Stihl TS410 issue....

[Carl358]

Not sure if this is the correct forum for this but if anyone can assist I’d be very grateful...

I have a Stihl TS410 Circular Saw which won’t start, It had no compression when I got it so I’ve replaced the head, piston, piston rings and bearings as the piston was badly scored by the snapped rings. It has new fuel in it and a good spark, now good compression, I’ve checked all fuel pipes and everything that I’d removed to do the piston fix but it still refuses to fire. I’ve swapped the carb for a known working one but still nothing. But it has got fuel coming through to the air filter, I’m assuming that this is happening because of trying to start it so often.

Does anyone have any ideas? I’ve exhausted all my avenues so far...

Thanks in advance

[spudulike]

Have you checked the spark as if you have compression and fuel, it is the other main constituent to a running engine.

[Carl358]

Hi, yes, it has a very good and strong spark

Edited August 16, 2019 by Carl358

[Ratman]

Have you checked the spark as if you have compression and fuel, it is the other main constituent to a running engine.

My TS410 isnt a patch on my old TS400, its had new pot, piston, crank, 2 coils, 2 carb rebuilds since i’ve had it, only had it about 3 yrs, not done mega work either, just flagging projects really. TS400 i’ve had for about 11 yrs, only thing its had is 1 carb rebuild, and bet its done 5 times more work easily, ?‍♂️ pot luck sometimes though i guess!

 

[Stubby]

If you have , comp , fuel and spark then perhaps the spark is not at the right time . Sheared fly wheel key maybe ?

[Ratman]

Piston in right way round? Arrow to exhaust side.

[Carl358]

16 minutes ago, Ratman said:

Piston in right way round? Arrow to exhaust side.

Yep checked that, but thanks for the suggestion 

[Carl358]

37 minutes ago, Ratman said:

My TS410 isnt a patch on my old TS400, its had new pot, piston, crank, 2 coils, 2 carb rebuilds since i’ve had it, only had it about 3 yrs, not done mega work either, just flagging projects really. TS400 i’ve had for about 11 yrs, only thing its had is 1 carb rebuild, and bet its done 5 times more work easily, ?‍♂️ pot luck sometimes though i guess!

 

I have a TS400 in bits all ready for a clean up and rebuild, hopefully it’ll give me less hassle! Lol

[Carl358]

35 minutes ago, Stubby said:

If you have , comp , fuel and spark then perhaps the spark is not at the right time . Sheared fly wheel key maybe ?

Now THAT is one thing I haven’t looked at! Maybe it’s slipped round half sheared? I’ll have a look at that tomorrow, thanks!!

[spudulike]

You often let some big backfires or kick back when the key has sheared but does depend on where the timing has ended up.

If you have spark, the compression needs to be over 150 psi then a carb issue is the most likely issue. 

General carb faults are gauze strainer blocked, perforated pump diaphragm, hardened metering diaphragm, stuck metering arm, check the needle will hold pressure to at least 10psi before popping off, possibly the check valve has stuck open and lastly, make sure the choke is operating as it should.

It could be the engine is flooded so pull the plug, turn the unit iodide down and pull it over hard a number of times. If petrol comes out of the plug hole. Let it dry for an hour, heat the plug with a plumbers torch and put it back in quick then pull the engine over hard holding the throttle open. If it still doesn't fire then try a bit of choke.

Back to the carb, make sure all gaskets and diaphragms are assembled in the correct order as it makes a huge difference. The pump membrane diaphragm should be closest to the carb body, the metering diaphragm should have a spacer gasket between it and the carb body!