Chainsaw, fuel problems, inexperience......

[Mith]

I got this chainsaw with scored barrel and piston. It is all fixed up and has compression with new rings and piston.
The problem is;
I can start it by putting fuel in through the spark plug hole but when the fuel in there runs out it stalls. It wont suck fuel up on its own. I have tried doing open carb surgery but cleaning the passages didnt help.
Whats up with it? Really getting annoying now, I hate small fiddly things that dont work!
Thanks for any help, very much appreciated.

Ooo, forgot to add, it has worked since i did the piston ect replace but it was a PITA to start the first time. I tried to start it the next day and no go.

 

[TroyR57]

the intake line is in the fuel tank on most U.S. chain saws, you need to make a hook tool, and fish the fuel line out of the tank, and put a new filter, or end on the line.

 

[taxidermist1]

What kind of saw do you have? I also had the same problem after rebuilding a Jonsehred. I tried everything! I finally bought a new carb and it fixed it. When talking with a saw mechanic he said the carb is wore out and caused the saw to lean out and score the piston and cylinder. HMM makes since to me.

Rob

 

[Mith]

thanks for the ideas
i will fish out the filter and clean ect, but it did run, so it used to get fuel
the saw is a stihl, when i got it it was basically unused, still got the paint on its first bar, the chain is origional and still sharp.
I cant think the carb is worn out therefore.
If the mix is real lean would it stop fuel getting to the engine even when choked? how do i set the mix ratio on a engine that wont start
thanks

 

[Egon]

Could this be related to reed valves??

Egon

 

[Mith]

if I knew what they were I may be able to answer /forums/images/graemlins/confused.gif
sorry dont have a clue man /forums/images/graemlins/confused.gif

 

[Egon]

Mith:

They should be the last insert before the crankcase. They are just plates that block the exhaust from the carburator. Lots of different styles.

Egon

 

[Mith]

how do i check/adjust or whatever them?
would they affect the engine in this way?
sounds good
thanks

cant really visualise them, but i only know the basics about 2 stroke

 

[Egon]

Really can't help with the troubleshooting on them Mith. Just know I cranked an outboard for hours before the lightbulb got a faint glimmer. Think I installed a carb kit and all was well.

Egon

 

[Mith]

ok thanks, ill have to look into it
cheers

 

[Deerlope]

That saw has a diaphram in the carb that pumps the fuel, it also has a small pulse tube (rubber) that is attached to the carb and the crankcase. If the tube or diaphram is bad it will not pump fuel. The diaphram gets weak or a small hole will start in it and that makes them hard to start if at all.

 

[em14]

I just had "hard to start problem" with my Stihl Chain Saw. I was very busy and did not think that I had time to fix so I dropped it off at the dealer to have him fix it. Two things were wrong 1.) old gas - even tho I had used stuff do protect against this and 2.) Clogged fuel filter. He replaced the filter and put in fresh gas and everything worked great. The dealer said that these smaller engines suffer from old gas much more so than a lawnmower.
Leo

 

[normde2001]

You have to clean all of the carb passages, even the little bitty ones, including under the welch plugs. Set the mixture screws at 1 1/2 turns.

 

[mrcaptainbob]

Join the Forestry Forum and pose your question in the chainsaw subject thread. Many saw pros and experts there.
http://www.forestryforum.com/board/index.php
(No afront meant against the good TBN'rs here!).

 

[Big_Lug]

Mith, I work on 2 stroke trimmers, chainsaws, etc. on my time off. 1st change old gas if applicable, check fire in plug, if compression is good and fire is good, then check diaphram in carb., if it is any bit brittle, change it, get carb. kit at lawn service either a Walbro or Zama, the number will be on the outside of the carb., but just bring it to let them see it. Clean all ports in carb with wire from wire brush, just take one out with needle nose pliers, run it through all holes. Make sure you take out needle valve and screens, watch little spring it will bounce. Do all of this in wide open space, cement floor preferably in case you loose something. If you have compression, fire, and gas it should work. Be sure all gaskets are in place and have no type of air leaks or are not stopping or covering up any intake holes. Also one other thing taht will not let it run is a stopped up exhaust. Take muffler off and check screen, it may be plugged up. Try to run it with muffler off.Let me know if this helps. Good Luck

 

[Mith]

Thanks for all your suggestions
havent got round to doing it yet, gearbox broke on one of the mowers, hopefully next weekend
thanks for your help

 

[B2400]

Mith,if it's a Stihl chain saw, you might look at the pulse tube which runs from the crankcase to the carburetor. This tube looks like a small fuel line with accordian folds in it and it's job is to provide vacuum pulses to the carb for the fuel pump. I've seen a couple of these crack which causes your initial problem( siezed top end) and won't allow enough vacuum pulse to pump fuel. Something to look at if it's a Stihl.