How easy it is to put a new pot and piston on an FS400?

[doobin]

I'm reasonably mechanically minded. Do I need any special tools? And can anyone point me in the direction of some online reference material?

 

Thanks

[MR TREEBUS]

It depends which saw? whoops just read it properly.......sorry

Edited March 28, 2011 by MR TREEBUS
not read post properly!

[burrell_]

easy mate just rip it apart

take ur time and things will be ok i stripped dads about 3 years ago i cant remember much about it but it was a easy saw to take to bits

i put a new pot rings small end in. just rebuilt it

[miker]

ive just done my stihl hedge cutters, nothing to it really, just make a note of where everything goes, carefull with gaskets if you are not buying new ones, most jobs on a stihl can be done with a torx bit, t27 i think, good luck

[burrell_]

i find a hand thing to have when taking anything apart is a old washing up bowl and put everything u take of the machine straight in it (u cant loose nuts,bults,springs etc)

[spudulike]

The job itself is relatively easy - if the saw has seized, determining why it has done so is worth investigating.

 

Ensuring the crankcase is airtight is important, if you are fitting a P&C kit then that is fine as they will be a matched pair - if fitting just a new piston then there are a few things extra you will need to know!

 

A compression check will prove out the new parts.

 

It all depends on your mechanical ability.

[doobin]

The job itself is relatively easy - if the saw has seized, determining why it has done so is worth investigating.

 

Ensuring the crankcase is airtight is important, if you are fitting a P&C kit then that is fine as they will be a matched pair - if fitting just a new piston then there are a few things extra you will need to know!

 

A compression check will prove out the new parts.

 

It all depends on your mechanical ability.

 

Thanks Spud. It's not siezed, just very low on compression, Decomp is OK. If i've got to take it apart to replace seals, etc then I might as well fit a £50 FS 450 P&C and have myself some more beans

[spudulike]

Thanks Spud. It's not siezed, just very low on compression, Decomp is OK. If i've got to take it apart to replace seals, etc then I might as well fit a £50 FS 450 P&C and have myself some more beans

 

If it is down on compression then changing all the seals bar the decomp and spark plug will have an almost zero effect, compression is determined by the seal of the piston and rings in the top part of the cylinder just past the exhaust port and the amount of squish between the top combustion chamber of the cylinder and the piston.

 

In general, lack of compression is caused by a piston that has fried or in laymans terms, over heated, transferred aluminium on to the cylinder wall and then freed up again (seized). Generally - etching off the aluminium, a light hone and new piston is what is needed to sort out this type of failure.

 

A broken ring will also cause this failure and will stop a single ring saw from running.

 

If a saw has signs of seizure then I would always pressure check the saw to ensure the crankcase is airtight and ensure the carb is set up with an experienced ear or tach.

[doobin]

Thanks Spud, good advice. I know what caused it, lending it to idiots on a nature reserve. Having said that, it paid off because I've got weeks and weeks of work ahead of me for them with the digger etc. I know about fourstroking etc, already removed the anti tamper on this saw.

[spudulike]

Just read the post again - FS400 dohh strimmer/brushcutter and not a saw - same applies though - good luck with it - just make sure you are careful with parts and how they come apart - it is always worth taking photos with a digital camera for those "bugger me, where did that come from " moments