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Carb won't suck fuel???

Started by shinnlinger, February 15, 2011, 02:29:07 PM

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shinnlinger

HI,

I have an old Partner f-55 that will start up if you pour gas in the carb but won't stay running.  I replaced the fuel line and filter and can now see that no fuel comes up the line to the carb.  This particular model tilltson has no vacuum line like I have seen on other models and I don't understand how the carb generates a suction w/out a line as I am no mechanic.

Any thoughts on what to do next?

Dave
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

Al_Smith

The impulse comes out of a little hole in the intake manifold instead of a line like a majority of more modern saws .

More than likely the carb needs rebuilt but if somehow the impulse hole gets blocked by a gasket shifting or improperely installed it won't work at all .

shinnlinger

Thanks Al,

That makes sense and I will check that.  How hard is a carb like that to rebuild?  I don't mind giving it a go, but am I out of my league? WHere to buy a kit?

Dave
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

weimedog

Quote from: Al_Smith on February 15, 2011, 02:56:56 PM
The impulse comes out of a little hole in the intake manifold instead of a line like a majority of more modern saws .

More than likely the carb needs rebuilt but if somehow the impulse hole gets blocked by a gasket shifting or improperely installed it won't work at all .

Ditto ditto ditto! can't tell you how many times a mystery ends up being the impulse hole or line. One other thing is the tank vent...that's caused a few head aches for folks as well.
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

Al_Smith

According to Mike Acres site that saw was made in 1975 and uses a Tillotson HS carb which is pretty common . The kits are pretty cheap. Baileys have them and just about any other place that sells carb parts .

If you go to Tillotsons web site you can down load the directions of how to rebuild the things which really is fairly simple .Just pay attention to how you assemble and disassemble the thing and set things up as per Tilleys instruction ,you'll be in business .

:D I get amused with 1975 and old in the same sentence .

nmurph

carb kits are pretty easy. just make sure to pay attention to the order of the diaphragm and gaskets. i would also check that impulse passage for blockage. it will be a small hole at the bottom of the intake and will have a corresponding opening on the manifold block. vents can be a problem, but they usually don't cause a saw to not pump at start-up. it is easy enough to check a vent. crack the tank lid, then start the saw. if the vent is bad, the saw will start and then die out after running for a little bit. the fuller the tank, the shorter period it will run. it will also hiss when you open the lid if the tank vent is bad and has created a vacuum.

Al_Smith

Just as a piece of information and certainly not picking on anyone because of their lack of experiance is the fact carb parts get stiff as a piece of cardboard after being in service for years .The diaphragms and check valve assembleys are made of a synthetic rubber compound more commonly called buna n .While this stuff is more or less resistant to gasoline it isn't so resistant to ethanol .Even with non formulated gas over time they will deteriate but with the newer mandated mixtures which contain ethanol the deteriation is more rapid .

Often times I read on these forums of people cleaning the carb but having not much better performance from them .This is because the soft components of the carb are no longer supple and flexable as they should be .

A chainsaw carb is basically a pump with two check valves .If any of those components fail the system will not work as it was intended to .Now there are liitle tricks to keeping one functional for a period of time but cutting to the chase not to mention the frustration it's far better just to rekit them and be done with it .

I would venture a guess that 90 percent of the chainsaws ,weed wackers ,blowers  and other two cycle engines I work on the problem can be traced to a faulty carb from deteriated parts .Fact more times that not it's the biggest reason these items become destined to sit on a shelf or in some corner of a barn .Ironically of all problems you could find with a two cycle this is by far the easiest to repair .

shinnlinger

Al,

I found a chainsaw rebuild video on youtube that touched on what you just said and helped to ID that indeed a rebuild is in order AND mitigate my fears of trying it myself.  You just shed some light as to why the Partner quick working as well.  I got it after it sat for a a long while and put ethanol gas in it as thats all we have around here.  It worked fine for a tank or two and then just quit. The vid rebuilt a Walboro not a Tillotson but they look to be very similar so just ordered 2 kits from Scott at Chainsawr and hopefully I will have two old saws up and running here in the near future.

Thanks.

Dave
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

Al_Smith

Well it's not unusual for somebody to have apprehensions about heading into previously uncharted territory such a saw carb . Then again I once had that concern myself,kind of but that it was with a new girl friend but that's another story best left to the imagination without  the details .To cut to the chase though I soon overcame that problem in my youth  :D

I get a kick put of so called muffler experts etc. that go into great detail the science and technoligy involved in "porting a muffler " Just how does one actually port the stupid thing ? Great secret my foot .You just rework it so it flows better ,port has nothing to do with it .Port maybe refering to wine or the left side of a ship when  aft facing forward .Left hand turn at sea so to speak or a place where sailors supposedly have a girl friend in each although it really isn't that way .

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