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'72 Midget Runs On 2 Cylinders at Highway Speeds

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Not sure. I know it ran fine for years on the Napa pump before this started happening. The pump tested fine. It filled a 5 gallon bucket during a prolonged test. I wanted to make sure it wasn't starting out normal, then dying off.

You thinking it's too high? Someone else mentioned a fuel pressure regulator.
 
Plug three looks very rich! I might lean out the back carb a bit. Do the needles match?
 
I don't recall you mentioning replacing the plugs in a while. If plugs get very fouled (perhaps for a reason that you have already fixed), they sometimes stay fouled.

Put a new set of plugs in it and gap them about 0.025" to 0.030"

Also, sometimes it's possible to have high voltage "bleed" through the plug wires, coil tower, etc. Even with new parts.

So try this:

Get a spray bottle (like a Windex bottle) filled with clean water.
Park the car in a very dark area during the evening (but not in a closed garage!)
Start the engine and get it to idle.
Spray water all over the engine, especially near the wires and coil.
Have a helper rev the engine up while you look around for sparks jumping around.
Sometimes, with a older car, they'll light up like an Xmas tree when you do this, but sometimes you'll just see a tiny spark here and there.
No sparks jumping around is good.
Easy to do and might be useful.
 
Thanks for the suggestion. The plugs were replaced about 20 miles ago and the new wires have never made it out of the garage. When I installed the new cap and wires I did a spark test just to make sure no arcing was happening between the wires. It tested good.

The jets look the same. I didn't get the calipers out, but the diameter looks the same to the naked eye. I could be wrong about this though, because I wasn't really looking for that when I cleaned the carbs.

I've read the mixture adjusting procedure out of the Bentley. It looks like you back out the adjusting nut going off the idle speed, etc. I need to learn it, but I also need to get it to pass emissions this year, which my local shop does.
 
Cloudbase said:
The jets look the same. I didn't get the calipers out, but the diameter looks the same to the naked eye. I could be wrong about this though, because I wasn't really looking for that when I cleaned the carbs.

I've read the mixture adjusting procedure out of the Bentley. It looks like you back out the adjusting nut going off the idle speed, etc. I need to learn it, but I also need to get it to pass emissions this year, which my local shop does.
Click to expand...

The needles should have numbers or letters on the base to tell you if they are the same.

Adjustment is one of the easiest jobs on the planet. Literally reaching under the carb and moving the nut, one flat at a time, clockwise is richer, anti-clockwise is leaner. (Someone confirm that please I'm trying to visualize as I type)
 
Alright I just re-read it. I looks like moving the nut upwards, what every direction that is leans it. When you say a flat (I see that mentioned here a lot), you mean turning the nut one "flat" of the hexagonal flats at a time right? Sorry my only carb experience is with a single weber on my old VW bus.

Also, this begs a great question. The symptoms presented intermittently at first when only under heavy loading like high speeds in 4th gear or going up steep hills Then slowly worsening. Would a carb just vibrate or come out of correct adjustment like that. Otherwise, if it's something else and I lean the carb to correct the symptoms of that failed component then am not just putting a bandage on the problem?
 
With the engine not running and the switch on(fuel pump pumping) lift the back throttle slide and see if your float needle's are doing there job. If they are start screwing the back carb jet adjusting nut in to see if you can get it to run better. If it does then I would say that you need to go thru the whole carb adjusting procedure.

Kurt.
 
One thing I like about the bugeye, is that one can see the SU pistons directly. In a '62, one should use a mirror to verify that both piston are reacting the same, i.e., both raising the same amount when the revs are raised. To richen the mixture, one unscrews the nut counter-clockwise (looking from the bottom up). To lean, it is clockwise. Make sure when the pistons are lifted (engine off) both fall at the same rate and make a clink sound at the bottom. If not one needs to center the needle. Good luck, Scott in CA
 
Cloudbase said:
^ To do that do I old the dampeners up by hand. That's the only way I can see in there.
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Yes, hold the dampners up any way that works. The carb adjustment procedure is'nt as difficult as some manual's try to make it. I have never had any luck with the listening for the hiss method on spridgets. I just make certain that the butterfly's are opening exactly the same. Then that the jet is exactly even with the bridge then 12 flats down on the jet. I then adjust the jets with the lifting pins to determine if they can be leaned or richened. Its a good idea to remove pistons and dashpots to make the first of this easier and when you do that you can determine if the float levels are right by how much fuel you see in the jets. should be equal and about a 1/16 down from the top of the jet when at the bridge. Be very careful when removing the dampners not to drop them and bend the needle. I always try to keep all adjustments between the carbs the same.

Kurt.
 
Cloudbase said:
Alright I just re-read it. I looks like moving the nut upwards, what every direction that is leans it. When you say a flat (I see that mentioned here a lot), you mean turning the nut one "flat" of the hexagonal flats at a time right? Sorry my only carb experience is with a single weber on my old VW bus.

Also, this begs a great question. The symptoms presented intermittently at first when only under heavy loading like high speeds in 4th gear or going up steep hills Then slowly worsening. Would a carb just vibrate or come out of correct adjustment like that. Otherwise, if it's something else and I lean the carb to correct the symptoms of that failed component then am not just putting a bandage on the problem?
Click to expand...

A flat is indeed one "side" of the nut.

What you might have is a spot on the needle that is too rich or too lean.

Coming back to a much earlier question, have you topped up the oil on the dashpots?
 
Thanks for the explanations, especially the procedure two posts above. The dampener oil is topped off. I checked the needle and didn't see any flat spots. I had to triage between car projects today. Too many projects and not enough time. I'm in the of some minor track prep for my M Coupe and devoted all of yesterday's time to the Midget. The Midget will need a smog soon anyway so I had it towed to my local shop for sussing out the carb issues, tuning, and an emissions test. The funny thing was that after not running right for a few weeks now when I started it up for the tow truck it purred like a kitten. I was like WTF! I let it warm up and drove it a few laps around the neighborhood and eventually was able to bring the running issue back. It would bog down and act like it was on two cylinders, but run normal if I backed off on the throttle.

I'll report my shop's findings.
 
nomad said:
I have never had any luck with the listening for the hiss method on spridgets.
Kurt.
Click to expand...

I am an expect with the above method. I can get one EXACTLY open TWICE as the other one. :wall:

Well, at least they sound the same. :whistle:
 
I should expect that your points have slipped closed a bit.
 
If it runs OK when cold, perhaps you have a condenser that is failing when it warms up. Many times ignition issues present themselves as fueling issues. IIRC there was a thread a while back all about the sad state of today's ignition condensers.
 
Cam you figure which two cylinders are falling off line??
 
Since your miss is a dynamic one, the best way to check it out is to first take the plugs out and clean them up. set the gap. Then take the car for a ride until it acts up. Immediately stop, and take the plugs out and look at them. A misfired plug way be black and may be wet with gas. If a pair of cylinders is bad, 1&2, or 3&4, then it could be related to a carb issue. Cheers, Scott in CA. take pictures to show us.
 
smaceng said:
Since your miss is a dynamic one, the best way to check it out is to first take the plugs out and clean them up. set the gap. Then take the car for a ride until it acts up. Immediately stop, and take the plugs out and look at them. A misfired plug way be black and may be wet with gas. If a pair of cylinders is bad, 1&2, or 3&4, then it could be related to a carb issue. Cheers, Scott in CA. take pictures to show us.
Click to expand...

Spot on advice.
 
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