Stihl 034 won't start & needs top end kit

[cuinrearview]

Just do what the sticker on yours says. Adjust from there, it usually isn't too far off.

 

[jpan]

Looks like I’m going crazy. The carb gaskets look like they were in the right order.

The check valve also appears to still be in place.

here’s some pics of the carb I just tore it apart real quick.

I’ll pull the cylinder here in a few minutes

 

[Mad Professor]

This might help

 

[jpan]

This might help

Thanks - looks like I had the gaskets and diaphragms all in the correct order.

Putting a parts list together so hope to get everything ordered and back together soon

pics of the piston and cylinder both showing exhaust side.

 

[brad ruch]

Have you confirmed good spark?if so it will definitely try to fire with a little gas/mix on the plug.i can't remember the last time I had a saw not at least fire for 5-10 seconds even if the carb needed rebuilding.sometimes would need to spray a little fuel in the plug hole but always fired.

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[jpan]

Have you confirmed good spark?if so it will definitely try to fire with a little gas/mix on the plug.i can't remember the last time I had a saw not at least fire for 5-10 seconds even if the carb needed rebuilding.sometimes would need to spray a little fuel in the plug hole but always fired.

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i confirmed spark. It did look slightly weak but I was also trying to hold the saw, the plug, and pull the rope so it may not have been grounded well. I’ll try to measure resistance of the coil while it’s apart. When I tried to put some fuel directly in the cylinder I still couldn’t get it to pop off. But the carb was still bone dry too

 

[drf255]

Looks like I’m going crazy. The carb gaskets look like they were in the right order.

The check valve also appears to still be in place.

here’s some pics of the carb I just tore it apart real quick.

I’ll pull the cylinder here in a few minutes

The check valve is inside the main nozzle. It’s a little flapper that’s tan colored knit nylon looking material. Sometimes you can see it therough the carb bore.

If you can’t, you have to drive the nozzle out through the carb bore by punching it through from the metering side. Carb kits will sometimes include a new flapper/valve for the nozzle.

Your carb kit pump diaphragm looks AM. I’ve heard some of the AM ones are stiff and don’t pump as well. They are generally tan colored like the check valve flapper.

 

[Totembear]

The carb can be bad and not deliver fuel but if you put fuel down the spark plug hole, and its got spark, it will fire up. I've never had a saw thats got spark fail to fire up that way. I'd put a new coil on it and see what happens. Also, I've had to prime saws that way too. Dont know exactly what happens, but if the spark plug is dry, put some mix down the hole and sometimes it gets the fuel flowing when it fires. Sometimes not, but if it fires then dies then I've got carb prolems. If it doesnt fire at all then I've got spark, or plug, problems.

 

[jpan]

I believe the carb kit was a Zama kit. this carb is a C3A-S4C. The kit purchased was a Zama RB-31 kit, but I suppose it's possible it was a knock off. I'm reading the Zama manual that Mad Professor posted and will test the check valves. I've got the parts ordered, so hopefully they'll be here sometime next week and I can get it put together and tested.

While I have the top end off, should I shoot any kind of oil into the crank bearings / rod bearing?

update: I reassembled the carb and using a fuel line on it I can neither blow or suck air through it. Does this mean the check valve is stuck?

 

[Mad Professor]

I believe the carb kit was a Zama kit. this carb is a C3A-S4C. The kit purchased was a Zama RB-31 kit, but I suppose it's possible it was a knock off. I'm reading the Zama manual that Mad Professor posted and will test the check valves. I've got the parts ordered, so hopefully they'll be here sometime next week and I can get it put together and tested.

While I have the top end off, should I shoot any kind of oil into the crank bearings / rod bearing?

Rinse out the bottom end with mix.

 

[drf255]

I believe the carb kit was a Zama kit. this carb is a C3A-S4C. The kit purchased was a Zama RB-31 kit, but I suppose it's possible it was a knock off. I'm reading the Zama manual that Mad Professor posted and will test the check valves. I've got the parts ordered, so hopefully they'll be here sometime next week and I can get it put together and tested.

While I have the top end off, should I shoot any kind of oil into the crank bearings / rod bearing?

update: I reassembled the carb and using a fuel line on it I can neither blow or suck air through it. Does this mean the check valve is stuck?

No, that’s normal.

An assembled carb should hold at least 15psi of pressure. It’s called “pop-off” pressure, which refers to the opening of the needle on the seal.

The check valve is simply a flapper that sits in the nozzle.

 

[drf255]

 

[drf255]

Here is the check valve. It’s simply stops air from entering the wet side at idle.

 

[drf255]

Some good reading.

https://www.helifreak.com/showthread.php?t=326599

 

[huskihl]

View attachment 762286 View attachment 762287

Voodoooooo.......

 

[jpan]

No, that’s normal.

An assembled carb should hold at least 15psi of pressure. It’s called “pop-off” pressure, which refers to the opening of the needle on the seal.

The check valve is simply a flapper that sits in the nozzle.

Thanks for the details! Hopefully it’s all set up now. I’ll Pressure test the carb too before putting it back on. All the parts will be here Wednesday. I’ll do another vac and pressure test after it’s together then see if she fires!

And you’re right....carbs have always been little voodoo machines. Ha!

 

[drf255]

Make sure you put a little mix in the line if it doesnt hold pressure. Sometimes a dry seat will leak.

 

[Mad Professor]

I know the 034 has the c3A Zama, but here are some more carb tech manuals members might find handy.

 

[jpan]

I ended up ordering the an 036 kit. Doing it somewhat on a budget since it’s for a friend and won’t be used regularly.

I know I’ll need to get the muffler switched to an 036 style or spaced out and trim the top cover. Any recommendations on an 036 muffler or spacer for the current 034 muffler? Some of the mufflers I’ve seen say you still need a spacer so could use some advice on which one to order that will fit. Thanks!

 

[jpan]

working On getting it back together. Man these piston circlips are a pain! Any tips on installing without bending them? Tried grooved small tuning screwdriver, a slot in a pair of pliers, but nothing works.

Or...anyone in KC that has the tool and needs a cold beer?