I'm stumped at this point.   1984 Brat w/  weber carb with no issues with the carb the last 12 years. Have fuel pressure regulator for weber. With full tank of gas was running fine, drove to 1/2 tank and parked it and the next day runs like crap.  Will idle but when you rev it,  motor bogs down and sometimes will die. No power to even move it up and down driveway.  Changed both fuel filters, cap/rotor.  Discovered vac advance was not working so swapped out disty for spare one. Timing is set correctly.  Still runs bad.  Fuel pump pumps and fills fuel bowl.  Pulled spark plugs all were absolutely black.  Put new ones in and with brat running for all of 5-10 mins with me reving motor and it running like crap, pulled new plugs and they all were black. Was thinking problem with primary circuit of carb dumping in gas ??  Got weber rebuild kit in it and reset float height, didn't see anything blocked in any jets or anything weird, still acted the same way upon restart. I'm moving this next week and need the brat running so I panic and order a new weber.  Put it on today and brat still runs the same.  Will start and idle no problem but when I rev the throttle you can actually see gas droplets flying up through the primary barrel into the air.  When you rev it also makes kinda a farting sound  which it also did with old carb ??   Definitely not the normal sound.  No vacuum leaks anywhere.  I don't have a compression gauge.  What am I overlooking ??  Thank you in advance !!!!---Brian

Edited January 23, 201610 yr by 84SOOB

Check timing friend...

Wires...

Timing was spot on with both distys.  I can try new wires.

all plugs are sooty black? Sort of makes think run too rich or not sparking right on all pots, maybe coil lead or inside coil tower - corrosion ? Can understand your panic. Is there an EGR or some sort of reburn function on inlet manifold ? dodgy PCV valve ?

Hi Jono, yeah all brand new plugs were sooty black from less than 10 min of run time.  EGR has not been hooked up for years.  I have not looked at PCV valve to see if stuck. Definitely running way rich suddenly is what I was thinking too.  I don't know if it could be coil issue.  A new wire set will include coil lead. I don't see corrosion issue between coil tower and inside coil lead as it is now.

I would check into the fuel regulator.. now that reread what you were saying..# i was at work# to me...fuel pushing up backwards out of the carb to me says either your mechanical timing is off and or the regulator is pushing fuel past the needle seats and flooding ya out..

Did you check the air filter ?  

It's getting to much fuel. Do you have a return line hooked up? The stock carb fitting threads right into it depending on the weber. You want the return line to be hooked up so it pushes fuel up instead off draining all the fuel down so you run out of flow after 25mph. Not having a return can cause fuel to go past the needle valve making it splill out the bowl which sounds like your problem or your regulator is bad. I bought a mr. gasket fuel regulator off ebay and right out of the package it didn't work. It didn't regulate flow and leaked from everywhere i couldn't return it since it had been a couple months since i bought.

The air filter is off and the timing was right on with both distys.  I have always had the return line right before the regulator on a tee.  Both of my webers have a blanked off boss opposite the fuel inlet where you would ordinarily put a fuel return.  I have the Mr Gasket regulator, it's definitely possible the regulator is suddenly not doing it's job after so long.

any way to check the spark? a weak spark might not ignite fuel so well, so wont burn nice and look like it is too rich. Did the new weber get the old webers jets?

Did everyone miss something here? Droplets of fuel flying UP through the barrel??? 'Farting' noise? You have a bad intake valve or seat somewhere that is not closing/sealing allowing exhaust to escape through it. OR.... An exhaust valve that is not opening fully causing pressure to remain in the cylinder which escapes through the intake. Last... A head gasket that is blown between cylinders causing exhaust pressure to cross between them and exit out the intake. Get a compression gauge. It's the only way you're going to find the problem. Cam, lifter, pushrod, rocker, valve, seat or HG. Find the culprit.

It's getting to much fuel. Do you have a return line hooked up? The stock carb fitting threads right into it depending on the weber. You want the return line to be hooked up so it pushes fuel up instead off draining all the fuel down so you run out of flow after 25mph. Not having a return can cause fuel to go past the needle valve making it splill out the bowl which sounds like your problem or your regulator is bad. I bought a mr. gasket fuel regulator off ebay and right out of the package it didn't work. It didn't regulate flow and leaked from everywhere i couldn't return it since it had been a couple months since i bought.

Would a quality fuel pressure regulator do the trick? I know the 32/36 turds out after about 3.5 psi

The cat converter was clogged.  Took out the plug where the oxygen sensor would go and just rodded the matrix out, problem solved.

The cat converter was clogged.  Took out the plug where the oxygen sensor would go and just rodded the matrix out, problem solved.

Since you moved/are moving back to Washington you might as well cut the cat open to gut it then weld it back shut or just cut the cat out.

Since you moved/are moving back to Washington you might as well cut the cat open to gut it then weld it back shut or just cut the cat out.

If "rodding it out" is what I think it is, he did that without welding. Just pop off the o2 sensor cover, stick in a breaker bar or screwdriver, and just bang it around til it's empty.

With a clogged converter I'm surprised you didn't get a CEL code.

With a clogged converter I'm surprised you didn't get a CEL code.

It doesn't even have a ecm so no codes. They only came with ecms if they had feed back carbs which where mostly in California, 82 model year equipped with carter weber carb, or 83/84 ea81t.

It doesn't even have a ecm so no codes. They only came with ecms if they had feed back carbs which where mostly in California, 82 model year equipped with carter weber carb, or 83/84 ea81t.

 

Wouldn't the oxygen sensor be affected by the clog ?

Pretty basic design, like 60's or 70's, no o2 sensor either. I am surprised the cat lasted this long. Most would have plugged many years ago.