Problems starting a o34 av

[renux]

Hello All,
My first time here and hoping that i can find a little help.   i am trying to get my dads o34av running by the weekend for a camping trip.  Last year it was running fine.  Now its just dumping gas in the carb and not starting.  On the first pull after sitting for a few weeks (with choke on) it started up and then died a few seconds later.  For the last 3 hours i got nothing out of it.   Its getting a spark (brand new plug) and the air cleaner is clean.   I reset the H & L speed adjustments and tryed different idle settings.   I then tryed a small amount of ether after drying out the plug and nothing....

I then dropped in some fresh gas and took the carb apart and sprayed every spot where i saw any debris.   Still nothing. 

Any ideas?

Thanks
-First time poster

[sawguy21]

Is that last years gas in the tank? If so, dump it out and add fresh, less than 6 weeks old. That is the maximum shelf life of the crud we get from the pumps. Shoot a spritz of fresh into the throat and pull. If it fires and dies, you have a fuel delivery problem. Change the pickup filter in the tank and the fuel line if it is soft and sticky. May also need a good carb cleaning and a kit.

[renux]

its new gas and the hose was replaced last year.

[Bill]

Ditto what Sawguy21 said. Sounds alot like old gas so mixing up fresh from the pump would help. Careful then not to flood it out with the new gas. Then I'd go for the filter or gas line.

There's also a good piece an carb adjustments on the Madsen web site.

Good Luck

[renux]

ok i looked at it some more and i wanted to make sure the flywheel was right.  at top dead center it was on "S", i think thats right but wasnt sure.  I also checked the kill switch wires and they were fine.  Like i said i am using fresh gas, new plug, have spark, getting gas yet doesnt start.... Any ideas?

[sawguy21]

Is the compression strong? Hold it by the rope handle with the switch off.  It should not drop from it's own weight. If it does pull the muffler and check the piston and cylinder walls for scoring.

[Bill]

Renux

Motors are usually pretty straight forward - they only need three things to start : air , gas & spark ( barring any weird stuff like someone blocking your exhaust with a potato or such ).

Air - air cleaner needs to be clean and nothing between it and the carb
Spark - should be able to see it between the plugs electrodes when you pull the rope w/ignition on - timing
          is important also and if   running   before . . .  well unless something changed it should be OK.
Gas - not too little nor too much. Experience w/saw will guide you as to how much to choke it hot/cold and in
         between. Too much will flood the motor ( you'd probably smell or see it & plug will be wet ) while too
         little won't fire

Since you were running fine last year you probably have a basically sound engine BUT looking back at your posts you mention carb dumping gas and drying the plug so I'm beginning to think it may be going right to flooding the engine. Maybe looking for why you're getting too much gas would do it. Plug should be a light gray if everything is working right certainly not dripping gas if you pull it out.


Good Luck

[renux]

I know the engines arent that complicated thats why its driving me nuts.   Even with a new plug and letting it sit over night it still wont start w/o the choke on.   I am very good with engines.....i own a 64 belair and a 91 harley and i do all my own work.   I think it might be the accelerator/float pump. .....not sure exactly what its called on the chainsaw carb.  the response on it was a little slow.  I know a accelerator on a harley CV carb or a mikuni is alot different.  Even though its not an actual accelerator pump the concept is pretty much the same.  Spring-loaded rubber coated canvas material. 

I actually had a similar prob with my lawn mower.  Todays gas and all its additives causes the rubber to dissolve after sitting for periods at at time.   I think i might just throw a rebuild kit on the carb and see what happens.   All the other ports and jets are clean and free of debris.

thanks for the help i will let you know after i get the kit installed.  I called all the dealers and no one has em instock for my model.

Luckily i found another one to use for this weekend.

-Renux

[sawguy21]

That is what buffalos you big stuff mechanics. These carbs are too DanG simple for ya. :D
There is no float or accelerator pump in it, just a fuel pump diaphragm in one side and a metering diaphragm in the other. Under the metering one there is a screw holding a pin, the metering lever, and the inlet needle. Under the lever is a tiny spring so be careful not to lose it. I do this on a white towel to make things easier to see. Once apart,clean everything with carb and choke cleaner or brake cleaner and reassemble with new gaskets and diaphragms.
There is a tiny screen in a well on the fuel pump side that gets clogged with varnish and lint from the fuel tank filter. Pry it out with a pick and replace it by pressing in the new one gently with a flat punch

[limbrat]

On the left side of the carb and filter is a plastic piece with a screw sticking out the top rear. You should be able to pull it straight up and out of the fuel tank. take the screw out and blow it out, you might wont to wash it with soapy water before the next step. After replacing the screw put the end that was in the gas tank in your mouth and try to suck air through it. You should be able to suck just a little bit if you cant ajust the screw. I dont know what the piece is called but it prevents vapor lock. It doesnt take much to over come that little diaphram pump. If the gas cap dont leak air is got to get into the gas tank from somewhere. If that dont work check the pump and hoses again.
hope that helps.


In my opinion you should never use ether on any engine