Blew up Husqvarna 3120XP when milling.

[CallumA]

As the title says! saw would not idle and very low compression. removed exhaust and low and behold piston scored up and jug is junk. So fitting a new jug and meteor piston. For all you chainsaw gurus is there any advantage to lowering the intake and polishing the exhaust and inlets on the new cylinder prior to fitting? The timing numbers are exhaust 98*, inlet 67* (total 134*), Blowdown 18* and squish with gasket 0.028". the inlet seems a bit low compared to the 390xp which is 150* total (with no base gasket). Also with the saw always on its side should I change the oil ratio from 50:1 to say 45:1 as already had flywheel bearing failed and wondered if it was due to position of saw in mill or would more oil of helped. I've attached pics of piston and cylinder and also the position of saw in mill (picture shows the 390xp)  Always ready to learn from my and others mistakes and experiences.  

[Ollie_M]

not a proffesional but im assuming your using a quality oil? amsoil, motorex, motul etc

[spudulike]

TBH, Forget all the timing figures but do ensure the saw holds pressure/vacuum and the fuel system is overhauled to ensure the saw doesn't go pop again.

You would probably find a bit of a muffler mod and lowering the squish to 0.5mm will up the power but the carb has no adjustment on the H setting making mods a bit more difficult to get the best performance.

[CallumA]

using red line racing oil (smells nice as well) The piston and cylinder got a little scoring when the main bearing failed. Spudulike is there a carb mod for making the H adjustable? I guess I'll just polish the ports and stick an extra pipe or two in the exhaust and see how she does. Also changing the air filter to foam as getting a load of fines in the carb intake with the fabric filter (filter p/n 503141802 and filter cage p/n 503141601) 

[spudulike]

I do remember some of the yanks modding carbs but the 3120 is relatively rare so never really took much notice of the mod.

I have heard of people fitting tights or socks over air filters when milling as the dust will cause wear on the inlet side of the cylinder, doing so will make the saw run a little richer but guess that will be a positive. The foam filter should help you.

 

 

[CallumA]

Well update on the 3120xp, drilled out high jet on carb + 0.1mm (Scoured American/Canadian sites and found a guy Donny Walker who says remove high jet and find drill that fits through the jet and then go one size bigger) This will also make the saw run a bit rich! which I guess is no bad thing lying on its side all the time milling. Also lowered the inlet 3* to 70* and total 140* polished as well.

Widened the exhaust and polished. 

Modded the exhaust

Runs like a good un  

[Stubby]

5 hours ago, CallumA said:

Well update on the 3120xp, drilled out high jet on carb + 0.1mm (Scoured American/Canadian sites and found a guy Donny Walker who says remove high jet and find drill that fits through the jet and then go one size bigger) This will also make the saw run a bit rich! which I guess is no bad thing lying on its side all the time milling. Also lowered the inlet 3* to 70* and total 140* polished as well.

Widened the exhaust and polished. 

Modded the exhaust

Runs like a good un  

I have had some saws from the " Walker Saw Shop " in the past . ( a couple of Husqvarna 394 s ) long since sold but the do know their shit

[CallumA]

just discovered him when looking for a carb mod for the saw! now love watching his YouTube channel, the wealth of knowledge the guy has is incredible.