140 won’t idle correctly

[SSTKO81]

Good morning! I’ve been running down ignition gremlins and now that I’ve got this licked it seems there could be a fuel problem. (Long story made longer)
this engine had to have a new crank and #2 piston due to spinning a bearing.So it’s been blown Apart and back together, timing set to 6* and will run if the idle is held up in the 1100-1500 range. When cold starting it will immediately try to run but dies. After that some pretty aggressive feathering of the throttle has to be done to find a happy spot. If you can get it up and running for a minute or two then you can bring the idol down to around 700 to 800 RPM long enough to make timing adjustments throttle adjustments etc. But as it continues to warm up it gets more difficult to keep running. RPMs will start dropping And you have to continually make adjustments to the throttle to keep it going when it does finally die it’s very difficult to restart. There’s a lot of backfiring in sputtering. I’m just not Sure where to start my search it feels like a fuel issue. But why would it only become an issue as the engine continues to warm up?

 

[Rick Stephens]

Coming off the choke it is running out of fuel. Needs a carburetor rebuild with particular attention to the idle circuits.

 

[SSTKO81]

Coming off the choke it is running out of fuel. Needs a carburetor rebuild with particular attention to the idle circuits.

I don’t use the choke.... not hooked up, never has been. Doesn’t mean you’re wrong tho. This carb has been rebuilt 3 times over the last 10 years and doesn’t have 6 hours on it....

 

[SSTKO81]

Coming off the choke it is running out of fuel. Needs a carburetor rebuild with particular attention to the idle circuits.

I don’t use the choke.... not hooked up, never has been. Doesn’t mean you’re wrong tho. This carb has been rebuilt 3 times over the last 10 years and doesn’t have 6 hours on it....

 

[Bondo]

Doesn’t mean you’re wrong tho. This carb has been rebuilt 3 times over the last 10 years

Ayuh,.... The choke richins the mix, yer motor says it's to lean,......

Ya mean somebody tried to rebuild the carb 3 times already,..??

Even after warmed up, it appears to still be to lean,.....

 

[Scott Danforth]

properly rebuild the carb
properly fix the choke
properly set the choke

go boating

 

[SSTKO81]

I like your optimism. -choke rebuild to follow

 

[SSTKO81]

I like your optimism. -choke rebuild to follow

 

[SSTKO81]

Ayuh,.... The choke richins the mix, yer motor says it's to lean,......

Ya mean somebody tried to rebuild the carb 3 times already,..??

Even after warmed up, it appears to still be to lean,.....

I mean the carb was rebuilt 10 years ago, then, suspecting a fuel problem rebuilt the next year, then again two years ago.

 

[SSTKO81]

I went out tonight and set the choke. Absolutely would not start unless I sat there and pumped the throttle. And then it would just rev up to 1500-2000 rpm for just a second or two then die. In my frustration I just held the choke open by hand and it actually turned over and ran. I let it warm up to temp then worked on setting the idle (from a turn &1/2 out) worked them in 1/4 turn at A time till rpm dropped and then backed out half turn. (By now choke was holding open by itself) Rpms were up about1200 at this point so I pulled back the throttle screw by a 1/4 turn and almost immediately it began to struggle and died. Tried to crank it back up and same thing repeatedly; it would try to start or sound like it was right there and then nothing. One of my kids had a popsicle so I took the stick and wedged it between the throttle screw and choke cam and it started right up and reved to 1600 rpm. I pulled the popsicle stick out and it settled back down to 1100. Tried to ease idle back down toward750-800 and it died again. -this all went on repetitively for half an hour until I finally decided the choke cam was to blame... thoughts or insight?

 

[SSTKO81]

Bump

 

[Bondo]

Bump

Ayuh,...... You still have a carb problem,.....

Sounds like the idle circuit is plugged up,.....

The choke cam ain't the problem,..... in boats, hi-idle is set by the operator with the control stick,.....

 

[SSTKO81]

Ayuh,...... You still have a carb problem,.....

Sounds like the idle circuit is plugged up,.....

The choke cam ain't the problem,..... in boats, hi-idle is set by the operator with the control stick,.....

So i don’t need to worry about replacing the fast idle cam? I’ve rebuilt the carb and carefully cleaned the idle circuit passages and replaced the needle/seat. Only thing missing is the cam, but if I don’t really need it....

 

[SSTKO81]

I’ve rebuilt the carb and paid close attention to the idle circuit. It’s as clean and pure as the driven snow. In my working I realized this carb probably didn’t originate on the engine based on the stamping (17059050). When I set the float level, drop and rod I went by the carb number, not the engine. Now it won’t start at all. Just acts like it’s not getting enough fuel unless I sit there and pump the throttle then it’ll try to sputter to life but will not run. Please see the attached picture and tell me what I should have set my carb to or does it matter? -getting frustrated with this pile!

 

[Tycer]

Do these help? I have a 470 carb on my 140. Just ordered the smaller jet for the 140.

 

[Scott06]

You have checked fuel pump delivery to the carb and needle and seat were replaced and float level is correct

 

[Rick Stephens]

Is that carb listed as one that is used in the 3.0L or just the 470? Hard to read the sideways screenshots

 

[SSTKO81]

Is that carb listed as one that is used in the 3.0L or just the 470? Hard to read the sideways screenshots

Looks like mine was originally on a 250 6cyl. Not a 140 so I’ve set my carb to the specs according to the 250. Is that wrong? And yes, new needle and seat, plenty of fuel getting to carb from pump

 

[Scott06]

Looks like mine was originally on a 250 6cyl. Not a 140 so I’ve set my carb to the specs according to the 250. Is that wrong? And yes, new needle and seat, plenty of fuel getting to carb from pump

If fuel is getting there and you're confident float level is correct and it won't idle, despite multiple rebuilds somewhere your idle circuit is clogged.

at higher rpms where it runs carb idle transition slots and main venturis start feeding fuel.

 

[Rick Stephens]

Another thing that will cause poor idling is an intake leak.