Hi Roebuck , thanks for that, but it isnt my problem, as much as i wish it was. Have had carby apart and it all works well. Have had similar problems on smaller B&S motors, but not on a bigger motor yet, touch wood. Thanks for the input Roebuck.
Hi Grumpy, have broken down motor and got some photos for you. As when i first broke it down i set it on TDC, dont ask why i just do, and as you can see from photos all timing marks are lined up.
First photo is crankshaft and counter weight.
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Second photo is crankshaft and camshaft.
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Have also got a few photos of decompression unit which is still in good working order,(thanks Grumpy),pin moves freely with no sign of sticking. [Linked Image]
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Did find something though. After doing what i have done so far i noticed some oil on the underneath of the head, which i have not noticed before. Got some photos so you can see what i am thinking.
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I am wondering if while the motor is only idling everything is good but when i try to increase the revs some of the compression is actually be pushed out past head gasket which could be causing the burn mark and oil build up,, and lack of power . ( yellow circles ) Correct me if i'm wrong.