Further Yamaha 5hp problems!

[Tim Good]

Ok so.... some of your kindly helped in this thread:

Yamahah 5hp 2 stroke - Idles ok, struggles with throttle?

From thatI understood my carb a lot better. I dismantled it and cleaned. Then added an inline fuel filter since the strainer in the tank disintegrated! And looked like this:



It then wasn’t great even after cleaning so I got some carb cleaner and just sprayed it into the air intake as the instructions said before dismantling the carb and cleaning again. Hey presto it was working.

So I took a nice trip up the river in Salcombe and was fine until it just stopped. Tried and tried and didn’t even sound like it was close. I checked the plug and it’s wasn’t wet and it was sparking.

I have single dismantled the carb again and all seems clear but I cleaned it nonetheless with carb cleaner. Refitted and still nothing. Not even close to ignition.

There is defo a spark and fuel is deffo getting to the float bowl at least as i tried draining it in situ.

So... I can’t think what else I could do.

Oh and I got rescued by a friendly passer by!

 

[VicS]

Have you tried a new plug?
How good is the spark? It should jump 5/16 to 3/8 inch in free air.

Have you tried spraying a little fuel directly into the carb. If the ignition is good it should at least fire and perhaps run very briefly..

 

[Tim Good]

Have you tried a new plug?
How good is the spark? It should jump 5/16 to 3/8 inch in free air.

Have you tried spraying a little fuel directly into the carb. If the ignition is good it should at least fire and perhaps run very briefly..

Standby. Going to test both now.

 

[anoccasionalyachtsman]

Sorry, replied in the wrong thread, having diverted to it from this one...

Water in the fuel has caused these symptoms on some engines I've used, so if you found some in the filter it's most likely that there was some in the float bowl.

 

[Tim Good]

Have you tried a new plug?
How good is the spark? It should jump 5/16 to 3/8 inch in free air.

Have you tried spraying a little fuel directly into the carb. If the ignition is good it should at least fire and perhaps run very briefly..

Once again you’ve delivered the goods. It’s working.

The spark has a good jump for sure. I then sprayed some petrol into the air intake and after 3/4 pulls it started. Left Idling for a few mines and then took it for a whirl against the flow of the tide (just in case).

All good and feels smooth.

What do you think could have been the cause if it’s been rectified by spraying fuel and forcing ignition?

 

[Topcat47]

Air locked tank? Is the breather clear? Methanol in modern pump petrol is a killer, it ate the fuel filters in my 2004 Bonnnie and my Tohatsu 3.5 (the mesh just disappeared; ( I don't know why they used plastic in the first place ). Is the tank clean? dirty fuel, whether from corrosion in the tank or just contamination can easily block small passages in the carb.

 

[mrangry]

My mariner 4hp 2 stroke starts and runs fine for a while but bogs down when throttle applied after running for a while. I ran it with the cover off and noticed bubbling around one of the lower cylinder head bolts. It seems to have a combustion chamber leak so will need to whip the head off and see whether a new gasket will cure.

 

[ip485]

Not wishing to be a pessimist I once purchased a new 9HP of reputable make. It never was really happy. Would run for a while and then play up for various reasons. Never started after being left for a winter season even with care to run it dry. In the end I traded it in and decided it was just one of those Monday morning products (or is it Friday afternoon). Always got it started but the problems just kept coming and in the end enough was enough. Taking the injector apart was always a lengthy excercise as well and usually this was the first place to start. I hate the modern fuel injected engines. Someone said get yourself a couple of good two strokes (I have one larger engine and a small light weight one). Never looked back. You can leave them all winter and they start after a few pulls. You definitely seem to be able to use and abuse unlike any of the modern brand of lower HP fuel injected engines.

 

[Dang2stroke]

My mariner 4hp 2 stroke starts and runs fine for a while but bogs down when throttle applied after running for a while. I ran it with the cover off and noticed bubbling around one of the lower cylinder head bolts. It seems to have a combustion chamber leak so will need to whip the head off and see whether a new gasket will cure.

I know this is an old thread but has same with my 5hp Yamaha 2 stroke 2004. I changed everything to find this problem…..
Ended up being someone had installed the reed 180 degree out half covering the carby intake - this causes severe restriction yet looks completely normal otherwise- the motor still worked- started but just ran really badly as it couldn’t fuel properly. There was nothing wrong with the reed itself (fibreglass) but replaced it with a Chinese knock off anyway - $20 metal so eventually will go back to the fibreglass set so the metal reeds don’t escape lol.