carburetor problems

[fairlady_1966]

How do i tune my carburetors rebuilt them but the car runs but it doesnt idle and it hesitates 1.6 r16

[spl310]

Where are you located?

[notoptoy]

Best write-up here: http://www.datsunroadsterranch.com/

[Gregs672000]

Yes, do look through the carb tuning info, great stuff there by people who really know them. We are happy to help with any questions as you progress, and may be able to route some folks to you if desired, once we know where the car is located... Welcome!

[revbang1]

My front carb is pulling way too much air and the back carb is pulling almost none. Tried adjustments to no avail. What am I over looking. Mark

[keith0alan]

Looks like the datsunroadsterranch.com site is down. I need to fix that. The info is also on 311s.org. Air flow balance is off. Check the valve lash and then look at my carb tuning info on 311s.org.

[nismou20]

Pulling the pistons and domes off allows you to see roughly where the butterfly valves are in relation to fully closed throttle. This may help you get in the ballpark if you are totally off. Then use the balance screws to fine tune. Also helps to get the nozzles close.

[RustBucket]

Couple questions:
1.Did you use a uni-syn or equivalent to measure flow? Adjust dog bones for open throttle, screws for idle. I think that dogbane adjustment is more important. I spend more time off-idle.
2.Check the oil in the carb pistons. I used 20wt motorcycle shock oil. This may help with acceleration hesitation. Check site for other oils that can be used (Marvel Mystery, etc...)
3.You could check the floats are still floating and that the valve is adjusted correctly too.
You can also check a multitude of other things, but start there.
The RoadsterRanch write up is awesome and really helped me. Its duplicated somewhere here on 311's.
I had to rebuild my carbs twice to get it right. Quick and dirty the first time and precision and clean the second time.
Good luck!
Rustbucket

[S Allen]

Write up is here in the wiki.

Keith's SU Tuning Write-up


Steve

[bossbob]

I haven't worked on my carbs in a while, but I noticed the center section of the Unisyn is adjustable, how much of a gap should there be to allow enough air through the Unysin so the carb doesn't choke out?

Just curious for the next time I tune the carbs.

[GeoffM]

I haven't worked on my carbs in a while, but I noticed the center section of the Unisyn is adjustable, how much of a gap should there be to allow enough air through the Unysin so the carb doesn't choke out?

Just curious for the next time I tune the carbs.

The ball should be approx. half way up the tube.

[bossbob]

This is what I was pointing at, found it on another site.

The Unisyn has a "dial" adjustment in its throat. It is a little adjustable
disc dial. Turn the disc dial one way and it lets more air in. Turn it the
other way and it lets less air in. You'll see the air gap increase and
decrease ( a little) in the throat of the Unisyn as you adjust this disc
dial. With carbs so badly out of sync, as yours undoubtly are, you will have
to start with a dissimilar adjustment of this "dial" for each carb. Adjust
the Unisyn for each carb so that the engine stays running, sllllooooowly
adjust the idle speed bringing them into a state where both carbs allow the
engine to run with the Unisyn in place. Unless the mixture adjustment is
really out of adjustment bad or unless you have a mechanical issue, this
should be fairly easy to accomplish. If the mixture is that badly out
causing a no idle condition on one of the carbs, this will have to be
corrected first. Usually I'll turn the mixture in till it misses and the
idle roughens, and then out until it smoothes out enough to stay running.

[GeoffM]

Don't know where you got that info but you want the unisyn to have as little effect on the air flow as possible while still being able to read vacuum. hence the ball in the middle of the clear tube is a good rule of thumb.

[Gregs672000]

The advantage of the "snail" version of the carb balancing tool is that you can hold the snail over the throat without changing flow much, allowing you to read it carefully, take your time and make minor adjustments. My car is very sensitive to different flow, and the Dellortos allow for balancing all 4 throats individually of needed, so the snail has been a must have tool.

[spl310]

Do y'all realize that the OP posted once 4 months ago - his first post - and never responded to anything else?