Vanguard engine help

[Ledburyjosh]

Hi I have a 18hp vanguard engine on my greenmech cs100. 

 

It frequently pops with extra compression evident out of the exhaust and the engine revs, whilst maintaining high rpm seem to fluctuate.

 

 

 

You can see in the video the extra force out of the exhaust with each poo the way it moves the woodchip.

 

Does anyone know what might be the cause of this or where to start looking?

 

Thanks

[maybelateron]

Wild guess - weak governor spring on the carb?

[eggsarascal]

I have the older 20hp Vanguard on my machine, it does the same thing. Get the carb cleaned and tacho'ed, they really don't like anything close to stale fuel.

[PeteB]

Some vanguards have always popped on the overrun - even had it on the Laski grinders when we were the importers! I have seen weakened governer system which could over fuel and cause a back fire!

[eggsarascal]

44 minutes ago, PeteB said:

Some vanguards have always popped on the overrun - even had it on the Laski grinders when we were the importers! I have seen weakened governer system which could over fuel and cause a back fire!

Overrun was the word i was looking, I'm fairly sure it was you corrected me when I asked about mine doing the same thing years ago, I wrongly called it a backfire.

[PeteB]

2 hours ago, eggsarascal said:

Overrun was the word i was looking, I'm fairly sure it was you corrected me when I asked about mine doing the same thing years ago, I wrongly called it a backfire.

Overfull on the overrun causing backfire! Helps with the running decoke! I the dark, sparks of carbon fly out of the exhaust.....

[Stubby]

Valve clearances not correct can cause popping  on overrun  . 

[Ledburyjosh]

OK thanks.

 

Stale fuel could be a contribution, its been sat for 6 weeks or so.. 

 

Maybe I'll look at draining it when I know it will be sat for a while.

 

I'll check out putting a new governor spring on it also and see if that helps.

 

Thanks

[woody paul]

15 hours ago, PeteB said:

Some vanguards have always popped on the overrun - even had it on the Laski grinders when we were the importers! I have seen weakened governer system which could over fuel and cause a back fire!

Fitted a vanguard to my old Timberwolf 100/18 a couple of years ago, and it popped shutting revs down since I fitted it. 

 

[GarethM]

Well it'll be direct drive without an overrunning clutch, so the mass of the ass will be still making it spin faster than the fuel it's getting.

 

Even happens on Kubota diesel timberwolf even when you throttle down.