Running Rich: Stuck Choke/ Rich Mixture?
Created by: Rosebud
Orig. Posting Date | User Name | Edit Date |
Aug 1, 2017 12:04PM | Rosebud | Edited: Aug 1, 2017 02:51PM |
Aug 1, 2017 11:20AM | dklawson | |
Aug 1, 2017 09:32AM | Rosebud | |
Aug 1, 2017 04:05AM | dklawson | |
Jul 31, 2017 01:36PM | Dan Moffet | |
Jul 30, 2017 11:09AM | Spank | |
Jul 30, 2017 10:37AM | Rosebud | |
Jul 30, 2017 10:19AM | malsal | |
Jul 30, 2017 08:33AM | Rosebud | |
Jul 30, 2017 08:10AM | malsal | |
Jul 30, 2017 08:03AM | Rosebud | |
Jul 29, 2017 03:33PM | Rosebud | Edited: Jul 29, 2017 03:39PM |
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Quote:
Originally Posted by dklawson
How have you got the toggle switch wired in? Is it a pushbutton to power the starter solenoid?
[EDIT] I misread your question. Yes, I've installed the new toggle switch. So far, so good.
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How have you got the toggle switch wired in? Is it a pushbutton to power the starter solenoid?
Doug L.
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Quote:
Originally Posted by dklawson
Michael, you have two threads running, one on ignition problems, one on fuel problems. The two issues may be interacting with one another. (i.e. Part of the running problem you are chasing with the ignition system may be associated with choke and mixture problems).
The missing/stalling issue occurred (once) 2K miles ago and again last week. Thought it was a coil issue until I realized that the starter button was also momentarily dead, which leads me to think the ignition toggle switch is bad. I'm swapping out the old 20A switch with a 30A this afternoon. Will advise. Thanks again!
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Michael, you have two threads running, one on ignition problems, one on fuel problems. The two issues may be interacting with one another. (i.e. Part of the running problem you are chasing with the ignition system may be associated with choke and mixture problems).
With that in mind (and I know I am coming to this late) if your HS4s have the bent sheet metal choke linkage to lower the jet, subtle differences in the shape of the bends can produce the binding your carb experienced. Lube may help for a while but the problem is likely to return. Later HS carbs were sometimes fitted with a rod shaped linkage with ball/socket ends. Those seldom seem to experience the binding problem.
With that in mind (and I know I am coming to this late) if your HS4s have the bent sheet metal choke linkage to lower the jet, subtle differences in the shape of the bends can produce the binding your carb experienced. Lube may help for a while but the problem is likely to return. Later HS carbs were sometimes fitted with a rod shaped linkage with ball/socket ends. Those seldom seem to experience the binding problem.
Doug L.
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But Spank: what species of wood should be used?
Nice summation of the facts of life SUs!
Nice summation of the facts of life SUs!
.
"Hang on a minute lads....I've got a great idea."
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far too many people, in my opinion, "tune" their carbs by adjusting them at idle or just slightly off idle and then expect them to run right all across the rev and load range. It doesn't take into account the hundreds of different needle profiles and the few different dashpot spring tensions.
I blame Haynes, which really just assumes your engine is stock and being reset and retuned to stock and, theoretically if you use the stock ignition system and the stock air cleaner and the stock exhaust system and the stock compression ration, camshaft, carburetor(s) and whatnot, then Yea, the stock needle should work so the prescribed means to set fueling using the idle setting as your measurement is adequate.
Setting the carbs for proper idle and the mixture at idle doesn't take into account what the fueling is like when the car is REALLY under demand, like going uphill and trying to pass someone. The only way to see if that's right is either a dyno run with an experienced operator or with a wideband sensor in the exhaust.
When I use a unisyn, I first set the idle balance and then I bring the revs up to 3500-4k rpm and check them again. It has to be done quickly / in a flash multiple times because when the unisyn is placed over the face of the carb the engine speed changes. And that just tells me the airflow is balanced. The fueling is a whole 'nother story. That's probably the main reason I'm a big proponent of a single SU. There is probably more performance potential from properly-setup dual carbs, the effort required to do that proper setup isn't really worth the minor performance benefits. I'll admit, though, that dual carbs really do look badass.
