026 wont run when it gets to hot

[mrdiesel]

Hey all,

I have a 026 fixeruperer which i have been tinkering with giving me some strange problems. Ive not come across this problem before.

When its cold it starts as no worries, when its hot it starts no worries, but when its hot if you do a long cut at full rpm it then the revs start to drop until it stalls after about a minute. As soon as the revs start to drop i remove it from the cut and try to get the revs up but it still dies. I have swapped carbies and the boot from a working 026 as well as replacing the ignition lead and plug but still no joy.

When it dies it sounds like its flooding. It generally wont start again until its cold. The stupid thing is i can start it from cold and it will idle on the ground for 15 minutes without a hiccup.

Looking for idea of what to check. Im wondering if the potted ignition gadget near the flywheel could be faulty

Cheers all

 

[Magnus]

I think it could be something else worth checking.
Out with plug and muffler and check piston and rings for wear or damages.
Take a rod and push on the ring, if it seats low in piston it is too worn.

 

[Husabud]

Replace the coil. My 026 killed two before finally eating a piston last week.

 

[Al Smith]

Often times badly worn seals will not show up until a saw is in a long cut.It's just a fact that the buna-n material will become hardened by usage and heat and given enough time they will fail .As it heats up during a long cut it lacks the resiliancy to expand and shrink as it did when the seal was fresh .--it's kind of like us old farts ,just not as spry as a cat any more ---.

 

[sawinredneck]

Coil, seals and tank vent are areas to check. Get it hot again until it dies. Take the gas cap off and listen for a hiss when you remove it. If it hisses its vapor locking and needs a tank vent. No hiss, check for spark. No spark, bad coil, spark, time for seals.
Check the simple things first.

 

[woodworkingboy]

I find that sometimes it can be a bit difficult to determine a weak spark, one that won't get it running, from a proper spark. They say a fat blue spark is good, but good sparks vary somewhat with different saws. An ignition problem can be fits to diagnose sometimes without the proper tester when the coil is still hot, better to throw a good one on there to check the results. Some peculiarities too, like a way richer setting on the low speed can get a poor spark saw at least running. Makes you think it's not the Some problem in the plug wire can be a possibility, wiggle it around when changing the plug and it starts up. The devil is messin with ya.....

 

[mrdiesel]

It looks like the fuel tank vent was causing the problem. If i run the saw on its side with the fuel cap loose it will start and idle after previously stalling. I haven't pulled it apart yet but im hoping is a easy and cheap part to replace,

Cheers gents

 

[woodworkingboy]

Carburetors often behave a bit differently when the saw is on it's side. It's the way that they are built. Something to keep in mind.

 

[mrdiesel]

Sweet, ill heat the saw up and leave the fuel cap tight then try it on the side

 

[Magnus]

If fuel vent is not working it will not let air in to replace the fuel taken out.
If fuel is taken out and no air get in the pump can not deliver and engine stop regardless of rpm or position.
Tilting it to side and let it sit there is not a issue, but will take a while if tank is larger. Enough fuel must be extracted to build a negative pressure high enough to prevent pump from doing its thing.
If it stops it will be hard to start as it can't get fuel until pressure is neutral or positive again.
Pressure in tank often flex and is never constant. Most important is that there is positive and neutral pressure minimum 2/3 of the time.
You can build pressure in tank by shifting saw from side to side on the bench for example. Makes new saws easier to get fuel up and run.
Saves 4-5 pulls in general on a saw.

If it changes rpm when it change position it is often a air leak that cause the change in rpm, usually it races before stop.
Side to side indicate crank seals, tilt front and it indicate cylinder casket, carb boot etc... Not 100% sure diagnostic's, but good enough to know if more time on bench is needed.

 

[rskybiz]

Magnus, Excellent post

 

[woodworkingboy]

Magnus's information about shifting saws side to side to get them started quicker, is a very valuable thing to know, I have concluded. Whoever said that pulling a starter rope to drop the level of chain oil in the tank when you have overfilled, to not have it run out when you put on the cap, I am still wondering why anyone would say that when it doesn't work? Maybe if you pulled it for an hour or so.....

 

[sierratree]

I agree. If the engine speed, at idle, changes when you till the saw up or down, or roll from side to side (this is call a "roll - out test") then strong possibility it's the crank seals. Also, there might be a pinhole in the flexible fuel line from the tank to the carb, which lets in air. Sometimes the pinhole in the line is in the tank ( usually caused when the operator uses a multi-tool, or some sharp object to pull out the line to check the fuel filter ), or the fuel line wears in a pin hole from the side of the casing where it leaves the fuel tank and is routed to the carb.

:roll:

 

[Magnus]

Whoever said that pulling a starter rope to drop the level of chain oil in the tank when you have overfilled, to not have it run out when you put on the cap, I am still wondering why anyone would say that when it doesn't work? Maybe if you pulled it for an hour or so.....

What saw would this be regarded for and why would pulling it make a difference?

 

[woodworkingboy]

The instructions were not saw specific. I just figured it would work if someone said it would. I'm a trusting sort. Without the pump functioning, it can't work. Someone at the treehouse said that. Anyway, no bother, I'll just continue to overfill.

 

[Magnus]

I think this could be about those 200's and flippy caps.
If so it is when they are over filled. I noticed that once on one here, and as I was to tip out the excessive I tilted it a bit and it bubbled. Problem solved.
There must be a compartment of air in them, I guess that was filled as I shifted it.

 

[Burnham]

I have noted that on my 200's.

 

[stig]

Yep, you can burp them like a baby.

 

[Burnham]

 

[Marc-Antoine]

With the ms200T, the overfilling is really annoying because it makes the flippy cap doesn't work properly and the spill out (part of it at least) goes directly under the starter cover, soaks the ignition module and makes there a mess with the wood dust/chips.

I burp my 200 each time I fill it, then fill it again to level (with care this time).
I do that to keep enough oil at the end of the gas tank. The baby burp can be pretty big, like 1/4 or 1/3 of the oil tank, and I fear to run out of oil too soon.

 

[mrdiesel]

Cheers all, it ended up being the fuel vent, i got the saw hot and cracked the cap. Once the air rushed in the saw restarted and ran faultlessly at any angle.

Ill be buggered if i can explain this but if the tank is full it stalls quicker when hot but if the tank is only a quarter full it doesn't seem to stall as much.

 

[woodworkingboy]

Good that you got it figured out. It's like Magnus said, the air has to displace the departed gas. More air in there to do that somewhat with a partially filled tank.

 

[Magnus]

Why did you crack the cap?

 

[woodworkingboy]

Magnus, "Cracked the cap", means that he opened it a small amount.

 

[Magnus]

Ah...
Ok, i get it now.