Another FB owner with idle issues
01-10-12, 05:51 AM
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Another FB owner with idle issues
I started and brought my 83 GSL up to running temp for the first time in about 2.5 years this evening. Its a project that has been either a side project and/or put on the back-burner thanks to school and my Formula SAE team.
The engine is out of an 85 GSL. I got rid of the rats nest recently and am running a Nikki off a 13b REPU I got for a great deal from Jeff20B. It has RB headers and otherwise is a stock powertrain.
The carb was fully functioning in August when I bought it.
NOTE: The fuel return line was blocked off when I got it and I haven't changed that for now.
My 7 starts up just fine and runs normally with the choke in. But once it gets warm, it dies as soon as I let the rpms drop any amount (not sure to what rpm though since the tach isn't functioning). The only way I can keep it running is if I have the choke plate partially closed. Amount of throttle doesn't matter.
--The fuel in both sights is about 2/3rds up the window.
--It was running VERY rich at first to where the RB headers were glowing.
--Spark plugs were almost fouled and had oil on them (could be from running premix and haven't yet removed OMP... figured on such a long time of not running that having too much oil was better than none). I cleaned them off with some sandpaper and acetone and put them back in the car.
--I then started following Sterlings steps for carb tuning (best I could with no tach) and leaned it out.
--Boiled my coolant briefly and plugs showed "lean" (figures), though still with oil on them.
--Haven't had a chance to start it since because my roommates told me that I was keeping them up.
I'm now at a loss. I make sure that I've tapped my understanding and researched as deeply as possible before I go for help. There are a ton of carb and idle-related posts here, but I couldn't find any with problems similar to mine. I'm still a beginner when it comes to carburetion so please go easy on me.
Any help is appreciated.
The engine is out of an 85 GSL. I got rid of the rats nest recently and am running a Nikki off a 13b REPU I got for a great deal from Jeff20B. It has RB headers and otherwise is a stock powertrain.
The carb was fully functioning in August when I bought it.
NOTE: The fuel return line was blocked off when I got it and I haven't changed that for now.
My 7 starts up just fine and runs normally with the choke in. But once it gets warm, it dies as soon as I let the rpms drop any amount (not sure to what rpm though since the tach isn't functioning). The only way I can keep it running is if I have the choke plate partially closed. Amount of throttle doesn't matter.
--The fuel in both sights is about 2/3rds up the window.
--It was running VERY rich at first to where the RB headers were glowing.
--Spark plugs were almost fouled and had oil on them (could be from running premix and haven't yet removed OMP... figured on such a long time of not running that having too much oil was better than none). I cleaned them off with some sandpaper and acetone and put them back in the car.
--I then started following Sterlings steps for carb tuning (best I could with no tach) and leaned it out.
--Boiled my coolant briefly and plugs showed "lean" (figures), though still with oil on them.
--Haven't had a chance to start it since because my roommates told me that I was keeping them up.
I'm now at a loss. I make sure that I've tapped my understanding and researched as deeply as possible before I go for help. There are a ton of carb and idle-related posts here, but I couldn't find any with problems similar to mine. I'm still a beginner when it comes to carburetion so please go easy on me.
Any help is appreciated.
01-10-12, 02:01 PM
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I might have discovered my problem. I don't have a coasting richer solenoid on the carb and may be getting a vacuum leak through where it is supposed to be.
Does this sound like it could be my problem?
Does this sound like it could be my problem?
01-10-12, 02:59 PM
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Update: I am pretty sure that this is the issue. What now confuses me is that the port to where this solenoid is supposed to be has no threads or way of mounting. See photo. Maybe my carb didn't have the solenoid to begin with and I'm chasing a dead end?
01-10-12, 08:23 PM
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no tach no trailing coil or ignotor as far as i know but could be wrong as im not that knowledgable but im sure someone will chime in on this for now check for spark on your trailing plugs or wait for other suggestions
01-10-12, 09:19 PM
#7
Notice the hole is unthreaded. That particular model never had a richer solenoid from the factory. Besides, a richer solenoid wouldn't cause or fix a lean idle. I think it's just for decel.
What I'd do is first stop all premix until you choose to remove the OMP. Either run it out of gas (if it will run safely) or drain it. I think you're right; it is getting too much oil.
Next check for spark on both ignition circuits. Next check that timing is accurate. Static align the leading pickup to the point on the reluctor on the machined flat side of the shaft. There are lots of procedures for setting timing on this forum so I won't go into that. But if you're sure it's close, check it with a timing light so the leading mark is at the pin on the front cover at whatever idle is supposed to be on a 12A. The other way is to rotate it left and right until the idle is strongest ie follow j9fd3s' advice and "give it what it wants".
