AWG81

That would be amazing, thanks for the offer! Shall I send you a message? Thanks all for the help on this.

Thanks both - yes, that was what I was worried about. Good to know. I'll hold off using the saw until I get the replacement screw then. I don't have the right security bit driver yet, so I'll get one and try the other screws for size. Good tip on the length of screw! I've tried L&S for a replacement but they've not been much help which is unusual. Cheers!

Hi all - I've just noticed a missing screw on my 550, it's on the cylinder assembly. Photo attached. I've tried to find a replacement screw but there isn't one listed on the parts diagrams I got from L&S. Just wondering whether it matters? I'm not sure what that part is that the screws are holding on, so I don't want to keep running it if there's a chance I could be introducing an air leak or anything. Any advice much appreciated, Cheers, Andrew

Just wanted to update on this - I swapped out the coil for another one and it seems to be working pretty good. I fixed the switch issue too. Used it all day today for work, and mostly all good after a bit of carb adjustment. Does seem to very occasionally backfire, and doesn't like to start with the decomp valve in so it's not perfect, but usable which is a big improvement on where I was. Thanks for the advice here, much appreciated. Cheers!

Thanks both. Yeah, it's running with the aftermarket coil. I have another one I can try. The decomp is genuine Stihl which I put on so that should be fine. It certainly does seem like it's flooding the chamber. I appreciate it's difficult to diagnose without seeing the machine. The suggestions here are super helpful. I'm sure I can get this thing sorted eventually and I will have learnt something along the way. Actually maybe the lesson is "don't buy cheap saws off eBay in the first place"...

Hi all, just an update on this MS 261. I bit the bullet and bought a new flywheel from L&S with the correct number. It now will fire up and run (hooray), but I'm still getting a bit of backfire and my decomp valve is popping out every time I pull it over. When it backfires I get a puff of smoke out the exhaust and decomp valve. I seem to be having trouble with the master control lever too and am wondering if it's related - if I have it set on the choke setting (all the way down) it pops back up on its own every time I pull it over without the engine coughing. It will only start when the lever is on the run position. Once it goes it seems to idle and rev up fine (although a bit smoky) but the starting issue is puzzling me. I'm about ready to throw this thing in the bin but I've spent too much time on it now to give up! Thanks for the help so far - it's running better than it was thanks to info provided here!

Thanks for posting this Chris. Now it all makes sense! Hopefully I can get hold of an older 261 flywheel from somewhere.

Just another update - I checked the flywheel with L&S and the part code should be 1141 400 1200 so it looks like I have the wrong flywheel fitted. I'm wondering if I change the flywheel it might work with the coil I have. Out of stock on L&S at the moment though...

L&S have given me part number: 1141 400 1331 for the coil. The OEM part is £138 which a little out of my budget at the moment so this saw is going to have to sit on the bench for a while! Thanks all for the help, I will report back here when I get the saw up and running.

Great, thanks Spud. I'll give L&S a shout today and see what they come up with. Will post back here.

Ah, the plot thickens - the part code on the flywheel is: 1141 400 1220 B Meaning, the saw probably has the incorrect flywheel fitted? Is it a case of matching the correct ignition coil to the flywheel? Or is the timing out because of how the flywheel is orientated on the crankshaft? Thanks for the help so far...

Great, thank you. I'll take the flywheel off tonight and check the part number. The only number I can find on the original coil is: 1106 0 621 which I think is for the rubber spark plug boot at the end of the lead. Should there be a number on the module itself? It just says ZhongfaTec. I'm wondering if this is non-genuine? Will report back later with flywheel info! Cheers!

Thanks Spud. I think I checked the flywheel pretty good, but I'll check again tomorrow and post a photo here. The key is part of the flywheel itself and it looked intact but I'll have a closer look. How would I go about checking I have the correct flywheel and coil? The serial number of the saw is: 175665202 if that helps. I couldn't believe it when it started running backwards. I had to check against my mate's saw to make sure I wasn't seeing things. I wish I'd taken a video...

Thanks for this Dan and Stubby. One thing I should have mentioned, I replaced the carb for a cheapo one just to see if it made any difference and it didn't. As for the piston and cylinder, I checked just now and I'm not 100% convinced either way - it looks like it has very light scoring, but it's really very hard to tell. Would scoring this light be enough to cause such drastic problems? I'll try and get a photo tomorrow and post here. I have it on the bench in bits at the moment - I'm happy replacing seals and the piston etc but I've not had anything to do with coils / timing before. Is there a definitive way of ruling this out? Thanks again.