Quadrajet

[knockdolian]

60EF8FD2-FBDB-4C29-8E49-F42145F57C23.MOV

(12.63 MiB) Downloaded 2027 times

Hi all. This is a proper technical question. My secondary’s don’t seem to be doing anything. The little diaphragm on the right hand side seems to be working in that it pulls in when running. The choke is working and the little secondary lock is coming off when hot. The little diaphragm as I said pulls in but when I punch the gas it doesn’t release so stops the secondary butterfly from opening. There doesn’t seem to be any manifold vacuum loss when I hit the gas.
I disconnected the vacuum hose while running and the diaphragm opens or goes out but still no secondary. Any ideas ?
Thanks

[knockdolian]

I can’t only pen the video. Can anyone else see it ?

[The Mindless Philosopher]

I can't see it. It requires the Quicktime plugin.

[knockdolian]

I can't see it. It requires the Quicktime plugin.

Thanks, no idea what that is ? It only shows the secondary’s not working. 3 years I’ve had the trike now and have just been playing on the primary’s which will still punch me in the back if I give it a handful and will do +130 Mph. I got scared after that.!!
I’m thinking the secondary’s have been disabled to save fuel. I’d appreciate a video of what should be happening at what RPM.
Am I right in thinking the Venturi butterfly (bottom ones) will be fully open on full throttle ?

[knockdolian]

Having done some reading on the internet it seems I won’t see the secondary’s even move while sat in neutral because there’s not enough vacuum ?
Does that sound right?

[The Mindless Philosopher]

Someone else will have to chime in. I am re-learning carburetor behavior after having spent a good portion of my life with computer controlled fuel injected vehicles.

See if Paul H or Carburetor Mike can give you some pointers. Carburetor Mike's phone is listed in another thread. It's pretty easy to find in a search.

[Foose1986]

I just tore my Edelbrock Quadrajet down to nothing on my 1997 SB during rebuild. I'm no carb expert, just a dumb mechanical engineer. Tearing my carb down for rebuild was my first experience with it.

The stock Edelbrock 750cfm has Mechanical Secondaries, not vacuum. The diaphragm for the choke shouldn't have any effect on your secondary butterflies. If the secondary lockout pin has moved out of the way, which I found happens after the high idle pin is down, then you just have an adjustment issue if they don't open when you get on it. Are you going Wide Open Throttle to see this? I ran my bike off the reserve tank and with my primary fuel tank off for a while while tuning and was able to visually see the secondaries open, but it wouldn't happen until roughly 80% or more throttle. Have you tried actuating the linkage by hand? Perhaps the throttle cable needs to be readjusted.

[knockdolian]

Goose 86, thanks for throwing a spanner in there !!!
With the engine at idle the choke release holds the secondary top ( chokes) closed and reving hard won’t release the vacuum. With the engine not running I can open the choke flap by hand, twist the throttle fully and see the secondary throttle butterfly open mabe 1/8 or less. I’ll try riding on the reserve with no filter and see if they open. I didn’t think of that. As I said giving the throttle a hand full it will punch the backrest in to my back and slightly lift the front end. Just wondering if I’m getting the full BH experience. I know there’s no LSD but I’d expect to hear one wheel squeal

[CanuckHoss]

Goose 86, thanks for throwing a spanner in there !!!
With the engine at idle the choke release holds the secondary top ( chokes) closed and reving hard won’t release the vacuum. With the engine not running I can open the choke flap by hand, twist the throttle fully and see the secondary throttle butterfly open mabe 1/8 or less. I’ll try riding on the reserve with no filter and see if they open. I didn’t think of that. As I said giving the throttle a hand full it will punch the backrest in to my back and slightly lift the front end. Just wondering if I’m getting the full BH experience. I know there’s no LSD but I’d expect to hear one wheel squeal

What is your elevation???

[knockdolian]

I’m at sea level most of the time. There’s nothing very high in the uk !!!

[knockdolian]

I just tore my Edelbrock Quadrajet down to nothing on my 1997 SB during rebuild. I'm no carb expert, just a dumb mechanical engineer. Tearing my carb down for rebuild was my first experience with it.

