50/50 - help either with a mower engine or my brain
Discussion
Hi guys,
I recently picked up a Honda petrol mower (GCV135 engined) and I've been giving it a good service etc.
The only thing I can't fathom is how the throttle linkage works.
It has two butterflies, the first being used for choke, the second the normal throttle which is directly linked to a governor arm, then via a spring to the cable pulled throttle link.
What's odd is that the second butterfly doesn't seem to have a closing spring- there's none listed on the parts diagram either. The linkage means it pulls it open easily enough, bit nothing to close it.
Can you run a four stroke engine this way or am I missing something obvious?
Top right is the linkage from governor arm to the second butterfly. In this photo it's at full throttle.
You can see the cranks for the butterflies on the left, the black one for the choke, the brass one is the secondary throttle. At the bottom of the picture is the governor arm spring which connects to the throttle mechanism, which rotates clockwise as it opens, tensioning the spring.
There's a "throttle return spring" threaded on the bar running from the governor lever to the throttle, but its force is actually to open rather than close the throttle.
I recently picked up a Honda petrol mower (GCV135 engined) and I've been giving it a good service etc.
The only thing I can't fathom is how the throttle linkage works.
It has two butterflies, the first being used for choke, the second the normal throttle which is directly linked to a governor arm, then via a spring to the cable pulled throttle link.
What's odd is that the second butterfly doesn't seem to have a closing spring- there's none listed on the parts diagram either. The linkage means it pulls it open easily enough, bit nothing to close it.
Can you run a four stroke engine this way or am I missing something obvious?
Top right is the linkage from governor arm to the second butterfly. In this photo it's at full throttle.
You can see the cranks for the butterflies on the left, the black one for the choke, the brass one is the secondary throttle. At the bottom of the picture is the governor arm spring which connects to the throttle mechanism, which rotates clockwise as it opens, tensioning the spring.
There's a "throttle return spring" threaded on the bar running from the governor lever to the throttle, but its force is actually to open rather than close the throttle.
Edited by Krikkit on Wednesday 26th September 23:17
Don't know this particular engine but the way these usually work is that the when you operate the throttle to full, you open the butterfly via a spring.
When the engine starts the butterfly is pulled partially closed against the spring by the governor to regulate the engine speed, there isn't usually a spring to close the butterfly.
When the engine starts the butterfly is pulled partially closed against the spring by the governor to regulate the engine speed, there isn't usually a spring to close the butterfly.
I may be wrong here but I've assumed it's a fan and wing/blade regulator?
If it is, when the engine runs air from the fan acts on the wing/blade and reduces the throttle opening by pulling against the spring on the end of the throttle cable, there is therefore no need for a spring to pull the butterfly towards closed.
If it is, when the engine runs air from the fan acts on the wing/blade and reduces the throttle opening by pulling against the spring on the end of the throttle cable, there is therefore no need for a spring to pull the butterfly towards closed.
It sounds like you've hit the nail on the head with the air movement causing the governor to close the throttle, that would explain it.
The engine ran, poorly, before I disassembled it, and it's not back together yet. I'll carry on getting it up to snuff, put it back in the chassis and see how it goes.
Thanks all.
The engine ran, poorly, before I disassembled it, and it's not back together yet. I'll carry on getting it up to snuff, put it back in the chassis and see how it goes.
Thanks all.
I overhauled and serviced my Honda Izzy last year. Couldn't work out how to reset the governer so downlaoded a PDF of the worksop manual and followed the instructions as it's simple to do, but needs to be done properly, it's not intuitive without the manual.
It might be worth you doing the same.
It might be worth you doing the same.
The governor is a centrifugal type, the long, light spring is to take the backlash out of the linkage so the rpm remain steady
In use.
The carbs can be an absolute pain with modern fuels causing corrosion when mower is laid up during the winter, this
Can be prevented by using a fuel system inhibitor,but....,if the carb is u/s the bay of e will provide a new one for under a tenner,
Bolt straight on,no adjustment needed, I keep one as a spare" just in case." HTH.
In use.
The carbs can be an absolute pain with modern fuels causing corrosion when mower is laid up during the winter, this
Can be prevented by using a fuel system inhibitor,but....,if the carb is u/s the bay of e will provide a new one for under a tenner,
Bolt straight on,no adjustment needed, I keep one as a spare" just in case." HTH.
Penelope Stopit said:
This may help http://seagointernational.com/new/Manuals/Honda%20...
Thanks for that, despite my best efforts I couldn't find one as detailed as that.I see now that the governor is more than just what it feels when fiddled with on the bench, so that's one question. It's back up and running, but like arse, taking the carb apart today it's full of rust and gunk so I've ordered a new one as the jets are all jammed in.
Krikkit said:
Penelope Stopit said:
This may help http://seagointernational.com/new/Manuals/Honda%20...
Thanks for that, despite my best efforts I couldn't find one as detailed as that.I see now that the governor is more than just what it feels when fiddled with on the bench, so that's one question. It's back up and running, but like arse, taking the carb apart today it's full of rust and gunk so I've ordered a new one as the jets are all jammed in.
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