I was about to add that you don't really know whether it actually is lean vs whether the timing is off without a wideband to see the actual AFRs, but that suggests tuning your idle with a wideband as a guide is one of the best ways to do it, but I've found that doesn't work out very well in the end. Instead it's best to give it what it wants. Forget the scope and/or wideband when tuning idle. Turn the mixture screw(s) and just tune it by ear until it runs best for YOUR engine, not some emissions friendly factory setup in 1983 with stock ports, stock manifolds with cats and restrictive stock exhaust.
I got that carb running decently on the fresh rebuilt 6 port 13B with a weird manifold that might have had a vacuum leak or two caused by a nasty crack which I filled with RTV as a temp fix. So if anything, your setup should be richer.
Glowing headers means rich in my understanding, not lean. Lean = hot running engine but cool headers. Rich = cool running engine but glowing headers. Lack of leading ignition = glowing headers. Retarded ignition = glowing headers. It's easy to make headers glow. You should have seen them on my brother's RX-4 wagon.
One more thing to make sure is correct is fuel pressure. Most gauges are not very accurate at 2.5 to 3 psi. That's why Paul Yaw recommended some expensive gauge for his carbs.
By the way when I had that carb apart, I never touched the float levels. Way too many people screw this step up. I've had to set several Hitachi floats back to stock after somebody changed the factory setting trying to correct for incorrect fuel pressure. Fortunately I haven't met many botched Nikki floats, and when I do, I've got enough spares to swap in.
Good luck and stop premixing!
What I'd do is first stop all premix until you choose to remove the OMP. Either run it out of gas (if it will run safely) or drain it. I think you're right; it is getting too much oil.
Next check for spark on both ignition circuits. Next check that timing is accurate. Static align the leading pickup to the point on the reluctor on the machined flat side of the shaft. There are lots of procedures for setting timing on this forum so I won't go into that. But if you're sure it's close, check it with a timing light so the leading mark is at the pin on the front cover at whatever idle is supposed to be on a 12A. The other way is to rotate it left and right until the idle is strongest ie follow j9fd3s' advice and "give it what it wants".
I was about to add that you don't really know whether it actually is lean vs whether the timing is off without a wideband to see the actual AFRs, but that suggests tuning your idle with a wideband as a guide is one of the best ways to do it, but I've found that doesn't work out very well in the end. Instead it's best to give it what it wants. Forget the scope and/or wideband when tuning idle. Turn the mixture screw(s) and just tune it by ear until it runs best for YOUR engine, not some emissions friendly factory setup in 1983 with stock ports, stock manifolds with cats and restrictive stock exhaust.
I got that carb running decently on the fresh rebuilt 6 port 13B with a weird manifold that might have had a vacuum leak or two caused by a nasty crack which I filled with RTV as a temp fix. So if anything, your setup should be richer.
Glowing headers means rich in my understanding, not lean. Lean = hot running engine but cool headers. Rich = cool running engine but glowing headers. Lack of leading ignition = glowing headers. Retarded ignition = glowing headers. It's easy to make headers glow. You should have seen them on my brother's RX-4 wagon.
One more thing to make sure is correct is fuel pressure. Most gauges are not very accurate at 2.5 to 3 psi. That's why Paul Yaw recommended some expensive gauge for his carbs.
By the way when I had that carb apart, I never touched the float levels. Way too many people screw this step up. I've had to set several Hitachi floats back to stock after somebody changed the factory setting trying to correct for incorrect fuel pressure. Fortunately I haven't met many botched Nikki floats, and when I do, I've got enough spares to swap in.
Good luck and stop premixing!
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01-11-12, 01:55 AM
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Thanks Jeff for the info! Very helpful. And yeah I noticed there was no way to mount a richer in there which added to my confusion. 
Sterling had mentioned on his website that a lack of a richer could lead to idle issues because of the vacuum leaks involved.
Ok that is good to know about the OMP. I was being paranoid since I blew up my Hondas engine a few years back due to oil starvation. I disconnected it until I run this tank dry.
I think I might get a fuel pressure regulator and run the return line regardless. We'll see if that's what she wants. I always liked running the return line and check valve, operation seemed more consistent in street driving.
Glowing headers does mean rich. You're correct in that. Excess gas that the flame front in the rotor was not able to burn off burns in the headers and superheats them.
Update: SHE DROVE! Tore up the cauldesac this evening!
