Haywire Haywood
Fiscal Conservative Social Retard
My 076 seems to spit a lot. I've read that worn piston skirts can be one cause. What are other possible causes for excessive spitback and... what is "normal" for a well used 076?
Ian
Ian
Carburetor Spitback Causes
- Thread starter Haywire Haywood
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GASoline71
Mr. Nice Guy
When my saw was chewin' snoose... it spit a lot too...
Heh, heh...
Gary
Heh, heh...
Gary
I think all saws spit some but the only cause I know of excessive spitting is a worn intake skirt on the piston. Can you hear it slapping the cylinder wall?
litefoot
Addicted to ArboristSite
Brad,
Can you explain how a worn piston skirt causes the blowback? I guess I'm not the sharpest knife in the drawer on this stuff. I'm just trying to get a visual of what's happening.
Can you explain how a worn piston skirt causes the blowback? I guess I'm not the sharpest knife in the drawer on this stuff. I'm just trying to get a visual of what's happening.
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Haywire Haywood
Fiscal Conservative Social Retard
When my saw was chewin' snoose... it spit a lot too...
Heh, heh...
Gary
Hey Hey... I'm the class clown... You're the oil guy. Stick to your assigned duties... LOL
Ian
GASoline71
Mr. Nice Guy
HAHAHAHAHA!!!
Gary
Gary
In a four stroke, it's a leaky intake valve. In a two stroke, a reed valve or the piston holds the charge from blowing back up the intake. Trimming the skirt or enlarging the intake port can do it, as can wear on the skirt.
jeeptj19992001
Addicted to ArboristSite
get a new pistton to fix it
RiverRat2
Serio Tree Freak
I think Gary's explanation is pretty good!!!!!!
LOLOL!!!! Just kidding,,,,
this phenomenom is more prevalent on piston ported two strokes,,,, or reed valve motos that have reed/piston wear issues,,,
with the piston rocking in the bore the worn skirt can no longer effectively seal the Lower compression zone below the rings in the fuel charge area,,,
so not all of the fuel charge is pushed into the transfers as designed,,,
so as you give the tired moto more throttle it tends to spit back through the carb because it has become inefficient from excessive wear,,
which in turn causes the airfilter to get soaked and the motor can actually run too rich,,, become hard to start fouls plugs,,, etc. etc.
A new piston and fresh rings will work wonders!!!!
on a reed valve moto piston/rings and reeds!!!!!
Hope that helps,,,,,
spitback
A plugged exhaust will cause that, check the arrester screen if you have one.
A plugged exhaust will cause that, check the arrester screen if you have one.
I always figured it was a guarantee of too rich, because some of the air goes through the carb forward, mixing it with gas, then goes through the carb backward, mixing gas into it, then goes through once more forward, picking up a third dose of fuel.
My little poulan was spitting real bad. Practicly squirting. It had a blown cylinder gasket. The cylinder was moving up and down a 16th". It has a reed valve by the way. It will still squirt if it's runing extremely rich. I found that out tinkering with the carb.
Haywire Haywood
Fiscal Conservative Social Retard
I'm thinking it may be a combination of a couple things.. It was hard starting yesterday come to think of it. I checked the air filter and it was oily and fairly clogged with fines and dust. I switched filters and it started right up, so I suspect it was running rich in combination with maybe some skirt wear. I'll have to check that filter more often than the 372 I suppose.
thanks,
Ian
thanks,
Ian
Understatement of the day award goes to...Ian!
Haywire Haywood
Fiscal Conservative Social Retard
Hehe... what the heck, an award is an award I suppose. It's just like the certificates of appreciation at work. Doesn't affect my paycheck at all. LOL
Ian
Ian
Yup. That about sums it up.
RiverRat2
Serio Tree Freak
yep!!!!!! Thats what they do!!!!!! its double edged sword!!!!!!
Keep a couple of plugs handy,,, if you are running the mesh type filter they are notorious for letting fines by which are not good for your moto,,, probably helped accelerate the wear on the intake skirt
We need to put a piston kit in that puppy and get a flocked filter!!!!!!
That piston slapping the bore isn't helping things BTW!!!!!!
:monkey: :monkey: :monkey:
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Haywire Haywood
Fiscal Conservative Social Retard
It is a flocked filter.... 
I haven't noticed any slapping sounds either.. Ran it this afternoon in some 30" hickory. I need to go check the filter again and pull the plug to see what it looks like. I got hot and sweaty, then wet then cold. I retreated indoors when I got back and got into some dry duds. I'll do some maintenance on it tomorrow after work and see what it looks like.
Ian
I haven't noticed any slapping sounds either.. Ran it this afternoon in some 30" hickory. I need to go check the filter again and pull the plug to see what it looks like. I got hot and sweaty, then wet then cold. I retreated indoors when I got back and got into some dry duds. I'll do some maintenance on it tomorrow after work and see what it looks like.Ian
