah, in that case there would be a hole in the piston or if it's a 4 stroke, a valve would be stuck in open position. Possible but not likely

Yea! I know, but they seem to have exploited most other possibilities  

[Vacuum]

Just now, pr9spk said:

If the valve was stuck, the dealer would not have been able to start the engine.

That's what I'm saying. Including the hole in the piston.

[SteveK]

1 minute ago, Vacuum said:

That's what I'm saying. Including the hole in the piston.

Yes, so very unlikely to be major damage, better to check the routing of the fuel lines. Sometimes, especially in hot and humid climates where they sometimes have water in the petrol, rust from the tank can build up and flake off, blocking the fuel line.

[Daffy D]

17 hours ago, simon43 said:

I was riding my bike as normal, absolutely no problems. Then the engine backfired once and stopped

Sounds like something suddenly gave way.

 

A fuel problem would have spluttered before stopping. But this Thailand and the normal laws of physics don't always apply 

[Vacuum]

5 minutes ago, pr9spk said:

Yes, so very unlikely to be major damage, better to check the routing of the fuel lines. Sometimes, especially in hot and humid climates where they sometimes have water in the petrol, rust from the tank can build up and flake off, blocking the fuel line.

Possible, however the OPsaid: "If I unscrew the drain screw at the bottom of the carb, then petrol comes out of the plastic drain tube."  That suggests to me, that it's a block inside the carb. I suggest for him to by a can of "Carb Cleaner", not that it cleans very well, but the can has this long and thin nozzle so he can check that all the 'holes'  in the carb are not clogged.

[vogie]

I just wonder if you have a stuck inlet or exhaust valve, if you don't have suction you will not pull any fuel through to the pot. Have you tried putting your thumb over the spark plug hole and turn the engine over to see if you have suction.

[Daffy D]

5 minutes ago, vogie said:

I just wonder if you have a stuck inlet or exhaust valve, if you don't have suction you will not pull any fuel through to the pot. Have you tried putting your thumb over the spark plug hole and turn the engine over to see if you have suction.

Putting your thumb over the spark pug hole for suction won't work as most of the suck will be through the air filter.

See my earlier post.

 

Putting your thumb over the spark plug hole will give some indication of compression. A primitive test for stuck valve or broken piston/rings.

[steve73]

I've had an occasional recurrent problem with a very old Honda wave.. Suddenly stopped mid run, and wouldn't start.. Checked spark plug and got a healthy spark so took it to my local repair shop to check the carb.. He put a brand new spark plug in and it started and ran fine.....100bt.

And it's happened a few more times since (maybe every 6-12 months) and a new Spark Plug has always fixed it. (So I now keep a new spare under the seat with the spanner)

Edited September 23, 2018 by steve73

[vogie]

4 minutes ago, Daffy D said:

Putting your thumb over the spark pug hole for suction won't work as most of the suck will be through the air filter.

See my earlier post.

 

Putting your thumb over the spark plug hole will give some indication of compression. A primitive test for stuck valve or broken piston/rings.

I hear what you're saying but that is how mechanics test for compression, again if the valve is stuck there will be no compression or induction, the only difference of course is a mechanic will use a compression guage and not his thumb, or that is how we used to do it in the year $#€€.

[steve73]

More thoughts... if it's an old bike, the rubber hoses may not be suitable for Ethanol mix in the fuel... You may not have knowingly used E20 but I'm sure some of the stations or local suppliers are not as careful.   There could be some of the internal fuel lines breaking down and blocking the fuel supply or jets.  Perhaps need to renew all the fuel lines.

Try leaving the spark plug removed but just touching the hole (so it still sparks) and the petrol vapour will usually get ignited as it blows out of the hole.

[simon43]

OK, more checks done...

 

I put my hand over the carb air intake and tuned over the engine - there is strong suction.

 

I stripped down the carb.  There are 2 jets, the large main jet (which is clear), and a smaller jet.  But with that smaller jet, I'm not sure if it is meant to have a hole all the way through..  I can see a couple of minute holes on the body of the smaller screw thread (the part that is screwed into the carb body).  but on the other side of this jet (with the large screw thread where you apply the screwdriver to unscrew this jet from the carb body, I cannot see a hole all the way through, (unlike the main jet).

 

Should there be a hole going all the way through that small jet??

