Briggs and Stratton Vaguard

[eggsarascal]

I've got the above engine V twin 20hp. A few weeks ago I serviced it and had a local company strip/clean and rebuild the carb, the company put the carb back on and tuned it, T'was sweet.

 

Today I used it and the battery was flat, so I tried to pull it over with the cord, it was stiff, very stiff to pull over but started second pull. This is when I noticed the engine is hunting at idle, when I upped the revs it back fired a couple of times.

 

Anyone got any ideas where I should start looking?

[eggsarascal]

The title should read Vanguard.

[aspenarb]

I've got the above engine V twin 20hp. A few weeks ago I serviced it and had a local company strip/clean and rebuild the carb, the company put the carb back on and tuned it, T'was sweet.

 

Today I used it and the battery was flat, so I tried to pull it over with the cord, it was stiff, very stiff to pull over but started second pull. This is when I noticed the engine is hunting at idle, when I upped the revs it back fired a couple of times.

 

Anyone got any ideas where I should start looking?

 

 

poq

 

˙ǝlʞƆIʇ ɐ spǝƎu ʎlqɐqoɹd qɹ∀ɔ ˙ʇɐ˥ɟ sɐʍ ʎɹƎʇʇɐq uƎɥM ƃuᴉʞuɐɹɔ ɯoɹɟ pǝƃɐƃNǝ llIʇs sɐʍ ɹoʇoɯ ɹǝʇɹɐ┴s Ǝɥʇ ǝsnɐɔǝq llnd Oʇ ɟɟᴉ┴s ʎlqɐqoɹd Sɐʍ ʇᴉ ' ƃפǝ ᴉH

[essential]

I help a chap out now and again and he has a tw 125 and his does that when it's idling . I thought that was what it was supposed to do .As for backing firing it happens but not regularly.

 

Sent from my SM-G925F using Arbtalk mobile app

[eggsarascal]

poq

 

˙ǝlʞƆIʇ ɐ spǝƎu ʎlqɐqoɹd qɹ∀ɔ ˙ʇɐ˥ɟ sɐʍ ʎɹƎʇʇɐq uƎɥM ƃuᴉʞuɐɹɔ ɯoɹɟ pǝƃɐƃNǝ llIʇs sɐʍ ɹoʇoɯ ɹǝʇɹɐ┴s Ǝɥʇ ǝsnɐɔǝq llnd Oʇ ɟɟᴉ┴s ʎlqɐqoɹd Sɐʍ ʇᴉ ' ƃפǝ ᴉH

 

Hay b0D MaTE, I hope you're right about the starter motor. I got reading on the web (silly thing to do) that it could be down to valve adjustment and compression release, whatever that means.

 

I spoke to the bloke that did the carb, he said run it in tomorrow.

 

Can't do that, I need it, the bluddy thing better hold out til Friday.

[Ilnumero]

I have two of these engines, one 20hp, one 23hp, and both will backfire at times if the throttle is opened quickly and sometimes if it's shut down quickly too.

 

The 23hp one is really difficult to pull over but I have learned that the technique is to turn the engine just onto the compression stroke on one cylinder and give a sharp pull. It usually fires up. Sounds just like yours.

 

My battery is often flat and it used to be a pain to hook up the jump leads but now I've mastered the technique, I haven't needed to get them out since.

 

The 20hp one was becoming harder to start, often needing 30 to 40 seconds on the starter motor. Something unrelated went wrong with the engine and I ended up resetting the magneto gaps on the rotor and the valve clearances. Now, it starts immediately, maybe two or three seconds on the key. It runs noticably better, so you may want to have a quick check of these items too.

[GardenKit]

Hi Egg

As said, check the valve clearances as if they are too slack the decompressor will not function, and the valves will also not be open long enough for proper scavenging. If they are too tight true valves may not fully close.

 

The backfire is only actually a 'BACKFIRE" if it occurs through the carb and is a result of timing issues, but this is rare on this engine as the timing is not adjustable. Tight valves can effect the timing though as the valves could be open too long, or not close at all, allowing the incoming fuel to ignite in the inlet manifold and 'fire back', hence the term 'backfire'

 

More commonly, what is often wrongly referred to as a backfire is actually an 'after burn' and results from unburnt fuel being ignited in the exhaust. Causes can be too rich a mix, or incorrect valve clearances. Explosions from the exhaust are never a true 'backfire'

 

The 'hunting' is quite common on these engines but should be possible to tune it out as long as the jets are clean in the carb and the valves are OK.

[eggsarascal]

Thanks for the replies.

 

I had time to call in on the place that did the carb, they tinkered with it and it's a lot better, but still not quite right. I've got nearly two weeks of subbing booked in after this week so I won't need the machine. Should give them plenty of time to get to the bottom of the problem.

[PeteB]

I've seem them hunt as the springs on the governor are a little weak, allowing the revs to go up and down as it finds a happy medium. The backfire thing is just a little unburnt vapour igniting in the exhaust, don't worry about it. The Kohler 27 which we used to out on grinders would occasionally bang off some seconds after the engine was switched off!

[Richard 1234]

I've seem them hunt as the springs on the governor are a little weak, allowing the revs to go up and down as it finds a happy medium. The backfire thing is just a little unburnt vapour igniting in the exhaust, don't worry about it. The Kohler 27 which we used to out on grinders would occasionally bang off some seconds after the engine was switched off!

 

 

I e got a 23hp kohler that does the bang after switch off sometimes.

Mind you it is a 1983 engine!