carbie tuning.. rough running car

[Guest subarugsr]

my 72' GSR runs twin carbies, currently it is running like a bag of sh**. its backfiring and spluttering about when i put my foot on the accelerator.. usualy over the past few days it didnt do it until i reach 3500rpm but now its doin it right the way through... ive been adjusting timing and mixture to get teh car going.. but the backfiring has steadily gotten worse.. does anyone know how i could remedy this problem?

 

cheers

[Guest jon61484]

try some carb cleaner on both... and get them retuned I spose.

[Guest Skip]

I have delt with twin carbie sets up a lot (Triumphs, Jags and AH's) Sounds like you have two or more problems.

First the accel pumps in one or both are not putting out enough fuel. This could be many things but it MUST be rectified before any tuning will help.

Second you need to balance them so they both pull the same amount of air simutaniously. A short length of garden hose can be used as a tuning tool. Place one end in you ear the other over the carb. At idle both carbs should sound identical. I have a special flow meter for doing this. Then make sure both throttle plates open simutaniously. (Throttle cable adjustments)

First off check the accel pumps then balance them.

Set the timing at ~ 10 deg BTDC (vac advance pulled and plugged.)

If you get them balanced - then you can fine tune both as far as idle mixture is concerned, then rebalance them.

REMEMBER the mixture screw ONLY adjusts the rich/lean condition AT IDLE, it has nothing to do with cruising speed mixture, this point has been brought up many times and most people fail to believe it.

Hope this helps

BTW

With none of your "profile" filled out, it's tuff to know where you are or email you directly about this problem.

If you by chance want to swap the set up for a good running two barrel Hitachi or sell them, please let me know. My email is in my profile.