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Post by sharkey on Dec 20, 2021 14:18:46 GMT -5
Howdy Folks, I started an XL rebuild project with an HDC carb rehab. The circuit plate and metering chamber were the worst Ive seen. The circuit plate was rusted and the casting it sat in was full of varnish. I soaked the carb in wd-40 for a couple days and then removed all the pieces. I used a set of small wire brushes to clean out the metering chamber and used a wire wheel on the circuit plate. I was very careful but bent the metering lever pretty good. This sent me to Ebay looking for a new circuit plate and lever. I ended up with a High Altitude Circuit Plate that I dont think I can use.
Im looking for some info on these circuit plates and what their application was? Are any of you guys using one of these High Altitude plates? Have any of you repurposed one of the high altitude plates by redrilling it back to seal level specs? Found out that The Walbro K10-HDC kit doesnt come with a lever? Anyone know if an HDA lever can be substituted for HDC, if I can get the pin loose?
Thank you.
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Post by blythkd on Dec 20, 2021 21:47:11 GMT -5
So how is a high altitude circuit plate different from a standard plate? Difference in the holes I'm assuming, don't know what else would be different.
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Post by sharkey on Dec 21, 2021 10:22:36 GMT -5
Hi blythkd,
The circuit plate is stamped with a set of numbers. For instance this plate is stamped .028? Any idea what a standard plate has its holes drilled at? Thanks for the reply.
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Post by blythkd on Dec 21, 2021 12:42:04 GMT -5
No I don't know. Most of these carbs just have a larger hole in the circuit plate for fuel to pass through and metering is accomplished by adjustment of the metering screw. I know there were some carbs on small saws with preset hi side so I guess maybe they used an orifice in the circuit plate but it's just been to long ago.
The only one I recall is the .020 orifice in an ST-100 carb. That was the tiny little Walbro without a fuel pump. The only reason I recall that one is because we used to drill them out to .021 occasionally when a trimmer acted like it needed more fuel. And all of that useless trivia does you absolutely no good.
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Post by sharkey on Dec 23, 2021 6:00:57 GMT -5
Hi Blythkd,
Thank you again for the help. The trivia does help because it gives me an idea about how the engineers were thinking, when they put this idea together. Ive got a contact at Walbro, I will give them a call after the Christmas Holiday. If the detailed drawings are still available, I will try to get us a copy and then we will all know. Merry Christmas All!
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