Qjet adjustments?
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 1,018
Likes: 9
From: Winston Ga.
Qjet adjustments?
so I am wasting time at work on the night shift and thinking about the 75 that will reapply the smile on my face on the drive home...
When warm it runs fine, no issues with performance other than its a L48.
1> When cold and I set the choke, it has to warm up in order to not bog down when I let the clutch out. I have to give it more gas than I feel I should and let the clutch out slowly or it will die.
I think the answer is to adjust the choke dial and richen it up a bit. Correct? It just seems like I need a bit more fuel.
edit: choke seems to function properly and seems to be aligned properly when set.
2> I know I want to go in and adj the A/F needles at some point just to make sure it is good. I plan on doing it with a mity vac as it is the only vac gauge I have. I need to use a manifold port correct? would the port directly on the intake be appropriate such as where the vac comes for the lights, or do I need to actually pull it off the carb?
When warm it runs fine, no issues with performance other than its a L48.
1> When cold and I set the choke, it has to warm up in order to not bog down when I let the clutch out. I have to give it more gas than I feel I should and let the clutch out slowly or it will die.
I think the answer is to adjust the choke dial and richen it up a bit. Correct? It just seems like I need a bit more fuel.
edit: choke seems to function properly and seems to be aligned properly when set.
2> I know I want to go in and adj the A/F needles at some point just to make sure it is good. I plan on doing it with a mity vac as it is the only vac gauge I have. I need to use a manifold port correct? would the port directly on the intake be appropriate such as where the vac comes for the lights, or do I need to actually pull it off the carb?
Last edited by jnealg; Jun 25, 2013 at 03:19 AM.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Lars Q-Jet papers will establish a great baseline for adjusting your choke. Everyone I've set up using his papers has been thrilled with the choke performance.
Question 2; by A/F needles do you mean idle mixture screws or the metering rods? The idle mixture screws you'll have to get samples from a few ports, esp with a dual plane. The screws only affect one side of the engine and a single port won't give you the complete picture. Actually, the power brake booster port bleeds from the center of the carb and is probably a better bet than the manifold fitting (which reads off the right hand port if I'm remembering right).
For the metering rod adjustment, any port is fine although I would probably tune that circuit by feel or by lambda (AFR) gauge.
Question 2; by A/F needles do you mean idle mixture screws or the metering rods? The idle mixture screws you'll have to get samples from a few ports, esp with a dual plane. The screws only affect one side of the engine and a single port won't give you the complete picture. Actually, the power brake booster port bleeds from the center of the carb and is probably a better bet than the manifold fitting (which reads off the right hand port if I'm remembering right).
For the metering rod adjustment, any port is fine although I would probably tune that circuit by feel or by lambda (AFR) gauge.
Last edited by Shark Racer; Jun 25, 2013 at 04:29 AM.
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 1,018
Likes: 9
From: Winston Ga.
Thanks and yes I meant the idle mixture screws.
I sent Lars an email requesting his papers.
I dont think I really need a rebuild although I doubt it's ever had one. We will see where I end up after adjustment.
I sent Lars an email requesting his papers.
I dont think I really need a rebuild although I doubt it's ever had one. We will see where I end up after adjustment.
