2 stroke carbs

[bnem]

I just got a 2 stroke blower and I have a few questions.

When I depress the primer bulb it squirts a good amount of gas into the return line, but when I let go it seems to **** air (not sure where from, but it's not from the return line). The next time I depress the bulb it then squirts a bunch of air. It does this over and over and never consistently squirts just gas. Is this normal?

Second, does priming the carb squirt fuel directly into the venturi? These carbs are new to me and I've been trying to understand the design. It seems to me that priming the carb just ensures gas fills the carb and there are no air pockets, but no gas is actually pushed into the venturi. This kind of fits with how my blower is behaving, because no matter how many times I prime it it always acts like it isn't getting gas the first pull.

Thanks!

 

[Mhyde52]

Does not send fuel into carb bore, just like a manual fuel pump. Probably leak in suction line from tank, or primer assembly.

 

[kctyphoon]

Just throwing this out there - not answering your question I know, but you'd be amazed how cheap OEM carbs are for the lawn and garden stuff.. I don't even try to mess with them anymore when things go bad, I've replaced 2 so far, (gonna get another one for my generator) and I've gotten both for $35 or less. It's not even worth the headache trying to rebuild these things in my eyes..

Anyway - check out YouTube.. There's thousands of vids on carb repair and rebuilds that might illustrate all you'd like to know.

 

[djdaredevil]

I would get new lines, which depending on the blower might come as a kit of like 2 or 3, and I would get a carb rebuild kit and primer bulb most of these carbs are super easy to rebuild and its cheaper to rebuild them. Plus then you dont have to throw out carburetors.

 

[LawnBoy-5247]

The primer bulb only sucking air is commonly caused by a sticking check valves in the primer base plate or a cracked primer bulb, this prevents the primer form pulling new fuel in and will pull air back in preventing the primer form working. bad gaskets and fuel lines cause this sometimes but in my experience is is more often the check valves on the base plate or a cracked primer bulb. Also you are correct in your assumption that the primer only circulates fuel fom the tank to the carb, you cannot flood the engine with the primer. On the other hand leaving the choke on for more than a few pulls will flood the engine and cause a no start condition. So prime it all you want bit use the choke sparingly.

Source: Certified Stihl and Briggs and Stratton service Tech

Hope this helps

 

[bnem]

Thanks everyone.

It's a brand spankin' new Maruyama blower, so the primer bulb and a few other things are likely out of the question. Maybe I should take it to a repair shop and see what they say. Maruyama's come with a 5 year warranty, so I'm good for a while.

One thing it might be is the return line, perhaps. The return line is a yellow translucent hose that's been pushed onto a barb and there's no clip to secure it. If it is though, it should have no impact on the operation of the carb since the air could only ever flow out and never back in.

 

[413dan]

great explanation lawn boy, thanks.


good luck bnem, Ill add though that if it's brink spankin new as you put it, why not just take it back and get a replacement. could be a manufacturing default you'll spend years chasing. not like it's an already known well working machine that started running afoul. new and not working, get another that should be good to go out of the box as this should have been. just my .02c

 

[bnem]

The store was clearing them out so there's no hope of exchanging it.

 

[theoldwizard1]

When I depress the primer bulb it squirts a good amount of gas into the return line, but when I let go it seems to **** air (not sure where from, but it's not from the return line). The next time I depress the bulb it then squirts a bunch of air. It does this over and over and never consistently squirts just gas. Is this normal?

As stated, it sure sounds like there is an air leak in the fuel line or bulb. After 2-4 pumps it should just be fuel, although it could be sucking air because the primer bulb gulps such a big slug of fuel at time compared to normal operation.

2 stroke carbs do NOT like air (vacuum) leaks and usually will not start.

It's a brand spankin' new Maruyama blower, so the primer bulb and a few other things are likely out of the question.

If it starts, well, that is just the nature of the beast. If the bulb gets hard after a couple of pumps, you are good.

The store was clearing them out so there's no hope of exchanging it.

Hmm ... I wonder if they have been siting around for awhile causing the fuel line to go brittle.

The best fuel line is for small engine in Tygon. Bright neon yellow-green and very flexible. No clamps required although sometimes the hoses are different ID/OD. Typical diaphragm carb.

The small space at the bottom is both the fuel pump AND the the "bowl". The little bulb pump is to make sure there is some fuel inside the diaphragm chamber before you start. Excess fuel is pushed back to the tank so only a tiny amount of fuel is in the chamber at one time.

 

[bnem]

Tygon, that's what the return line and vent line look like. The actual fuel pickup seems to be rubber, though that may just be to the tank and inside might be different.

 

[gdocktor3]

If you fill the fuel tank up completely full, and still get air, you can rule out fuel lines. You'd get fuel leaks if it were outside the tank. It's the bulb itself which dry out and crack or a valve. Pull the carb off and bring it down to your local mom n pop mower shop. They have the parts and experience to fix it, probably cost $20. I recently brought a 1950s Farmall tractor carb to a shop and they had a specific machine to clean everything out, and then rebuilt it with all new gaskets, jets, etc. It cost $35 and wow what a difference. Yours is brand new, I know, but let someone who knows what they're doing fix it. Or order new one off eBay as KCTYPHOON said. I ordered a few for my landscaping equipment and it's sooo much easier.

 

[laser3kw]

It's a brand spankin' new Maruyama blower,

Never heard of it!
now get off my lawn