The MS 660 is getting stuborn again with me

[alsayyed]

 Hello fellows again the MS 660 by Stihl dose want to start again. I have purchased new carb, new plug, fresh gasoline and piston good, it is got be stubborn. I have removed the plug and fired the engine I saw spark is coming from the plug.
I am very tired with this machine. Can somebody who run into these situation before give little push in solving this dilemma?

[liketocut]

Dose it run good after it starts?

I'm kind of new at this.....but I do have two 066's and a 660

Fule filter, fule hose, impulse hose and tank vent are a few
thinks to check.

Tank vent should just let air in, not out and seems to help
them start when pressure builds in tank (helps push fuel to carb)
or if it won't let air in tank is bad to.

[joe_indi]

I think this is the same 660 about which you had posted earlier.
If you recall, I had asked you to check the flywheel.
In the past 4 months I have replaced 2 more flywheels on 660s.The center which goes onto the crankshaft twists whereby the ignition timing gets retarded.
When this happens starting is difficult. If at all it starts the saw does not rev up fully.It has very low power.
Symptoms are in someways similar to when the portion of the piston between both the rings break up and the engine runs without much compression. ]

Joe

[alsayyed]

 I appreciate your answers for both of you. The machine start and stop I mean I can hear the engine is running but for few seconds then stops. I have changed the fuel cap and fuel filter and carb from ms 650 into the ms 660 and still having hard time starting it. I have checked the flywheel it seems to me ok spark is coming into the plug I do not see anything wrong here. This is confusing.

[rebocardo]

When my Husky 365 was acting weird and no power, would die in a cut, it was the compression relief valve being clogged with carbon.

[jokers]

I have checked the flywheel it seems to me ok spark is coming into the plug I do not see anything wrong here. This is confusing.

Alsayed, unless you are absoulutely sure that the flywheel hasn`t moved at all you might be misleading yourself by simply verifying that you have spark. You could have spark but have it at the wrong time as joe_indi is saying.

Forgive me for asking such an elementary question Alsayed, but is your air filter plugged? How about the quality of your gas? I`ve seen saws with stuck piston rings from deposits from poor gas. Low compression and the saws would eventually not run.

[joe_indi]

A damaged flywheel will deliver a spark.The question is when? Probably when the piston has crossed TDC and starts the downward stroke.

I have posted images have a look.
Also switch the ignition module with that of your 650, that too could be the cause(Maybe)

Joe