Docsis510 Posted March 7, 2009 Report Share Posted March 7, 2009 After a long time serching for this carbs i finally found a good set with manifold and linkage. they are a little dirty but i just want to try them before i start cleaning the engine. the carbs start fine but they wont idle. i tried everything i can think of to adjust them but i just cant. i was wondering if any of you guys that might have a set can help me out. mabe theres some steps i have to take. here are some pics of the carbs Quote Link to comment
Skib Posted March 8, 2009 Report Share Posted March 8, 2009 check out http://www.ztherapy.com and order the Just SU's video. and heres a few links to tuning SU tips and info. http://www.jetlink.net/~okayfine/sutech.html http://www.datsun2000.com/tech/su.htm Quote Link to comment
MikeRL411 Posted March 8, 2009 Report Share Posted March 8, 2009 It might help if you hooked up the choke cables. Quote Link to comment
Skib Posted March 8, 2009 Report Share Posted March 8, 2009 will it still not idle after the cars warmed up? Quote Link to comment
zerow Posted March 8, 2009 Report Share Posted March 8, 2009 It might help if you hooked up the choke cables. ^^X2 And route something to the PCV valve or plug it altogether. Sounds like you're getting too much air. Quote Link to comment
Skib Posted March 8, 2009 Report Share Posted March 8, 2009 if its relatively tuned but not warmed up itl run like that with out the chokes on but will run fine when its warm. thats how mine is (I dont have choke cables) Quote Link to comment
zerow Posted March 8, 2009 Report Share Posted March 8, 2009 if its relatively tuned but not warmed up itl run like that with out the chokes on but will run fine when its warm. thats how mine is (I dont have choke cables) I've seen them ran w/o cables. It can be done. Just run them a little richer than usual. (Docsis510: turn out the bottom screw on the carbs a 1/4 turn at a time until the idle is maintained) I want a little more control of my carbs, and I have a good idea for cables, mounting, etc (more to follow, with pics) Quote Link to comment
Skib Posted March 8, 2009 Report Share Posted March 8, 2009 I've seen them ran w/o cables. It can be done. Just run them a little richer than usual. (Docsis510: turn out the bottom screw on the carbs a 1/4 turn at a time until the idle is maintained) I want a little more control of my carbs, and I have a good idea for cables, mounting, etc (more to follow, with pics) ya iv always run them a little rich to prevent that untill recently. lol i havent used my chokes since iv owned the car going to EFI at the end of the month so i just put up with it till then :lol: Quote Link to comment
zerow Posted March 8, 2009 Report Share Posted March 8, 2009 ya iv always run them a little rich to prevent that untill recently. lol i havent used my chokes since iv owned the car going to EFI at the end of the month so i just put up with it till then :lol: lol Nice! I'm running the L20B and the carbs until I kill one/both. And I don't plan for a Kevorkian type death either. Just run them the way they were meant to be run. And often! Quote Link to comment
Docsis510 Posted March 8, 2009 Author Report Share Posted March 8, 2009 it idles after warming up but shakes like hell. i didnt know you can move the bottom knob. thanks for the comment on my car. Quote Link to comment
Jason Posted March 8, 2009 Report Share Posted March 8, 2009 Well, best to start from scratch here. Check and verify the ignition, wires, plugs, rotor, cap, points if still there and adjust. Then go ahead and adjust the valves. After all that you start in on the carbs. I turn the mixture nut on the bottom on both all the way in (counterclockwise) to zero the mixture and then turn them out 2 full turns for an initial setting. Go and set the balance screw on the linkage so that the carb linkages move even amounts. Fire the car up and set the idle to about 1000rpm using the idle speed screws. Get the Unisysn out and then balance for airflow and re set the idle back to 1000rpm. Go for a long drive, pull the plugs and check the colour. Light white too lean, dark black to rich and adjust mixture accordingly. Rebalance airflow and adjust idle. Repeat as many times as needed to get the mixture right..... Quote Link to comment
Docsis510 Posted March 8, 2009 Author Report Share Posted March 8, 2009 what does the unisysn look like? Quote Link to comment
