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Help with carbs

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usaflm

usaflm

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Just had the carbs on my 67 Sprite, HS2's, rebuilt. Threw them on the car started it up and I'm getting fuel vapor shooting out of them every few seconds. Also since the car sat for about 5 years it's hard to get started and once I do, if I push on the gas pedal it takes about 5-10 seconds to bring up the rpm's. It's not peppy like it should be, very sluggish. But the whole time is has the vapor backfire from the carbs. I ran it a bit and now I'm getting a nice backfire from the exhaust, too much fuel going through I'm guessing. Also, while it was running I pushed in the clutch and the engine just quit. Any advise/suggestions?
 
Do you have a haynes manual or similar to walk you through initial enrichment settings, balancing carbs and such?

And... fresh gas and new fuel filter I hope.
 
Yes, on the manual. Yes on the new fuel filter. The book says to listen for a hiss from the intake, can't do that because of the fuel backfire coming out the intake.
 
1. Valve lash holding the the valve open too long or opening it too soon so that the compression stroke is forcing air backwards through the intake.

2. Timing off.
 
Valve lash. I had this problem when I installed a rebuilt head on my bug. Heavy valve springs caused the timing chain to become critical. When accellerating it ran smooth but slack in chain caused backfiring etc. I spent countless hours fooling around with the carbs. Replaced timing chain and no problems.
As to carbs, University Motors has videos on youtube about setting up carbs. Make sure pistons move freely and drop with a clunk. Springs are the same length and look good.
 
Could also be sick-rich with badly adjusted float heights with new float needles(stuck?) Start the engine and disconnect/block the fuel line. If things smooth out after a second or two...........


Glen
 
And if it's sat for that length of time, odds are the centrifugal advance mechanism in the dizzy is frozen up, that'll cause sluggishness for sure -
 
OK, let's sort this out a bit.

Was this the first start-up after 5 years of sitting, or was it running OK (except perhaps for the needed carb rebuild) before the carbs were rebuilt? If it were running OK, it seems unlikely that the valve lash or timing would have suddently changed, coincidentally with working on the carbs.

If the latter, it sounds to me like raw fuel is getting dumped into the intake. This can happen if the float height is too high, piston is sticking, or the float valve is not closed all the way. It's possible to have a situation where the float valve is not quite shutting off, so the fuel level in the bowl is too high, but it's not leaking so badly that you get gas out the overflow. I've had this problem on my H1s.
 
The car sat for about 5 years back in my parent garage not running. I drove it 5 years ago, parked it, and that was the last it ran. I tried to start it again this past year and it started but I could not get it to run for very long. It was struggling to stay running. I would pump the gas and it would either bog down or slowly, and I mean slowly, increase the RPM's. It would be a fight to keep it running. It never had the quick pick-up in RPM's that it should. I put maybe 3 or 4 gallons of 93 octaine in with the old gas, there wasn't much in it to start. I put on a new fuel filter to help with all the junk I was sure would be coming through and it still wanted to bog down. So I just assumed it was bad carbs. I checked the timing about 6-8 months ago and it seems like it was on but I'll check it again this weekend when I have time.
 
Your initial timing probably has not changed. What will have changed is the advance mechanism is "frozen" up. The weights and springs under the breaker plate in the distributor, control the amount and timing of the ignition advance. As the engine speed increases the timing needs to increase with it or you get the exact symptoms you are describing.

A quick test that may help. Pop the distributor cap off. Grab the rotor and with it held securely on the distributor shaft turn it one way and try the other. It should move a few degrees in one direction and return to where it started from by itself.. Don't use gorilla strength buy may need 4-5 lbs on initial movement.

If it doesn't move freely and return freely time to get it rebuilt....
 
RonMacPherson said:
.

If it doesn't move freely and return freely time to get it rebuilt....
Click to expand...

It may not need a rebuild unless the shaft is wobbly, or the lobes are worn. It's relatively easy to take a dizzy apart and grease up the advance plate(s). The caveats are getting the springs back in without stretching them out, putting the weights back in and most importantly, not changing the orientation of the cam on the shaft. (It goes either way, and will put the dizzy 180 degrees out if put back in backwards)---(been there, done that)
 
I agree in principle. But from the information we were getting, sounds like this is something that should be "attacked" by an experienced professional. I think Jeff at Advanced Distributor is one of the best roi's going as far as maintaining a LBC.


To me it would be much easier, better to unbolt the distributor, ship it off, receive it back and reinstall it, than tear it apart. Have a spring go flying, or broken and no replacement for it, or strip a screw... Known to happen on distributors that are more than a couple of years old...
 
I never miss an opportunity to tear something apart and see how it works and if I can fix. I usually figure it out and learn a lot and have fun. Nothing to loose and lots to gain. Worst case scenario, give up and send it in. If you like tinkering. I'd never torn down a dizzy before but I did one and even figured out how to limit the mechanical advance (wrong dist for the motor) learned a ton, was successful, cost me nothing and had a ball.
 
Man, there are so many things that could be bad--best thing is to go through them one by one and make sure all is OK. The fuel could be bad, the tank full of crud, dirt/moisture in the high-voltage part of the ignition, virtually anything that should move might not be moving,... you get the picture.

You might take a look at Tony's article on awakening a sleeping MG, https://www.theautoist.com/awakening_a_sleeping_b.htm
 
Sounds to me like you may have 90 weight oil in your carb dash-pots.
If you reach down the throats of the carbs (with the engine NOT running) and lift up on the pistons do they move relatively freely or does it take a long time (3 to 4 seconds) to lift them?
Bill
 
It takes some effort to lift them, and 3-4 seconds would be best case, that's with the plunger installed. When I take the plunger out they rise and fall with ease. I would think it would be hard to push up no matter what weight oil is in there.
 
You may want to take off the top halves of the carbs and dump out all of the oil, reassemble them and try it. If there is a significant change then fill them with "3 in 1" oil and try it again.
May make a difference.
 
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