stihl saw TS 410

[aljaxon]

ive got 2 x ts410's. both were faulty. a new carb and replacing a split hose got one of them running perfectly. the other needed a full engine rebuild but after replacing crank seals bearings cylinder it wont start up. i stripped carb down blew out passages replaced all the gaskets but still no joy.
one thing i did notice. i dont get a spark when i pull the cord. but if i put a drill on the rotor nut and spin it about 200 rpm just guessing but got to be 3 times as fast as pull speed i get a spark. but if i slow the drill down a bit the spark disappears.
so i guessed faulty coil. i borrowed the coil off the working machine. that did exactly the same. no spark below 200 rpm so thinking it was the rotor or flywheel i tested both coils on the working machine. and guess what. no spark unless you are doing like 200 rpm. both coils. one machine starts up very easily. the newly rebuilt motor one wont.
so how the hell do these things start up?
unless i am getting the tiniest of sparks that my 60 year old eyes cant see even in the pitch black.

ive been messing with 2 stroke motors most of my life. i like to do things by the book , i even filed the rings to give me the correct ring gap. but this has me stumped. plug is getting wet.
wont fire.

 

[addjunkie]

Try it in the dark and see if there is a weak spark hand pulling.

 

[JOEPRO]

Could be low on compression. What is the compression reading? Needs to be 90 / 100+psi or above for it to fire

 

[Turbo]

The spark on modern 2 stroke saws can be very hard to see. They don't have the nice big fat spark of older machines.
You also need to spin them over quite quickly.
I found that on a few machines I've been working on lately so I bought a spark plug tester.

https://www.amazon.co.uk/Sealey-SEA...hvtargid=pla-2281435177338&psc=1&gad_source=1

 

[trigger3]

havent messed with a saw but on other 2stroke if you have to much airgap between coil and magneto it likely wont spark good

 

[dobbslc]

Have you swapped the carbs over?

 

[aljaxon]

Try it in the dark and see if there is a weak spark hand pulling.

thats the only way i check for a spark. im sure i mentioned pitch black in my post.

 

[aljaxon]

havent messed with a saw but on other 2stroke if you have to much airgap between coil and magneto it likely wont spark good

yeah ive tried narrowing it down so its virtually touching. still the same

 

[aljaxon]

Have you swapped the carbs over?

no. i have 3 carbs. 2 genuine stihl carbs used and the new one cheap chinese copy. and thats the only one that works. ill try fitting the other carbs to the working machine to find out what works and what doesnt. im getting quicker at removing and replacing stuff and what was once daunting is a 10 minute job.

 

[aljaxon]

Try it in the dark and see if there is a weak spark hand pulling.

pitch black. when im hand pulling my head wobbles all over and cant see anything. ill have to recruit the wife to give me a pull. normally you see and hear the spark on all the other motors ive worked on.

 

[aljaxon]

Could be low on compression. What is the compression reading? Needs to be 90 / 100+psi or above for it to fire

its a new cylinder and piston kit. and crank and seals bearings etc. you can tell its decent compression when you pull it. as good if not better than the one that fires up. i never use the decompressor. i suppose thats why i go through so many pull cords

 

[aljaxon]

The spark on modern 2 stroke saws can be very hard to see. They don't have the nice big fat spark of older machines.
You also need to spin them over quite quickly.
I found that on a few machines I've been working on lately so I bought a spark plug tester.

https://www.amazon.co.uk/Sealey-SEA...hvtargid=pla-2281435177338&psc=1&gad_source=1

are they any good? at £5.99 its a no brainer if so. bought one anyway thanks for link.

 

[aljaxon]

i m wondering whether to get my wife to assist me by putting her tongue on the plug to check for a spark.......
maybe not. were gonna try her pulling and me watching closely in the dark. might even film it. if the spark is weak then i could have missed it looking for the big fat one you get at 200 rpm.

 

[JOEPRO]

i m wondering whether to get my wife to assist me by putting her tongue on the plug to check for a spark.......
maybe not. were gonna try her pulling and me watching closely in the dark. might even film it. if the spark is weak then i could have missed it looking for the big fat one you get at 200 rpm.

Swap the coil over from your good working saw. Only takes a couple of minutes

 

[aljaxon]

Swap the coil over from your good working saw. Only takes a couple of minutes

did that during the testing phase yesterday. both did the same. no spark uless you are doing 200 rpm.

 

[addjunkie]

did that during the testing phase yesterday. both did the same. no spark uless you are doing 200 rpm.

If you like a peaceful quiet life….buy a battery saw!

 

[JOEPRO]

did that during the testing phase yesterday. both did the same. no spark uless you are doing 200 rpm.

Swap the flywheel too then could be weak magnets. Rare but it happens..

Also - pur a compression tester on the engine as already mentioned. Guessing doesn't work.

 

[aljaxon]

thanks for all the replies help and advice.
i just got wife to pull while i observed and no spark on either. i was earthing the plug using some 1mm tig wire to the cylinder
as a last resort i used a screwdriver to the plug hole and to the plug and on the working machine got a spark every rotation. tried it on non worker and i only got a spark every third or 4th pull. so i assume coil or flywheel is defunct. or ht or ht lead.

just for kicks i tried to start the non starter despite having no airfilters or cover fitted. and as i locked the trigger i noticed it didnt stay locked but dropped down to near but not quite tickover level. so i used a tie wrap to get it where it should be and hey presto started first pull. took choke off and it continured to run for 30 seconds until i killed it to fit filter.

so the error was maybe the tig wire not grounding it fully until the spark was juicy enough? and it has been sparking all along.
and is simply the trigger assembly needs looking at.

but you would think 1mm tig wire is conductive enough surely?
im off to ebay to buy some big plug sized crocodile clips and make an earthing lead.

 

[aljaxon]

If you like a peaceful quiet life….buy a battery saw!

cant beat a screaming 2 stroke.

 

[aljaxon]

Swap the flywheel too then could be weak magnets. Rare but it happens..

Also - pur a compression tester on the engine as already mentioned. Guessing doesn't work.

yeah i tried both coils on either flywheel. no spark unless you were doing 200 rpm. but thats with tig wire which ive now discovered wasnt earthing it properly.

no need to check compression. it was as healthy as the starter. i was starting to think maybe ive fitted piston wrong way around. arrow to exhaust. on mobylettes the arrow points to inlet. prob the only odd one out but you never know what stihls policy is?

anyway both machines now work. just need some fettling with the trigger lock mechanism.