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H6 carb balancing

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NutmegCT

NutmegCT

Great Pumpkin
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I could have sworn I read a thread here about using a rubber hose to "listen" to the carbs and balance them.

Anyone know how to do this?

Or are we all now gadget-obsessed and using Uni-Syn carb synchronizers or Synchrometers ...

Plain vanilla dual H6's.

Thanks all.
Tom
 
The Chief Boffin here at HSTRL Soggy Bottom is guilty of using the rubber hose method to balance H6 carbs. It's simple, very inexpensive, yet effective.

Just stick one end of the hose in your ear and the other end next to, but not blocking, the intake on each carb in turn. Just make sure you put the hose in the same place on each carb. Then adjust the idle screw(s) until the hiss sounds the same on both carbs. Voila! (Can't make italics on Quick Reply)

I have tested the balance with a fancy tool after setting carbs by ear, and the tool thingie showed that the carbs were balanced.
 
Tom,

I use a two foot length of 5/8ths hose for this. Make sure you disconnect (loosen) the throttle spindle connecting rod folding coupling so each carb rpm adjusts independently. The trick is to get the rpm slow idle at 500rpm and have both carbs hiss at the same sound level. The initial settings are to screw the mixture adjusting nut fully up then back off 2.5 turns. then set the throttle idle adjusting screws so they can hold a thin piece of paper between the throttle idle screw and throttle idle screw stop when the butterfly valve is held closed. Then screw the throttle idle screws in one complete turn.

start your engine and let it attain full operating temperature. Then adjust each idle screw to get the correct hiss out of each carb. Once the hiss is equal and the rpm is at 500rpm, mine is at 600rpm it refuses to stay running at 500 rpm /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif , you can then start to adjust the mixture setting for each carb.
 
Lot's of ways to do the same thing Tom. I used a hose for a long time, but I don't trust my ears any more.

Then again, I don't trust my eyes without the reading glasses, so I don't know what I'll try next year.

Tough getting old.....
 
SU's are the easiest carbs I've ever worked on and I believe the hose tech works because of that.
Although why you'd want to trust your ears when the synch tools tell you exactly what your carbs are drawing is beyond me.
 
I have used the hose technique for 49 years. You want to use it like John describes. Loosen the tiny nuts and bolts where the two carbs are connected between them, They will be balanced when both carbs have the same HISSSSS. If they are not balanced, one will have a HISSSSS and the other will have WHOOOSH. I hold the lower end of the hose with my fingers so that the end of the hose touches the bare flange at the carb air inlet (throat) opening (after removing the air filters) then I quickly move the hose to the same spot on the other carb.
 

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prb51 said:
Although why you'd want to trust your ears when the synch tools tell you exactly what your carbs are drawing is beyond me.
Click to expand...

We do it this way because we are Eccentric Old Geezers.
 
This is where the expression "tuning by ear" came from. /bcforum/images/%%GRAEMLIN_URL%%/driving.gif
 
If you just remove the damper caps & dampers, you can hear the same "hiss" from the top without removing the air filters. Just have to listen more carefully.
D
 
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