Some help required to diagnose a problem with starting a mower

[jpadie]

Thank you. I reset the throttle/choke cable and ensured that the butterfly valve was fully closed and retightened. Unfortunately that did not resolve the issue and the nozzle was clean when disassembled.

closing the engine side butterfly valve does consistently start the motor however. The governor does not seem to leat the butterfly valve go further than about half closed.

Is this a sign of a bad carb or a bad governor? or both?

 

[bertsmobile1]

It is a sigh that the governor is not adjusted properly.

 

[jpadie]

thanks @bertsmobile1

can you explain what a well adjusted governor should look like or perhaps how best to adjust it on this motor?
I have the willingness and (possibly) intellect, but not the experience!

 

[bertsmobile1]

with the engine off loosen the pinch bolt on the bottom of the governor lever
Note that the end of the shaft that pokes out of the engine has flats on it so you can hold it with pliers, wrench etc.
Now look at your carb and see if the governor arm has to pull of push to open the throttle butterfly fully .
If it pushes ( most do ) then rotate the shaft counterclockwise as far as it will go
Then push the governor arm to fully open the throttle
While holding thm both in that position tighten the clamp bolt using your 3rd & 4th hands

 

[jpadie]

Thank you. I guess I will need a tachometer to gauge the engine speed after that.

I am wondering whether the issue may also be due to the mower having had the blade stop a few times in long grass. I don't know whether this mower has blade keys or similar but the blade does seem to spin somewhat freely of the shaft (high friction but definitely movable by hand). Symptoms that worry me are the backfiring through the carb, the nasty metallic sound when the choke is open and the engine cranked and the occasional sever backlash on the starter rope. Can a problem at the blade assembly lead to a no-start issue?

 

[bertsmobile1]

Setting the governed speeds on Honda engines by ear is a problem because they are a lot quieter than Briggs , Kohlers & Honda knock offs
Add to that Hondas generally run a bit slower ( usually 3000 to 3200 ).
If some one walked into my shop & asked me to check the high speed I would do it gratis.
If they wanted it adjusted then it would be $ 10 ( AUS)

As for the blades, most 4 stroke push mowers that have the blade on the crankshaft require the blade to be there and to be tight because they use the weight of the blade to act as a flywheel
So many will not start or run a low speed without the blade

However if they have a blade clutch then they will start & run with a loose or missing blade.

Not familiar enough with Stigas to take this bit any furher

 

[jpadie]

Thanks @bertsmobile1

in fact what was happening was that the blade retention lugs had sheared and the blade was increasing the drag rather than adding to the rotational inertia and assisting the flywheel. Removing the blade allowed the motor to fire up perfectly. and replacing the blade support of course solved the problem. I had tightened the blade bolt up to create friction but evidently not enough to overcome the drag on the blade.

I knocked up a quick tachometer using a reed switch and relying on the magnet in the fly wheel to switch it. On fast it seemed to be averaging 3240 RPM so I did not adjust the governor in the end. To my untrained ear it sounded a bit slow - but my friend has got it back now. Just in time for a week of rain.

Many thanks for the support.