non genuine piston and pot - any advice?

[agg221]

In answer to your questions in order:

 

You could fit a 47mm kit. It would give a little bit more power, but I really wouldn't bother unless you're going for a race saw. For a general slogger, the power increase will be negligible, and non-standard makes life unnecessarily complicated if you're ever looking for more parts in the future.

 

In your bottom picture, if you look at the face that bolts onto the crankcase, you can see the two pairs of channels (left and right of the image) through which the mix is transferred from the crankcase to the chamber above the piston. These channels are the transfer ports. These particular ports are closed, in that they are box-section channels with cylinder bore wall enclosing them. If the bit of cylinder wall that caps them off was removed, making them into 'U-channels' then they would be open.

 

No definitive knowledge of auto-decompressors, but if you can get a cylinder without one then yes, fitting a normal decompression valve (or a plug if you decompression valves as much as I do!) then that should do the trick.

 

Alec

[Peter]

Are you going to try cleaning the cylinder up or is it too far gone?

[spudulike]

Firstly - the piston is toast - use it as an ashtray if you smoke!

The cylinder looks like it will clean up IMO - you can't be 100% until you have done it but looks like a bit of aluminium transfer to me which you can remove chemically - avoid using abrasives - just fine grit emery for a light clean after removal of the aluminium.

 

Don't use a hone for a cast liner - you will take off all the Nikasil plating.

 

The real important part is the area above the exhaust port where compression is made!

 

If you go aftermarket - ask the seller if the cylinder supplied has open ports or closed ports - your OEM cylinder is closed as you can see where the fuel vapour goes in to the side transfers and comes out in to the combustion chamber, open ports have visible channels running up the cylinder.

My 346 kit from GHS was open port and I havent used it as it should be closed - most pro larger saws are closed. ArbIreland had a nice 346 kit but missed this when I purchased mine.

 

If it was my saw, I would clean up the bore and fit a meteor/episan piston if I could get hold of one or a golf with OEM clips.

 

The EPA decomp can be removed, a standard one fitted and the lower crank brass tube the pipe was fitted to can be plugged - I have used a bit of fuel pipe pushed on to the pipe pluged with a bolt glued and screwed in to the tube - make sure this is completely sealed and for Gods sake don't forget to plug it!

You can plug the decompresor hole in the cylinder and do away with it - you don't really need one but it may wear the starter gear a little quicker.

 

Also check the notorious carb boot has the husky metal clip mod, if it doesn't then use a jubilee clip that I personally prefer as it can be clamped harder.

 

I would also pressure check and then make sure the carb is retuned - if you don't know why it has seized then this is a must.

 

If you don't understand the above, lay down the tools, step away from the saw and give it to someone that knows their craft!

I can look at it for you if you like or do the cylinder work - choice is yours!

Edited June 21, 2011 by spudulike

[Chris Sheppard]

Am open to trying to clean the barrel, but what chemical would you suggest to use?

 

Yep, I'd tend to agree about the piston, it can sit with the 372 one that I have still (which makes the 357 one look mint!)

 

I'll pop up a pic of the auto decomp tube - all I can see is a short bit of pipe coming out of the side of the barrel and going back into it lower down and i didn't need to undo anything during dissasemble.

 

Think I've grasped the open and closed ports bit now, cheers guys

[Peter]

I cleaned my 660 up with a brake cylinder hone and lots of wd40.

[Megatron]

You could fit a 47mm kit. It would give a little bit more power, but I really wouldn't bother unless you're going for a race saw.

OEM 46mm cylinder will produce more power than virtually all aftermarket options, regardless of 46mm or 47mm.

 

I would also pressure check and then make sure the carb is retuned - if you don't know why it has seized then this is a must.

Regardless of whether you know how the seizure occured a vacuum test on the crankcase is a must. If it fails the vacuum test use pressure to find the leak. It is possible for oil seals to pass a pressure test but fail under vacuum (which is what they will do in operation on the saw) hence the order of the tests. Granted it is rare but correct proceadure none the less. Also checking of fuel line is a must.

I agree carb should also be tuned, which can be done at a shop/dealer but it is best for anyone to learn themself. This is because saws should be tuned for winter/summer conditions and for the altitude in which it is being used.

 

Am open to trying to clean the barrel, but what chemical would you suggest to use?

Hydrochloric acid is what most people use but Sodium Hydroxide works also. Wear a face shield, resistant gloves, no short sleeves etc and work in a well ventilated area.

 

I cleaned my 660 up with a brake cylinder hone and lots of wd40.

It is never recommended to do that because if the hone catches in a port it can chip off the Nikasil/Alusil/Chrome etc coating.

[Chris Sheppard]

The plot thickens - just been havign a closer look at the barrel and found a split in the tube from the auto decomp - possible cause maybe?

[spudulike]

Very possible this is the cause of the seize - the new decomp and associated tubes are around £30 and the normal decomp only - £10 - would fit the standard one and blank or plug this crankcase connector - looks a little different from my 359EPA.

 

You are getting some good advice on this thread!

[Chris Sheppard]

Nice one

 

So, plan of attack, try cleanign the current barrel with acid (next question - where would I be able to easily lay my hands on the acid?). If re-usable, get a new piston fitted, sort decomp, vac and then maybe pressure tests, all being well jobs a good un

 

Thanks for all your helpful advice so far guys, I hope other's will find it as usefull in the future

[spudulike]

Will PM you