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Carb problem?

Started by Mikeinkaty, July 23, 2016, 06:10:01 PM

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Mikeinkaty

My old Practica finally having problems.  Last week when halfway through a large log, it bogged down and quit.  Giving it throttle did nothing.  Let it set couple of hours.  It again started good then halfway through the log it bogged down and died.  Just before this problem started I had put a new fuel line on.   Fuel line looks to be good.  This was a 36" log.

So I'm thinking I need a new carb kit.  Ordered one from Tollitison and installed it.  Now I can't get it to hit at all.  I pulled off the carb 3 times checking for correct installation of the kit.  Looks ok.  I have the idle screws turned out 2 turns from the stop position.   I have tried putting a little fuel in the spark plug hole.  Nothing.  Plug has good fire.

Any ideas?

Mike

sharkey

Check the orientation of the gaskets to the diaphragms, inside the carb.  They are opposite from the pump to the metering side.  For example on the pump side the diaphragm is first, followed by the gasket and then the cover.  On the metering side the gasket goes first, then the diaphragm and then the cover.  Look up the carb and follow the schematic if your not sure. 

Mikeinkaty

That was the first thing I looked for.   The yoke that holds the needle valve - the  old yoke and the new one have about 1/8" clearance to the top rail.   It is working though cause when I blow through the inlet pipe it's blocked until I depress the diaphragm.   I'm not finding any gasoline on the spark plug.

Shouldn't I get a grunt out of it though when I put gasoline in the spark plug hole?

sablatnic

Did you change the fuel filter, in the tank, at the end of the fuel line?
And is the filter in the carburetor clean - it is located opposite the needle valve.

dougand3

Quote from: Mikeinkaty on July 23, 2016, 08:37:23 PM

Shouldn't I get a grunt out of it though when I put gasoline in the spark plug hole?

Yes, a tbl spoon of fuel mix in carb throat or plug hole should give a burp and 1-3 secs run time. (May take 10-20 pulls cuz will be floody.) This is even if whole fuel system is wonky.

And when you say "gasoline", you do mean fuel mix at ~40:1, right?
Husky: 372xt, 272xp, 61, 55 (x3)...Poulan: 315, 4218 (x3), 2375, 2150, 2055, 2000 (x3)...Stihl 011AVT...Homelite XL...Saws come in broken, get fixed or parted, find new homes

Mikeinkaty

New fuel filter in tank.  It came with the new line.  If you mean the screen wire about 1/4" in diameter, then yes I changed it with the new one in the kit.   I have wondered about the silver colored domes.  The kit came with both but I see no way to get the old ones out.  Looks like they have to be seated in with a special tool.

Mikeinkaty


dougand3

Those domes are welch plugs. Can be varnished underneath and need to come out and clean. Sharp pick removes old one. Allen wrench or wooden dowel ~ 80% of plug size and light tap with hammer installs new one. Usually 4 tiny holes under welch plug need to be clean and free flowing. I use carb cleaner spray.

Is this a Husky 61? They have AM carbs for $10-15 online. Same carb as 268 or 272.
Husky: 372xt, 272xp, 61, 55 (x3)...Poulan: 315, 4218 (x3), 2375, 2150, 2055, 2000 (x3)...Stihl 011AVT...Homelite XL...Saws come in broken, get fixed or parted, find new homes

Mikeinkaty

Husky Practica 61. I bought it new in 1979, I think.  This is its first major problem.

I ordered a Chinese 61 replacement carb.  It least that might tell me if it is a carb problem.  Tomorrow I will try to get the welsh plugs out.   Will the carb cleaners in a spray can work or should it be soaked?   I did blow it out with an air chuck. 

dougand3

You can get plug out with a sharp pick. If nec, go in fairly horizontal, poke hole and lever out. I use spray can carb cleaner but don't hold straw too close or too much pressure. Soaking in chem dip would probably work fine. I'd still blow it out with 40 PSI air.
Husky: 372xt, 272xp, 61, 55 (x3)...Poulan: 315, 4218 (x3), 2375, 2150, 2055, 2000 (x3)...Stihl 011AVT...Homelite XL...Saws come in broken, get fixed or parted, find new homes

joe_indi

If there is any moisture in the cylinder, you wont get a peep out of it. So you might have to pour in a bit more and crank with the plug out to make sure there is no moisture.

Quote from: Mikeinkaty on July 23, 2016, 08:37:23 PM
Shouldn't I get a grunt out of it though when I put gasoline in the spark plug hole?

Yes, if the compression is good in a moisture free engine.
A good spark alone does not make the ignition healthy. Are you getting that spark at the correct timing?
Check whether the flywheel has twisted out of its key.

Mikeinkaty

I'll check the flywheel after my sweat drys off!

