Help I am having issues with my 385 xp.

[Stumped]

My 385 burnt down so I replaced piston & jug, intake manifold,and seals. The jug and piston were for a 390. I ran it for about an hour and it bunt down again? wth? An yes the mixed gas is 50:1

[ladylake]

 It's running lean

1   Just tuned lean, learn how a properly tuned saw should sound. If it really screams don't run it fix it.

2  Carb gunked up

3 Bad fuel line, put in a new one  about  $8

4  Air leak, seal or carb boot, boot could be shot

5 Tank vent could be clogged

                                                           Steve

[joe_indi]

I would have checked for the reason why the first piston seized before replacing it and starting it up.
They dont seize just like that, without a reason.
Primary reason being leaning out of fuel supply.
By a blocked pickup body (fuel filter), wrong adjustment of the H screw or a blocked strainer in the carburetor.
Other probabilities are a blown cylinder gasket or oil seals.
Old fuel mix could be the simplest of reasons.
Joe

[1270d]

The early 385 s were famous for the carb boot tearing.  And the cluch side crank seal going out.  You can check the boot for a tear easy enough, but if you don't have many tools, someone else should pressur test the engine for you.

[lumberjack48]

I always set my saw as lean as i could, as long as i ran it right i didn't have a piston issue.

You can tell right away when their sucking air, you have quick throttle response, when you let off the throttle it runs away on you.
When running a saw don't stay in the throttle for any long period of time, work your throttle giving the saw some breathing time.
I could burn up any new saw off the shelf, just stay in the throttle on till it quits running, i called it walking out of the piston.
The way i checked for a air leak was with a can of starting fluid. Start the saw an spray around the back, in between, rewind, sprocket, as soon as it revs up you found the leak.

[Stumped]

Thanx guys I had it adjusted too lean. The first time was a torn boot and that got replaced.

[1270d]

Just rembember when tuning the high side to always keep a flutter on the top end.  If its a smooth scream its too lean.   Or use a tiny tach.  385 s are max 13500 rpm I think.

[ladylake]

Also saws will cut faster tuned a bit rich rather than a little too lean.  Steve

[Bigredfaller]

We run our 390 xp's at close to 14,500.... Ported and polished of course...have to replace the stock coil thats rev limited with the old style black ones and use a digital tach to set it up....

[1270d]

I didn't realize the new ones had a limiiting coil.  How does the tuning on the 390s effect engine life/fuel consumption?

[Bigredfaller]

The blue coils are limited, there is a # on the side that should be 13000 or 13600... some guys replace the stock 13000 with the 13600 but the difference is small. The black coil is unlimited.
Definitely a little harder on fuel, I get about 20-25 minutes a tank in steady cutting, more in smaller wood.
As for life of the saw, its been a long time since I blew one up, the ground and timber type we work in is unforgiving so they tend to get smashed before that happens!
We expect to get 200 days out of them, anything after that is a bonus.