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i have a 502 with a quadrajet i get it up to right about 400 rpms and it bogs down if you give it a little more throttle. if you continue to throttle it up more you can get it past the bog and to 4200 4300 rpms and up to 5000 with no bogging. Does anyone have any idea what could cause this? Metering rods, secondaries not opening soon enough? thanks for any help
Gold Member
Make sure the accelerator pump is working by removing the flame arrester and looking down into the primaries while someone pumps the throttle for you , engine off of course . You should see two streams of fuel with every pump of the throttle if it is working . If it is not working , every time you move the throttle forward your engine is taking a gulp of air instead of fuel hence the bog . If you find this to be your problem let me know and i can hook you up with a guy that sells quality ethanol proof parts for your Quad .Originally Posted by riverrunner242
yeah accelerator pump is working. any other ideas?
Gold Member
Sounds like maybe dirt or varnish in the primary circuit . Take the lid off and hit those circuits with carb cleaner then blow it out with air . Did it set with untreated fuel for awhile ?? Also make sure acc pump is pissing two strong streams of fuel not weak or dribbling . Does it idle ok in and out of gear and at what r.p.m. Make sure you have no vacuum leaks . A faulty choke pull off can also cause this .
Last edited by the deep; 04-23-2012 at 10:28 PM.
502 with a quadrajetcontinue to throttle it up， to be frankly , not understand .sorry .
bathroom light
yeah right at 4000 it loses it than you throttle it up more and it takes off. rebuilt carb i just bought recently ill pull the top off and check it out
Gold Member
Just a suggestion , you may be happier with a Holley 800 for that 502 . Take the numbers off your Quad , they are located on the port side right above the secondary linkage and lets see what engine it came off of .
There is a torsion spring that preloads the air valve (butterfly) on the top of the carb for the secondaries. If it is set too lightly the air valve will open too soon and lean it out causing a bog. There is an ajustment screw up under the top plate that is used to adjust this to get the bog out. If I remember right you adjust the screw until it just starts to tension the butterfly then go another 1/2 turn on the screw. Then you adjust it from there to fine tune the bog away.
I had similar problems i put a bigger flame arrestor on the carb and did a couple passes and it ran up with no problems
adjust air valve like bluethunder said, there is setscrew from underneath. you need to loosen it while using small screwdriver to hold tension adjuster. setscrew maybe hex or torx(t10?) tighter sometimes helps, as engine airflow will pull airvalve open.
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