Author Topic: carb air screw adjustment  (Read 6729 times)

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Offline dhall57

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carb air screw adjustment
« on: May 30, 2010, 07:44:46 PM »
Here's a picture of one of the carbs on my 1976 CB750. Checked plugs and all 4 look to be running too lean.  Each plug looked almost identical. The air screws on my carbs have a stop tab on them which will let you turn them only one turn in either direction. Was this type of set up only on the K6. I checked out the FAQ on carbs and it said to turn screws all the way in and than back them back out a turn and 1/2. Of course I'm not able to do this with mine because of the tabs. Whats the correct position for these screws to be in to help me with the lean condition. All in all the bike runs and idles good, but a little to much gas smell at idle and acceleration for a 750 seems a little flat.
1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline Spanner 1

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Re: carb air screw adjustment
« Reply #1 on: May 30, 2010, 10:08:19 PM »
If you bust those plastic 'tabs' off you will find the screws are already at 1and 1/2 turns out , plus or minus the small adj. until the tab hits the stop...... prolly not yer prob with under par running.. time for a tune-up?
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....

Offline bird

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Re: carb air screw adjustment
« Reply #2 on: May 30, 2010, 10:19:01 PM »
Yep, save yourself a lot of heartache and have the carbies tuned and balanced by a good mechanic, then she'll run sweet. Good luck. ^^

Offline Gordon

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Re: carb air screw adjustment
« Reply #3 on: May 30, 2010, 10:28:10 PM »
Yep, save yourself a lot of heartache and have the carbies tuned and balanced by a good mechanic, then she'll run sweet.

Please tell me you're joking.

Offline Spanner 1

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Re: carb air screw adjustment
« Reply #4 on: May 31, 2010, 07:53:16 AM »
Yep dhall57, you are , hands-down, the best mechanic for your bike.... !!
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....

Offline dhall57

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Re: carb air screw adjustment
« Reply #5 on: May 31, 2010, 05:33:13 PM »
This is a pic of my #3 plug on my 76K6. #1,2, and 4 are almost identical to #3. I didn't find my camera until I had put the others back in. Does this plug look too lean or about right.
1970 CB750KO
1971 CB500KO-project bike
1973 CB350G- project bike
1974 CB750K4-project bike
1974 CB750K4
1976 CB750K6
1977 GL1000
1997 Harley Wideglide

Offline medic09

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Re: carb air screw adjustment
« Reply #6 on: May 31, 2010, 05:39:56 PM »
It's a little hard to tell from the photo, but it might be a bit hot/lean.  Still looks okay.  Should be very lightly toasted.  I assume you checked gap as long as they were out, eh?

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html
Mordechai

'78 CB750K
'76 Triumph T160 Trident (rebuilding)
'07 aprilia Caponord

Santa Fe, NM

Offline bird

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Re: carb air screw adjustment
« Reply #7 on: May 31, 2010, 05:55:41 PM »
No joking. I'm a bumbling find your own way and try and fix it yourself Honda Four owner just like pretty much everyone on this forum. But there comes a time when you don't have the gear or expertise or time to fix everything and you find an old school mechanic who can. And I did. But anyways dhall57, you give it your best shot and have fun tuning your bike. Hope it works out for you. Good luck.

Offline Spanner 1

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Re: carb air screw adjustment
« Reply #8 on: May 31, 2010, 07:46:22 PM »
dhall.... looks too lean esp. if those plugs were just 'pulled' and not the result of a plug 'chop'.... plenty of airflow in the carbs, need to remove the jets ( start with idle/slow )... bet their gummed-up pretty good..... K6 carbs will 'blacken' the blugs pretty quick if the bike is left idling for even a few mins. ( normal ) , takes a little riding to clean the plugs up....
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....