357xpg starting problems

[GaryW]

Hoping someone can offer some advice please.

Got a 357xpg, been running great then the other day after 30 mins use started chugging, cut out and won't start. Started the usual checks and the plug boot came off in my hands and the wire look pretty shot, got a new coil for a tenner so just replaced the lot assuming this would fix it. Unfortunately it didn't, I've checked for a spark and that's fine but the plug is bone dry. I'm going to try and get to the bottom of it, if anyone has a checklist of potential things to check I'd appreciate it as I'm no expert.

I've also been reading about the walbro carb problems and some say replace with zama, is this a worthwhile maintenance thing just to change it? Don't want to spend money for the sake of it but if it makes the saw more reliable for the future is it worth it?

[spudulike]

Hoping someone can offer some advice please.

Got a 357xpg, been running great then the other day after 30 mins use started chugging, cut out and won't start. Started the usual checks and the plug boot came off in my hands and the wire look pretty shot, got a new coil for a tenner so just replaced the lot assuming this would fix it. Unfortunately it didn't, I've checked for a spark and that's fine but the plug is bone dry. I'm going to try and get to the bottom of it, if anyone has a checklist of potential things to check I'd appreciate it as I'm no expert.

I've also been reading about the walbro carb problems and some say replace with zama, is this a worthwhile maintenance thing just to change it? Don't want to spend money for the sake of it but if it makes the saw more reliable for the future is it worth it?

 

Couple of things to try, the first -

 

Pull off the air filter, remove the four screw cover off the carb (can be done in situe) and see if there is fuel under the diaphragm - use a sharp craft knife to slide it off.

 

You could try lifting the metering arm up around 1/2 mm - you are looking at a slight adjustment here - reassemble and try again.

 

If this doesnt work, remove the carb, take off the single screw carb cover and check the gauze filter is clear of sawdust - it is quite possible it is clogged up!

 

Depending on what sort of tank breather you have, this may possibly be the issue but is less likely - the breather is by the fuel pipe inlet and may need a clean but have seen a few types - some with rubber hoses that won't need cleaning.

 

BTW, Walbro make good carbs so personally wouldn't change it!

 

If this sorts your problem, you may like to read the bottom of my signature:001_huh:

[GaryW]

Cheers for taking the time spud.

Tried all your suggestions and unfortunately still no joy. There is fuel on the outside of the cylinder under the pressure release valve, not sure if it should be coming out?

[spudulike]

Cheers for taking the time spud.

Tried all your suggestions and unfortunately still no joy. There is fuel on the outside of the cylinder under the pressure release valve, not sure if it should be coming out?

 

You said earlier that the plug was dry and now there is fuel coming out of the decomp valve - I reckon that is pretty much impossible:001_rolleyes:

 

Is the plug dry or wet and is the "pressure release valve" the decomp valve?

 

Sounds like the saw is badly flooded - take the spark plug out, turn the saw off, turn it completely upside down and pull it over fast a few times.

 

With what you have now said, I would pull the muffler off and check the piston through the exhaust port - it is possible the saw has seized and now is lacking the compression to fire the engine!

[GaryW]

Cheers Spud, yeah was bone dry when first checked and dry after fitting new coil and trying.

Since removing carb and doing the checks yesterday its started leaking from the decomp valve (excuse my incorrect terminology).

 

When checking the piston what am I looking for?

 

Thanks

[spudulike]

The piston front should look like wet light grey smooth aluminium, if it has vertical scores that look a maniac has been at it with a file then it has seized - you can post an image on here or just take a look at the first post on my "whats on your bench" thread!

[GaryW]

Looks like you are exactly right Spud. So would you recommend a new piston and ring?

 

 

 

 

 

[JAMIE1]

Yup, thats your problem, new piston kit required and a little bit of work on the cylinder.

[spudulike]

The saw has lean seized and that has dropped your compression making firing impossible.

 

First thing to do is find out why the saw did this and put that right, common reasons are old fuel, straight fuel, air leaks or incorect adjustment of the carb.

 

Once that is done, you will need to clean all the aluminium transfer off the bore to the point you can't feel any roughness and then fit a decent quality piston like Meteor.

 

I would recommend vac/pressure testing the crankcase once reassembled, just to be sure all is well.

[GaryW]

New piston and ring in, seems to be sorted now cheers.....until next time.

 

I suspect it will have been the old fuel in it, should have emptied it....lesson learnt