bjorn773
ArboristSite Operative
Gotta go make some money wrenching on cars for now. I will report back later when I have a chance. Thanks guys!!
55psi with new piston???
- Thread starter bjorn773
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I think you might be on the right track. Put that baby back together and run it. If it runs good, you'll know your guage is bad.
bjorn773
ArboristSite Operative
Ring gap is the same all the way up the cylinder. The decomp seems to be closed and nothing in it. I'll throw it together and see what happens.
Oldsawnut
Addicted to ArboristSite
Just a thought but you tightened your cylinder down all the way first right? If not then it would have too much squish. You said it wasn't totally assembled first so just checking.
John
John
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opcorn:
AUSSIE1
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What was your squish reading?
Sealer both sides of the base gasket will add to it.
Sealer both sides of the base gasket will add to it.
Take the piston ring off and drop the piston in to the jug with your finge over the spark plug hole - the piston should slide slowly toward the spark plug hole.
Place the ring in the jug and check the end gap, 5 thou is good, 10 thou is getting too big.
I reckon your gauge is bad or the piston is 1mm undersize (an incorrect one)- could be the wrist pin to piston crown being wrong. Check it against the old one.
A new piston without a ring should get to 50 - 60 PSI
Spud
Place the ring in the jug and check the end gap, 5 thou is good, 10 thou is getting too big.
I reckon your gauge is bad or the piston is 1mm undersize (an incorrect one)- could be the wrist pin to piston crown being wrong. Check it against the old one.
A new piston without a ring should get to 50 - 60 PSI
Spud
Take the piston ring off and drop the piston in to the jug with your finge over the spark plug hole - the piston should slide slowly toward the spark plug hole.
Place the ring in the jug and check the end gap, 5 thou is good, 10 thou is getting too big.
I reckon your gauge is bad or the piston is 1mm undersize (an incorrect one)- could be the wrist pin to piston crown being wrong. Check it against the old one.
A new piston without a ring should get to 50 - 60 PSI
Spud
called piston height, i thought someone mentioned that earlier, but good point.
bjorn773
ArboristSite Operative
I didn't measure squish. I plan on tearing this saw back down later to try my hand at some porting. I figured I'd do more measuring then. I just wanted to get it running. I got it to fire earlier on carb cleaner into the plug hole. There was very little fuel in the tank. I haven't had a chance to mess with it any more. I don't know what exactly caused the piston failure. The saw was given to me by a friend who got it from another friend. I can only assume it was run on straight gas. I want to try another compression reading with my hold in gauge as opposed to my old thread in one. Anyway, I'll update as soon as I have a chance to mess with it further.
Nitro-Fish
ArboristSite Operative
You did get a 45mm piston for a 353 didn't you? A 45mm piston for a 51 has different specificatons, i.e. pin height etc.
Lots of new saws have more than .010".
Stock/new clearance, at the base/skirt should be about 0.004". On yours with 0.015" on the skirt, with new rings, after seating, will run good until the piston, grenades [Usually broken skirt or seize due to a "rocking" piston]........how long????....... days, weeks, years (if you cut a few tanks a year),........
Don't have a manual but 0.018 seems a bit much too on the rings............
Is this a Keeper or a pass on/selling.
That's just what I think............everybody else can comment some more.....
He said he CAN'T get a .015 feeler guage in there.
bjorn773
ArboristSite Operative
Well, as I suspected there is a gauge issue with my other gauge. The press in type has a schrader on the tip. I pulled with it several times and I have 125psi. Still not great I suppose, but it should run. However, it still does not. I have to do some further diag tomorrow. I also need to replace the primer hose to the tank prior to any further work... leaking lots o gas.
bjorn773
ArboristSite Operative
I suspect some kind of ignition issue now. I am getting a wet plug but it never seems to fire. I pulled the recoil and I couldn't see the ignition due to so much grime in there. I don't know why I didn't notice this earlier when I was blowing everything off. Anyway, I blew all the grime off with compressed air. I don't know how much this grime would affect the magneto operation, but I know it can't help. I'll try tomorrow after I replace the leaking primer hose.
wigglesworth
Booned
im not an expert, but wont that create a massive air leak? That may be why it wont run. My buddy's trimmer wouldnt run with the primer bulb busted.
bjorn773
ArboristSite Operative
The primer is ok. The hose that connects it to the tank was swelled at the tank nipple. I trimmed enough off to get it to grab better, but I think now the hose is too short. It pulled off while I was trying to start the saw earlier. I need to get a new piece of hose. I looks to be clear hose like what I can get at the hardware store. I imagine I am wrong, though, and it will have to be a special fuel grade hose from a small engine shop. Anyone?
Nitro-Fish
ArboristSite Operative
If you have a local Husqvarna dealer, you should be able to get the OEM fuel line for less than $5, while you're at it I would get a new filter too. If no husky dealer is close, get the right size tygon fuel line which should be available from any small engine shop. Be sure and check all lines, the impulse line is kind of under everything and on the carb boot. It is probably shown in the service manual.
bjorn773
ArboristSite Operative
Ok, I'm at a complete loss here. I replaced the primer fuel line today. I drained the tank and looked long & hard at the fuel hose inside. I couldn't see any flaws, so I opted to leave it alone. I checked the air gap of the magneto, set it with a .3 mm feeler. I pull the rope and seem to have a good spark with the plug laying on the cylinder. The plugs are getting wet, so I believe I'm getting fuel as well. I've even tried spraying carb cleaner directly into the cylinder. I don't get so much as a sputter. Compression reads 125 psi. I am using the same gas that I have been running my 359 on. I've tried several plugs to no avail. My only thought is ignition timing. Can these flywheels spin? Is there a key or something like on a 4 stroke that can be giving me spark at the incorrect time. Help, I'm ready to shotput this saw into the next block.
Did you put the right size piston in?
