034av idles but wont rev... 2nd post right forum..my bad.

[deer slayer]

Hello all, I'am working on an STIHL 034av of a friends. I initialy got it not running at all and in poor condition ( ie dirty, wrong bar & chain, missing bolts) I adjusted the low screw and got it to idle. Pulled muffler & piston looked great, not knowing any history of it off to the store I go. Replaced A/F, F/F, fuel line & rebuilt carb with kit, replaced missing bolts cleaned it up. I had a 20" bar and chain that fit, pulled cord idled fine. Adjusted low screw and went to rev for high adjustment with no luck. Seems to be starving for fuel is my guess, when W.O.T. it bogs out, if I release throttle quick enough goes back to idle if not cuts off, one pull goes to idle fine. I have been playing with the adjustments for hours now with no luck it wont run/tune on the the top end????? Just for the hell of it I have tried a different used spark plug, same results ...

 

[peter92]

its sounds like carby related, try winding out both h/l srews 1 turn and see what happens, it should run and rev at that
regards peter

 

[peter92]

i have the same thing with my 365 husky, ran fine until i changed the fuel and now it does the same as yours apart from my revs but stalls on the wood
hope some one can help you
regards peter

 

[deer slayer]

Thanks,, already tried.. I have started from 1 turn out from bottom to almost 3.5 to 4 back to bottom on H in 1/8 turn increments. I do not know a lot about the coils or leak testing one. I have never come across those issues, 99% of what I do is fuel related.

 

[rupedoggy]

I can't remember if the 034 has a pulse line but that could cause it and you did not mention checking it. That tiny screen inside the carburetor is troublemaker also.
Your high speed passages may be clogged. As a quick and dirty way to try to fix, remove the high speed needle and squirt carburetor cleaner into the hole. Replace the needle to 1 and 1/4 turn and try it. If no luck you will have to take it all apart and sonic it with the welch plugs removed. When you re-assemble be sure to get all the gaskets correct and the needle height perfect.

 

[deer slayer]

Thanks for the input, a pulse line im assuming goes from the baseof the cyclinder to the carb?? It is solid no cracks that I could see but I have not replaced it.. will try in the am. I am through with the carbs, I have done many & agree 100% with you. I can physically see the end of the needle in the H and L holes when it was disassembled. Cleaner ,compressed air and even ran a piece of small wire through them. I dont know of any other thing to do to the carb except replace and I got luaghed at by my local dealer...Came up with a price of $100.00 and N/A..I have also removed the tank vent thinking maybe a vapor lock... No help.

 

[rupedoggy]

Yes that is good you can see the end of the needles. That is not the end of the story. Think of where it comes from to get there and where it goes when it is past that. That is why I said remove the welch plugs. Or it could be a clogged high speed jet. There are a lot more passages than what you see looking at the end of the needles. Did you know there is a small disk in the jet to keep fuel from leaking into the saw when it is not running? What if it gets plugged? Not very likely but there are dozens of things to check. I can't do it for you on the computor, you have to think and do it for yourself or pay a pro.
Now as to the pulse line being good. Check the fittings where it plugs into the pulse line. Broken, cracked, or loose can cause problems. It may even be plugged in the cylinder with carbon. Try to think of everything not just the carburetor.

 

[deer slayer]

Again thanks for replying and sorry for not being as detailed for what I have done. When I say I rebuilt the carb it got everything including the removal of welch plug. I litteraly put a small strand of wire thru each hole to ensure no blockage, compressed air blown thru each port with air coming out in another portion of carb. I have moved on from the carb thats why I am here. Could it be a coil?? do you know how to test one ?? could it be a crank seal going bad?? I dont know, I have never experience a saw with that problem... The pulse line was helpfull, replaced, made sure wasnt blocked on each end as you stated, same results.. but far as ("I can't do it for you on the computor, you have to think and do it for yourself or pay a pro.) Is not what I come here for. Thanks again!!!

 

[peter92]

hi, i know your still having trouble but have you gone in to the manual thread and asked for one, it my help you alot
hope this helps and sorry i couldnt be of any more help
regards peter

 

[deer slayer]

Thanks peter92.. It never crossed my mind but will do so. Thanks again!!

 

[husqvarnaguy]

Muffler may be clogged up and sometimes if the low side can throw the high side off if incorrectly adjusted.

 

[fearofpavement]

Restricted muffler as stated by previous poster is a very good idea to check for. It would exhibit the symptoms you are experiencing.

Have you tried different fuel? Don't laugh, people have found success with that in the past.

If the timing is off it can cause the symptoms you are describing. Not sure what electrical system you have but if points get too close of a gap an engine will idle all day but have no power. Check that.

A bad plug lead or chafed wire to the shut off switch is another area to investigate.

You'll figure it out eventually. Oh, on the coil test, about the best way to test for that is try a known good coil and see if it changes anything.

 

[ch woodchuck]

One more time on this side....Check the tank filter,(which is not the fuel filter)Idling saw,turn on side,loosen gas cap,If it revs.....wot it is...or a bad gas cap.I change my huskie vents anually.