Trouble Shooting for Carburetors.

Bruce Hopf

A while ago I started to post some helpful tips for Carburetor Problems that some one was having with his Chain Saw Bogging Down. Unfortunately my Computer Crashed while I was posting, so I'll repost it here again.


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Condition = Carburetor Floods; Engine Stalls.

Cause = Inlet needle not sealing. Foreign Matter in Valve Seat or
Cone damaged.

Remedy = Remove and clean or replace Inlet Needle, clean Fuel Tank, Pickup Body and Fuel Line if necessary.

Cause = Inlet Control Lever sticking on Spindle.

Remedy = Free off Inlet Control Lever.

Cause = Helical Spring not located on Nipple of Inlet Control Lever.

Remedy = Remove Inlet Control Lever and refit correctly.

Cause = Perforated Disc on Diaphragm is deformed and presses constantly against Inlet Control Lever.

Remedy = Fit new Metering Diaphragm.

Cause = Inlet Control Lever to high (relative to design position).

Remedy = Set Inlet Control Lever flush with top of Body, or bottom of the Metering Chamber.

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Condition = Poor Acceleration.

Cause = Idle Jet "too lean".

Remedy = Back off Low Speed Screw slightly.

Cause = Main Jet "too lean".

Remedy = Back off High Speed Screw slightly.

Cause = Inlet Control Lever too low (relative to design position).

Remedy = Set Inlet Control Lever flush with top of Body or bottom of Metering Chamber.

Cause = Inlet Needle sticking to Valve Seat.

Remedy = Remove Inlet Needle, clean and refit.

Cause = Connecting Bore to Atmosphere blocked.

Remedy = Clean Bore.

Cause = Diaphragm Gasket leaking.

Remedy = Fit new Diaphragm Gasket.

Cause = Metering Diaphragm damaged or shrunk.

Remedy = Fit new Metering Diaphragm.

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Condition = Engine will not idle, idle speed too high.

Cause = Throttle Shutter opened too wide by Idle Speed Screw.

Remedy = Reset Idle Screw correctly.

Idle Speed Screw (LD) opened too far.

Remedy = Adjust Idle Speed Screw correctly.

Cause = Idle Speed Screw (LA) opened too far.

Remedy = Adjust Idle Speed Screw Correctly.

Cause = Machine leaking.

Remedy = Locate and repair Leak.

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Condition = Engine stalls at Idle Speed.

Cause = Idle Jet Bores or Ports Blocked.

Remedy = Clean Jet Bores and Ports with Compressed Air.

Cause = Idle Jet "too rich".

Remedy = Screw down Low Speed Screw slightly.

Cause = Setting of Idle Speed Screw incorrectly - Throttle Shutter completely closed.

Remedy = Set Idle Speed Screw correctly.

Cause = Setting of Idle Speed Screw (LD) incorrect.

Remedy = Set Idle Speed Screw correctly.

Cause = Small Plastic Plate in Vain Jet does not close.

Remedy = Clean or renew Valve Jet.

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Condition = Engine Speed drops quickly Under Load - Low Power.

Cause = Air Filter Plugged.

Remedy = Clean Air Filter.

Cause = Tank Vent faulty.

Remedy = Clean or replace Tank Vent if necessary.

Cause = Leak in Fuel Line between Tank and Fuel Pump.

Remedy = Seal or renew Connections and Fuel Line.

Cause = Pump Diaphragm damaged or fatigued.

Remedy = Fit new Pump Diaphragm.

Cause = Main Jet Bores or Ports blocked.

Remedy = Clean Bores or Ports.

Cause = Fuel Pickup Body dirty.

Remedy = Clean Pickup Body, fit new Filter.

Cause = Fuel Strainers dirty.

Remedy = Clean Fuel Strainers.

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This information that I have given here is from my Carburetors Manual from Stihl, that I received when I went through my Stihl Authorized Factory Service Technician Coarse, a few Years ago, so I thought I'd share it here with you all. . Bruce.

__________________
McCulloch chain saws
1- Pro Mac 60, 1- Pro Mac 700, 2- Mac 10-10 Automatic's, 2- Mini Mac 30's, 2- Mac 110's,
2- Mini Mac 35's, 1- Mac 140 with Automatic Chain Sharpener,
1- Pro Mac 10-10, 1- Mac Cat, 2- Eager Beaver
2.0's, 1- Mac 1-10
Stihl chain saws
2- 044's, 2- 034's, 2- 024's, 1- 064, 1- 084,
Strunk chain saws
1- Busy Beaver, 1- SpeeDemon Special
Stand Back, I Have A Very Extreme Case of CAD (Chain Saw Addiction Disorder).

petesoldsaw

Hello Bruce
Just thought I would say Thanks for posting that information, it will sure help me in the future, if I ever get my hands dirty.
Thanks Again Bruce

backwoods

bruce il print that ty for the chart

KevinE

Great post Bruce! Thanks! (got the same problem ATM, thus searching for answers)