What's on your bench today?

[spudulike]

stage 3 ???????????

 

oh beat mattys 560 :lol:

stage 4 pop up piston

 

 

Looks that way, poop or bust

 

We have the technology to build the first.........

[burrell_]

there u go spud the chain thats on it is what i brought as soon as i got the saw the over chain is what came with it ent done hardly any work

here the pic u asked for

[burrell_]

last one

[spudulike]

Cheers Martin, details passed on and will see what occurs!

[swinny]

Looks a good saw that solo!!

[burrell_]

it is a good saw and will will be up for sale soon i will be putting it in arbtrader

 

trying to thin some of my stuff out i have to many toppers

[Adamam]

Yesterday I fired up this 254xp that I've been trying to nurse back to life, and it works! Woohoo!

 

So far I've done the bare minimum to get it running (piston, few gaskets etc).

 

It's running pretty well considering it almost certainly is desperate for a carb rebuild, but compression wise (only a quick look) it's still low.

 

It's reading about 120 with a new piston and ring.

 

The decomp valve was jammed closed when I got it (out position), and I'm wondering (hoping) that the decomp is faulty, which is why the compression reading is low.

 

Possible? Likely?

 

Also, with a new piston/ring, should I expect to see decent compression readings immediately, or does it need to run in? I only ran it for a few minutes at idle with a couple of tiny bips.

 

Sorry for yet more noob questions!!

 

[spudulike]

Yesterday I fired up this 254xp that I've been trying to nurse back to life, and it works! Woohoo!

 

So far I've done the bare minimum to get it running (piston, few gaskets etc).

 

It's running pretty well considering it almost certainly is desperate for a carb rebuild, but compression wise (only a quick look) it's still low.

 

It's reading about 120 with a new piston and ring.

 

The decomp valve was jammed closed when I got it (out position), and I'm wondering (hoping) that the decomp is faulty, which is why the compression reading is low.

 

Possible? Likely?

 

Also, with a new piston/ring, should I expect to see decent compression readings immediately, or does it need to run in? I only ran it for a few minutes at idle with a couple of tiny bips.

 

Sorry for yet more noob questions!!

 

 

Had a similar low compression readings on a 254 I was doing but generally you are straight in to 145 - 155psi with a new piston in an old bore, could be the bore has worn slightly oval over many years.

 

Did you clear all the aluminium transfer off the bore - this was probably my issue and another clean and new piston cleared it.

 

The quality of the piston will also make a difference - that is bore to skirt clearance.

 

120psi is low and will give problems with starting when hot - looks like you have some issues somewhere.

 

I believe these saws have got a large starter pulley as mine now pulls 160psi but still feels on the low side on the recoil.

 

It is worth pulling the muffler again to check the piston front for damage - I think I left some slight traces of Aluminium on the exhaust port - unusual for me:001_rolleyes:

 

What piston did you use, mine was Golf and they are fairly good quality - couldn't get a Meteor this time.

[Adamam]

Thanks for that Spud! Awesome information as always!!

 

I've tested it again, first with the throttle open (120 again) then closed (160ish). Weird. Then tested open again, 120 again. Then again closed (160) then open it tested 160 too.

 

Strange. Probably will just run it in for a while (don't have a bar or chain for it at the moment) and try again.

 

Seems worth persevering with anyway. Seems like a potentially really fun saw!

 

It's a mako piston by the way. Seemed okish. The old piston had cracked and mercifully doesn't seem to have messed the cylinder up at all.

 

You reckon (of the non-Meteor pistons) that Golf is the best option?

Edited June 1, 2012 by Adamam

[spudulike]

Not heard of Mako, new one on me, my recommendation is: -

 

1) Meteor

2) Episan

3) Golf but use the OEM circlips

4) White box Chinese

 

I do rate the Golf pistons above the typical Chinese kit - had rings snap on the unbranded kit, a few minor problems with Golf but zero problems with Meteor - always top notch.

 

Your compression is weird, my usual method is to make sure the saw has run a day to hours before testing, put the throttle on fast idle, pull the saw over, check the first hit - this should be around 1/2 maximum comp - then give it another 5 pulls until it won't rise any further.

 

145-155 is typical of a good engine, higher on a really fresh or modded saw.