The 84 Brat started acting up today. Basically when in park you can get the engine to whatever RPM you want but only with part throttle. If at say 2500 rpm and floor it the engine just literally sucks air. If you put it in gear it won't go; it just stalls out. The carb is a rebuilt from about 9 months ago and has been working great. I've had the top of the 2-barrel Hitachi off twice and no change. What about EGR or the air valve thing? I'm going out to put on the old carb and see what happens.

Check to see that all the vaccum hoses are in place. I had a simular problem, it was the smallest vaccum hose going into the air filter canister drivers side rear bottom. Hurray for those 70's vaccum everything............

I checked almost all the vacuum lines. It idles fine and at increasing rpm's; it just can't handle anything past part throttle. I'll check around the canister for loose hoses though. I pulled and cleaned the EGR valve but no changes. If I back off full throttle when in park the engine races up in rpm; back in the throttle it tries to stall.

Sorry man, I've lucked out since then and i have other Subes to double check that a couple of hoses weren't switched. Did this just start acting up on its own, or was it after some tinkering?

No, just out of the blue it started. I've been to busy lately for tinkering (the GL-10 was the tinker toy). It just stalled on my son on the way to school. It hasn't been the same since. I'll swap out carbs on sunday and see if it changes, get worse or stays the same.

start by checking the fuel filter. it may just be starvation.

 

double chek your ignition timing.

 

i put a motor together and it ran fine, then it started to fall flat at 3000 rpm or if you get enough into the gas.

 

then i used another carb, same thing. '

 

then i used another carb, sputtered and coughed when i hit the gas. then i turned the distributor and now it runs fine.

 

i would bet that was my problem to begin with

 

something o consider..............

I swapped carbs and seems to be the same thing going on. Your statement "then it started to fall flat at 3000 rpm or if you get enough into the gas" describes it well. It goes flat and sputters, back off the gas and it revs again. But it seems related to the throttle position as once I load the engine (put it into gear, auto) it dies. I'll check the distributor, coil, etc. The sight gauge on the carb stays full of gas but I might try replacing both fuel filters again. I'm running out of ideas and time.

Would the air suction valve cause problems like this? Too much air?

also when checking the timing, check the vacuum advance and see if it holds.

 

remember to disconnect the vacuum advance and plug the line when using the timing lite to set the distributor. after you get that done, hook up the vacuum advance, and rev it up, and see if the timing mark moves around thru rpms

now it won't even fire. I suspect timing is off caused by a bad distributor? It has spark at the plugs and gas in the carb/accel pump. It won't even sputter with a starting fluid. It will have to wait until I can get back on the troublshooting and I'll check the distributor alignment when #1 is at TDC. Before it quit it had 4psi for fuel pressure and good flow into a can.

funny thing, because i swapped a carb on jims brat and it still fell flat. i turned the distributor up and it helped, but would not get over 4000 rpm's.

 

you said you get spark. you didn't take the distributor out did you? others on the board have experienced a "pig tail" wire coming loose in the distributor, but if that was the case, you wouldnt have spark.

 

maybe the spark plugs crapped out. i put a motor together, idled rough, whenever i set the timing to spec it wouldnt run. turns out it had 2 bad plugs.

 

yank them out and take a look. sometmes a fould plug will still spark, although weekly. if the spark looks yellow, it's bad.

 

a normal plug condition the insulator should be a nice tan color, that of a toasted marshmallow