Put new pistion cylinder on husqvarna50 chainsaw done conpression test reads only 70psi saw starts not very good power what eles can cause bad compression apart from pistion rings

Check the filter by blowing through it with your mouth, if there is any resistance replace it. You should replace the fuel filter at least once a year. Make sure to replace with the all white Porex filter as any other filter is only half as good. It is a false economy to re-use a fuel filter. When the saw is left up for any period of time the fuel dries out leaving only a kind of lacquer partially blocking the inlet, which takes a while to dissolve and there is always the chance that the reduction in fuel supply will make the saw run weak and risk it overheating and seizing. You have just spent a lot on the cylinder and piston, don't wreck them by using an old filter.
If the saw will still not pick up after you have fitted the new filter just open/unscrew the high needle mixture screw (the one furthest away from the cylinder) an 1/8th of a turn which is 45 degrees and see if that helps. Then set the carburettor in the way that I have described on one of my other posts here: http://www.fixya.com/answer/answerpageslideview.aspx?ctg=328&fml=0&brd=0&thid=25319159
Jim

Replace the condenser. You'll still get spark with a week or dead condenser, but no fire under compression.

If all parts are installed properly, then the problem has to be in the cylinder / compression. Have the saw checked for compression and have a pressure / vacuum test done to the saw.

Sorry but the only true way is to put the unit on the machine, set the air gap to 0.3mm diss connect any wires on the unit that go to the switch, assemble the starter, use a new plug or spark tester with a wide gap, earth well against the cylinder, crank the engine as if you were going to start it, if there is a spark the unit is ok, if not then its bad. There are expensive testers on the market, but if the unit does not spark on the saw what is the point of testing it.

sure sounds like you did it all.
Was the Plug wet with gas when you took it out to fuel it directly? I would take the plug back out, blow out or let the Cylinder totally dry. Then spray a bit of Starter fluid in the carb and see if you get life.
Old gas left in a saw is a Carburetor killer. The paper components in these carbs can not stand the new 10% ethanol gas.

The 235 in my opinion was not a good saw, there were numerous issues with it, the mai bearing on the drive has a habbit of the bearing cage breaking away, this travels up the side of the pistion and nips the ring in on the transpher port side, they then refuse to start or rattle badlt if they do start, the only cure is to strip the whole saw down to check the condition of the piston,cylinder and bearing cage, let me know if you need help pulling it apart, i have done loads.

70psi compression indicates it's rebuild time; the compression should be double that. You can confirm what the compression should be with good rings by putting a few drops of oil in the spark plug hole and testing compression "wet". That figure will be what a new saw would have.

Is this you?
http://www.fixya.com/support/t3950480-no_spark_changed_ignltion_modual_no
If all this has been done it must be the flywheel or the ignition unit. I might try the local Husky dealer just to maintain my sanity. He can swap the ignition unit into a known good saw in a couple of minutes and verify good or bad. He might even be willing to honor the Husky warranty on a bad coil. Please reply with the outcome.
Lou

It’s possible the ignition module has gone bad do this first. If it’s good and the saw will start it may quit when it gets hot. I don’t think that is true but keep it mind. If it does suddenly just quit running, immediately test the coil before it can cool.
Ignition Coil Test
SmallEng.com
http://www.youtube.com/watch?v=L7WNBDRG4C4
You may need to use a jumper wire between the threaded part of the plug and the cooling fins. You don’t have to bend up the electrode.

You refueled it and it wouldn’t start? Any chance you put straight gas in it?
Was this saw perhaps operated without oil mixed with the fuel?
· Remove the spark plug wire and plug.
· Remove the muffler, hold a light at the plug hole and inspect the cylinder through the exhaust port. Is it smooth and shiny or does it appear speckled with dull gray spots or smears?
· Pull the starter slowly, inspect the piston as it rises and falls. Is it a dull gray without scratches and gouges?
· Hold the light at the exhaust port and inspect the cylinder, above the exhaust port, through the spark plug hole. Is it shiny and smooth or speckled with gray spots or smears?
Any spots or smears on the cylinder or deep scratches and gouges in the piston indicate the saw was operated in a lean condition. Repair of this on a home owner quality saw often exceeds replacement cost. A repair estimate by the independent saw shop should be considered.

It might be a bad fuel vent? Not likely if you just refueled, more likely if it staves after running for a few minutes. Loosen fuel cap when it starts to sputter (rotate saw if necessary) if it picks up again bad vent.

Most likely it was flooded. A flooded saw can be extremely difficult to restart. Did you try to choke a hot saw? That is almost guaranteed to cause it to flood.
Start Procedure
Cold:

1. Ignition on/off to on
2. Set compression release – optional step even if saw is equipped with a compression release
3. Pull (close) choke, set fast idle (done when choke closed on some saws); pull starter and listen for an attempt to start. once heard (usually two pulls, if not heard after 6 pulls stop! Something is wrong)
4. Set compression release – optional step even if saw is equipped with a compression release
5. Push (open) choke pull starter until it starts. (usually first pull)

Warm:

1. Ignition on/off to on
2. Set compression release – optional step even if saw is equipped with a compression release
3. Pull (close) choke, set fast idle (done when choke closed on some saws) - Don’t pull with choke closed.
4. Push (open) choke, pull starter until it starts. (usually first pull)

Hope this helps
Lou
If it was flooded it should start easily if it has been sitting for a couple of days. It could still be coil or vent problem.

The damage may have been done before this tank, or can of gas, Does anyone else have access to saw?
Only about 3 things can cause damage,
1, dirt or foreign object entering cylinder.
2. Unmixed gas or old gas the will cause gumming of rings.
3. overheating of cylinder due to clogged air fins.
Ok there probably a couple more but that is main things.
Put a new Kit in it and keep it away from everyone else. Or have your friend replace only what is needed if the cyl cant be saved.
Saws should have a trigger lock so no-one can borrow them.
Bill Czerkie