STIHL 041 AV BACKFIRE

[Mayers123]

I do hope that someone can help, my 041 suddenly on cold startup would backfire  heavily through the muffler.to get it to start another heavy pull and it starts fine, not sure why it just suddenly happened, will pull the magneto off tomorrow to have a look, recently purchased a OEM Stihl puller, brilliant piece of kit, not sure what to look for apart from checking the the keyway??

[Stubby]

8 hours ago, Mayers123 said:

I do hope that someone can help, my 041 suddenly on cold startup would backfire  heavily through the muffler.to get it to start another heavy pull and it starts fine, not sure why it just suddenly happened, will pull the magneto off tomorrow to have a look, recently purchased a OEM Stihl puller, brilliant piece of kit, not sure what to look for apart from checking the the keyway??

Could be the key way has sheared and put it out of time slightly ?