Turns out that I had a slight leak in the the EGR fitting on the manifold that I found by spraying the clogged vacuum fittings down with WD40 (momentarily clogs the leak and makes idle jump up, do it fitting by fitting and you can pinpoint which one leaks). I also had turned it about 4 or 5 turns too lean on the idle mixture screw. Finally, the throttle stop was too slack.
She now idles beautifully, but after I give her some revs, she's unenthusiastic to return back to idle. Not sure what that problem stems from.
Any ideas?
Once again, thanks for the help.
--Evan
Now I get to start a build thread! I'll take some photos of her so far and get a plan in order and get that thread up in the next few days!
Sterling had mentioned on his website that a lack of a richer could lead to idle issues because of the vacuum leaks involved.Ok that is good to know about the OMP. I was being paranoid since I blew up my Hondas engine a few years back due to oil starvation. I disconnected it until I run this tank dry.
I think I might get a fuel pressure regulator and run the return line regardless. We'll see if that's what she wants. I always liked running the return line and check valve, operation seemed more consistent in street driving.
Glowing headers does mean rich. You're correct in that. Excess gas that the flame front in the rotor was not able to burn off burns in the headers and superheats them.
Update: SHE DROVE! Tore up the cauldesac this evening!
Turns out that I had a slight leak in the the EGR fitting on the manifold that I found by spraying the clogged vacuum fittings down with WD40 (momentarily clogs the leak and makes idle jump up, do it fitting by fitting and you can pinpoint which one leaks). I also had turned it about 4 or 5 turns too lean on the idle mixture screw. Finally, the throttle stop was too slack. She now idles beautifully, but after I give her some revs, she's unenthusiastic to return back to idle. Not sure what that problem stems from.
Any ideas?
Once again, thanks for the help.
--Evan
Now I get to start a build thread! I'll take some photos of her so far and get a plan in order and get that thread up in the next few days!
Last edited by MeCalledEvan; 01-11-12 at 01:57 AM. Reason: wanted faces
01-11-12, 03:20 AM
#9
Congrats on getting further along! lol Sterling mentioning the richer solenoid and vacuum leaks. Yeah, only if it was drilled from the factory and you forgot to reinstall it during your rebuild. Eh Sterling?
Evan, you got a better carb than most because it lacks something that could potentially go bad and cause a vacuum leak some day. If I ever boost prep a Nikki, I'll look for one like it. I'd imagine the little pin might get pushed by boost pressure and cause weird things to happen. It's only spring loaded and is pulled by a solenoid when energized. Otherwise it's normally supposed to stick out and block a vacuum line in the carb. Ormaybe it's the other way around?
Anyway it's late. I'll see if I can explain your slow return to idle. This happens when the idle isn't adjusted right (duh). Can't recall which way but yes I've been there. A few times. But I always figured it out in the end and got a quick rev and a quick return to idle. It's a combination of mixture screw and throttle stop screw. The fact you got it driving pretty well means you're closing in on it running right.
Evan, you got a better carb than most because it lacks something that could potentially go bad and cause a vacuum leak some day. If I ever boost prep a Nikki, I'll look for one like it. I'd imagine the little pin might get pushed by boost pressure and cause weird things to happen. It's only spring loaded and is pulled by a solenoid when energized. Otherwise it's normally supposed to stick out and block a vacuum line in the carb. Ormaybe it's the other way around?
Anyway it's late. I'll see if I can explain your slow return to idle. This happens when the idle isn't adjusted right (duh). Can't recall which way but yes I've been there. A few times. But I always figured it out in the end and got a quick rev and a quick return to idle. It's a combination of mixture screw and throttle stop screw. The fact you got it driving pretty well means you're closing in on it running right.
01-11-12, 11:57 AM
#10
My sterling has the richer valve JB welded, lol. Whenever my header glowed it was from the old beat up points ignition. Once I swapped to 2gdfis, replaced plugs, and changed timing everything was as it should be.
I've always ran a fuel return line. Even on the old sidedraft Weber with a regulator.
Most of the time the way the car runs has little or nothing to do with the carb. Unless it has been tampered with or abused (mixture needles pressed in too hard or sat for too long and clogged). My Sterling came second hand with 160s in the primary main jets... How the PO got it to run at all was a miracle.
I've always ran a fuel return line. Even on the old sidedraft Weber with a regulator.
Most of the time the way the car runs has little or nothing to do with the carb. Unless it has been tampered with or abused (mixture needles pressed in too hard or sat for too long and clogged). My Sterling came second hand with 160s in the primary main jets... How the PO got it to run at all was a miracle.
