Small Engines (Lawn Mowers, etc.): Victa Pro12 B&S 12HP I/C Low Power, zero volts, pro12

Question
QUESTION: I have a Victa Pro12 with the B&S 12 I/C motor. Whenever I engage the blades the motor almost dies. It is also wants to die in all but the shortest grass. It also will not key start, except after having replaced the battery. For the first few times it started from key but after a couple of weeks idle the battery is flat (ie zero volts) and only a pull start works it again. The ameter shows it is charging but I have a feeling there is a short somewhere. Any ideas?

Thanks,

Damian

ANSWER: How old is the enigne?  Did the lack of power happen suddenly or did the mower sit for a while?

Does the engine speed sound normal?  Are the carburetor linkages binding?  Does the governor maintain engine speed?
Does the enigne have plenty of power without the blades engaged?
Now the obvious.  Are the deck bearings alright?  Are the pulley brakes fully retracting with the blades engaged?  Is there anything under the deck causing excessive binding?

Are Victa mowers manufactured and sold only in Australia?  I have not seen Victa mowers in the States or Hawaii.

Let me know the answers to the questions to narrow down the problem.
Eric



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QUESTION: Eric,

Victa is an Australian company and I believe that the Pro12 was a rebadged product from the US, possibly MTD. The mower is grey, was manufactured around 1992-93 and came with either a 12 or 16 HP engine. Mine has the 12 I/C B&S engine. It gets used every couple of weeks and has probably been getting worse over a couple of years use. The engine speed is normal but what we find is that the throttle control does not stay in place so you have to manually hold it at maximum level without moving into the choke position (the throttle pulled fully towards the operator). The mower moves pretty well without the blades engaged however it is still pretty low on power due to its age. The blades spin quite freely if disengaged from the motor. According to Victa one of the blade engagement switches may be trying to stop the engine at the time the blades are engaged however the low power during cutting tells me it is an engine problem.

I have noticed a backfire when stopping the engine recently. Is this a timing issue? Is there some type of enginee flush that can be applied to clean out the rings? Is it an electrical problem that is putting pressure on the motor itself?

Thanks,

Damian

ANSWER: The electrical systems are fairly simple on small engines are pretty dependable.

Based on the age, I would check the valve clearances.  I would tell you to check the compression but Briggs does not publish compression specs due the variation across engines.  The old test Briggs used to recommend was to rotate the flywheel, by hand, opposite the normal engine rotataion.  The engine should have enough compression to snap the flywheel back to the normal rotatation direction.

The newer procedure to check compression is to use Briggs leak down tester.  While we have one, we rarely use it.

Do you have or know anyone with a single cylinder tachometer?  I would like to know how many RPM the engine produces at full throttle.  

Do you have a multimeter to check the charging system?
Usually if you have a bad safety switch the engine will shut-off as soon as you engage the blades...so I doubt you have a safety switch problem.

Can you send me the engine model number, type and code number?  Also the mower model number located on a sticker or metal plate.  I can look up the valve clearances for you.

Let me know about the tach, multimeter and if you have some basic tools including feeler gauges.
Eric

---------- FOLLOW-UP ----------

QUESTION: Eric,

I have checked out the electronic safety system and everything is working as expected. I also checked the valve clearance and there isn't any between the valves and their push rods (for both intake and exhaust). Is the adjustment done via tappets, from under the flywheel, or do you grind the valve ends (someone told me this was a way of doing it).

The compression is pretty low as I could turn the flywheel both ways. I did clean the valves and piston face when I had the head off the engine. There is oil getting past the rings which causes white smoke at initial startup.

I didn't have a micrometer to measure the maximum opening of the valves but each was at least 1/8th of an inch at maximum.

I did find that the lack of electric start was due to the total collapse of the inside of the B&S starter motor. I will replace this if I can get the engine running better.

The details of the engine are as follows.
Model: 281707
Type: 0213-01
Code: 89062211

I have attached a photo of the mower in case it reminds you of a US brand and model.

Thanks,

Damian

Answer
Just to be sure you are checking the valve properly did you follow this procedure.

1. Rotate engine to Top Dead Center (TDC), piston at the top of the cylinder on the COMPRESSION stroke.  Follow the valves, as the intake begins to close and come back to TDC you are on the compression stroke.  At TDC on the COMPRESSION stroke, continue to rotate piston 1/4 inch past TDC.  This is Briggs recommended procedure.

2.  Check valve clearance with a feeler gauge.  
Intake:  .005-.007 inch
Exhaust:  .009-011 inch

3.  If vavles on not within spec, remove and grind stem to clearance.  Start with the minimum.  Once the minimum is obtained, remove and lap valves starting with corse and followed by fine lapping compound.

Ensure all lapping compound is removed from the valve face, seat and stem.

After lapping, re-check valve clearances and adjust as necessary.  

Since the engine is 18 years old I would expect some oil to get past the rings since they are probably wore.

I would be careful how much time and money you put in this old of an engine.  If the mower is in good shape it may be cheaper to replace the shortblock or the entire engine.  Again, you would have to price out both options.

Let me know if this helps.
Eric