Ts410, sorry another

[Mike the builder]

New plug, piston, rings and cylinder fitted. Also replaced all filters and carb. Fires up and starts briefly but I’m waiting a new start switch before I assemble it fully. I think the wiring or the switch is breaking down and shorting out after a few seconds. If I pull the unit over with plug out it sparks fior first couple of times I pull it over 5hen the spark stops, if I wait a few secs and try again it again sparks but only for first couple of pulls. Dis connect it totally and it fires up etc but with no covers on its tricky to keep it running. Look like we are on the home stretch now. Thx 

[Mike the builder]

Before anyone asks, I did disconnect the start stop right at the beginning of this project to check it wasn’t a problem

[ChrisNewport]

Disconnect the 2 switch wires from the coil and use the choke to shut it off if it starts and runs, this will tell you if the switch is faulty. We'll never know what the origional problem was if youve replaced the p+c and carb in one go. Nearly there though.

[Mike the builder]

I might yet swap the old carb back in to see what happens, but not 7ntilmthe switch is done. 

[Darkslider]

On 10/10/2021 at 22:24, spudulike said:

A compression gauge for small engines will typically have an extremely light gauge schrader valve mounted in the part you screw in to the engine. The valve type is chosen because you can only spin the engine over for a few revolutions unlike a car engine that you can hold on the starter for a few seconds.

The valve being close to the engine stops the tube acting as part of the volume of the combustion chamber and lowering the compression.

Car type compression gauges can have bicycle type schrader valves in them and will give lower readings than small engine gauges.

The Gunson "HiGauge" is one that works although I modified mine to take Presta valves as I was destroying the schrader ones with modified engines making 200psi+

The rings.....put them in the cylinder, make sure they are nice and square, measure the gap and it should be 7-15 thou, much more and the compression will suffer badly.

The light part of the cylinder ADW mentions may well be the Nikasil plating worn through - try scratching with a craft knife and if it scratches on the light part, it is through to the aluminium.

If you have another of these machines, just pull them over slowly and compare them. 75 or even 105 psi is pretty low. An engine in good condition will make 170psi.

This is my Gunson comp tester, would you say this should be pretty accurate on smaller saws?

[spudulike]

That is the Gunson HiGuage and is fine on saws. If you have some high compression engines, you can rupture the schrader valve which causes it to leak but the gauge is fine as the valve is in the very end of the union that screws into the engine and the schrader valve is very lightly sprung. 

[spudulike]

On the Stone Cutter, you started by saying the spark was no problem but now it is playing up and it sounds like you are on your third coil!!!

So, have you tried closing the coil to flywheel gap right down using a piece of thinner card than a business card - perhaps a magazine cover thickness - if the gap is too large, you can get a spark that lasts for a short time after starting. I have sorted many weak magnets and dodgy sparkers in this way.

The fact the coil sparks for only a few pulls can be a sign of a faulty coil. I have seen this before on Japanese strimmers.  You can bend the end electrode out at a 45 degree angle on an old spark plug to make a rudimentary spark tester.

You can remove the kill wire from the coil to eliminate the kill switch and associated wiring. This switch actually CONNECTS the coil to earth so unless the switch is somehow closing, it is unlikely to be the switch as most fail to connect and the symptom is the machine can't be turned off rather than what you have. Sometimes kill wires chafe and you can get a faulty spark hence the comment about disconnecting the kill wire from the coil.

Lastly, are these OEM coils as some of the Chinese ones are pretty Micky Mouse!!

 

 

[Mike the builder]

I’ve gauged the gap between the coil and the Manet using a piece of paper folded once. 
As for the kill switch, engine didn’t try to start with it connected and in run position, did try to start the kill switch gone. Can only be switch or wiring. Well for that fault. 

[Mike the builder]

Next instalment, I want to cry.

new, piston, rings, cylinder, spark plug, ht lead, ignition coil, stop start switch, complete carb and both filters.

yeah it started ok, smoked well for first 30secs due to oil assembling. Left it ticking over for 30secs and stopped to go for dinner. 
now it won’t start again, plug wet, cleaned pug, starks well, compression still good. Changed fuel. 
doesn’t even seem to be trying, not even kicking back a bit. 
now I’m really stuck. 

[Mike the builder]

Pt2

tried again this morning, 12-15hrs later. 20+ pulls and quite a bit of engine trying and stopping,  It’s starts and ticks over, revs ok. Bit jumpy on tickover. 
no idea if it will start again in a few hours though.