550xp fuel valve / auto tune

[Boy English]

Obtained a 550 from a friend that had stopped working

 

(Died while left on idle, never ran again)

 

I've had it to bits and am 90% confident that a new fuel vale / auto tune will sort the issue.

 

I've seen that abbey garden sell them separate in the area of £45 (so the website indicates anyway) but can't find one anywhere else online?? Just whole carbs including the valve for around £90 on eBay..

 

Anyone bought one on its own? If so where from?

 

Many thanks

[spudulike]

I don't believe you will get away with just fitting the part as you will need to programme the autotune with your serial number, coil type etc and will most likely find it will not run. The machine type, serial and running info is all stored on that single part!

The software does the click valve test and should tell you if the valves are faulty as probably the fuel settings on the read-out would.

Have you checked the spark yet?

[Sveriges]

You can no longer get the auto tune unit separate. You would need a new AT12 carb and as above it would need to be programmed with software only available to authorised dealers. Others may have the tool and somehow have access to the firmware but this is very soon about to change! 

 

Having said that the auto tune unit is mostly reliable. Does it not even try to fire? Make sure the air gap is good and the wiring connector to the carb is connected properly. I take it it is mechanically sound? 

Edited September 27, 2017 by Sveriges

[Boy English]

Hmm ok chaps, thanks for the info..

Saw sparks fine but immediately floods when pulled over, i.e. 2 pulls and cylinder is full of juice..

Coil is putting 5v to the solenoid and opening the valve but at no point does the valve close

[Boy English]

By full I mean chucking it out of the decompressor full, take the plug out and turn it upside down to drain, if you rest the plug in the hole and go for a gentle pull its fireing on the fumes / decent compression etc..

[spudulike]

Are you sure the metering valve is OK? Try pressure testing the fuel inlet and see if it holds pressure.

[Boy English]

I'll have a look but I'm guessing if it doesn't I'm still in the world of a new carb / auto tune unit and a trip to dealer?

[spudulike]

I had a 560XP in and had done the trips to the dealers etc etc, poor running, no power, bogging etc.

 

Simple fault - the pump flaps on the pump diaphragm had perforated around the holes that they should have sealed. the Autotune is just one part of the equation and old school diagnostics shouldn't be ignored. Swapped diaphragm and it was as good as gold!

[Boy English]

I had the carb to bits to start with but couldn't find any issues, I'll have a super thorough check through it again..

Can't beat old school engineering, first auto tune thing I've played with and already it's pissing me off [emoji6]

[spudulike]

With the volume of fuel that is being pulled through, it sounds like a stuck metering needle or the height has been incorrectly set. If you don't have a pressure checker/pop off tester, attach a piece of fuel hose to where the fuel pipe is usually connected and blow down it. It should hold pressure but if it doesn't, the needle isn't sealing correctly and as soon and you pull the saw over, fuel will be forced straight through the carb and in to the engine. Make sure the metering arm fork is under the little pommel on the needle not above it and make sure the spring is located correctly.

You can also take all the carb and elbow off the saw, prise the fuel line out of the back plate, push it on to the carb and then take the fuel cap of and put it back on and see if fuel pisses out of the carb. My betting is that it will.