01-11-12, 07:59 PM
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NCross: I am using shitty $1 Autolite plugs at the moment just to get the car up and running. I'll be switching to NGK Iridium plugs soon. I'll take a look at the points. I'm planning on switching to the 2gdfis soon, it just depends on when my schedule allows me to look for an FC, and my college-student budget allows me to afford the part.
Jeff: Thank you! I was dancing around with excitement after I got back from tearing up the neighborhood. That was the first time I had driven that chassis (since I bought it as a shell).
The solenoid should pull the pin in, not push it out. That is usually how they work from my understanding.
Thank you once again for the carbs, manifolds, and parts. I'm going to start tearing into the spare nikki soon so that I can get a better visualization of how it functions (which is how my brain works). Also will use its parts as practice for modifying the one on my car, as you suggested.
I do have a question about it: do you remember what the jet sizes were in that carb?
Also thank you. Looking forward to the explanation. I might add another return spring on the opposite side of the carb so-as I don't tweak the shaft and see if that helps at all.
I also decided to purchase the fuel return line and pressure regulator. It was like $30 at Schmucks/O'Reilleys so I figured Why the hell not? Cant hurt.
I can't wait to get it running better and registered so that I can go hooning around! Once it is further along in the build, I'll make sure to swing it by your place to show it off as well.
Jeff: Thank you! I was dancing around with excitement after I got back from tearing up the neighborhood. That was the first time I had driven that chassis (since I bought it as a shell).
The solenoid should pull the pin in, not push it out. That is usually how they work from my understanding.
Thank you once again for the carbs, manifolds, and parts. I'm going to start tearing into the spare nikki soon so that I can get a better visualization of how it functions (which is how my brain works). Also will use its parts as practice for modifying the one on my car, as you suggested.
I do have a question about it: do you remember what the jet sizes were in that carb?
Also thank you. Looking forward to the explanation. I might add another return spring on the opposite side of the carb so-as I don't tweak the shaft and see if that helps at all.
I also decided to purchase the fuel return line and pressure regulator. It was like $30 at Schmucks/O'Reilleys so I figured Why the hell not? Cant hurt.
I can't wait to get it running better and registered so that I can go hooning around! Once it is further along in the build, I'll make sure to swing it by your place to show it off as well.
01-12-12, 01:51 AM
#13
Autolite could be most of your problems right there. I'd get some cheap NGK BR8EQ-14 and call it good.
Yeah I know the feeling first time driving a new-to-you chassis. I never buy running cars.
I thought I said it pulls it in. That's what I was visuallizing. I was kinda tired though, as I am now.
Stock Nikki jet sizes are 92 primary and 160 secondary fuel jets. The air bleeds vary. The primaries can be 60, 70, 80 or sometimes 90 (depends on model) and 140 secondary (but I've seen 120 a few times).
I wouldn't bother with a second spring on the other side (nobody does this). Just be careful when you mash the pedal and make sure the throttle stops when the pedal stops ie fully floored = fully open without opening past perpendicular stressing the shaft. There should be a little throttle stop that's factory set, so doesn't need adjusting.
If anything, remove the emergency return spring. Hmm, I think it's already been removed, actually. You're welcome!
If you run a return line, I wonder if you also need the one way valve? You know, to prevent fuel flow-back into the carb which causes flooding. It is inline in the 1/4" return hose between the carb and firewall hardline. A little aluminum thing about an inch long. All 12A cars got one. Your chassis might not have it. I have a spare if you need one.
Yeah I know the feeling first time driving a new-to-you chassis. I never buy running cars.
I thought I said it pulls it in. That's what I was visuallizing. I was kinda tired though, as I am now.
Stock Nikki jet sizes are 92 primary and 160 secondary fuel jets. The air bleeds vary. The primaries can be 60, 70, 80 or sometimes 90 (depends on model) and 140 secondary (but I've seen 120 a few times).
I wouldn't bother with a second spring on the other side (nobody does this). Just be careful when you mash the pedal and make sure the throttle stops when the pedal stops ie fully floored = fully open without opening past perpendicular stressing the shaft. There should be a little throttle stop that's factory set, so doesn't need adjusting.
If anything, remove the emergency return spring. Hmm, I think it's already been removed, actually. You're welcome!
If you run a return line, I wonder if you also need the one way valve? You know, to prevent fuel flow-back into the carb which causes flooding. It is inline in the 1/4" return hose between the carb and firewall hardline. A little aluminum thing about an inch long. All 12A cars got one. Your chassis might not have it. I have a spare if you need one.
