390XP rebuild - help needed

[blue beastie]

My 390XP had an oiling problem yesterday which I thought i'd fix last night before going to bed - it's now 5:15am and I have a pile of bits on my living room floor that used to be my favourite saw.

 

Tried all the usual flushing the oil tank tricks which didn't work so to get to the oil pump i'd removed the clutch etc. I couldn't find my piston stop so thought i'd try the "feed a piece of rope in there instead" trick.

 

Mistake number 1! The rope got snagged up inside and wasn't coming back out, long story short a bit of it is still in there....

 

So, off came the exhaust but all I could see through the port was piston and a tiny portion of said rope. Oh well I thought to myself for the sake of a new gasket, might as well pull the head, retrieve the rope, bung a new gasket in and then get back to the oiling problem.

 

The head won't budge. I've removed the four allen bolts that hold it on, disconnected the carb and anti vibe but just can't seperate it and the piston!!

 

Apart from finishing this beer and getting a couple of hours shut eye, what's my next move fellas?

 

Cheers.

[MattyF]

Pack it in a box with all the bits and send to spud, Maybe beg him to do it before his hols..

[spudulike]

Pack it in a box with all the bits and send to spud, Maybe beg him to do it before his hols..

 

Cheers Matt - wife a bit happier about the hedge trimmer, less so about the saw for fixing we are picking up when we are away and this one may be tha stick that broke the donkeys back:001_rolleyes:

 

Anyway - back to the issue in hand - when you use rope, turn the engine over until the exhaust port is covered and then cram the rope in the plug hole - this is what would have stopped your issues happening:thumbup:

 

You should be able to bolt the head back down and then use a socket wrench on the flywheel to turn the engine over to lower the piston and get to the bits of rope through the exhaust port - if the clutch has the hex nut on the end of it then you can turn the engine over with this - I haven't had a 390 in bits yet.

 

If the head needs to come off then if you have removed the bolts and the head isn't moving, give it a tap with a mallet to shift it as it is probably bonded to the crankcase by the base gasket, moving the thing may be difficult if rope fibres are jammed down the side of the piston and turning it over with the clutch or flywheel may be a lot easier but go easy and hope it hasnt done any damage to the engine.

 

Let us know how you get on!

[blue beastie]

Thanks for the above both

 

Just found my bloomin piston stop that started all this, thanks for explaining how the rope trip should he done though spud! Sounds like you're in demand.

 

I maybe didn't explain things too well this morning. The head is free of the crank case, but the rope is so well wedged between the cylinder & piston that you can't lift it off. I'm not sure how hard it's safe to pull though?

 

I'll have a crack at the flywheel after tea and see if I can get it to move from there.

 

Fingers crossed!

[spudulike]

Sounds like you have done a real job on it:001_rolleyes: personally I would get thehead back to the crankcase by rotating the crank and thus pulling the head down, would bolt the cylinder down, get a good load of WD40 down the bore to lube it up and then try to rock the crank to and forth to loosen it up.

 

I am just hoping that the transfer ports havent been distorted by the rope or caved in! If the worse comes to the worse, you could heat the head up very hot with a gas torch to melt the rope and get the piston moving when hot - extreme but ok as a last option!

 

You could try the WD40 with the cylinder loose and try a SLIGHT rotating movement of a few degrees - dont go to far as it may cause damage from the ring to the ports.

 

The oil pump - blast carb cleaner/WD40 down the oil tank pipe after removing the pump - do the same to the oil outlet, attach a tube on to the oil pump inlet or outlet and blow down the tube and rotate the oiler gear - at one position you should be able to blow a little air through the pipe - if not - the pump is plugged.

 

Check the pinion gear - this is the most likely problem - sometimes the thread may have a slight distortion of flat that can stop it working - place it in to the pump and rotate it one revolution to make sure it turns the gear consistantly.

That is about it - good luck

[blue beastie]

Got it

 

Side cover off, spanner on nut at flywheel, and it turned with the slightest pressure. Now to inspect for damage & find the oiling fault....

 

Big thanks spud, I owe you one

[spudulike]

Got it

 

Side cover off, spanner on nut at flywheel, and it turned with the slightest pressure. Now to inspect for damage & find the oiling fault....

 

Big thanks spud, I owe you one

 

Think I am owed a brewery in total from a few guys on this site - long way to go for a pint:001_rolleyes:

 

Glad you got there in the end - just re-seal the base gasket with a smear of grease - should be OK.

 

Carefully check the oiler pinion for damaged thread and flat spots - it is very easy to miss a damaged thread on it - when they are stripped bare it is clearer. I place them in the removed oiler and turn the pinion to make sure it rotates the oiler gear correctly!