365sp with 52mm big bore kit tuning

[SawTroll]

Unless the cylinder is about to be ported by an expert, your best performance likely would be from an OEM 50 or 51.4mm top end.

Aftermarket "BB" cylinders usually mean less performance than OEM stuff, not more. Some of them can however perform very well, when ported by an expert.

 

[MCW]

Not that far away then I do a bit of business with a firewood guy down there named Rob Lusher. His business is Tatiara Trees. Also did a forestry falling course with him.

 

[Terry Syd]

I had a flash of insight and decided to measure the hole sizes on a 044 carb. That carb is generally recognised as a good upgrade on some saws in the 70cc range.

First thing I learned was my assumption that the second air bleed hole would be the biggest was wrong. On both the HD5 and the 044 carb, it was the first air bleed hole that was the largest.

I measured the drills that would fit through the holes, the holes were probably just a tad larger in order for the drills to slip through the holes.

On the HD5 the first hole used a drill .62mm and the second hole used a drill .48mm.

On the 044 carb the first hole used a drill .72mm and the second hole used a drill .62mm.

For a 77cc engine it looks like the Walbro could be drilled for the 044 specs and be close. I'd probably go a size larger on the first hole.

The optimum holes sizes can only be determined by trial and error. Ya gotta go to far to know where 'to far' is. Somebody that has a few extra Walbro carbs sitting around could try a few combinations and come up with something, but I don't have that option.

Good luck.

 

[jamessouthaus]

thanks for the help and advice guys. got it tuned buy an old guy here that used to be a husky dealer. seems to run good and up heaps on power to what it was so i'll stick with that for now.
MCW i'll definatly keep you in mind when chasing parts next. will be handy as there no husqvarna dealer here now it's a long drive to get stuff.
next step will be carby mods but will get another one to mod so i can still put original back on sounds like terry might be the guy to talk to when i go down that road