B & S won't start...backfires

S

shiftsuper175607

Lawn Addict
B & S Vanguard 15.5 HP model 280777 type 0691-E1 on a Dixon ZTR 4515B
Hello everyone,
I hit and 16 inch log about 3 inches diameter, motor died immediately.
I pulled it back to the shop.
When I tried to start it was trying to backfire.
I removed all covers and flywheel bolt.
The flywheel and crankshaft seem to be in correct alignment with the key intact.

I thought I would ask you guys if you had any ideas beyond a partially shared key.
But again, everything look straight.

I have not been able to get the flywheel off yet, still working on that, so I came in to ask you guys for some help.


Thanks a lot.shift

PS. what is the torque for the flywheel bolt?
 
I would check to see if the valves are opening and closing like they are supposed too. Turn flywheel by hand.
 
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BlazNT said:
I would check to see if the valves are opening and closing like they are supposed too. Turn flywheel by hand.
Click to expand...

Found the top push rod collapsed/bent

Would that be the intake or exhaust valve side?

Also, does anyone have a link to a repair book for setting the valves?

B & S Vanguard Model 28Q777-0691-E1

Thanks for the help, as always.

Shift

PS...notice that area of the push rod is necked down and appears to be weaker...by design? was it spinning and wore down?
 
shiftsuper175607 said:
View attachment 30065

Found the top push rod collapsed/bent

Would that be the intake or exhaust valve side?

Also, does anyone have a link to a repair book for setting the valves?

B & S Vanguard Model 28Q777-0691-E1

Thanks for the help, as always.

Shift

PS...notice that area of the push rod is necked down and appears to be weaker...by design? was it spinning and wore down?
Click to expand...

IF the bent/broken area is about an inch down from the rocker arm end, it is caused by the aluminum push rod working back and forth while resting on the fiber/plastic guide which is why I always recommend reversing the push rod whenever adjusting the valves.

I can send you Detailed Instructions for adjusting the valves plus a Service Manual IF you like. Address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com
 
Tinkerer200 said:
IF the bent/broken area is about an inch down from the rocker arm end, it is caused by the aluminum push rod working back and forth while resting on the fiber/plastic guide which is why I always recommend reversing the push rod whenever adjusting the valves.

I can send you Detailed Instructions for adjusting the valves plus a Service Manual IF you like. Address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com
Click to expand...
________________________________________________________________________

The necked-down part of the rod is polished as if it was turned on the finest lathe.(see picture above) It is amazing to me that it could polish/turn so evenly.

________________________________________________________________________
Thank you, Walt

I will do that. That is very generous of you to offer.

shift
 
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