Jason Posted March 8, 2009 Report Share Posted March 8, 2009 Here you go, shouldn't go fiddling dual carbs of any sort without one ..... http://store.summitracing.com/egnsearch.asp?N=700+115+304497&D=304497 Quote Link to comment
zerow Posted March 8, 2009 Report Share Posted March 8, 2009 what does the unisysn look like? If you are in a rush, you can use a length of vacuum line and use your ear to tune the carbs. It'll get you real close. Of course, the UniSyn is the best way to go for synchronizing the carbs. Quote Link to comment
Skib Posted March 8, 2009 Report Share Posted March 8, 2009 check out http://www.ztherapy.com and order the Just SU's video. ^^everything you need to know about SU's in one video Quote Link to comment
Wharf Rat Posted March 8, 2009 Report Share Posted March 8, 2009 Nice car, after you understand how them SUs work you will love them. pull and release the choke arm and see how they pull the jet tubes away from the needle all this is doing is inriching them, the adjustment knob is like a stop, when you take the choke off make sure they return all the way. (common problem) They are pretty basic. I have set tons of them on brit stuff mostly. They like to build up crap in the tube that runs from the float bowl to the jet tube. It's real easy to give them a quick on the car clean job. I can talk you through them if need be. Peace WRAT Quote Link to comment
philip1 Posted March 9, 2009 Report Share Posted March 9, 2009 (edited) basic sync: (engine off) have someone floor the throttle then grab the linkage for the front carb and see if it moves. If it does you will need to adjust it to where it just hits the limiter as the front carb does. close the throttle all the way then grab the front linkage and see if there is any movement before the rear. if there is movement adjust the carb mounted idle screw till they both start to open at the same time. Fuel mix: turn the large knob in (as you look down counter clockwise) all the way till it stops then back it off two turns. fire engine and adjust idle to 750rpm. once engine is warm reach in the rear carb and gently lift the slide if the engine quits turn the front big knob out (clockwise) 2 clicks and repeat test. once the engine will stay running on 2 cyl with the rear slide lifted repeat the same on the rear carb by lifting the front slide. This should get you running a Unisync is the best way but this will get you running. Edited March 9, 2009 by philip1 Quote Link to comment
Docsis510 Posted March 9, 2009 Author Report Share Posted March 9, 2009 is the slide the one where the fuel mix knob is??? Quote Link to comment
philip1 Posted March 9, 2009 Report Share Posted March 9, 2009 look in the throat of the carb you will see what looks like an aluminum barrel that is the slide. Quote Link to comment
Docsis510 Posted March 9, 2009 Author Report Share Posted March 9, 2009 oooh ok now i know what your talkin about Quote Link to comment
CorAce Posted March 12, 2009 Report Share Posted March 12, 2009 You may consider removing the retune spring on linkage since the SU Quote Link to comment
Docsis510 Posted April 8, 2009 Author Report Share Posted April 8, 2009 ok so im getting pissed at these stupid carbs!!! i tried everything you guys told me. i got the car to idle but when i step on the gas they choke and then accelerate. sometimes they even pop. sounds like a gun shot. my next door neighbors came out scared lol. any one from san diego that can come and help me out? i realy want to drive my baby. im getting to the point were i want to sell the carbs. i bought the unisyn but i think it was a waist of moneyn or i just dont know how to use it. when i hook it up to the carb the car just shuts off. heres how they look now. thanks Quote Link to comment
datsun 160J SSS Posted April 8, 2009 Report Share Posted April 8, 2009 check the floats they may be full of fuel if you like call me 8059082280 mike daytime please :) Quote Link to comment
dgi Posted April 8, 2009 Report Share Posted April 8, 2009 Read through post http://forum.ratsun.net/showthread.php?t=11037 Check the oil in the carbs! Note where I describe dumping the throttle and the hesitation symptom. Sounds like to me you are going instantly lean causing a backfire. This often occurs with hot cams or advanced timing and a lean condition. However, if you are really looking to sell, I am in the market for a complete SU setup. PM me. Quote Link to comment
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