QuestionQUESTION: My Ride-on Mower is fitted with a Briggs & Startton Vanguard 16 hp motor 28Q777 - 0636A1 - 9601254A. When the blades are turned on it runs very roughly, misses and backfires a lot. The local dealer has replaced the head gasget and says the bore is in good condition. But after 5 hours running the plug was fully oiled and carboned up so that there was no gap left for a spark. It uses very little oil and blows a little smoke only occasionally. It runs rough with the blades off also but not as bad. Someone suggested too much fuel might be getting into the cylinder. The dealer says he does not have the time to trouble-shoot the problem and I can only use the mower for about 1 hour before I have to turn it off because of this rough going. It won't rev up sufficiently either. Also can you suggest where I might be able to download a workshop manual for this motor. Many sincere thanks if you can help - or thanks anyway for trying. Alan.
ANSWER: Hello Alan:
>>You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model (5 or 6 Digits) and Type Numbers (first 4 digits Only). Example: 28Q777-0636. Then Double Click on the Model in the Results Area. Select Sectional Index. Now you can Select the Section of the Engine you Wish to View.
>>Briggs Does Not Offer a Service/Shop Manual for Online Download.
>>You can Purchase a Shop/Service Manual for this Engine from www.outdoordistributors.com/ .
1->>Clean the Crankcase Breather/Vent(#8 in the Breakdown).
>>The Crankcase Breather/Vent is Shown in the Crankcase, Sump, Cylinder, ect File.
2->>If this Engine Uses a Walbro Carburetor, then Replace the Carburetor Nozzle (#142 in the Breakdown).
>>The Carburetor Nozzle is Shown in the Carburetor File.
>>On Engines with the Walbro Carburetor the Problem you Described Occurs when the Carburetor Nozzle becomes Worn or Damaged.
>>Please, Do Not Hesitate, If you Hit a Snag, if I Missed Something 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
Hello Again Alan:
>>Thanks Greatly for the Comments and Ratings.
>>Most Dealers would Spend the Few Minutes it Takes to Perform a Diagnostic and Never would have Allowed the Engine to Leave the Shop if it was Not in Proper Running Condition , Especially After just Replacing the Head Gasket. I'm at a Loss as to Why this was Allowed to Happen and I can't Seem to get this Out of my Head.
>>One Quick Suggestion; Check the Valve Clearances for me Please. Thanks.
>>The Following is a Basic File I made for Setting the Valve Clearances. Any Input is Appreciated.
>>**I Do Not Use the Setting Called for by the OEMs. I have Found that the Following Works Best.
>>Remove the Valve Cover (on the Dead Cylinder for Twin Cylinder Engines).
>>Check the Push Tubes and make Sure they are Not Bent.
>>Set the Cylinder you are Setting the Valves on to Top Dead Center on the Compression Stroke When Setting the Valve Clearance. Now Loosen the Valve Adjuster Lock and Using a Blade Style Feeler Gauge, Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .006in - .008in. Loosen and Tighten the Rocker Arm and the Feeler Gauge is Placed Between the Rocker Arm and the Valve Top where the Rocker Arm Pushes on the Valve.
>>***BE SURE TO TIGHTEN THE ADJUSTER LOCK AFTER YOU HAVE THE PROPER VALVE CLEARANCE***
>>I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. Be Sure the Piston is at TDC on the Compression Stroke.**
>>If you Remove the Valve Cover and then Turn the Engine by Hand, you can Watch the Intake Valve Movement. When the Intake Valve Closes, the Piston will Just Starting the Compression/Power Stroke.
>>On Some Engines you can Us a Straightened Coat Hanger and Feel the Piston.
>>Be Careful and Don't Jam the Wire in the Cylinder. Usually the Piston will Push the Wire Out of the Spark Plug Hole with No Problems.
>>Please, Do Not Hesitate, If you Hit a Snag, if I Missed Something or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please and as Always, 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: Hello again, John. Thank you so much for your wonderful help. I have only just now picked up your second comment about the valve clearances and so on so have not had time to do that yet although I know the dealer would have used those settings as he, like you, uses these and advised me to use those with a previous motor some time ago. He is normally very good and helpful, often suggesting how I could fix things to save money. He is overloaded at present and I think a little tired. Regarding your previous advice, I cleaned the oil breather (thanks for the helpful diagrams) and took the (decompression??) valve out to check it - the little button thing inside moved very freely without much pressure so I didn't know how well it had been working. I was amazed that when I took the air filter off the carby housing the base of the housing where the air goes into the carby was full of oil and the carby itself had alomst as much oil in it as petrol. No wonder the plug was only lasting a few hours at a time before blocking up. As a trial, I disconnected the little hose going from the breather to the air intake and blocked up the hole in the base of the air filter housing (as yet no oil coming out the now unplugged breather hose). I used the machine for an hour and it went very well - almost normal - nothing like before. The only problem was that I could not get quite enough speed out of the motor to really cut and throw the grass away from the mower far enough. It seems like it needs carby adjusting. I have not been able to get the nozzle you suggested as no one here has one in stock and I will have to send away for one. As the motor is running almost normal now, nothing like before, I wonder if I should try tuning the carby before ordering the nozzle. It is the Walbro carby and I am trying to get instructions for tuning it and will let you know about any success. Without your help I would have had no mower as no one could help and it is about 8 weeks delay to getting it booked in to someone who might have been able to help. Thanks once more most sincerely. And may The Almighty bless you and yours also. Kindest regards, Alan.
AnswerHi Alan:
>>I Usually Try to List the Components in the Order in which they are the Most Common Cause to the Least Common Cause for the Problem the Questioners Describe to me. That is why I Listed the Crankcase Vent/Breather First.
>>Do Not Order the Nozzle.
>>From you Latest Description it was the Crankcase Breather/Vent Allowing enough Crankcase Oil through it into the Carburetor and this was Causing the Original Problem.
>>Now, either the Crankcase Vent was/is Bad and if Cleaning it Did Not Correct the Problem; then you need to Check the Compression to Determine if there is a Ring Cracked or Stuck/Frozen on the Piston or Replace the Crankcase Breather.
>>The Small Decompression Valve in the Crankcase Breather/Vent is Supposed to Allow Internal Compression that Seeps by the Rings to Escape to the Carburetor and be Burnt with the Air Gas Mixture and Prevent Oil from Entering the Carburetor. If the Valve Sticks Open, there is Too Much Compression Seeping by the Rings (as in a Cracked or Frozen/Stuck Ring) or the Crankcase is Overfilled with Oil; you will have the Original Problem you Described.
>>Does the Engine Still Runs Rough, Misses and Backfires a lot with the Crankcase Breather/Vent Attached to the Carburetor? If Yes, then
>>Check the Compression and/or Replace the Crankcase Breather.
>>Please, Do Not Hesitate, If you Hit a Snag, if I Missed Something 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
