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I'm working on a 14" Echo chain saw that someone had thrown away.

I discovered after almost complete disassemble that the reason it was locked up was because the flywheel had crashed into the magneto.

I finally got it all put back together, but it won't run.
It has good spark, it has good compression, and the carb looked very clean.
I can't get the fuel to ignite.
I even removed the plug, and put some fuel right into the cylinder, and nothing???
I removed the muffler, and still nothing.

Now I'm wondering, did I put the piston in backwards?
Perhaps it has compression, but not at the right time?

Does it sound like that could be the problem?

Thanks,
Gary

Bumb,
Has anyone experienced something like this before?

Would putting the piston in backward create such a problem?

I removed the muffler to see the piston action, but couldn't tell by looking thru such a small hole.

Do I have to remove the cylinder, and if so, how does the piston orient to the intake port and or exhaust port? Are there markings, relief spaces on top?

Echo is a great chain saw... I've had one for a lot of years... But I have never had the occasion to take it apart to the point you have... I don't follow what you are referring to about the piston being backwards??

Hope someone may have an Idea whats up... :smile:KennyV

While trying to find the problem with the locked up flywheel, I thought I would have to remove the clutch. It was attached to the crankshaft, which holds the piston as well. In that effort, I removed the piston from the rod, without paying attantion to it's orientation. After that, I discovered the real problem, fixed that, but now I wonder can the piston be put in backwards? As in rotated 180 degrees from where it should be?

Thanks for the feedback, and I'll post back if I can solve the problem.

Gary

I did find the answer.

I found a DOnyboy73 video on You Tube, where he is rebuilding a piston on a Husqvarna chain saw.

He shows that there is an arrow on top of the piston, and that arrow is supposed to point toward the exhaust port.

I will hopefully tear that back down tomorrow, and perhaps I can post back that it is fixed.

Gary

Gary.. Great, YouTube has almost EveryThing...
While you have it apart... click some pictures while you can... let some of us see the insides that don't get exposed to sunlight often... :smile::smile:KennyV

Donboy73 has a video series on this chainsaw and one has a piston rebuild on utube hope this helps

If the piston is reversed then that is definitely the problem. On a two stroke the piston acts as the valve for letting in duel/air and letting out exhaust. If it is backwards the ports in the cylinder wall won't line up right on the piston.

Here are a few pics.

I re-installed the piston, but couldn't see any arrow, and couldn't tell one end from the other.

I reversed the pistons orientation from my previous install; re-assembled it, but now it has kickback, as though key is bad on the flywheel.

I'll have to tear it back apart, at least the flywheel.

Well, at least I'm gaining experience........

Gary

That piston looks pretty symmetrical. It may not matter how it goes in. Keep plugging away at it. You will get it. A two stroke is a very simple engine.

More research, if the opening gap on the ring is on the exhaust port side, it can apparently get stuck in the port and break the ring. I'll have to teat it down again this weekend.

In the mean time, today I picked up an Electric Mac chainsaw that someone threw away.

I have an Echo CS 450 that my buddy fell through a pool cover and into the water with it. I dried it all out and of course changed the fluids. Blew it all out put it back together but it won't run. I can get it to idle rough and randomly it will rev up like the saw of old. The only thing I can think of is that the coil must have some intermittant problem now after falling and being submerged. Anybody have any suggestions I would appreciate it. This saw is only a couple months old.

Papaw50 said:

Here are a few pics.

I re-installed the piston, but couldn't see any arrow, and couldn't tell one end from the other.

I reversed the pistons orientation from my previous install; re-assembled it, but now it has kickback, as though key is bad on the flywheel.

I'll have to tear it back apart, at least the flywheel.

Well, at least I'm gaining experience........

Gary

Click to expand...

The piston only goes in one way, usually there is a mark or arrow on top of the piston direction towards the exhaust port, also the ring/rings should be oppsite the exhaust port as well to eliminate catching on the port, did you have a broken flywheel key? also change plug even though you have spark out if cylinder you may not have it in the cylinder.

My guess is since the engine was stopped by the flywheel jamming on the (loose?) ign coil, the running engine sheared the key.