The stock Edelbrock 750cfm has Mechanical Secondaries, not vacuum. The diaphragm for the choke shouldn't have any effect on your secondary butterflies. If the secondary lockout pin has moved out of the way, which I found happens after the high idle pin is down, then you just have an adjustment issue if they don't open when you get on it. Are you going Wide Open Throttle to see this? I ran my bike off the reserve tank and with my primary fuel tank off for a while while tuning and was able to visually see the secondaries open, but it wouldn't happen until roughly 80% or more throttle. Have you tried actuating the linkage by hand? Perhaps the throttle cable needs to be readjusted.

Ok having read all I can find and the little I think I know. My carb is vacuum secondary’s. Why ? Well everything I’ve read says vacuum for automatic transmission and there is only one accelerator pump. A mechanical secondary manually fully opens the butterflies with the accelerator mechanism, has two pumps and is fitted to a manual transmission. It’s a 1901, well that’s what the tag says. I’ll give riding without the tank to solve this. Now I’m just a dumb Brit who’s only ever played with SU carbs so more than happy to be educated . Thanks

[CanuckHoss]

I’m at sea level most of the time. There’s nothing very high in the uk !!!

Then you should be able to spin the tires from my experiences at sea level in Florida...given stock tires sizes and a working carb...4 barrels should not be needed from a stop to do that.

[Orlando606VetteTrike]

If it were me I know where that Quadrajet would be headed. lol

[knockdolian]

If it were me I know where that Quadrajet would be headed. lol

Not a fan then !!

[502wingman]

A couple of years ago the guy at Mike Kellys shop (sorry dont remember his name) worked on my Quadrajet.

He said, after beeing trained at Edelbrook, that the vaccum is only for saftey reasons (open slowly) and you dont really need it.

So he took off my vacuum canister and siliconed the ports.

Then he adjusted the tiny little spring that keeps the secondarys closed so they would open at a sudden throttle opening. The carb/engine itself creates enough vacuum to flipp the secondarys open.

The result is that the bike is suddenly jumping ahead without hesitation when you give it full throttle and accelerating like crazy.

This worked flawless for me for many years. Of course this is dangerous but after a while my right hand knew exactly when they would open or not....

[CanuckHoss]

A couple of years ago the guy at Mike Kellys shop (sorry dont remember his name) worked on my Quadrajet.


Then he adjusted the tiny little spring that keeps the secondarys closed so they would open at a sudden throttle opening.

The result is that the bike is suddenly jumping ahead without hesitation when you give it full throttle and accelerating like crazy.

This worked flawless for me for many years. Of course this is dangerous but after a while my right hand knew exactly when they would open or not....

Peter,

This guy never got used to to his quick response Quadrajet!!!


https://www.facebook.com/crbvl.gravityp ... TUxOTE4NA/!

[Grand Canard]

Here's some good info for you carb guys running Quadra-jets.
https://www.dragzine.com/tech-stories/f ... arburetor/

Rick

[hogv8]

All I can say I don't see how I could get any quicker response or better ecceleration than I have now with my Stage ll Quadrajet . Thing is instant .

[knockdolian]

Thanks Rick, I like carbs and have some experience but not with big American ones. I’ve been in contact with carb Mike who has given me some useful information. I think the issue is just settttings. Personally I think the quadrajet is a thin of beauty .

[knockdolian]

Well don’t I feel like a f*****g a*****e. Seems my throttle cable wasn’t tight enough to fully open the throttle enough to open the secondary’s. Test ride tomorrow to see if I can get the wheels spinning.

[knockdolian]

All I can say I don't see how I could get any quicker response or better ecceleration than I have now with my Stage ll Quadrajet . Thing is instant .

Was it you some time back, made a rotary throttle linkage. Seems my throttle won’t pull my linkage to fully open the secondary’s

[Paul H]

IF that's the case, you could drill another hole
to mount the cable in closer to the T shaft.
That will require less cable to open thing up all
the way.

Paul H

[knockdolian]

IF that's the case, you could drill another hole
to mount the cable in closer to the T shaft.
That will require less cable to open thing up all
the way.

Paul H

Good idea. I’ll look at that thanks

[The Mindless Philosopher]

All I can say I don't see how I could get any quicker response or better ecceleration than I have now with my Stage ll Quadrajet . Thing is instant .

Carburetor Mike works magic with these things! Mine is a Stage II as well.

[knockdolian]

All I can say I don't see how I could get any quicker response or better ecceleration than I have now with my Stage ll Quadrajet . Thing is instant .

Carburetor Mike works magic with these things! Mine is a Stage II as well.

Even a stage 11 mikes carburettor won’t work with no fuel. Sorry mate, couldn’t resist !!!