How to prep used cylinder for new piston.

[272super]

if it was wasnt running before it could be carb diaphram but its quite possible if it ran to lean when it was super hot could have melted the seals...a leak/pressure test on the crankcase would let you know on bikes I just made 2 plates one for the exhaust one for the intake on the intake side drill hole put in a tire/shradder valve pump some air into with a pressure gauge im not sure what max pressure would be but maybe between 10-20 psi make sure piston is at tdc or not blocking the intake port.

Pressure should be 6-7 psi.

 

[MrGiggles]

well if its sealed up it should hold air for a very long time if it dont your crankcase is sucking "extra" air from somewhere and extra air mixed with the fuel makes it more lean you said it was sitting for a good while...depending on where it was sitting and the temp and conditions you might have a dry rotted seal or bad gasket when you leak test it most of the time your going to hear the air comeing out somewhere and if you dont use some soapy water if its leaking air im sure you will find it rather quickly if you pump air into it and it has a small leak put more pressue in it until you find it just think about all those times you fixed your bikes innertube

Pressure should be 6-7 psi.

I will give that a shot tomorrow hopefully.

We made sure the line was clear and not pinched or cracked. Same stuff.

 

[MrGiggles]

I did the pressure test and there was a leak on the intake boot but that's because it was on wrong. We tore the whole thing down anyway and replaced the crankcase gasket, the crank bearings all looked fine. We also flipped the piston around just to see if it helped. Which way should the arrow on the piston point?

We put it all back together and it started and revved good for a second and went back to doing the same crap again. What the heck? The only thing I think might be wrong is the carb needs to be rebuilt. Possible?

 

[angelo c]

Arrow always points to the EXHAUST. Should be the natural flow of air is how I remember it. air doesn't come IN the exhaust....
A

I'm betting on your LA jet being either worn or joggled up with some crud. take it apart again and make sure all the passages are free.

 

[pepsifreak28]

could be

could be the low jet like angelo said might also be a bad carb diaphram some people think the diaphram is part of the card technicly it is but the carb has a build in fuel pump.. so one side pumps it in and the other side meters it so if there is a pin hole in the diaphram it wont pull up fuel the arrow points to the exhaust always it sounds like its not getting fuel did the leak test hold air? besides the intake boot? what i use to do to test the pump diaphram is take a hose and on the engine side of the card is a hole or the pulse line hole stick one eng of those hose in your mouth and push the hose up aginst that hole and blow in lightly if its got a hole it will leak a little

here is the site that gives you the walkthough with diaphram carbs even though walbro there allmost the same..
http://tech.flygsw.org/walbro_tuneup.htm

 

[MrGiggles]

could be the low jet like angelo said might also be a bad carb diaphram some people think the diaphram is part of the card technicly it is but the carb has a build in fuel pump.. so one side pumps it in and the other side meters it so if there is a pin hole in the diaphram it wont pull up fuel the arrow points to the exhaust always it sounds like its not getting fuel did the leak test hold air? besides the intake boot? what i use to do to test the pump diaphram is take a hose and on the engine side of the card is a hole or the pulse line hole stick one eng of those hose in your mouth and push the hose up aginst that hole and blow in lightly if its got a hole it will leak a little

here is the site that gives you the walkthough with diaphram carbs even though walbro there allmost the same..
http://tech.flygsw.org/walbro_tuneup.htm

It didn't hold air because the plastic mount for the carb was slightly pushed out causing the leak. I didn't hear any other leaks though.

I will try that tomorrow if all goes well.

 

[MrGiggles]

I just realized it can't be a carb problem because we swapped the carb from the running 50 special and it did the same thing. Would an intake leak cause this? I'm going to go over the fuel lines again today.

 

[pepsifreak28]

re carb

it very well could be as you said it idles but as soon as you go to throttle it it dies out it has to be something to do with the intake or carb or fuel one thing you might try and do is use an old tank off something and hold it above the saw to gravity feed the carb if it still does it then you would know its not fuel lines or something along those lines product of elimination thats about how you fix about anything just be patient I have had things stump me for a long time and i leave it alone for a few days and it just hits me

 

[angelo c]

I have had things stump me for a long time and i leave it alone for a few days and it just hits me

You just described my wife to a "T"....she stumps me, leaves me alone for a few days, then just hits me.

 

[MrGiggles]

it very well could be as you said it idles but as soon as you go to throttle it it dies out it has to be something to do with the intake or carb or fuel one thing you might try and do is use an old tank off something and hold it above the saw to gravity feed the carb if it still does it then you would know its not fuel lines or something along those lines product of elimination thats about how you fix about anything just be patient I have had things stump me for a long time and i leave it alone for a few days and it just hits me

Don't have any spare tanks with that size fuel fitting.

I've pretty much eliminated everything accept the intake tube. I changed the fuel line today and it didn't help anything. It won't even idle anymore.

 

[MrGiggles]

Where is the fuel tank on these things?

I think that is the problem. With the gas cap in, if I blow in the fuel line the tank doesn't vent and it spits fuel back at me for a second. With the cap off air comes through the line and the gas bubbles like it should.

 

[pepsifreak28]

tanks

the one close to the throttle handle is the gas the one on the front is the oil the gas tank dont have really a super vent they dont suck enough fuel to really need a vent vent allthough they do have one but since the saw is tipped sidways and such a vent would leak fuel so the vent is very minimal if it does your husky is like my 266xp husky are you sure your putting the fuel in the right tank?
if you could take some pictures and post them and let us take a look at what your working with might help..

 

[MrGiggles]

the one close to the throttle handle is the gas the one on the front is the oil the gas tank dont have really a super vent they dont suck enough fuel to really need a vent vent allthough they do have one but since the saw is tipped sidways and such a vent would leak fuel so the vent is very minimal if it does your husky is like my 266xp husky are you sure your putting the fuel in the right tank?
if you could take some pictures and post them and let us take a look at what your working with might help..

I meant to say tank vent. I know where the gas a fuel tanks are.

I did find the vent and took it out. I poked out the little piece of plugged foam and stuck in a new piece of gray foam. The tank is venting correctly now.

The saw still won't rev at all though. Idle sucks as well.

 

[pepsifreak28]

spark plug

what does the spark plug look like? does it smoke a lot? when it is running?

 

[MrGiggles]

what does the spark plug look like? does it smoke a lot? when it is running?

Only when it first starts up from being torn down. Other than not not much more than a normal 2 stroke.

The spark is perfect. We even swapped in a known working coil and it didn't help.

 

[angelo c]

have you pressure and vac tested yet ?

http://arboristsite.com/showthread.php?t=56907

Also a search on mity vac would pull up a few pages as well.

 

[MrGiggles]

Well, I have no idea what I did, but it's running good now. Here's how it went down. The other night after I fixed the vent it was doing the same crap. In the process of pulling and pulling the recoil lost tension. I fixed that today, started it up, same crap. So I let it idle while I went into the shop, and it stalled. Surprise surprise. I restarted, and boom it runs like a dream. Adjusted the carb and it cuts great. I now need a clutch bearing, and two bar adjustment screws.

Thanks for the help.

 

[pepsifreak28]

Glad you got your saw going I was loseing sleep over it