Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Continuation of thread:  Poulin rear engine engine pulley question.

   The value issue was due to the cam lobes being fitted plastic lobes that slipped their position.  Plastic lobes on a
 metal shaft driven by the crank of an 8.75 horse power engine.  It's impressive that they lasted 3-4 years which is the
age of this machine.  I got the rider free from a guy who had a fairly small lot with a slight slope, not a taxing piece of
property. 
    The cam is very light and the plastic gear feels very cheap in your hands.  The center section is very thin and molded
to six skimpy spokes which go out to the gears.  You can felx the gear easily with your fingers.  It's a piece of
crap.
    With a little effort I could move the lobes on the cam and that force is nothing to what an 8.75hp crank can put out.

    Not sure what the gizmo is between the lobes but the guess is it controls the compression release.

     All in all this is a very cheap engine.  The rider does not even have a throttle control.  It's a one speed engine, start
and it goes to full speed cold.  Not the best. 

    People bark about cheap Chinese engines.  This is not an example of that.  This is Briggs specifying to the Chinese
we want cheap crap and the Chinese happy to oblige.  This experience will give me great pause to ever get anything
from Poulin or Briggs without doing some extensive checking into what I'm getting.

   The Poulan rider smoked on the original purchaser. and died without any strange noises.  I found gas in the oil, the
valves way off and low spark.  I fixed those.  The valve lobes were probably off also which contributed to the valves
being off.  It may be during the fix the lobes or a lobe got pushed back into position.  ??
 
    After the fix I took it for a ride and was going well for about 15 minutes.  In the back yard there are some mild slopes
and the grass wet.  The wheels slipped and caught a few times and right after the thing died.  I think the slope and
slipping wheels were enough back pressure in the drive system to make it back to the cam and pushed a lobe out
of position.  What crap.
    Before all this happened I looked into replacing this engine.  This engine can be bought on the net for $129 and
shipped to me for $160.  I now see why it's such a low price.

Other than spinning, the lobes look fine. Any way to see where they should be positioned and drill a hole and pin them to the cam?

Shryp,
   The lobes look ok in the picture but the tip on one had enough wear to slightly change the timing.  The worn section
was now much rougher than the original surface and would be wearing at a much faster rate than it had been.  It
probably would have lasted for another year before it affected the timing enough to be no good.

>>I was going to say something about a plastic cam.  But I really didn't think there would be one in a Briggs.
   Me to, at first thinking there was a sleeve type lobe in there but then said, no way, it can't be that.

>>With the different expansion and contraction rates of steel and what ever material the lobes are made of.
I don't see how this wouldn't eventually happen on every engine they have built like this.

   Good point.  I'd like to know the failure rate of these engines.  I'm ok with plastic gears in Tecumseh engines I
started seeing years ago for parts like the governor gear.  I checked around and found Briggs is fitting plastic
timing gears onto cranks so again metal to plastic on the crank and a plastic timing gear to a plastic cam gear. 

    The plastic cam would probably be ok for light duty service but even then I would not expect a long life for the
engine and certainly nothing like the many old Tecumseh's 60's and 70's that are still running.

    The Poulan rider had a 26 inch blade, metal deck, the weight of the rider body and the weight of the driver.  Push
and driven mowers have 6.5hp engines these days and struggle with tall grass.  The Briggs on the Poulan rider
was 8.75hp so not a lot more hp for a vastly increased load.  The total design of this rider a looser.

   None of the three dealers I spoke with sold this rider.  They were marketed through Walmart,  Home Depot
and other low end outlets. Shame on them.


    I'm stuck for options with this thing.  The replacement cam online is $41-48 plus shipping.  If it was 5 bucks
there's no way I'd put in another plastic cam.  An older Briggs I/C might work or a low horsepower Kawasaki.
I don't know much about riders or vertical engines i.e fitting & crank ends & etc.  I'll have to snoop around and
see if something else could be planted.