Carburetor spacer for Briggs and Stratton Sno/Gard 62000 (Snowblower Hako 6009H) by szalat

Last crawled date: 3 years ago

I have a Hako Snowblower with fairly rare Briggs and Stratton Sno/gard 62000 two cycle engine. Bought for cheap with carburetor problem. My attempt to overhaul original carburettor failed. Original diaphragm set for this carburetor costs about 100$! I've tried to make DIY diaphragms but no luck.
Finally I have decided to go with stock universal diaphragm carburetor for brush cutter. Here is a link to ebay (just for example, random seller)
Biggest problem with this carburettor was that it is a bit different. Wrong bolt spacing, wrong throat diameter, and worse of all - it needs to be mounted in position 90 degrees different from original carburetor and impulse channel is on surface of engine/carburettor.
I've took old carburetor, old carburetor spacer, new carburetor and a caliper and start drawing in FreeCAD. This is what I've designed. Most challenging was impulse channel design.
Printed in PET-G. Sanded inside surface then covered it in epoxy glue (for fuel resistance) then inserted upper bolts (M5 afair) with epoxy. It is designed to put between old carburetor spacer and new carburetor. Fits well, engine works like a charm, PET-G doesn't melt or deform (yes it does, see UPDATE 2).
One thing I did not manage is engine governor (see update below). Original carburetor has metal throttle valve that turns without applying virtually any force. New carburetor has different construction - it has throttle in form of drilled cylinder and internal spring (that is essential for carburetor, cannot throw it out). This makes turning throttle fairly heavy and governor has no strength to overpass its resistance. Governor is not working right now (see update below).
UPDATE
Just updated project files for another carburetor from chainsaw (Walbro WT series) that has brass round plate as a throttle that turns without effort. Not tested yet but seems like it should work with original governor.
króciec-gaznika-odsniezarki-v4-gaźnik-pilarki.stl - spacer for chainsaw carburetor
króciec-gaznika-odsniezarki-v4-gaźnik-pilarki-kółko.stl - lever (wheel-form) for chainsaw carburetor
króciec-gaznika-odsniezarki-v4-gaźnik-pilarki-nakrywka.stl - anti-garbage protective cap for chainsaw carburetor. It is bolted on top of the carburetor and protects against falling small particles or parts inside of a carb throat. It is near identical to cap from original carburetor. It should also work with brush cutter carburetor.
Interesting fact: many snow blowers doesn't have air filter. Seems like in snowy winter conditions there is no dust floating everywhere.
UPDATE 2
Ended up with this part machined by hand and MIG welded from scrap metal parts. There was no problem with softening PETG when engine was running. During work engine is cooled efficiently by its fan and flow of air/fuel mixture. It softens just after engine was running few minutes and stopped. Seems that internal heat comes out from engine mixture channel and mounting bolts. It rises temperature of bottom part of the printed carburetor spacer making it soft and deforming.
In conclusion:
part invention and testing process was very simplified by CAD and 3d printing. Although printed carburetor spacer itself was not suitable for real life work, it has proven that concept realisation is just working. Then it was very simple to make such part from metal knowing shapes, dimensions and angles.