Carburetor Question

Reply

  #1  
Old 05-14-02, 08:19 AM
Pasta
Visiting Guest
Posts: n/a
Tecumseh Dia Carb

I'm working on an old Sears Craftsman lawn edger. It has a Craftsman Model 143 631042 (Tecumseh engine). This engine uses a diaphram type carb Sears P/N 630989. I have installed a new diaphram and thoroghly cleand the carb but can't seem to get it adjusted properly. it has a dead spot when going to full throttle. If I advance it very very slowly it will rev. I don't believe there is any type of accelerator pump involved in this carb. It does have two adj screws. both are in good condition. I beleive the one closest to the filter is the high speed and the one closest to the engine being idle, but I'm not sure. Does anyone have any experience with this type of carb. I'm looking for ANY advice.
Thanks,
Pasta
 
Sponsored Links
  #2  
Old 05-14-02, 10:48 AM
Fisher
Visiting Guest
Posts: n/a
The one closest to the engine is the low speed mixture
screw, turn it ccw a little and see if that helps your
acceleration problem.
Fish
 
  #3  
Old 05-14-02, 08:16 PM
Sharp Advice's Avatar
Admin Emeritus
Join Date: Feb 1998
Location: The Shake and Bake State USA
Posts: 10,440
Hello and Welcome Pasta to our Do-It-Yourself Web Site and our Small Engine forum.

The screw with the {"L"} marking is the Low Speed screw.
The screw with the {"H"} marking is the High Speed screw.

The problem your having is generically referred to as an off idle acceleration hesitation or stalling problem or condition. The low speed adjustment screw is adjusted inwards to much, resulting in a lean low speed fuel flow. The engine will seem to run well at low speed but not accelerate to high speed quickly.

To correct this, increase the Low speed fuel volume by turning the "L" screw outwards slightly. Retest the engine. Repeat the fuel adjustment and testing proceedure until the problem is corrected.

If the carb was rebuilt correctly and the fuel ports are cleared of any restrictions, the increase in low speed fuel will correct the problem.

The misunderstanding is that the low speed fuel adjustment only controls low speed. Not so. The low speed fuel circuit also supplies part of the fuel required to run the engine at high speed.

When both low and high speed fuel settings are adjusted and set correctly, both fuel circuits work together to prevent stalling during acceleration between low speed and high speed.

Regards and Good Luck, Small Engine Forum Moderator
Tom_Bart.....TCB4U2B2B.....Company Enterprises.
Fast...Fair...Friendly & Highly Efficient Services....
"Accurate Power Equipment Company"
Small Engine Diagnostics Services and Repair.

During installations of some parts which may not fit exactly perfect, it may be necessary to apply "BRUTE" force in order to compel compliance......... {....just humor folks... }

Personal Quote:
"If it ain't already broke, don't fix it, tinker with it or $#@&*&%$#@! with it until you do break it!"
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes