gas spraying out of carb?

[DiscoInferno]

I have a 32cc Ryobi trimmer that I bought the 10" pole-saw attachment for last year when I needed to dismember a tree that had partly fallen over. The trimmer is about 12 years old and seldom used. When I was using the saw it would start fine and would run OK in half-choke, but if I opened the choke fully it would generally die when I tried to accelerate. So I ran it on half choke, finished that job, and put the trimmer aside. Today I finally got around to rebuilding the carb; it was pretty clean and in good shape inside but I sprayed it out good and changed the screen and diaphragms anyway. Put it back on, and now it doesn't die right away when I accelerate with the choke open, but what it does do is sputter and shoot a gas-air mist out of the carb's air intake! It might have been doing this before also, but I had the air filter on and wouldn't have noticed. The other odd thing is that a little gas is bubbling out the pressure-relief hole in the gas cap, like the gas tank is being pressurized somehow. I thought it should be depressurized if anything. Anyone have any idea what the issue is? I'm in over my head at this point.

 

[wooddope]

Check to see if the exhaust port or muffler is restricted by carbon especially if it has a spark screen

 

[DiscoInferno]

The muffler actually was coming loose in the midst of this testing, so I pulled it off. Exhaust port was clean, and if the muffler does have a screen it's not visible. The muffler output is effectively a 90-degree bend (there's a plate held at a 90 to the exhaust flow), so I think it's just using the wall of the 90 to block sparks. Overall it doesn't seem restricted, but I'll look more carefully.

 

[smokinj]

Look at all your fuel related lines.....Should be 3 of them but not sure on that model. One fuel one back flow and another impulse line Maybe. Just a guess here but sounds like the return line is shot or pinched.

 

[DiscoInferno]

I replaced the fuel lines back when I first hauled it out, as they were all cracked. Gas freely flows from the tank through the carb and back to the tank when I squeeze the primer bulb. There is no separate impulse line.

I guess what confuses me is that I thought that's where the engine drew air in. If fuel is spraying out, then where is that air coming from?

 

[smokinj]

I replaced the fuel lines back when I first hauled it out, as they were all cracked. Gas freely flows from the tank through the carb and back to the tank when I squeeze the primer bulb. There is no separate impulse line.

I guess what confuses me is that I thought that's where the engine drew air in. If fuel is spraying out, then where is that air coming from?

I really dont know. Weedeaters are something I have never had or worked on, But if the air filter off i would expect some gas spraying. Is there any Carb adjustments on this thing?

Also check gas cap for vent if there is one make sure it is clear and working?

 

[DiscoInferno]

It has the usual H, L and idle. I've fiddled with them without much success.

Why would you expect gas spraying with the air filter off? Would it be normal for gas to spray into the air filter when it's on?

 

[smokinj]

It has the usual H, L and idle. I've fiddled with them without much success.

Why would you expect gas spraying with the air filter off? Would it be normal for gas to spray into the air filter when it's on?

No, but with it off and running its just hard to tell. Even fires can start in extreme cases. How about the cap is it vented? Without impulse line it seems there should be a vent whole and it could be plug.

 

[DiscoInferno]

The gas cap? It does have a vent, and in fact there is air blowing out of it when the engine is running. I can tell because there are gas bubbles on top of the cap. That's something I don't recall it doing in the past.

 

[smokinj]

The gas cap? It does have a vent, and in fact there is air blowing out of it when the engine is running. I can tell because there are gas bubbles on top of the cap. That's something I don't recall it doing in the past.

Anything in the carb rebuild you could have missed? This a new or old jet? Its pulling gas hard.

 

[DiscoInferno]

Probably, since it's the first and only carb I ever took apart. But it was doing pretty much the same thing before, which is why I rebuilt it. Frankly the carb looked almost brand new inside, which surprised me considering I would leave the same gas in it for years at a time. One thing I didn't do was remove the H and L screws, next time I get a chance I'll pull the limiters and do that, and check the muffler too.

 

[MasterMech]

It's pretty normal for an older 2-stroke to "fog" a bit out the carb. Generally it is due to exhaust restriction or wear on the piston/ring. It shouldn't be cause for worry unless it's pretty extreme.

This unit sounds like it was starving for fuel (as Jay pointed out.) initially and less so now. Hence instead of stalling it only "stumbles". I'd re-visit the carb with the can of carb cleaner and pay particular attention to the main jet. It may have a coat of varnish that you can't see and only restricts it slightly.

How does the carb respond to the "L" adjustment?

 

[DiscoInferno]

One thing I think I didn't mention is that if I open the choke fully while at WOT it initially seems to run fine. After a few seconds at WOT it starts to modulate speed some, but generally keeps running. It's after I let it drop to idle then gun it again that it craps out. To restart at this point requires closing the choke. I did fiddle with the L screw some, thinking that was the problem, but it didn't seem to help. I will give the carb another look next weekend and pull both screws.

 

[MasterMech]

Blow some carb clean down the scew bores. Sounds like a lean surge to me. Good Luck!

 

[smokinj]

Blow some carb clean down the scew bores. Sounds like a lean surge to me. Good Luck!

Try straight sea foam in the gas pull the spark plug wire.....Pull the cord a few time every 15 mins or so until its empty. Its got a clog some where flush the whole fuel system.

 

[DiscoInferno]

Update for posterity: I finally got around to removing those idiot caps. Had to destroy them to do it, they had a metal cage inside that quite effectively prevented brute-force pulling. I retuned the carb from scratch, and found that as suggested the L screw was the key to the behavior I was seeing. I question now if the caps were actually turning the screws or were just spinning freely. It's running reasonably well now.

 

[wkpoor]

What your seeing with the fuel is normal ops with a piston ported 2 cycle engine. Might seem worse when its running poorly. All my chainsaws do it too.

 

[DiscoInferno]

It's doing it a whole lot less now that it's tuned properly. But if that's fairly normal, where does all that gas/oil mix go? Seems like it would saturate the air filter in no time.

 

[wkpoor]

Right back in the cylinder when the piston goes down. Your wacker has no reeds. Its just a cylinder with a goes oucha and a goes inya and some little additional passages called transfers. It sucks and blows real fast and airflow is getting turned off an on through the carb with single cylinder.

 

[MasterMech]

Update for posterity: I finally got around to removing those idiot caps. Had to destroy them to do it, they had a metal cage inside that quite effectively prevented brute-force pulling. I retuned the carb from scratch, and found that as suggested the L screw was the key to the behavior I was seeing. I question now if the caps were actually turning the screws or were just spinning freely. It's running reasonably well now.

If simply re-tuning the L screw fixed the problem then you're getting more air from somewhere. You're problem may or may not re-surface down the road (will eventually get to the point where re-tuning won't correct it) but for in-expensive wackers it's not worth chasing down seals/gaskets just yet IMO. Also sometimes if the problem was caused by a very, and I do mean VERY, small piece of debris in the L passage, opening/closing the L screw might have allowed it to pass. Either way, glad to hear it's giving you less of a headache now.

 

[DiscoInferno]

I did remove both screws and sprayed out everything again, but it looked pretty clean. I suppose I should clarify that in removing the caps I lost track of the old setting of the screws, so I don't know how the new and old settings relate. While retuning I saw and fixed w/ the L-screw the previous bogging and cutting-out behavior, but I never saw any volume of fuel shooting out. Either I never had the L-screw bad enough or it was caused by something else. In any case it's put away for 6 months now unless some trees need trimming, we'll see if it still runs well in the spring.