Stihl MS341 Ignition Problem

[timmy2013]

Hi All

 

Been reading this site alot but this is my first post, mainly because every problem I have hit has normally been covered by the helpful people on here, however this one has me stumped.

 

A couple of weeks back my saw (Stihl MS341) wouldn't start, assumed it was a fuel issue so stripped and cleaned carb, checked filters, hoses etc. all seemed fine.

 

So checked spark plug (took out turned over whilst holding it against the engine) and had no spark. So changed the plug and still no spark, checked the new plug in another saw and had a good spark. I did notice that I would get a tiny spark between the case of the plug and the engine if I moved the plug back and forth (on the broken saw) but nothing on the electrode.

 

Checked all the wiring, seemed fine no breaks or wear on them or any of the connectors. Checked the coil, seemed fine, gave it a clean and readjusted it. Not an expert on adjusting it made it about 2 sheets of paper gap, but also tried adjusting further out and closer in. No Joy

 

So replaced the coil assuming it must be the problem, however after fiddling with the new one endlessly I'm still not getting anything but a tiny spark as before.

 

The one question I still can't answer is how the coil is grounded to the engine, the two cables coming off it seem to be just the two sides of the kill circuit, neither connect to the engine or anything even metal. The coil is screwed into metal bolts moulded into the plastic body, so can't tell if it is connected to the engine that way.

 

Apologies for the length of the post, am self taught with all this so wanted to include all the steps I have done in case I am missing something obvious.

 

Any help at all would be really appreciated

[Matthew Arnold]

Have you checked the HT lead. We recently replaced one on one of our 341,s as we had the same problem but if we moved the lead a certain way the spark when back to being the brightness it should be.

[Ray1]

Sounds like the magnets in the flywheel have gone or have considerably weakened.

[Stubby]

Im going with magnets to . Coil is grounded by its mounting bolts ?

[timmy2013]

Cheers all, was wondering if it could be an issue with the flywheel but wanted to check for any other ideas before splashing out on a new flywheel.

 

The new coil came with a new HT lead, having said that though the way the spark plug adapter attaches to it is not exactly robust, hence the endless fiddling mentioned above.

 

Will try and figure out how the mounting bolts connect to the engine, must be metal moulded into the plastic body. If I can't find anything wrong there, flywheel it is. Does anyone no what might cause the magnets to weaken?

[Ray1]

They wear out with time, how old is the machine? A new flywheel is £££'s. Stihl changed the flywheels at some point and dont produce the earlier versions anymore, so if you buy second hand make sure you get an exact part number match.

[Rich2484]

I hill billy way to test the flywheel is to hang some tools from the magnets. See how many it holds before it lets go. So a spanner or two.

 

Then find a flywheel the same size and do the same thing. Most you can feel with a screwdriver and the pull of the magnets. I found this with a 088 and an old flywheel from a 036, the 036 grabbed the screwdriver for my hand yet the 088 didn't.

 

Try another ht lead from another coil. Although you have said you changed the coil so I'm not drawn to the coil.

 

Check the wires by the switch aswell. When its on no wires should be touching anything.

[timmy2013]

The saw is about 2 years old, but has done a fair bit of work.

 

Tried the hill billy test and the magnets still seem pretty strong, certainly comparable to my other saw which produces a good spark.

 

Looked at it again today and realised the body is metal with a plastic coat not plastic and given that the bolts and holes they go into are clean I think that rules out the chances of me finding a grounding issue.

 

Will try the HT lead from the old coil just in case, if not will probably need the shop to take a look. Will let you know what I find out.

[Rich2484]

Are the points on the flywheel blue?.

 

I'm ist reacted from the coil itself as its new and should be working. The only option it really leaves is the short circuit wiring.

 

Or the control switch is shorting. Try disconnecting the circuit wiring from the coil and see if a spark is given. This eliminates the circuit wiring as a problem.

[spudulike]

Disconnect the Kill wire from the coil and set the coil to flywheel gap to the thickness of typical A4 paper - this is a bit close for normal but hear me out.

 

Strap the wires away from the flywheel replace the recoil and give the saw a decent hard pull in subdued light with the plug earthing on the cylinder.

 

If you still get no spark, meter out between the plug cap and the kill wire connection - you should get a reading - can't recall what it is but it will NOT be open circuit - if it is and you have had to fit the spark plug cap parts - spring bit that pushes through the HT lead - it is this that is the issue.

 

I wouldn't expect the magnets in the flywheel to go after two years:confused1: