Chainsaw help

[Jacob Dryer]

My buddy loaned my his mom's chainsaw which has been buried in her shed for at least 3 years now. I managed to get it to fire up but it won't stay running. The only reason it even started at all was because I sprayed some carb cleaner into it. So I'm sure it was only running on the cleaner.



Is the oil/gas mix the same for all chainsaws and if so what is the ratio? I can get the model if that will help.



I don't know much about 4 strokes let alone 2 strokes so I'm really lost

I'm sure the gas/oil is old so I was going to change that first and go from there.

 

[zaffo oxnard]

The passages in these small gass engines are very small. A bit if varnish or gummy oil will stop it cold. Try draining the tank, filling with a ounce or two of seafoam / carb cleaner, etc. priming like mad, pull it 20 or 30 times and let it sit for an hour. Drain this. Pour in an ounce of fresh gasiline and try and start. If nothing, you will likely have to take the carb appart and clean it (brush and carb cleaner) don;t tear any gaskets and make sure you get a vey fine needle to clean out the tiny idle and main jet. DO NOT BREAK THE NEEDLE OFF in a jet!



Anything that is not used often and has a tiny carb (motorcycle, jet ski, generator, etc) that will not start - I clean the carb. Only once in 30 years was it a bad spark plug.

 

[Fred]

And for the gas/oil mixture question, use Promix, or some other 'one size fits all' oil and you don't have to worry what it calls for.

 

[Aaron Yarbough]

+1 on Tony's suggestions, try the seafoam first and if that doesn't work you will have to disassemble the carb and cleaning the needles/jets which is not complicated. You have a 95% chance of it firing up after reassembling the carb. If it's been sitting for 3yrs, I highly suggest installing a new spark plug as well.......

 

[Wes Davis]

Yep dirty carb from sitting. Clean carb and air filter, lube chain, new gas and oil mix and will probably run like brand new.

 

[EddieS'04]

My brother works on small engines as a bussines. He has told me the worst problem with 2cycle motors, is that the fuel pump in the carb will dry out from sitting. The other is gunk from old gas left in them. My bet would be the fuel pump diapfram has dried out or cracked...

 

[Jacob Dryer]

Well I don't know what the fuel pump diaphram is/looks like.



It's still not running. Doesn't seem to be getting any gas, it will fire everytime I spray carb cleaner directly in and thats it then it dies.



I took apart the carb, cleaned all the parts with cleaner, and sprayed it out to make sure everything seems to be clear of any blockage.



So it does sound like Fast Eddie is right, but I don't know how to fix it.



Other input?

 

[Gavin Allan]

Fuel pump is on the side of the carburetor, opposite of the fuel metering side (with the inlet needle).



The diaphrams get stiff and do not pump well after sitting with old fuel in it. You need to disassemble and clean the carb again, but this time replace the parts included in the carb kit. Not too difficult-- but you do need to ensure that you get the gaskets and diaphrams put back in the correct sequence. Also, you will have to adjust the level of the lever that operates the inlet needle before reassembling it.



Your fuel filter may also be clogged. Get a piece of wire with a hook bent on the end and pull it out of the fuel tank and change it. If the fuel like is gummy and soft, change it too.



Two-cycle engines don't tolerate vacuum leaks very well. Make sure any vacuum lines, gaskets, and rubber bellows (like between the carb and the engine) are in good shape. Also, if crankshaft seals are worn and leaky, this will cause trouble.



Use fresh fuel mix-- anything older than three months should not be used in two-cycle engines. If you keep the fuel fresh, and be sure to drain and run out the fuel when done using it, two cycle engines will run well for a long time.

 

[Aaron Yarbough]

When you took the carb apart, were you able to remove the needle and jets to clean the orifices? The jet usually unscrew from the center of the carb........

 

[Brian Curry]

buy a new carb kit (about $6) dismantle carb,soak in Kleen flow combustion chamber cleaner , about 20 min. Assemble, set fuel mixture screws about 1 turn out from seated.

 

[Gavin Allan]

Don't forget to replace the inlet valve seat. Most are rubber-- and it easiest to blow them out with compressed air in the fuel inlet. A properly sized blunt punch can be used to firmly install the new seat. Be sure the beveled "seat" side is toward the needle valve.



I haven't seen removable jets in chainsaw carburetors. The older ones had removable/adjustable mixture screws.



Many chainsaw carbs have "welch" plugs that need to be removed to clean the orifices. New ones come in the carb kit. After cleaning, you can just press them in to the appropriate receptical and expand them slightly by tapping them with a large blunt punch or other flat surface.

 

[tom prudhomme]

If the chain saw is needed for routine trimming under 7-9", go with an electric one for under $70.

 

[Richard L]

Chainsaws use two cycle engine that require mixing the gas with 2 stroke oile. If the saw is put up with fuel in the system it will gum up the works real bad.



You might want to try some carb cleaner and also run sum Fuel Injector cleaner mixed in with the gas/oil mixture. If that does not work you will probably have to remove the carb and clean it with solvent.



Another problem can be old fuel. When fuel sits it goes stale and some of the components evaporate making the fuel thicker. If you don't empty the tank and burn all the fuel before you but the saw up for the winter, you should at the very least use a fuel stabilizer like Stabil. I use some Homelite 2-stroke oil that includes a fuel stabilizer, so you should see about using that.



Most chainsaws use about a 15:1 gas/oil mix but I have seen some that will use 12:1 and up to 20:1. If you don't know, or it's not printed on the gas cap or on the saw, then you can probably safely use a 15:1 or 16:1 ratio



Another problem with chainsaws is the reed valves (little flapper doors) They tend to need replacing every few years.



...Rich

 

[Gavin Allan]

My Stihl uses a 40:1 fuel/oil mix ratio. I'd read the manual, check the manufacturer's website, or ask a dealer before I'd assume that all saws use a certain mix ratio.



Also, try to use fresh unleaded regular without any alcohol. Even the 90% gas/10% ethanol blends have been known to screw up two-cycle engines. Premium fuel will also cause problems for two-cycles (causes them to run hotter, I believe). In any case, use what the manufacturer recommends.



Reed valves (if the saw even has them-- most have ported intakes) should last for years if the air filter is maintained properly. Exhaust ports and spark arrestors should be checked and carefully cleaned every 50 hours or so.

 

[Jacob Dryer]

Well I haven't had much of a chance to mess with it any more. The carb was definiatly gummed up, but it's going to be a few more days before I get to look at it some more.



Thanks for all the input, I'll keep you posted