Got the new welsh plugs installed.  Blew out all the holes with carb cleaner then let it soak.  After that I blew it out with an air chuck.   Still not a grunt out of it.  Tried the old spark plug.  Nothing.

Mikeinkaty

Flywheel looks ok.  When the piston is AT TDC, the center of the magnet is past the center of the pick-up maybe 5°.  Just an eyeball measure.

I need to check the compression.  Where can I get one that screws into the spark plug hole?  I don't think compression is a problem, but would like to check it.

sawguy21

Pick the saw up by the starter handle, if it doesn't drop compression is good.
old age and treachery will always overcome youth and enthusiasm

joe_indi

If the engine is good, you dont need the carb to get it to run for a couple of seconds.
Remove the carb.
squirt some fuel into the intake and pull the starter.
It should fire up, run a second or so and then stop.
If it doesn't do this you will need to really check the compression (cylinder &piston) and the ignition.
Without doing this if you proceed any further you are only going to stretch that arm a bit more and learn some new cuss words  ;D

Post Script: Also try disconnecting the wires from the ignition coil that go to the switch.
http://www.acresinternet.com/cscc.nsf/ed1d619968136da688256af40002b8f7/f83fc7f9a47cc6c788256b520015ac96?OpenDocument

motohed

I would check the plastic manifold for cracks , look closely around the the pulse hole through the manifold , I'm sure you have a crack or maybe some dirt clogged in it , when you changed it . Isf it's not that then make sure the orifice in the jug is clear . This is what drive the fuel pump in those saws , they are much like the new pulse line on newer saws . I would also get a kit for the old carb and rebuild it , the old carbs , are better built than the newer replacements .

motohed

Quote from: motohed on July 25, 2016, 08:54:51 AM
I would check the plastic manifold for cracks , look closely around the the pulse hole through the manifold , I'm sure you have a crack or maybe some dirt clogged in it , when you changed it . Isf it's not that then make sure the orifice in the jug is clear . This is what drive the fuel pump in those saws , they are much like the new pulse line on newer saws . I would also get a kit for the old carb and rebuild it , the old carbs , are better built than the newer replacements . If that fails , I would do a preassure test on the saw for an air leak , you may want to do that first . Just wondering if you did a compression test at all , it maybe time for a set of ring or a new piston and rings . Do some systematic testing to rule out the possibilities .

Mikeinkaty

I checked the plastic manifold and gasket.  Looks good, pulse hole clear.   While there I check what little of the piston I could see.  Clean as a whistle, no scratch marks at all.

I devised a chuck for my cordless drill to spin the engine.  Put some light oil in the plug hole and spun it up fast.  Good blue spark.

I put the plug in and spun it up to like maybe 100 rpm and got no hits at all.  I had even put fuel in the horn of the carb.   I'm bumfuzzled.   There seemed to be plenty of compression.  Even tried another spark plug.

Mike

motohed

I would suggest checking the flywheel key , and do a compression test . Thats really all that left . If you have fuel , compression , and the right spark timing , there is no reason it shouldent run . pull the muffler and look at the piston , you can make sure it's not scuffed .

joe_indi

Also try a start with the muffler removed and fuel squirted through the exhaust port directly onto piston top. No choke but fast idle.

Bill Saf

Did you check the gas tank vent if clear. you could have had crank seal go out check clutch side for movement of crank.

Mikeinkaty

Pulled the flywheel.  It and the key were fine.   Now to fine a cheap compression tester that's reasonably accurate.   Any recommendations?   O'rilleys, Sears, ???  Quite a few auto parts stores around here.   

Should I be able to pick up the flywheel with a screwdriver on the magnet?

Mikeinkaty

Ok, think I'm getting somewhere now.  When I put the flywheel back on I spun it up again.  Getting good spark at high rpm but NO spark at low rpm.  No way would it make a spark pulling it with a rope.   Now, the flywheel gap is as small as I can get it.  Smaller than the thickness of my thinnest business card.  I seem to remember that several years ago I set it to the thickness of two layers of wax paper.  The magnet on the flywheel seem weak.   So I think the flywheel should be replaced.  Probably aught to do the pickup module and the power coil while I'm at it.   Are the electronic ignition components inside the pickup module?

Where can I get these parts?  Can the wheel be re-magnetized?

Mike

Mikeinkaty

Oh, where is the gas tank vent??

Bill Saf

Quote from: Mikeinkaty on July 26, 2016, 09:54:44 PM
Oh, where is the gas tank vent??

heres a link to the IPl for your saw look on page 5 part # 501  62  96-01

http://www.husqvarna.com/ddoc/HUSI/HUSI1984_AAaa/HUSI1984_AAaa_I8400015_.pdf

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