Rebuilding a 2012 390xp, any advice.

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Muzencab

Y'all ain't as smart as you think you are.
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To get to the point gentlemen I'm rebuilding some chainsaws and the one I'm rebuilding right now that 390xp. The biggest thing will be ignition coil, cylinder head piston, and rings. Everything else on it is sound as a pound.

I want to see if I can find an Italian cylinder head with cabbar piston rings, and possibly a pop up piston.

I'll keep it a 55 mm as I don't know of anything else ≤ that can be put on there.

I will be smoothing out the air paths, but I'm not going to hog it out and it's not going to be polished.

I am definitely looking for the best function and not a complete crazy hot rod.

What kind of advice do you gentlemen have for me?
 
To get to the point gentlemen I'm rebuilding some chainsaws and the one I'm rebuilding right now that 390xp. The biggest thing will be ignition coil, cylinder head piston, and rings. Everything else on it is sound as a pound.

I want to see if I can find an Italian cylinder head with cabbar piston rings, and possibly a pop up piston.

I'll keep it a 55 mm as I don't know of anything else ≤ that can be put on there.

I will be smoothing out the air paths, but I'm not going to hog it out and it's not going to be polished.

I am definitely looking for the best function and not a complete crazy hot rod.

What kind of advice do you gentlemen have for me?
Check the boot between cylinder and carb for cracks, crank shaft can spin in the bearing & wear on the clutch side, pressure/vac test!, gasket delete with std piston usually gives good squish & good compression (be sure to check squish), mod muffler, check all bolts after a couple of runs. Good luck
 
Check the boot between cylinder and carb for cracks, crank shaft can spin in the bearing & wear on the clutch side, pressure/vac test!, gasket delete with std piston usually gives good squish & good compression (be sure to check squish), mod muffler, check all bolts after a couple of runs. Good luck
Appreciate that, quick to the point, good information. So you're saying standard piston and no pop up?

I my thoughts exactly on the gasket, really appreciate the rest of the info.

And I'm going to be modding a "ported" .5" muffler to .75" id. (Did the same to another Muffler thats on a 54 mm build.)

Thank you again.
 
I would not reccommend a Meteor cylinder for that. The pistons are good. I've seen/read/heard from multiple sources the jugs are the same castings as Hyway, which are not the most consistent. I would try to clean up the original jug if possible. If not, OEM top ends can be found for not much more $$ than Meteor or sometimes less. I picked up a 55mm OEM p+c this year for $93.
 
A pop-up piston will up compression without altering port timing (if you keep the gasket), but the effect of the gasket delete is minimal & you'll have more options with a standard piston. I'd pick a good used OEM cylinder over new aftermarket. Remember, more compression means more heat & possibly the need for higher octane fuel.
 
There are plenty of ported saws out there with over 200psi running just fine on pump gas. A gasket delete and popup isn't getting you near 200 on almost any stock saw.
 
There are plenty of ported saws out there with over 200psi running just fine on pump gas. A gasket delete and popup isn't getting you near 200 on almost any stock saw.
If memory serves me right, my 385xp with gasket delete, standard piston, muffler mod & mild porting was about 210psi last time I checked it. It runs fine on 91 but I prefer to put 95 in it
 
If memory serves me right, my 385xp with gasket delete, standard piston, muffler mod & mild porting was about 210psi last time I checked it. It runs fine on 91 but I prefer to put 95 in it
I did say most. How is the detonation situation?
 
Hasn't blown up yet... & It's far more saw than the stock 390xp is. I can't say that I've experienced (that I'm aware of) pre detonation with any saw before... How exactly does it present?
It doesn't. At least not that I've ever seen, heard of, or read about other than people being afraid of it based on un-related engine types.
 
Agreed, but both pop-up piston & gasket delete could cause excessive compression (with other issues) & not be something I would recommend
You bring a lot of good information JD.

Basically I'm just building some chainsaws for fun, really not looking to make money on them. Just enjoying building and taking my time and learning more about them, but if any of our people out there fighting wildfires need a chainsaw, I'd be more than happy to sell it to them at cost.

Essentially I'm building these chainsaws with the mindset of our guys out there in the forest battling fires. I would prefer these to be powerful, but they need to be reliable.
 
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