husky 576xpg autotune strange one

[forest tink]

ok the story is,saw cutting away fine,no problems,i stop,clean the air filter,sharpen etc,fire her up again no problem,ticks away fine,everything working until i rev it and its like when the chokes half out,underpowered and a bit shuddery at full revs,piston seems fine,no marks,no loose bolts on head,no play in the crank,everything seems ok at first look,its only when rev'd up the problem arises,ticks over evenly,heated handles work any ideas anyone ??

[gdh]

I had a similar problem on mine that was caused by a perished fuel pipe.

[adw]

Change the auto tune unit on top of the carb, they are not madly expensive about £30 from memory.

[njm]

ok the story is,saw cutting away fine,no problems,i stop,clean the air filter,sharpen etc,fire her up again no problem,ticks away fine,everything working until i rev it and its like when the chokes half out,underpowered and a bit shuddery at full revs,piston seems fine,no marks,no loose bolts on head,no play in the crank,everything seems ok at first look,its only when rev'd up the problem arises,ticks over evenly,heated handles work any ideas anyone ??

 

Bad for air leaks , base gasket and seals , crank bearings , early saws tended to destroy piston skirts

[forest tink]

will have a check on the fuel line,also have a new autotune unit in the shed so will try that too,never checked the little bearing that the pin for the piston goes through so will do that last,nothing worse than saw bother

[Treemoose]

Had a tiny hole in our fule line. Changed it and it sorted it out

[spudulike]

Treat the autotune carbs as normal carbs and check the gauze strainer and pumping diaphragm. Once you have checked it over, if everything else is OK then it may be the autotune part but had a 560 in recently, local dealer "fit a new P&C" .....I found the pumping diaphragm was holed....bit of a radical change of destiny and bill!!!

 

Fuel line is a good call, they often chafe a little around the compression fit going in to the tank.

 

The juddering - is it a rich flubby judder, a lean pulsing or a mechanical judder?

 

What is the colour of the plug like?

[forest tink]

the juddering is as if the head is loose,harder you rev the harder it judders,only starts to do it once you hit about half revs though,the plug is light brown,i tried changing it already and it ran fine apart from this juddering thing,i replaced the breather recently aswell as it had broken clean of where it goes into the fuel tank,the new one made no difference,it ran the same,i will have a look at the carb tonight,i have a new set of diaphrams already and a new carb and autotune unit aswell if all else fails,bit of a head scratcher this one lol

[Stubby]

the juddering is as if the head is loose,harder you rev the harder it judders,only starts to do it once you hit about half revs though,the plug is light brown,i tried changing it already and it ran fine apart from this juddering thing,i replaced the breather recently aswell as it had broken clean of where it goes into the fuel tank,the new one made no difference,it ran the same,i will have a look at the carb tonight,i have a new set of diaphrams already and a new carb and autotune unit aswell if all else fails,bit of a head scratcher this one lol

 

Any fins broken off the flywheel ? Putting it out of balance .

[spudulike]

Worth checking the main bearings out and looking at the piston through the exhaust port as well!

 

Sounds like a mechanical issue but difficult to tell!