Zelus
Active Member
Alright, update. This is a long one.
Firstly: I'm pretty sure the secondaries are fine. However, according to 666mopower666, they should be mechanical. What I'm seeing on mine, is that they are BOTH mechanical and vacuum driven. The larger, upper plates (that look like they're stuck partly open) seem to be vacuum driven. If I hold those open, I see a second set of plates below them, that move with the throttle. Those appear to be fully closing. Thusly, I don't think I have a problem with my secondaries. This carb is less than four years old, lightly used, and always with good clean fuel.
Secondly: I had to revisit 73AbodEE's suggestion that the throttle linkage might be binding up. He was on to something. Out of desperation, I removed the bolt holding the throttle linkage in place while the engine was running, and sure enough, it dropped the idle. Apparently, the position it was in was causing it to stick open, just a little. It didn't feel tight at all, but it was definitely tugging the throttle open.
With the above straightened out, it seemed like everything was fixed. The engine had warmed up, I set the timing, idle mixture, and idle speed. Hooray! She's ready to cross the state!
Not exactly...
About 120 miles into the 240 mile trip, the something goes wrong with the idle. Instead of a healthy 700-750, it's a stumbling 550-650. I figured I'd just set the idle mixture wrong; like it was drowning or starving. It was also starting to really hesitate coming off of idle. I also noticed the timing was a bit advanced (a light clacking going uphill in 4th gear, heavy load situations, exacerbated by my awful rear-end ratio; but hey, 20 mpg highway).
After two-stepping a few stoplights and making it to work, I left it, planning to correct the mixture and timing afterword.
After work, didn't start. REALLY didn't start. Not even a pop. I check the spark, tweaked the timing, etc. It wasn't until I actually flooded it trying to start it that it caught, sputtered and died. So I upped the idle (a lot) and set the idle mixture to very rich.
I attacked it with the carb cleaner looking for vacuum leaks. I wasn't successful; the engine would rev hard, sputter out, return to normal, and repeat, all on its own. I could never tell if the rev was due to the carb cleaner, or just the engine's own cycling. Now I'm out of carb cleaner.
Regardless of that, is this sounding like a vacuum leak to anyone else? One thing I noticed, is that my original problem, the hard-rev while stopping, is much worse. It will rev +500 rpm, and then hang there for a good while before calming back down. It's also hesitating hard coming off of idle.
I'm wondering if it could also be a generic fuel delivery problem? The only thing I can think of is that while stopping, all the fuel in the float bowls and the tank are pushed forward, easing the load on fuel pump, and possibly pushing more fuel out of the carb.
Anyway, if it IS a vacuum leak, I'm afraid it will be around the intake runners. Is this something tightening down the manifold would help (it's aluminum)? Or am I going to have to get a new gasket and re-install the manifold for a third time?
Firstly: I'm pretty sure the secondaries are fine. However, according to 666mopower666, they should be mechanical. What I'm seeing on mine, is that they are BOTH mechanical and vacuum driven. The larger, upper plates (that look like they're stuck partly open) seem to be vacuum driven. If I hold those open, I see a second set of plates below them, that move with the throttle. Those appear to be fully closing. Thusly, I don't think I have a problem with my secondaries. This carb is less than four years old, lightly used, and always with good clean fuel.
Secondly: I had to revisit 73AbodEE's suggestion that the throttle linkage might be binding up. He was on to something. Out of desperation, I removed the bolt holding the throttle linkage in place while the engine was running, and sure enough, it dropped the idle. Apparently, the position it was in was causing it to stick open, just a little. It didn't feel tight at all, but it was definitely tugging the throttle open.
With the above straightened out, it seemed like everything was fixed. The engine had warmed up, I set the timing, idle mixture, and idle speed. Hooray! She's ready to cross the state!
Not exactly...
About 120 miles into the 240 mile trip, the something goes wrong with the idle. Instead of a healthy 700-750, it's a stumbling 550-650. I figured I'd just set the idle mixture wrong; like it was drowning or starving. It was also starting to really hesitate coming off of idle. I also noticed the timing was a bit advanced (a light clacking going uphill in 4th gear, heavy load situations, exacerbated by my awful rear-end ratio; but hey, 20 mpg highway).
After two-stepping a few stoplights and making it to work, I left it, planning to correct the mixture and timing afterword.
After work, didn't start. REALLY didn't start. Not even a pop. I check the spark, tweaked the timing, etc. It wasn't until I actually flooded it trying to start it that it caught, sputtered and died. So I upped the idle (a lot) and set the idle mixture to very rich.
I attacked it with the carb cleaner looking for vacuum leaks. I wasn't successful; the engine would rev hard, sputter out, return to normal, and repeat, all on its own. I could never tell if the rev was due to the carb cleaner, or just the engine's own cycling. Now I'm out of carb cleaner.
Regardless of that, is this sounding like a vacuum leak to anyone else? One thing I noticed, is that my original problem, the hard-rev while stopping, is much worse. It will rev +500 rpm, and then hang there for a good while before calming back down. It's also hesitating hard coming off of idle.
I'm wondering if it could also be a generic fuel delivery problem? The only thing I can think of is that while stopping, all the fuel in the float bowls and the tank are pushed forward, easing the load on fuel pump, and possibly pushing more fuel out of the carb.
Anyway, if it IS a vacuum leak, I'm afraid it will be around the intake runners. Is this something tightening down the manifold would help (it's aluminum)? Or am I going to have to get a new gasket and re-install the manifold for a third time?
