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Setting mixture on HS4 carbs
- Thread starter GaryBeu
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Up leans; down richens.
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davester
Jedi Trainee
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The way to easily remember this is to visualize the jet needle as a tapered cone sticking down into the jet. When you raise up the jet, the cone plugs up the jet, thus cutting off the gas and leaning out the mixture. For me, the hard part is remembering that when I'm looking down on the carb, a clockwise turn of the jet adjusting nut is actually counterclockwise (loosey and richer) if I was looking at it from the bottom.
Thanks Dave...that helps.
I can't seem to get things set properly and she seems to run well for a couple of miles and then start backfiring again. I'm attaching a couple of pics of the plugs I just took out and maybe they will tell someone something. Not the best pics so I don't know. From left to right they are from back to front. Thanks.
Wel, I can't remember how to attach a photo from Photobucket :frown: Any help with that first??
I can't seem to get things set properly and she seems to run well for a couple of miles and then start backfiring again. I'm attaching a couple of pics of the plugs I just took out and maybe they will tell someone something. Not the best pics so I don't know. From left to right they are from back to front. Thanks.
Wel, I can't remember how to attach a photo from Photobucket :frown: Any help with that first??
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Gary:
From your Photobucket account, click to save the image code under the picture you want to post, then when you make a post here, you'll see the image icon (4th from the left above the typing field); click on that and enter the url you saved from your picture.
Mickey
From your Photobucket account, click to save the image code under the picture you want to post, then when you make a post here, you'll see the image icon (4th from the left above the typing field); click on that and enter the url you saved from your picture.
Mickey
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Sending PM...
Hap Waldrop
Yoda
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I build alot of these carbs, in fact building a set today. For good starting point, regardless if you have the solid needles or the bias needles, remove the dashpot, dampning spring and piston, with the end of dial caliper set the jet down from the bridge at aprox..070", that's where I set all of mine, it's textbook setting, and half my customer never even touch them set there.
Hope this helps.
Hope this helps.
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YAY!
But, BOO! Those look pretty lean.
But, BOO! Those look pretty lean.
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Yep - try this: Run the adjustment nut on each all the way up, but not too tight, counting how many turns each takes. This will let you know where you are now, in case you need to go back to that point. Back it down 1/2 a turn past where you are now and see what effect it has. Trial and error at this point; back and forth until you get it where you want it.
Oh, and make sure your dashpots have oil!
Or, try the method in the link I posted earlier.
Oh, and make sure your dashpots have oil!
Or, try the method in the link I posted earlier.
DGill
Freshman Member
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I believe that if you want to change the setting from rich to lean you need to buy a new set of needles for the dash pots. The adjusting nut is really just setting the idle mixture. Moss motors sells the needles, you will need to remove both existing needles and check that they are indeed the same. It's very possible that over the years someone may have matched a carb that appears to be the same. Check the number tag on the float lids to see if you have matching carbs. Another thing to check is the vacum advance plat in the distributor under the points. The floating advance plate runs in a grove and after years of viberation the floating plate will hang up during exceleration causing a cold blooded runner and a barker on deceleration and a tuners nightmare.
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DGill, you can change the setting from lean to rich with that nut. Of course though you are correct that the other way is to change the needle. At some point it would probably make sense for Gary to ensure that the needles match. But, we also know that this car has been running well, and we don't want to confuse the poor man too much. So, I suspect getting the settings matching and Gary driving is the critical thing.