Small Engines (Lawn Mowers, etc.): starting problem, craftsman riding mower, cold cranking amps

Question
QUESTION: Paul, I have a Craftsman riding mower with a Briggs and Stratton 31H777 0202e1 motor.  When attempting to start, the starter slowly turns a time or two and stops without starting the motor.  The battery charge is full with plenty of cold cranking amps (320).  If I use a jumper box, the starter continues turning slowly but will eventually start the motor.  All of the terminals and connections appear to be clean.  Do you have any ideas?  Thanks

ANSWER: hi greg

you mention battery is full charge and plenty of cca ( cold cranking amps) is the starter solenoid giving a solid click or does it give a rapid clicking or buzzzzz and is starter is getting full voltage from battery ?

1st thing to try being an ohv engine is to reset tappetts -remove valve tappett cover
btm valve is inlet ( alloy push rod ) / top valve is ex ( steel push rod ), remove plug    set engine to tdc compression stroke the run piston  1/4 inch past tdc on power stroke  the set valve clearance  to 0.003" inlet & 0.005" ex
tighten loc nuts and check again before fitting  cover  should be a sliding fit   

have you cleaned all  earth return leads and tried a earth bypass  wire in case of bad earth
especially around battery to chassis   and starter motor to engine

try using a test light and clip the clip end to earth and the probe end to starter terminal at starter motor   crank the engine  if   test lights up  problem could be in the starter motor

ie bad armature/shorted windings/insulation break down/ broken magnets / worn armature bearings   these things cause hi current draw

poor brushes will not cause hi current draw

remove starter motor and bench test

give it a try  and let me know  cheers  paul





if these check out with no excess resistance  then

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

QUESTION: Hi Paul, the starter is getting power as it slowly turns over.......not quite enough juice to start the motor.  There is no buzzing or clicking sounds and the solenoid is working fine.  Is it sounding like a bad starter?  If so, should I get a new one or try to repair the one I have?  Thanks

ANSWER: hi steve

have you checked out earth leads and grounds for battery and starter motor  ?
and checked for correct valve clearance and decompressor action

does test light on starter motor terminal  when engine is trying to crank light up the test light ?   if so  

then yes i would pull starter motor and check  comutator segments for  continuity to each other
hi resistance between segments   - shows fault  , if no continuity  shows fault
and check insulation of each segment to central shaft ( should be  infinity ohms resistance )
anything less would be  breaking down  to ground  , check the end cap bearings as well
does the starter motor smell or show any signs of burning ?

check brushes , but if any of the above exsist   may be better to  get another starter motor

from what you tel me sound more the starter motor, but just like to be sure havent missed the simple stuff  

cheers  paul


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

QUESTION: Hi Paul, I cleaned the ground terminals and the motor will now start but turns over very slowly until it fires up.  Battery is new and fully charged.  Something still seems off.  I will try the valves next......never done valves before.  Can you give me some ideas on how to find tdc and the compression stroke?  Thank you

Answer
hi greg

pull the plug, rotate engine untill you feel compression - remove rocker cover ,
rotate engine further  while watching the inlet valve ( btm one ( push rod is alloy ) it should open fully then close  ( you will see it open very slightly near tdc as it closes ( this is the decompressor action - make sure you rotate the engine past tdc compression stroke and stop when you have moved the piston 1/4 inch down the bore on power stroke

set the valve clearance to 0.003"  inlet  and 0.005' exhaust with feeler gauge

clearance should be a sliding fit , be sure to hold position while tightening loc nut
recheck clearance and  re adjust as necessary - refit rocker cover and plug

you could try testing the solenoid contacts for resistance or burning

disconnect both battery and , starter motor leads from  solenoid  
to check for resistance - apply 12 vlt + battery voltage to solenoid input tab  and connect  neg
battery to earth ground  heavy contacts with make contact  and you can measure resistance accross   contact with ohm test meter if ohms  read zero or close to  it  solenoid is in good condition  but  a high reading in ohms indicates burnt contacts
replace solenoid

remember to refit  positive leads back onto to solenoid before  trying to test again  

cheers paul