Tecumseh HS40 (3) carbs giving me fits, they won't idle right.

danford1

danford1

#1
#1
I have 3 HS40 engines and 4 Tecumseh carbs. I've taken the carbs apart, soaked them in carb cleaner overnight to no avail. I put in a new carb kit which is just gaskets, o rings and a needle...

One carb works better than then the other 3. It will idle and runs well at Wot but sometimes has a transition bog off idle, other times it is fine. Let's talk about the other 3 carbs...

None of them will idle right. I've played with these for a couple days adjusting needles etc and I'm getting nowhere.
It doesn't matter which engine I put the carb on, it won't idle correctly. It is either running to fast or stalls out after idling for a second or two. There isn't much middle ground. All 3 carbs must have the same issue but I can't figure it out.
I need your help.
They all run good at WOT and the high speed screw (bottom) works as it should. It is the idle circuit that is giving me fits.
ALL of the carbs sat around for many years without being used if that helps any.
I can see some very tiny holes in the bore right about where the butterfly is at idle. I figure those are the fuel delivery holes for idle and transition. There is a welch plug on the outside closing off the access to those holes. Am I supposed to pry that out and clean it there? Is that my problem area?
I've sprayed carb cleaner and brake cleaner in those holes for what seems like hours and it hasn't fixed them.
What do I do?
Danford1
 
creia

creia

#2
#2
You need to probe those small passages with a tiny wire (we use torch tip cleaners)- soaking alone will not cut it on the carbs with the history you have described. Do you know anyone with an ultrasonic cleaner? We have got many carbs to finally perform correctly using an ultrasonic cleaner that did not respond to previous "traditional" (read: soaking, spraying) methods. One of the very best investments were ever added to our home shop was the HF (larger and heated) ultrasonic cleaner.
Michael
 
ole4

ole4

#6
#6
the nut on the bottom of the carb is the main jet and if it has a needle or not if you look carefully on the side you will see a tiny hole which is what allows idle fuel to mix with the air and if it gets gummed up you need to use some small wire to dig out the crap. The symptom is no idle but you can get it running off idle and rev it up OK just when it goes to idle it will die. I used old guitar strings that were not wound.
 
manchester1

manchester1

#8
#8
One of the old timers taught me this. Take the carb off and hold the float. Shake the carb, if you don't hear that little ball shaking in the "closed" tube, the carb is junk. I had the same problem as you. Checked everything 4 times and kept rebuild the carbs and still wouldn't run right. You could always buy the 20.00 :chinese: carbs. I hate to admit it but they work great.
 
danford1

danford1

#9
#9
Where do you get the $20 carb and what is the part number?
I'll try the shake test tomorrow.
I'm sick of farting around with these...

Danford1
 
danford1

danford1

#11
#11
buckeye said:
What Karen said.
Ebay is where I have bought them.
No problem no more.
Click to expand...
Excellent! Now, what do I search for, a $20 carb?
I need a part number or item number. There are hundreds of carbs. I've seen a lot of HS40 carbs with the choke lever on the clutch side, I need a Long choke lever on the flywheel side. It needs to clear the air cleaner. The exhaust pipe and muffler are on the other side...
See picture below of carb without air cleaner. #418 6G6
Thanks
Danford1

File_000 (22).jpeg
 
Last edited:
Ding Ding

Ding Ding

Well-Known Member
#12
#12
danford1 said:
Excellent! Now, what do I search for, a $20 carb?
I need a part number or item number. There are hundreds of carbs. I've seen a lot of HS40 carbs with the choke lever on the clutch side, I need a Long choke lever on the flywheel side. It needs to clear the air cleaner. The exhaust pipe and muffler are on the other side...
See picture below of carb without air cleaner.
Thanks
Danford1

View attachment 90762
Click to expand...
This is the one I've purchased.

Carburetor W/ Gasket for Tecumseh 631918 HS40 Engines | eBay

The choke lever can be formed to better fit your application.

Otherwise just search HS40 carb.
 
MB165

MB165

Active Member
#13
#13
that's right they have a small pin in the idle mixture passage, it looks similar to the float hinge pin and its used on carbs with the long idle mixture needle. if its stuck you wont get them to idle. you can hear it rattle if its free, and it will hit the needle and bend if you screw it in tight upside down. sometimes soaking for a extended time will loosen them up. or boiling helps melt the old gum which builds up, just depends on how valuable they are to ya.
 
joshua. c.

joshua. c.

Well-Known Member
#14
#14
the carburetor that bogs while revving up may be to rich on idle. I've found these carbs like the idle a little leaner than it should be so it doesn't go rich when you pin it, this is going to make it idle a bit to slowly to keep running so you have to adjust the throttle position screw pushing on the butterfly to up the idle back to the normal speed. also these carbs are sensitive to dirt so always run a fuel filter. when these carbs are adjusted right they idle really well and rev perfectly. and as far as cleaning iv always used compressed air and carb cleaner to blow out any junk, it seems to work well.
 
C

canuk

#15
#15
if you have a carb with reduction rod in idle passage make sure when you dont mixture screw in with the carb upside down or it will hit the rod and obstruct movement of adjustment screw.also I have had the plug for the idle passage thats beside the main fall out there brass and I think they loosen up from blowing air through for cleaning I always check this plug and put a dab of JB weld on it eveytime
 
danford1

danford1

#16
#16
I gave up on the carbs and bought some new ones from Amazon. They were $15.50 each with Free shipping. They work great! I wish I would have done than sooner rather than waste all the time I did fooling with them.

Speaking of air cleaners, besides the Tecumseh big round set up, what are some other options? The choke lever on the carbs I bought hit the stock air cleaners...

Danford1
 
danford1

danford1

#18
#18
minikenny said:
Transfer the choke lever & shaft from your old carb. :thumbsup:
Click to expand...
I did that on one but can't on the other two. THe spring pin is in the wrong spot.
I'll just cut off the lever and weld something on that will clear the air cleaner. I just thought there would be other air cleaner options for a Tec... guess not ...

Danford1
 
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