Chainsaw headache

[Bobupndown]

I'm losing my sanity with this.
My dad gave me his old Husqvarna 136 chainsaw, wasn't running in a few years. One of the exhaust threads in the barrel was stripped and the second one gave way tightening it up. It also had a scored piston. I picked up a good used bare engine for it and rebuilt it. Tried starting it. No joy. Discovered the carb was gunged up. Tried a rebuild kit on it. Not getting fuel through it. Bought a new aftermarket carb for it and fitted it. It still does not seem to be getting fuel through to the cylinder??
So I fired some pre mixed fuel straight through the carb and it still won't bl00dy start. It has good compression, it has got a spark. I'm out of ideas here.
I don't think the timing can be out, can it?
Any 2 stroke experts on here can offer suggestions?

 

[Guineafowl]

Timing is usually fixed with a key between flywheel and crankshaft. Worth a check if you’re desperate. Undo the nut with a rattle gun (check it’s not LH thread), screw back on a bit and give a sharp tap with a copper hammer.

Check for a clogged exhaust/spark arrestor screen.

Play in the crank bearings? Might need a pressure test.

Check coil poles are about 0.012” from the flywheel magnets.

Sparking outside the cylinder doesn’t guarantee sparking inside, under compression. Suspect the coil or plug if it won’t fire with easystart.

 

[8ob]

I'm losing my sanity with this.
My dad gave me his old Husqvarna 136 chainsaw, wasn't running in a few years. One of the exhaust threads in the barrel was stripped and the second one gave way tightening it up. It also had a scored piston. I picked up a good used bare engine for it and rebuilt it. Tried starting it. No joy. Discovered the carb was gunged up. Tried a rebuild kit on it. Not getting fuel through it. Bought a new aftermarket carb for it and fitted it. It still does not seem to be getting fuel through to the cylinder??
So I fired some pre mixed fuel straight through the carb and it still won't bl00dy start. It has good compression, it has got a spark. I'm out of ideas here.
I don't think the timing can be out, can it?
Any 2 stroke experts on here can offer suggestions?

No fuel could be shot crank seals. crankcase pulses sent to the diaphragm bring the fuel up. I would vac test it before spending any more on it.

Bob

 

[zzr1200]

Disconnect the stop switch, it's not un-usual for the kill switch to fail.

Strip the carb, put it in an ultra-sonic bath cleaner and leave going high temp for at least 30 mins....if not longer.

I normally do an hour minimum at max temp

 

[Smallfry]

Could be the flywheel key sheared, which will put the timing out. Assuming the checked the replacement engine for any bore scoring, which will affect the way the carb works. New spark plug, an NGK, not effing Champion. Fuel pick up filter in the tank. If it looks at all dark coloured, it will be inhibiting flow. Also check the pick up pipe all the way from filter to carb. Any split will leak air and prevent starting.

 

[Bobupndown]

Timing is usually fixed with a key between flywheel and crankshaft. Worth a check if you’re desperate. Undo the nut with a rattle gun (check it’s not LH thread), screw back on a bit and give a sharp tap with a copper hammer.

Check for a clogged exhaust/spark arrestor screen.

Play in the crank bearings? Might need a pressure test.

Check coil poles are about 0.012” from the flywheel magnets.

Sparking outside the cylinder doesn’t guarantee sparking inside, under compression. Suspect the coil or plug if it won’t fire with easystart.

I've used 2 different plugs, coil possibly? Assumed sparking outside meant sparking full stop.

No fuel could be shot crank seals. crankcase pulses sent to the diaphragm bring the fuel up. I would vac test it before spending any more on it.

Bob

I'm leaning towards this thought. Nothing to test it with.

Disconnect the stop switch, it's not un-usual for the kill switch to fail.

Strip the carb, put it in an ultra-sonic bath cleaner and leave going high temp for at least 30 mins....if not longer.

I normally do an hour minimum at max temp

New carb fitted. If it's getting sparks surely the kill switch isn't faulty?

Could be the flywheel key sheared, which will put the timing out. Assuming the checked the replacement engine for any bore scoring, which will affect the way the carb works. New spark plug, an NGK, not effing Champion. Fuel pick up filter in the tank. If it looks at all dark coloured, it will be inhibiting flow. Also check the pick up pipe all the way from filter to carb. Any split will leak air and prevent starting.

Bore and piston look perfect.
It's had a new filter. I will replace fuel line too but don't see any defects. New quality plug might be better.

