Stihl ts400 backfires

[Ian Brand]

1 hour ago, spudulike said:

I wonder what happened!

Hi, tried the filter every way I can think of, had saws backfire before, especially k760s, always managed to cure the problem, I thought there was only two different coils, 2 or 3 bolt fittings, it is a 2 bolt coil, pretty sure it is the correct flywheel, I'll stick it aside for a while

[adw]

I still think it’s to do with the compensator carb, I haven’t done many 410s, but I know if the compensator is blocked on the Husqvarna this is very much the way they react, the back firing is because it’s starts to run lean.

[spudulike]

I have only known a machine to backfire when a coil has failed, incorrect coil/flywheel has been used or the flywheel key has failed. 

The only exception is the 372XPT and Echo CT2511 where I reckon the ignition retardation on the coil starting circuit was a tad too much causing a backfire on startup but disappears once running!

 

[adw]

I accept completely what you Steve, however these machines are ignition governed to 9800/10000 rpm, when they lean off  the ignition goes into over drive, free running they will spit and pop, and even shoot flames from the muffler, the 410 also has a type of centrifugal air cleaning, there is a fan on the back of the flywheel, the incoming air to the carb comes via an aperture and rubber grommet behind the flywheel, it then takes a torturous route through galleries in the side of the fuel tank, this can also fill with crap and cause issues. If the compensator in the carb is part blocked for any reason the machine will start to run lean as there is no vent hole in the metering cover, with the filter and cover off it will better allow the compensator to work, anyway I feel this may well be the issue with this machine, over and out.

[ChrisNewport]

17 hours ago, adw said:

I accept completely what you Steve, however these machines are ignition governed to 9800/10000 rpm, when they lean off  the ignition goes into over drive, free running they will spit and pop, and even shoot flames from the muffler, the 410 also has a type of centrifugal air cleaning, there is a fan on the back of the flywheel, the incoming air to the carb comes via an aperture and rubber grommet behind the flywheel, it then takes a torturous route through galleries in the side of the fuel tank, this can also fill with crap and cause issues. If the compensator in the carb is part blocked for any reason the machine will start to run lean as there is no vent hole in the metering cover, with the filter and cover off it will better allow the compensator to work, anyway I feel this may well be the issue with this machine, over and out.

Its a ts400 not a 410 

[adw]

Bugger another senior moment.

[spudulike]

I didn't like to say

[adw]

Wish you had, look a right tit now.

[spudulike]

1 hour ago, adw said:

Wish you had, look a right tit now.

That's OK, I think you got away with it!

[john87]

If you have tried everything else, what about crank seals...

 

john..