QuestionQUESTION: I am working on a Honda GX610K1 (QAD2 #QCAC 2027393) in a Cub Cadet 4x2 utility vehicle. There are 800 hours on the engine. The engine bellows out large clouds of white smoke and the engine speed goes up and down. The engine slows down so much it will cut off unless the choke is closed. If I close the choke the motor will smooth out for about 30 seconds or so, then it will repeat the cycle. I don’t notice the engine speed changes when I am driving the vehicle, but when I apply the brakes, the engine stalls if I don’t pull the choke. I thought it may be burning oil, so I did a compression check. I got 100 psi on one cylinder and 115 on the other. I also checked the vacuum, which was 13-15 when the motor was smooth, but the rougher the motor ran, the more wildly the needle would move. At worst it was moving rapidly between 5 and 25. The plugs were black, even though they had less than one hour on them. They were also wet. I pulled the carb apart, soaked it, and cleaned every thing I could find. It was very clean to start with. Very little varnish anywhere, a tiny spot on the needle valve was all I could find. I began to change the oil. I drained the engine, but there seemed to be a large amount of gas in the oil. I am now stuck on what to try next. Any help is appreciated. Thanks.
ANSWER: Hello Cliff:
Usually the Gas in the Crankcase Oil or White Smoke is Caused by a Bad Diaphragm in the Fuel Pump, a Blown Head Gasket between the Cylinder and Push Tube Galley, the Crankcase Vent Stuck/Frozen/Broken or the Carburetor Flooding the Engine. If the Engine is Running Good but Smoking White Smoke, 1- Block the Outlet Port and Pull a Vacuum on the Fuel Pump. If it Holds Vacuum, then it is Good. If Not, then the Diaphragm is Busted and the Pump Requires Replacing. If the Fuel Pump is Good, then Check the Crankcase Oil for Gas Contamination. If the Crankcase Oil is Contaminated, then Drain and Refill the Crankcase Oil with Fresh Oil. 2- **If the Mower has a Manual Gas Shut Off Valve: Check the Manual Cut Off Valve and Make Sure it is Cutting Off the Gas Flow to the Carburetor. If Not Stopping the Gas Flow, then Replace the Valve. If the Mower Does Not have a Manual Cut Off Valve: Install a Manual Cut Off Valve and Turn Off the Gas Flow when the Engine is Not in Use.** 3- If the Valve is Good or has Been Installed, then Remove the Cylinder Head. On the OHV Engines the Head gasket will Blow Between the Cylinder and the Push Tube Galley. This Allow Oil to be Sucked Into the Cylinder from the Crankcase and the Extra Oil is Just Enough to Cause the White Smoke. 4- Check the Crankcase Breather and Make Sure it is Clean and Operating Properly. If the Crankcase Breather Sticks, then Oil is Pulled from the Crankcase into the Carburetor Throat and this Causes the White Smoke. 5- Clean and Rebuild the Carburetor. **Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl (if Applicable), Float Pin (if Applicable), Float (if Applicable) and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required.** 6- I Listed the Possible Causes in the Order they Usually Occur. I have had Some People Ask me Why I do the Diagnostics in the Order I Use and it is Simply that Over the Years I have Made a List of the Equipment, the Models and the Problems they have When I Receive them for Repair. Then I Listed the Cause and Repairs Made. I Suggest you Purchase the Service Manual for this Engine. It will have All the Information you Require to Maintain and Keep this Engine Running Good for Many Years. I have Seen So Many Different Makes and Models of Equipment Over the Years, that I Use the Manuals Always for Any and All Repairs. The Basics are Not My Worry; it's the Specifications that Change. Thanks for Using All Experts. Did you Change the Float Needle Valve? You can View a Breakdown/IPL of the Mower/Engine at this Site Addy, http://hayward.arinet.com/scripts/EmpartISAPI.dll?MF&app=ASP&lang=EN&TF=Mainfram and Select the Catalog American Honda. Select the Engine File and Scroll Down and Select your Engine. If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: Thanks for the help John. I was able to get the beast back running smoothly again. I followed steps 1, 2, and 5. The carburetor was very clean to start with, but I went through the steps anyway. The fuel pump held a vacuum well and the manual shut off valve functioned properly. The crankcase was full of gas, so I drained and refilled. Although the motor is running well now, I am not confident that I found the source of the problems. I was unwilling to pull the head to check the gasket since I didn't have a spare gasket on hand. I also skipped the check on the breather due to lack of tools (I need to pull the flywheel). The breather has me concerned since I noticed oil not only in the carb throat, but also in the air cleaner housing. Since it is running for the moment, I've bought some time until the service manual arrives. One thing I noticed during the fuel pump check has me curious, though. On the pump is a small circular area the appears to be many small pins all pushed together. Out of curiosity, I pulled a vacuum on the vacuum port of the pump and heard air wheezing around the circle of pins. It wheezed because the circle was filled with dirt and oil. I sprayed the circle with carb cleaner and then applied a little air pressure to the vacuum port, which pushed out most of the crud out of the circle. Is the circle some kind of vent for the diaphragm or should I be able to draw a vacuum on the vacuum port? Also, can the oil in the carb and air filter assembly be attributed to anything else besides the breather? Thanks again for the information.
AnswerHello Again Cliff:
If you ever Leave the Manual Cut Off Valve Open when the Unit is Not in Use and the Carburetor Float Needle Valve is Not Seating Correctly; then the Gas Floods the Carburetor and Goes Into the Engines Compresson Chamber. Then the Gas Seeps by the Rings and Contaminates the Crankcase Oil. The Thin Oil and the Crankcase Being Over Filled will Cause the Crankcase Breather to Allow Oil/Gas from the Crankcase to be Sucked Into the Carburetor through the Crankcase Breather Tube. If the Gas/Oil Contamination is Bad Enough, then the Carburetor and Air Filter will be Saturated in Oil. That is the Only Cause for the Carburetor and Filter Assembly to be Saturated with Oil (except bad Piston Rings). The Area of the Pump you are Asking About is the Vent. It Sounds like it was Half Clogged. If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.
Respectfully
John