The dual carb setup is wonderfully forgiving. The SU in general is wonderfully forgiving. I mean, if a Porsche 924 can have it's throttle body yanked and an SU carbed plunked on with a wood spacer and the fueling "ballparked" by just going "Well, if 2 turns down is good for an 1275, 4 turns down will be good enough for 2.0L..." If a 2-liter engine can run off of a single 1.75" SU (and repeatedly friggin LAP me in my professionally dyno-tuned +.060 1275 89hp at the wheels mini running the exact same carb and needle!), then this whole blabber about needing dual carbs to get more power is hooey.
And yes, a dual carb setup can seem to run perfectly fine off of mostly just one carburetor. But under very high demand, the lean side will run very lean and eventually burn up a head gasket or valves in the lean cylinders.
I blame Haynes, which really just assumes your engine is stock and being reset and retuned to stock and, theoretically if you use the stock ignition system and the stock air cleaner and the stock exhaust system and the stock compression ration, camshaft, carburetor(s) and whatnot, then Yea, the stock needle should work so the prescribed means to set fueling using the idle setting as your measurement is adequate.
Setting the carbs for proper idle and the mixture at idle doesn't take into account what the fueling is like when the car is REALLY under demand, like going uphill and trying to pass someone. The only way to see if that's right is either a dyno run with an experienced operator or with a wideband sensor in the exhaust.
When I use a unisyn, I first set the idle balance and then I bring the revs up to 3500-4k rpm and check them again. It has to be done quickly / in a flash multiple times because when the unisyn is placed over the face of the carb the engine speed changes. And that just tells me the airflow is balanced. The fueling is a whole 'nother story. That's probably the main reason I'm a big proponent of a single SU. There is probably more performance potential from properly-setup dual carbs, the effort required to do that proper setup isn't really worth the minor performance benefits. I'll admit, though, that dual carbs really do look badass.
The dual carb setup is wonderfully forgiving. The SU in general is wonderfully forgiving. I mean, if a Porsche 924 can have it's throttle body yanked and an SU carbed plunked on with a wood spacer and the fueling "ballparked" by just going "Well, if 2 turns down is good for an 1275, 4 turns down will be good enough for 2.0L..." If a 2-liter engine can run off of a single 1.75" SU (and repeatedly friggin LAP me in my professionally dyno-tuned +.060 1275 89hp at the wheels mini running the exact same carb and needle!), then this whole blabber about needing dual carbs to get more power is hooey.
And yes, a dual carb setup can seem to run perfectly fine off of mostly just one carburetor. But under very high demand, the lean side will run very lean and eventually burn up a head gasket or valves in the lean cylinders.
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Quote:
Originally Posted by malsal
1. Pulling the choke cable should pull both jets down equally, check the linkage is in synch.
2. I use a 2 foot length of 1/4" fuel hose to balance the carbs as that is the way i learnt to do it in the 70's.
2. I use a 2 foot length of 1/4" fuel hose to balance the carbs as that is the way i learnt to do it in the 70's.
2. I can see how that would work. The Uni-Sync worked well, too. But I'm tossing the Color-Tune.
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Pulling the choke cable should pull both jets down equally, check the linkage is in synch.
I use a 2 foot length of 1/4" fuel hose to balance the carbs as that is the way i learnt to do it in the 70's.
I use a 2 foot length of 1/4" fuel hose to balance the carbs as that is the way i learnt to do it in the 70's.
If in doubt, flat out. Colin Mc Rae MBE 1968-2007.
Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.
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Quote:
Originally Posted by malsal
Both carbs are connected so if one sticks they both effectively stick and run rich so all four plugs will be sooty.
Note: I'm a little disappointed in my Gunson ColorTune. Even with my over-rich condition, the ColorTune was telling me everything was fine.
