I just came across a Poulan 361. I rebuilt the carb and it purred like a cat, but I had to remove it and upon redoing the mix screws, I can't get it to run right again. Can someone tell me what the default mix settings are? I know last time I had a goofy setting 1.75H 3L.
It is like the game Jenga, it ran fine. As soon as I touch it, i ruined it. :-(
On those carbs I always start with the high speed at 1 1/2 turns out from lightly seated and idle at 1 1/4 turns out from lightly seated.
#3
upupandaway
I looked at it and here is what I found: I replaced the fuel hose with a Tyvek hose and I see it is pulling fuel.
I opened the carb and looked for any dirt\double checked the passages to the mix screw and from screw to passage, neither are plugged.
My last test, I poured some gas\oil in and it started up and gradually ran faster(lean) leading up to dying. I tried your setting but went up to 2.75 turns for both mix screws, still no go. Why is is pulling in gas but not enough gas is going into the engine?!?!?!?. I wish I left it alone the first time when it ran(the oil pump is barely pumping any chain oil)... :-(
When a 2 stroke dies rich it gets a soft deep exhaust note
When it dies lean it gets a sharp higher pitched exhaust note .
On the settings you were using either you have transposed the jets or it has obstructions in the L passageway
With that many turns on the L needle it will be running way too much on the L at full speed
If you do a lot of small 2 strokes consider buying a "Gunsons Color Tune" a cleaver little tool that allows you to see inside the cylinder during combustion so you can see the colour of the combustion flame
The oil in 2 stroke mixes makes them a bit funny but rich will always be a strong thick looking flame while lean will always be a translucent flame
Your problem could also be in the fuel tank , try it with the fuel cap loose
I know. That's what it is doing. after I spray some gas in the carb, It starts normal then gradually climbs in RPM then dies so it is running lean.
Thing is, I replaced the fuel line with a clear Tygon tube and I see it is pulling fuel into the carb.
I tried opening high and low up to 3 turns but still no go- I pour in more gas and it runs for a few seconds so it confirms the carb runs lean.
btw, the fuel cap has a hole in it- gas easily leaks out if I tilt it.
Leave the fuel lines connected
slide the carb off turn it sideways
Blow air through it ( high volume low pressure is best ) from the filter side & note how much vapour blows out the engine side
Empty the fuel tank 1/2 way & try again
If it is substantially less then you have connected the fuel lines wrong
Also check that there is a good impulse feed into the fuel pump .
Very easy to get the gaskets backwards or partially block the impulse hole
Did you pressure test the carb after you rebuilt it ?
#8
upupandaway
I think I am playing Whack-a-Mole or something. 2 days ago, I gave up left it after setting the mix screws to 2 and 2.25. I pulled it out yesterday without adjusting anything, and it started! high, idle ok. stopped and started the saw 4 times like clockwork.
I am thinking maybe adjusting and trying to start is is what I said. Letting it sit, maybe the excess fuel evaporated or something?!?!?!? Will try a few more times days apart and see if goes back to normal and runs like it did before removing the carb....
*UPDATE* I fired up the saw after work today and it is fine, so it apparently decided to go on a vacation for a few days but it is back again now.
You can get fuel condensed in the crankcase ( oil as well ) so leaving it for a few hours to vapour off and away it goes
When doing these types of engines I always let them sit after final adjustments overnight then try to start them in the morning many times before they go back
You can get fuel condensed in the crankcase ( oil as well ) so leaving it for a few hours to vapour off and away it goes
When doing these types of engines I always let them sit after final adjustments overnight then try to start them in the morning many times before they go back
Yeah, that's what I think happened even though every time it was running lean....
I have had this happen before when xyz just won't start. I put it away and use another trimmer, blower, etc and next time, the trouble machine starts fine.
As I posted, playing Whack-a-Mole, maybe some extra gas inside so i adjusted too lean, then too rich only to flood, etc, etc.
Like you said, maybe leaving the screws in the correct setting(although it is still open further than standard but it runs...), and some excess fuel evaporated over night in this case. So far 3 days in a row it runs so I'm good.
FWIW
I generally adjust the L with the H closed up fully as in theory only the L is in use at start up
IF it won't start like that then the throttle stop has been wound in too far holding the throttle too far open
Once I have it starting reliably then I play with the H
Wound out till the engine just starts to miss then in just enough to get it to run clean
Thus it will usually be a little rich
Also the head must be on and the full length of string must be out to loa the engine .
FWIW
I generally adjust the L with the H closed up fully as in theory only the L is in use at start up
IF it won't start like that then the throttle stop has been wound in too far holding the throttle too far open
Once I have it starting reliably then I play with the H
Wound out till the engine just starts to miss then in just enough to get it to run clean
Thus it will usually be a little rich
Also the head must be on and the full length of string must be out to loa the engine .
As a DYIer describing the method of 2-cycle carb tuning is like describing to a kid how to ride a bike with no training wheels. If you keep at it and keep practicing eventually a light goes off!
To help me know if I'm getting warm, I use a tach to measure rip-ems, which the pros gauge by ear.
The method of starting with the L jet and T with H jet closed really works. Then on to the H jet. The H jet still occasionally gives me grief when doing different saws-- when you get into 4-stroking, tune in wood etc. Also you may notice the saw runs different in summer than in late fall/winter which could mean a fine tune session between seasons.
FWIW
I generally adjust the L with the H closed up fully as in theory only the L is in use at start up
IF it won't start like that then the throttle stop has been wound in too far holding the throttle too far open
Once I have it starting reliably then I play with the H
Wound out till the engine just starts to miss then in just enough to get it to run clean
Thus it will usually be a little rich
Also the head must be on and the full length of string must be out to loa the engine .
So you mean start everything at idle? Just about everything I have starts with partial if not wide open. I added a button to hold the throttle open a hair on my McCullough 1-42 as it won't start at idle for the life of me.
This would goof up the H screw closed, no?
Oh well, I set them to default and it works 99% of the time to get it running, then I tune it.
BEing part of the white pimple on the brown bum of the world ( always loved Prime Minister Keatings description ) and not having access to much in the way of dealer information I have needed to lear ways around it
Many models span several different tiers of EPA regulations and on top of this a lot of US factories dump stuff down here so in the same year I could get 3 new engines with 3 different base carb settings and this is before the owners who "have not touched it" have set the needles to all sorts of strange positions
Old stuff is easy as most will start on a 1 - 1 setting and I can go from there but some of the EPA carbs can be as high a 3 or 4 turns as they have finer adjustments .
Chasing up the information can ( and usually does ) take a lot longer than having a stab
On CUBE carbs with 2 needles I use the set the idle first with the H closed then bleed in the H till it will run WFO and still idle
What most do not understand is both needles work all of the the time unless there is a check valve on the H jet
because of this a H that is so little as 1/12 th turn too open will dominate the idle jet
The idle jet provide fuel 100% of the time but because the H is orders of magnitude bigger anything over a fast idle it swamps the volume of fuel supplied by the L jet
If a cube carb will not start with the H closed then there is a major problem with the L setting
