I have a Edge Sidewinder that has a XT600E engine it it. I bought it as a semi finished project and have been rectifying all the issues with it (which has been extensive)but have got a couple that I haven't as yet. I thought this may be a good forum who may be able to give me some pointers.

Main issue - starts up easily, runs well for a short period till it warms up then starts making metallic noises, run rough then stops. If I try to re start it backfires. If I let it cool down for 10 minutes it will then start fine again.

Things to note -
I've rebuilt the carby's and upsized the main jet 5 points. I tried installing a larger idle jet but the motor ran rough. When I reinstalled the stock idle jet it ran fine. Secondary jet is stock
Tank is on side of buggy so it uses a fuel pump. I've installed a fuel pressure regular now as I thought this to be the problem. Set to 1 psi. No dice.
I've fiddled with the float level. No dice.
I've tried changing spark plugs. No dice.
I've changed the oil and filter. Oil seeps from bleed screw if loosened so appears to have oil pressure
I've installed a new set of headers and seals
It has a unifilter setup
It has a straight through style muffler

The metallic noise is the worry. Why does this start after warming up?

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