 

[JOEPRO]

You are welcome to use my Mityvac - I am in Co Tyrone maybe too far but offers there

 

[Bobupndown]

Thanks Joe appreciate the offer.

 

[zzr1200]

New carb fitted. If it's getting sparks surely the kill switch isn't faulty?

The stop switch probably isn't faulty but pulling the wire off of it would totally rule it out.

Your "New Carb" is it an OEM supplied part from a chainsaw dealer or an Ebay Pattern type part????

Is the carb intake boot in good condition possibly cause a lack of pulse from the crankcase to the fuel pump, are the metering valves set correctly........ all a possibility....

 

[Memmeddu]

Husqvarna 136 , a lot of memories from 2 years ago...
I have a jonsered 2036 turbo, which is practically the same saw
Impulse tube is most of the times the cause of all the problems with those chainsaws.
Clean your carb don't waste money on cheap carbs .
I'd check tank vents too .
It should have started anyway with mix into the cylinder

 

[frank horton]

nobody has mentioned the tank fuel filter yet.....

 

[Bobupndown]

The stop switch probably isn't faulty but pulling the wire off of it would totally rule it out.

Your "New Carb" is it an OEM supplied part from a chainsaw dealer or an Ebay Pattern type part????

Is the carb intake boot in good condition possibly cause a lack of pulse from the crankcase to the fuel pump, are the metering valves set correctly........ all a possibility....

Yes it's an eBay carb. Don't intend to spend much money on this until I know if it's worth fixing. The carb boot is in good condition.

 

[Islander71]

The impulse tube which operates the carb diaphragm seems very finicky and awkward on these saws and needs to be fitted perfectly.

 

[Guineafowl]

nobody has mentioned the tank fuel filter yet.....

‘E did…

Fuel pick up filter in the tank.

To my mind, if you add fuel directly, and it doesn’t fire, it’s a no spark. Complicated by other things, such as flooding.

I use FACTS as a reminder:
F uel
A irflow (intake -> exhaust)
C ompression
T iming
S park

First and last ones being the most common.

 

[Bobupndown]

The impulse tube which operates the carb diaphragm seems very finicky and awkward on these saws and needs to be fitted perfectly.

This particular carb doesn't have a separate impulse tube, there is a passage way between the rubber intake manifold and the carb itself.

 

[dobbslc]

If there's a gasket make sure it's not the wrong way round and blocking the passage.
Are the flow and return fuel pipes the right way around?

‘E did…

To my mind, if you add fuel directly, and it doesn’t fire, it’s a no spark. Complicated by other things, such as flooding.

I use FACTS as a reminder:
F uel
A irflow (intake -> exhaust)
C ompression
T iming
S park

First and last ones being the most common.

@Guineafowl
Do you do corporate motivational talks for a living?

 

[zzr1200]

This particular carb doesn't have a separate impulse tube, there is a passage way between the rubber intake manifold and the carb itself.
View attachment 459243

Was dab of silicone used or even the old gasket used again???........possible blockage or air leak.....

Ebay carbs can be hit n miss as to working.

Note:-

I purchased a Parker Brand leaf blower, it run ok but was never really strong.

After a couple of years I decided it needed a carb rebuild, looked into buying a carb kit or a new carb, with the cost of a new carb and gasket set it was only another £20>£30 more expensive to buy a new blower, which worked perfectly out of the box, I'm sure the carb was the cause of the bad running. Now I have all the spares I need apart from a carb.....

 

[Guineafowl]

Do you do corporate motivational talks for a living?

The opposite
In a former life (vet), coming up against ‘corporate’ things like DEFRA, I was more likely to ‘motivate’ them to stop throwing bits of interfering paper at me and get a proper job.

 

[Bobupndown]

Well got it to start at last, not run though.
The key in the crank had sheared and the 'flywheel' was in the wrong position. Managed to get it back into the original place and tightened the nut down. Hopefully the taper will hold it in place.
New fuel line and filter fitted but not starting still. Shot of fuel into the carb now has it running momentarily. I did notice however that it is sucking petrol up from the tank as you pull the starter so assuming it's getting pulses in order to do that, otherwise there is no way that it will flow uphill? (There is no primer bulb on this saw). So it's obviously just not getting the fuel through the carb.
Will have a further play with it in due course to see if I can persuade it back into action.

 

[Guineafowl]

See what the H/L screw settings are, then set them both about 1.5 turns out if in doubt. Should get you in the ballpark.