Stihl TS410 Disc cutter won't start.

[Carrot Cruncher]

I've exhausted my normal diagnostic routes with a Stihl TS410 disc cutter. Handed to me by my boss as an unknown it ran ok but with a tonne of smoke, the engine then backfired and cut out like the ignition had been cut and hasn't started again since!

 

It has good compression and fuel which I have changed for a fresh mix. The spark is good so to my mind it should go or at least fire! I've had the flywheel off in case the woodruff key had moved or semi sheared but all is well. I've also disconnected the stop switch in case that was causing a fault. I think it has reed valves and I have no knowledge of these. I've also removed the very dirty air filter which made no difference and I've tried lobbing some fuel directly in the bore. It hasn't even had the courtesy to fire once.

 

Ideas please and tell me what I've missed.

 

Phil.

[adw]

There is no reed valve in the cylinder, if it soaks the plug before it can fire then concrete dust has scored the inlet seat in the carb, if there was any sign of concrete dust under the paper filter it will have cylinder wear, by good compression what have you checked, concrete dust and fuel mixed and entering the cylinder is lapping paste and will remove the cylinder plating and erode the piston skirt and ring, other that that they are not the best power cutter out there when new, you should never clean the paper filter or blow out with an air line, this will open the pours in the paper and allow dust through.

[bmp01]

14 hours ago, adw said:

...... you should never clean the paper filter or blow out with an air line, this will open the pours in the paper and allow dust through.

Every day's a school day.

[spudulike]

I have to say that I read the list of things tried and came to the conclusion that it should work if all the info was correct.

As ADW says, I have heard 100 psi being described as good compression! 

The needle valve may be stuck open on the carb or partially leaking or the spark may die under engine compression and YES, it goes happen as I found out recently on an 020t giving a spark across 6mm and nothing under compression.

[coppice cutter]

First of all you really need to put a compression tester on it to see if there genuinely is compression. Wouldn't be the first time that someone mistook compression for scraping a badly seized piston up and down a bore.

 

Then you need to dry the plug and put it back and see if it's wetting it. If it is and there's proper compression then you need to look at your spark. If it's not and there's proper compression then you need to look at your fuel supply, including crank seals.

 

If there's proper compression, a fuel supply and a good spark at the right time it will go, I've never seen an engine yet defy the laws of physics. If it doesn't go then there's a problem somewhere. 

[spudulike]

1 hour ago, coppice cutter said:

If there's proper compression, a fuel supply and a good spark at the right time it will go, I've never seen an engine yet defy the laws of physics. If it doesn't go then there's a problem somewhere. 

Pretty much my thoughts with the few exceptions I have found to be a semi leaking needle valve slightly flooding the engine and a coil/HT lead sparking in air but not under compression....it does happen believe me and the spark was at least 6mm long and blue on the tester!

The rest is as you said!

[Sviatoslav Tulin]

22 hours ago, adw said:

There is no reed valve in the cylinder, if it soaks the plug before it can fire then concrete dust has scored the inlet seat in the carb, if there was any sign of concrete dust under the paper filter it will have cylinder wear, by good compression what have you checked, concrete dust and fuel mixed and entering the cylinder is lapping paste and will remove the cylinder plating and erode the piston skirt and ring, other that that they are not the best power cutter out there when new, you should never clean the paper filter or blow out with an air line, this will open the pours in the paper and allow dust through.

Its B A N A N A S,plz  no one listen to this man, clean filter when needet, as u normally do! 

[adw]

And that my freind is why I am a service engineer of 42 years and you are an idiot!

[bmp01]

13 hours ago, Sviatoslav Tulin said:

Its B A N A N A S,plz  no one listen to this man, clean filter when needet, as u normally do! 

Although its not said directly adw is implying fit a NEW paper filter every time ..... doesn't seem too wrong, concrete saws have just about the worst working environment.

 

 

[Sviatoslav Tulin]

12 hours ago, adw said:

And that my freind is why I am a service engineer of 42 years and you are an idiot!

My, advice still the same, Do not listen this man, he miss big part if his education, if he had it at all. END. My second one in 16 years, 2 years old, regularly cleaned paper filter, air from compressor or my mouth 😂, no dust after filter a bit of oil, mostly used dry, according to my dairy about 300 hours on it, still original filter, thats for genius ADW.

Edited January 31, 2021 by Sviatoslav Tulin