 

When the carb is in place, the carb tank chamber fills up fine.  If I unscrew the chamber drain screw, then the petrol starts to drain out, indicating that fuel lines are all fine.  The throttle cable and slider all work fine and don't stick.  The choke control opens/closes the air intake valve fine.

 

Since there is suction when the engine is turned over, and the jet is clear, the fuel must be sucked up into the cylinder intake, (unless my question above about the smaller jet is the problem).

 

If the air/fuel mixture is being drawn into the cylinder, then it should ignite/backfire/whatever if it reaches the spark.  With spark plug removed and turning the engine over, I can see mechanical up/down movement inside the cylinder.

 

I'm open to more suggestions!!

 

Update - I forgot to mention - I'm in Myanmar.  Absolute lack of Honda dealers who know about this bike - they only deal with the scooter type of Honda bike.

 

I'm thinking again about that pilot jet - surely it should have a tiny hole that is visible to the naked eye??

Edited September 23, 2018 by simon43

[Psimbo]

I'm glued to this now- dying to find out the outcome! ?

[Vacuum]

55 minutes ago, steve73 said:

I've had an occasional recurrent problem with a very old Honda wave.. Suddenly stopped mid run, and wouldn't start.. Checked spark plug and got a healthy spark so took it to my local repair shop to check the carb.. He put a brand new spark plug in and it started and ran fine.....100bt.

And it's happened a few more times since (maybe every 6-12 months) and a new Spark Plug has always fixed it. (So I now keep a new spare under the seat with the spanner)

You must have other problems than the spark plug. They should last at least 2 years.

[Vacuum]

52 minutes ago, vogie said:

I hear what you're saying but that is how mechanics test for compression, again if the valve is stuck there will be no compression or induction, the only difference of course is a mechanic will use a compression guage and not his thumb, or that is how we used to do it in the year $#€€.

OP have already ckecked this. Suction is  a ok.

[Vacuum]

18 minutes ago, simon43 said:

Should there be a hole going all the way through that small jet??

Yes!

[simon43]

Should there be a hole going all the way through that small jet??

Yes!

 

.. and if the pilot jet were completely blocked??

[steve73]

3 minutes ago, Vacuum said:

You must have other problems than the spark plug. They should last at least 2 years. 

It had a old Saleng attached, and had many other problems, but for 100bt for a newplug it wasn't worth spending more time or effort checking..

[Vacuum]

20 minutes ago, simon43 said:

and if the pilot jet were completely blocked??

You'll have no idle, but you should be able to start the engine with som throttle.

Edited September 23, 2018 by Vacuum

[simon43]

OK, I just spent a few hours bouncing over the potholes on a motorbike taxi in the rural Burmese countryside...

 

We finally found a dusty old bike accessory shop that looked straight out of a Dickens novel.  The owner found a replacement pilot jet with (indeed!) a visible hole.

 

So I've put the carb back together with the new pilot jet.  The bike still won't start, but I guess this is maybe because there is no air/petrol mixture at all in the cylinder head/fuel intake of the engine.  I'll recharge the battery and try to start the engine again later this evening.

[johng]

Is there a vacuum activated fuel valve between the fuel tank and carb ? If so you can temporarily bypass it to get fuel to the carb...but it might flood all over the floor when parked if the float valve is a bit dodgy.

[simon43]

No vacuum activated fuel valve - the petrol gets to the carb float chamber just fine ?

[steve73]

Take the spark plug out and pour a little petrol (5-10cc) into the chamber.. put the plug back in and see if you get even a small kick..

[simon43]

See my previous posts - I already did this and yes, it fires for a second or so.

[Vacuum]

16 hours ago, simon43 said:

No vacuum activated fuel valve - the petrol gets to the carb float chamber just fine ?

Yes, your problem is that the fuel doesn't get to the carb from the float chamber. So you should use some aerosol can with carb cleaner, 556, wd-40 or whatever to locate what 'hole' is blocked.

[simon43]

See one of my previous and recent posts.  The pilot jet was completely blocked and uncleanable.  I was able to find a new jet in a dusty Burmese shop!  The bike still won't start, so I'll try a new spark plug.

 

(The pilot jet blockage makes absolute sense - the bike was running fine at medium/high speeds ==> main jet.  I slowed down at a corner and the bike spluttered to a stop ==> using the pilot jet at low speeds.)