Carburetor talk - fuel puddling

[Sloughfoot]

Years ago (mid 1990's) I had an 026 that was having issues at idle - a local long-time small engine tech told me to notch the throttle plate in front of where there was a secondary opening in the throttle bore part of the carburetor. I notched it about 1/16" (roughly doubling the size of the small existing notch). My idle problems went away and the saw ran great.

I'm starting to think there's a trick unique to most every 026 made to make it run right. The few that run great off the shelf are the exception.
I had to carve on my switch rod in 3 places to get the throttle to idle position on choke.

 

[SawAddictedFarmer]

I'm starting to think there's a trick unique to most every 026 made to make it run right. The few that run great off the shelf are the exception.
I had to carve on my switch rod in 3 places to get the throttle to idle position on choke.

The one I rebuilt seemed just fine. Anything ruber got replaced with aftermarket, proline carb. Easiest saw to tune I've worked on yet!

 

[Sloughfoot]

The one I rebuilt seemed just fine. Anything ruber got replaced with aftermarket, proline carb. Easiest saw to tune I've worked on yet!

You're fortunate.
My air filter cover, air filter, throttle choke switch rod on the thumb switch, at the trigger contact, at the air filter contact have all gotten a little foredom time to get it working. Runs great but still doesn't cold start as it should. Doesn't flood easily though so I'll take it. Might try drilling the hole in the choke butterfly a little bigger.
I'd like to look a stock 026 over that runs right and see what the difference is.

 

[SawAddictedFarmer]

You're fortunate.
My air filter cover, air filter, throttle choke switch rod on the thumb switch, at the trigger contact, at the air filter contact have all gotten a little foredom time to get it working. Runs great but still doesn't cold start as it should. Doesn't flood easily though so I'll take it. Might try drilling the hole in the choke butterfly a little bigger.
I'd like to look one over that runs well stock and see what the difference is.

Well I guess I just got lucky? Hot and cold starts perfectly, it does drop about 100rpm once you set it down but never dies and revs right back up. It's my boss's saw so I haven't run it a ton but I couldn't find anything wrong and he's happy. He was straight out giddy after running it coming off of 5 years of only having a wild thing.

 

[edisto]

Years ago (mid 1990's) I had an 026 that was having issues at idle - a local long-time small engine tech told me to notch the throttle plate in front of where there was a secondary opening in the throttle bore part of the carburetor. I notched it about 1/16" (roughly doubling the size of the small existing notch). My idle problems went away and the saw ran great.

In terms of jacktheripper's puddling problem, do you think that increasing flow past the plate allows fuel to flow for a longer part of the intake cycle, allowing the same amount of fuel with a leaner jetting of the idle circuit?

 

[Sloughfoot]

.

 

[Sloughfoot]

Well I guess I just got lucky? Hot and cold starts perfectly, it does drop about 100rpm once you set it down but never dies and revs right back up. It's my boss's saw so I haven't run it a ton but I couldn't find anything wrong and he's happy. He was straight out giddy after running it coming off of 5 years of only having a wild thing.

I went through all the basic stuff as you did. Pressure/vac test, new oil seals, new oem manifold, impulse, fuel line, fuel filter. Mine idles a little fast initially then settles down a few hundred rpms, too. Not sure what that's about. Fuel puddling on initial start getting burned off?

 

[jacktheripper]

Im going to modify a throttle plate or two for science. Modifying the throttle plate on my 562xp coupled with lowering the pop off pressure got rid of my off-idle hesitation earlier this year, but that’s a different issue.

My 064, 026, and 044 all have this fuel pudding issue, so I might as well try. All three of them have had the intake ports worked lightly to prevent any lip from sticking up.

 

[jacktheripper]

One more thought: I’m at about 5600 feet in elevation, and I frequently cut up near 10,000 feet. I am used to tuning carbs as I transition back and forth in elevations. One thing that I have noticed is that in addition to needing to lean the saw out at higher elevation, the idle speed often has to be adjusted higher as well. I think this is due to the air density at altitude affecting the efficiency of the Venturi.

My elevation down near town at 5600 feet may still be affecting the efficiency of the Venturi to pull fuel, and I wonder if notching the throttle plate would be even more effective for me at this higher elevation than for people down near sea level.

 

[SawAddictedFarmer]

I went through all the basic stuff as you did. Pressure/vac test, new oil seals, new oem manifold, impulse, fuel line, fuel filter. Mine idles a little fast initially then settles down a few hundred rpms, too. Not sure what that's about. Fuel puddling on initial start getting burned off?

This one did like 105 going off the tach.

 

[jacktheripper]

I minorly opened up the throttle plate bypass notch last night in the hd14 on my 044. Today I tested it and it was better, but not perfect. I was able to turn up the idle a bit more and richen the low jet, and after doing that the puddling is practically gone. I’d call it a success. Now I’ll do the same to the C3M on my 440 and see what happens. I may also do the WJ on my 064

 

[jacktheripper]

I minorly opened up the throttle plate bypass notch last night in the hd14 on my 044. Today I tested it and it was better, but not perfect. I was able to turn up the idle a bit more and richen the low jet, and after doing that the puddling is practically gone. I’d call it a success. Now I’ll do the same to the C3M on my 440 and see what happens. I may also do the WJ on my 064

My theory is now that turning the idle up cracks open the throttle plate enough at the bottom of the carb body to allow air to sweep any un-atomized fuel collecting at the bottom of the intake tract into the crankcase. I’d like to try making a notch at the bottom side of a throttle plate to test my theory.

 

[Sloughfoot]

My theory is now that turning the idle up cracks open the throttle plate enough at the bottom of the carb body to allow air to sweep any un-atomized fuel collecting at the bottom of the intake tract into the crankcase. I’d like to try making a notch at the bottom side of a throttle plate to test my theory.

What would that do, allow only more air through where more idle would increase both air and fuel?

 

[redneckhillbilly]

this reminds me of the gadgetman groove, esentially a groove on the housing around the part of the throttle plate that opens, supposedly it creates more manifold vacum and gives better atomization. theres alot of youtube videos on it.

 

[jacktheripper]

What would that do, allow only more air through where more idle would increase both air and fuel?

It would be more about directing flow through a particular spot in the intake tract

 

[Sloughfoot]

Ahh. Directing it low to atomize the puddle

 

[edisto]

this reminds me of the gadgetman groove, esentially a groove on the housing around the part of the throttle plate that opens, supposedly it creates more manifold vacum and gives better atomization. theres alot of youtube videos on it.

I watched one with his explanation...it didn't make a lot of sense to me.

The groove builds up air pressure that gets released when the negative pressure drawn from the piston stops?

 

[redneckhillbilly]

I watched one with his explanation...it didn't make a lot of sense to me.

The groove builds up air pressure that gets released when the negative pressure drawn from the piston stops?

I honestly cant remember the theory behind it other than the guy was trying to attain higher manifold vacum. at part throttle or idle.