atomicduck123

Will do!

Thanks again pleasant and spudulike for your replies. I'll give it a try at repairing the original with a new piston in that case. I had a read of the MS880 thread so I'll follow all that you've written here and there and hopefully resurrect the original. Looks like you can get Meteor pistons for £30 on ebay (I couldn't seem to find the ebay link you added for some reason) I'd not heard of an impulse line before, I've only worked on little Puch Maxi engines haha, I gather it sends crankcase pressure to the carb to draw fuel though, so I'll be sure to check that to. I'll be sure to go easy on it in that case pleasant and hopefully won't have to join the top end club! The fuel was bought that day and mixed with Stihl oil and the aftermarket kit was made by Aumel, I'm guessing they're terrible!? Thank you though for all your help, with everything being so expensive at the moment, I really appreciate you passing on the knowledge to aid fixing it at home! Joe

Hi all, Thank you all so much for taking the time to reply. I've just pulled out the spark plug, given the cord a good pull and the engine is easily able to complete a stroke without any abrupt stopping. In regards to what you said Spudulike, I did line the bore with oil before installing. I took some photos whilst I was there of the original cylinder, looks like a genuine Stihl head. I've added a couple of pics of the scoring and the condition of the piston. On closer inspection, those piston rings look like they've become one with the piston itself. Would that be a result of heat? The fuel was mixed 50:1, it wasn't a particularly large log and the chain had just been sharpened. Do you think it would be at all possible, in its current state, to save the original cylinder head? Thanks, Joe

Yeah that's what I wondered, it's almost like the decompression valve closes before the engine has had a chance to fire up. I've ordered a replacement so I'll see how that fairs but doesn't appear to be any visible defects The old cylinder head and piston didn't have this issue of the abrupt stopping/decompression valve. Perhaps, as you say, the make up of the aftermarket head isn't quite fit for purpose? Would it be possible for an aftermarket part to create too much compression, hence the decompression valve closing too early? I did try honing the original cylinder, placed it back on but had no luck there. I tried to do a compression test and discovered my tester is faulty, but a new one is in the post so will give that a try as well. I've never done a pressure and vacuum test so will look into that to and let you know how it goes

Hi All, I recently bought a secondhand Stihl MS660, fired it up, ran it through a couple of logs and as I finished going through the last one, the idle dropped and shortly stopped all together and was unable to get it started again. I went through a number of checks, cleaned the carb (ended up replacing it altogether), checked the fuel line was clear including the fuel filter, air filter looks brand new and clean, spark plug is firing nicely, spark plug gap is spot on, tried a new spark plug altogether as well. I also checked the flywheel key which is perfectly intact, the exhaust/muffler is clean, set the carb to recommended settings - all of which made no difference, so I decided to take the head off. Upon doing so, the cylinder looked a little scored and the piston was mostly black so I ordered an aftermarket replacement kit. I installed it today, popped the choke on and after 2/3 tugs it fired up for a few seconds. I then went to try and start it again, this time it wouldn't start. If I pull relatively softly, it will pull as it normally should and I can feel the piston moving. If I give it a harder pull, i.e enough to actually start the engine, the decompression valve pops and as soon as it does, the pulling comes to an abrupt stop, almost as though the piston is hitting something. As soon as I press the decompression valve down again, the piston can freely move, until I pull hard again. Does anyone have any ideas at why it is doing this? I took the head off again just to check I had installed everything correctly and to check nothing in fact had broken off inside the engine and it's all fine, piston rings are intact and in position, the little clips holding the piston in place are also intact and in position, the piston arrow is facing the exhaust port, presuming that is correct and nothing looks scored, really bizarre. I really can't figure out what the problem is though and have been trying to get it running for the last few weeks without much luck and wondered if anyone here had experienced a similar thing and new a remedy. Many thanks in advance, Joe