357xp starting issue

[Acerforestry]

I'm running a 357 for cutting chestnut and the model I use has been going great until a few days back. Once started on choke, when you yank the recoil again it will climb rapidly on the revs (and I'm not touching the throttle), and then after 10 seconds just stop. Everything that I can see is working normally on the switchgear, any ideas please what's occurring thanks

[AngrySquirrel]

@spudulike will be along with his Breakdown truck

[Stubby]

9 hours ago, Acerforestry said:

I'm running a 357 for cutting chestnut and the model I use has been going great until a few days back. Once started on choke, when you yank the recoil again it will climb rapidly on the revs (and I'm not touching the throttle), and then after 10 seconds just stop. Everything that I can see is working normally on the switchgear, any ideas please what's occurring thanks

I think you have an air leak from somewhere .

[spudulike]

This could be a number of things but it sounds like your saw is getting enough fuel/air to fire and start. It does sound like once started, it is either getting not enough fuel or too much air (air leak). It is also possible that the throttle is stuck open but I would expect the machine to keep running and not stop.

So.....possible causes: -

1) Fine wood pulp in the carb internal gauze strainer....common on all saws.

2) Impulse line has come off - this is the small rubber hose to the clutch side of the saw just below the inlet manifold.

3) Split inlet manifold - they are prone to failing around the impulse connector but isn't possible to see without taking it off which can give another load of problems with refitting if not done correctly.

4) Bad crank seals - unlikely as they are pretty good in that area.

5) Air leak elsewhere - possible if the cylinder is loose.

6) Split fuel line - they commonly split where they push through the fuel tank wall.

7) If the saw has a Walbro carb, they have issues with accelerator pumps that cause issues very similar to yours as described and to the MS200T issues - unstable idle, rising and then dying - they can be slight to impossibly bad but the fix is to fit the Zama replacement, the factory did this but make sure the H screw is a good two turns out as the check valve is a bit light on flow and it needs a bit more on the H screw to compensate.

I would be surprised if it isn't one of these but difficult to tell without seeing the machine - Does it have the automatic decomp valve? If it does, make sure the rubber pipe is in good shape and it is possible it has stuck open - they were a shyte idea and not reliable!

[spudulike]

Does feathering the throttle or holding it wide open have any effect on the 10 secs and die issue?

[Acerforestry]

Spud, no effect at all however you touch the throttle- but I'll go through all the possible faults and that is a great help thanks

[Acerforestry]

And Stubby thanks also the reply didn't go unnoticed

[spudulike]

My advice is to tackle the easy ones to cross them off the list. It is easy to check the impulse line, less easy to check some of the other stuff but these are the things I would check. The Walbro carb thing is a real possibility but rarely happens overnight, it is more of a time related thing!

Just work through them, if you do pull the manifold off, let me know before refitting as there is a right way and a way others do it!!

[adw]

If the saw had an auto deco valve and has been converted to manual, then check the rubber boot has not come off or split on the connection at the cylinder base, r/h side.

[Acerforestry]

Ok thanks for above