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1. Loosen the choke cable off the linkage and operate the choke by hand to see if it works correctly. Sometimes the jet binds other times it may be a linkage issue. Make sure there is a small amount of side to side play in the linkage that connects the two carbs. You may be able to use a spray lubricant to free things up.
2. Both carbs are connected so if one sticks they both effectively stick and run rich so all four plugs will be sooty.
3. if no lifting pins are present you just lift the pistons with your finger to check the mixture which is sometimes difficult with the factory elbows, if so just remove them to set up. You can also loosen up the dampers and tilt them sideways a little then pull up this will have the same affect. Correctly set when the pistons are lifted the rev's should rise a little them drop off.
2. Both carbs are connected so if one sticks they both effectively stick and run rich so all four plugs will be sooty.
3. if no lifting pins are present you just lift the pistons with your finger to check the mixture which is sometimes difficult with the factory elbows, if so just remove them to set up. You can also loosen up the dampers and tilt them sideways a little then pull up this will have the same affect. Correctly set when the pistons are lifted the rev's should rise a little them drop off.
If in doubt, flat out. Colin Mc Rae MBE 1968-2007.
Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.
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Quote:
Originally Posted by Rosebud
Question #3: From the diagram it looks as if I should easily see and/or feel the lifting pins. I cannot, so I'm assuming my carbs don't have a lifting pin. Now what? Haynes doesn't offer any help beyond telling my to press the nonexistent lifting pin. How do I go about adjusting the mixture w/o a lifting pin?
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I noticed an unusually strong exhaust smell a couple of weeks ago. When I inspected the spark plugs I discovered that my formerly golden brown plugs and tailpipe have become black and sooty. Turns out that the choke mechanism on the bottom of one of my SU HS4s isn't fully releasing after engaging the choke. My carbs were new 4k miles ago so I shouldn't think they're in need of rebuilding.
Question #1: What's the best way of freeing the sticking choke mechanism? I can push it back into place but it still hangs up about one-eighth of an inch after pulling the choke knob again. Can I clean and lube it in place or do I need to remove and clean & lube? What kind of lubrication; silicone, oil, grease, dry graphite?
Question #2: All 4 plugs are equally sooty. I would expect that only the two plugs fed by the offending carb would be sooty. Maybe both carbs are running rich?
Because all 4 plugs are sooty I thought I better make sure both carbs are properly adjusted. I have never done this before. I synchronized the carbs using a Uni-Syn device and I'm now ready to adjust the mixture. Following Haynes, it says "To begin, press the piston lifting pin upwards." It goes on to say that "the pin is omitted on later models." Swell.
Question #3: From the diagram it looks as if I should easily see and/or feel the lifting pins. I cannot, so I'm assuming my carbs don't have a lifting pin. Now what? Haynes doesn't offer any help beyond telling my to press the nonexistent lifting pin. How do I go about adjusting the mixture w/o a lifting pin?
Thanks!
Question #1: What's the best way of freeing the sticking choke mechanism? I can push it back into place but it still hangs up about one-eighth of an inch after pulling the choke knob again. Can I clean and lube it in place or do I need to remove and clean & lube? What kind of lubrication; silicone, oil, grease, dry graphite?
Question #2: All 4 plugs are equally sooty. I would expect that only the two plugs fed by the offending carb would be sooty. Maybe both carbs are running rich?
Because all 4 plugs are sooty I thought I better make sure both carbs are properly adjusted. I have never done this before. I synchronized the carbs using a Uni-Syn device and I'm now ready to adjust the mixture. Following Haynes, it says "To begin, press the piston lifting pin upwards." It goes on to say that "the pin is omitted on later models." Swell.
Question #3: From the diagram it looks as if I should easily see and/or feel the lifting pins. I cannot, so I'm assuming my carbs don't have a lifting pin. Now what? Haynes doesn't offer any help beyond telling my to press the nonexistent lifting pin. How do I go about adjusting the mixture w/o a lifting pin?
Thanks!