gordon_dunn Posted August 8, 2009 Share Posted August 8, 2009 Preparing to take off yesterday- what would have been the 3rd flight for the day.. warmed up the engine, about to clip in, and the engine suddenly stopped. All attempts to restart failed- presumed it was the recoil starter at fault. I had a spare one in the hangar, so I didn’t panic, and packed up. Looking at the engine today I foundthe walls, and some debris in the tuned pipe also. As yet uncertain where the wire came that the starter was indeed faulty- seems like the spring has gone- changed it, but still wouldn’t start the machine- seemed as if there was no compression in the head. Popped off the plug for a look, and noticed some shiny deposits on the plug- not a good sign. The mixture was right, so I knew that it couldn’t have just burnt a hole in the cylinder. Removed the head to look at the piston and noticed a lot of debris inside the cylinder- and a piece of wire protruding right though the cylinder…. The wire has obviously entered the combustion chamber and penetrated the piston. There are some marks on the ports and inside the cylinder head where it has gouged out from… But seems to have come from the induction side of the engine- somewhere after the carb outlet…... Anyone seen this before? Here are a few pictures- Piston, with the wire protruding through the top surface at the bottom right. Detailed view of the wire Debris/soot in the cylinder- due a de-coking anyway after 120 hours. Visible damage to the edges and the piece of wire visible at the 5o’clock position Damage to the cylinder wall and ports Detailed view of the ports Detailed view of the ports Detailed view of the wire, and damage to the ports Damage to the cylinder head- contact with the wire. Thankfully it happened on the ground, and not in the air. Regards, GD Quote Link to comment Share on other sites More sharing options...
Farmer_Dave Posted August 8, 2009 Share Posted August 8, 2009 Ouch Gordon. Points to the air filter I suppose. I only hope she was due for a rebuild soon. Dave Quote Link to comment Share on other sites More sharing options...
gordon_dunn Posted August 8, 2009 Author Share Posted August 8, 2009 Ouch Gordon. Points to the air filter I suppose. I only hope she was due for a rebuild soon.Dave Cant see how it could be air filter... Between the carb and the main block there is a 'V' shaped gauze with very fine aperture... it's intact, and i dont think that wire could penetrate it.... I think whatever it is must have come from within the main body of the engine, and got blown with the fuel/oil mixture into the cylinder.... perphaps a bit of the crank assembly/fixings???? Quote Link to comment Share on other sites More sharing options...
bendmeroundthehedge Posted August 8, 2009 Share Posted August 8, 2009 Don't know but it looks like a needle roller bearing to me. If you are running with an air filter it is impossib le to get anything in there. Kev Quote Link to comment Share on other sites More sharing options...
gordon_dunn Posted August 8, 2009 Author Share Posted August 8, 2009 I suspect you're right there- obviously there has been more than one of these particles through the cylinder... just one of them must have hit 'end on' and penetrated the piston.... forcing it to stop. The exhaust caught a lot more debris, but the lumps there had been melted. I thought that perhaps some elements within the baffles of the tuned pipe had failed and they had been drawn back into the chamber during the compression stage- but everything inside the pipe is solid- It will need a good blowing out before it's reinstalled though. Quote Link to comment Share on other sites More sharing options...
Guest Posted August 8, 2009 Share Posted August 8, 2009 As above I recon. Too small to be a ring? SW Quote Link to comment Share on other sites More sharing options...
tj Posted August 8, 2009 Share Posted August 8, 2009 Hi, Knowing nothing about engines I can't be any help whatsoever. Sorry! However, I was wondering where one might go to be edumacated about 2 stroke engines to be able to 'do it yourself' in the field/home/a friendly hangar where you may be based. Cheers. Tj Quote Link to comment Share on other sites More sharing options...
gordon_dunn Posted August 8, 2009 Author Share Posted August 8, 2009 2 stroke engines are suprisingly simple when you understand how they work- There is a good presentation on Youtube on the principles- This illustration below is a great summary- especially as it takes the tuned pipe into consideration also- Quote Link to comment Share on other sites More sharing options...
pete_b Posted August 8, 2009 Share Posted August 8, 2009 Hi,Knowing nothing about engines I can't be any help whatsoever. Sorry! However, I was wondering where one might go to be edumacated about 2 stroke engines to be able to 'do it yourself' in the field/home/a friendly hangar where you may be based. Cheers. Tj We can run a basic course on this if there are enough interested. Pete b Quote Link to comment Share on other sites More sharing options...
Guest Posted August 8, 2009 Share Posted August 8, 2009 I recon, I could blag a bench at the Parajet Factory for that one. SW Quote Link to comment Share on other sites More sharing options...
spigot Posted August 9, 2009 Share Posted August 9, 2009 Thats the remains of your big end bearing. .. I assume the piston is still where you left it on dismantling and you have not tried to turn the crank over. I fear the crank shaft has departed from the crank...............ouch! Ive got bits just like it sorry to say.........its fudged but it can be fixed Quote Link to comment Share on other sites More sharing options...
nirmal Posted August 9, 2009 Share Posted August 9, 2009 I would agree with the needle bearing suggestion. It is extremely unlikely for a piece of metal that size to get past the air filter and reed valve. It would be interesting to see the state of the bearings when you strip the engine. Quote Link to comment Share on other sites More sharing options...
cobra Posted September 9, 2009 Share Posted September 9, 2009 I think its the little end as this is made up of long thin rollers, its prob fell apart hence the rollers going through the piston. you may get away without a re bore I dought it being the big end as these are hugh bearings, the rest of the little end will be lying in the bottom, you may be able to get it all out without splitting the crank cases, but to be on the safe side I would split the crank and replace all bearings and seals they are cheap to buy Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.