How To Bore Ventruis on a HW 5200 w/simple tools

[MercuryMarc]

Thanks To Addo for suggesting how to do this with tools available in my garage! And thanks to Xctasy for help with the dimensions!

Disassemble carb and remove the fuel nozzles that span the venturis using gentle tapping pressure from below

Find a piece of PVC pipe that barely fits in the venturi and then fabricate a sanding/grinding rod. I used 3M sandpaper pads with self adhesive on the back. I attached the pipe to my drill by using a hex drive bit that was smaller than the internal diameter of the PVC tube, then wrapped electrical tape around the bit until it was a snug fit in the pipe.

Patiently move the sanding rod back and forth across the venturi, checking with calipers every few minutes to check for roundness and diameter. I used a 80 grit, then 120 grit, then 400, then 600 grit to polish the venturi once it was close to the desired diameter.

Using this method I enlarged to 26 mm primary venturi to 29 and the 27 mm secondary venturi to 31.

Ventruris Before (Standard 26/27) and Ventruis After (Bore to 29/31)

I'll let everyone know if the carb works once I get it on the car, but the enlarging of the venturis is simpler than it may appear.

 

[ASMART]

You never let us know how it worked!

 

[MercuryMarc]

It worked almost as well as my Carter RS!!
Except my Carter does not stall on left turns and has none of the dreaded bog...
I tried at least 4 jet combos and I finally gave up. I think to do it right you'd need to have:
1. O2 sensor for fuel/air adjustment
2. Lots more patience then I have.....

But it was fun trying...

 

[ASMART]

What did you do to get rid of the bog?

Did you adjust the accelerator pump to give a larger/longer shot? It seems like you can also enlarge the hole where the the fuel from the accelerator pump comes out to deliver more fuel quicker.

 

[MercuryMarc]

I got rid of the bog by using a Carter RBS.....

I ran out of patience...
Every time I made a jet change I had to drive a while, then pull the plugs, take notes, etc. I did not get around to changing the pump shot or other things (but these do seem like good suggestions, but I just did not have that kind of time, energy, or enthusiasm).