KOPON

Yes, I think that's good advice given what I found in the crank case.

OK SJT, I finally found a way to view the diagram and very informative it is too. Good work finding it and sharing. Thanks.

Thanks, Sauen. I suppose the speed of the transfer is what effectively prevents blowback i.e. proximity of inlet port to transfer port.

Thanks for the reply. Sorry but I can't seem to open the file. On my laptop it says I'm trying to download an app. On my iPhone it says 'download completed' but then I can't find the file in my downloads. I've googled how to do it but again lots of instructions to follow that don't work for me. I've obviously got a bad iphone and a bad laptop!😊

Thanks for the replies. Yes the piston and cylinder both look good. I've now got into the crank case and found a flood of oily fuel so I've washed it out with clean fresh petrol and left to dry overnight. Tomorrow I'll make up a fresh fill of 2 stroke at 40:1, fit a new plug and see how it behaves. There are numerous diagrams on line apparently showing a typical 2 stroke engine operation, e.g. https://thundercoastmarine.com/blogs/blogs/understanding-2-stroke-engines-how-they-work This is one of many similar and obviously misleading sites. Nevertheless, I'm still trying to understand how the fuel mixture is not partially forced back through the inlet port prior to being forced into the transfer port.

Hi all, New to the forum but I can see some well informed members here regarding the workings of the 2 stroke engine. In my case it's a chainsaw that only goes when it has sat for about 6 months and then only until I stop it and won't start again. The spark plug becomes soaked with fuel regardless of choke or throttle position. So I've stripped it down for a look and with the plug out, the carb off and the exhaust off I can see the piston in action. My (nonsensical) question now is this: Why is there no valve visible on the inlet port to prevent blow back on the down stroke of the piston?? Some diagrams online indicate that there IS a one-way valve here but no information on what it looks like. My limited mechanical knowledge tells me there OUGHT to be a non-return valve on the inlet port to encourage the fuel mixture to exit the crank case via the transfer port for final combustion. What am I missing? Thanks for any assistance on this.