01-12-12, 11:16 AM
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NCross: Right! My bad. Brain fart! Might need a new dizzy cap though...
Jeff: I'll give the better plugs a try and let you know.
I've bought 5 cars so far in my life (well... one was free...). 3 running, 2 non-running. Blew the engine of one of the running cars too. Getting non-running cars going has always been so satisfying! This is my first rotary diy too so that's been new and fun.
Ok. I'll assume that mine are 92/160 then. Eventually I'll tear apart that carb as well and find out.
I also have a hook-up at a local bike shop to get Mikuni jets that fit the Nikki, are cheaper than OEM jets, aaaand come in half sizes.
I'll get to that and the mechanical secondaries after I cage it -- I have an independent study in school based around reverse-engineering a rally-car roll cage for the car and building it. I'll be boxing in the suspension and seam-welding a few things (that won't require jigging) during that time as well. To practice welding, before I start on the cage, I'll make a mid-pipe to replace the stocker. Should be a fun project, though I am a little worried about finishing it in time before the quarter is over. I have 9 weeks to go and am analyzing the rules currently to decide on the best elements to include in the cage for the cockpit.
Where is the throttle stop? I was unable to locate it with my friend when we were tuning the carb. We used the throttle cable length as the throttle stop: throttle was "stopped" and closed when the cable came to full length. If I loosen the cable all the way so the throttle butterflies come to full close, I then end up with my original problem of the car wanting to die.
I do have another carb-related question: on the idle mixer, when going richer you're backing it out. Is it possible to back it out all the way so that it falls out of the carb? I know you can do that on most motorcycle carbs but I wasn't sure about the Nikki.
Ok. Thank you!
Wait... that doesn't make sense. The fuel-return is already plugged so there should be 100% flow-back as it stands. If I add the return line and pressure regulator, it would actually allow fuel to flow back to the tank and potentially lean out the carb slightly. Am I right?
If not and I do need one, I'll buy one from you if you don't mind shipping it up to me. South Seattle is a bit of a drive for me to pick something that small up, now that I'm back up north in Bellingham.
Jeff: I'll give the better plugs a try and let you know.
I've bought 5 cars so far in my life (well... one was free...). 3 running, 2 non-running. Blew the engine of one of the running cars too. Getting non-running cars going has always been so satisfying! This is my first rotary diy too so that's been new and fun.
Ok. I'll assume that mine are 92/160 then. Eventually I'll tear apart that carb as well and find out.
I also have a hook-up at a local bike shop to get Mikuni jets that fit the Nikki, are cheaper than OEM jets, aaaand come in half sizes.
I'll get to that and the mechanical secondaries after I cage it -- I have an independent study in school based around reverse-engineering a rally-car roll cage for the car and building it. I'll be boxing in the suspension and seam-welding a few things (that won't require jigging) during that time as well. To practice welding, before I start on the cage, I'll make a mid-pipe to replace the stocker. Should be a fun project, though I am a little worried about finishing it in time before the quarter is over. I have 9 weeks to go and am analyzing the rules currently to decide on the best elements to include in the cage for the cockpit.
Where is the throttle stop? I was unable to locate it with my friend when we were tuning the carb. We used the throttle cable length as the throttle stop: throttle was "stopped" and closed when the cable came to full length. If I loosen the cable all the way so the throttle butterflies come to full close, I then end up with my original problem of the car wanting to die.
I do have another carb-related question: on the idle mixer, when going richer you're backing it out. Is it possible to back it out all the way so that it falls out of the carb? I know you can do that on most motorcycle carbs but I wasn't sure about the Nikki.
Ok. Thank you!
Wait... that doesn't make sense. The fuel-return is already plugged so there should be 100% flow-back as it stands. If I add the return line and pressure regulator, it would actually allow fuel to flow back to the tank and potentially lean out the carb slightly. Am I right?
If not and I do need one, I'll buy one from you if you don't mind shipping it up to me. South Seattle is a bit of a drive for me to pick something that small up, now that I'm back up north in Bellingham.
Last edited by MeCalledEvan; 01-12-12 at 11:18 AM. Reason: grammar
01-14-12, 05:50 PM
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Update: Well, now I can't get it to start. I'm thinking it might be the cold weather (it's now in the driveway and not the garage and I haven't had time during the day to work on it). Or fouled plugs. Or a combination. I'll be getting new plugs tomorrow and should have some time to tinker with it. Hopefully I can get it to start then!
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