1980 EA71 1600, runs great, little fast idle, if I roll into the gas slowly it revs to ~4500 before it starts misfiring/bucking/stumbling.

 

If I mash the gas, once above 3000rpm, it farts and stumbles and feels like it's missing. Stock hitachi carb, only 120K on it. Could this be Valves out of adjustment? Cold or hot, makes no difference, once the secondaries open, it runs like it's running rich, BUT no black smoke from tailpipe. Fuel filter is brand new, carb was sprayed and seafoamed for 2 tanks. It almost feels like a miss, but all wires ohm out correct and are new, just replaced NGK vpower plugs, cap, rotor. timing is an unknown but never looks to be moved judging by condition of bolt and grime on motor.

 

Any thoughts?

 

and NO WEBER CONVERSION...I only paid 300 for the car, not going to dump another 3 into a carb LOL.

1980 EA71 1600, runs great, little fast idle, if I roll into the gas slowly it revs to ~4500 before it starts misfiring/bucking/stumbling.

 

If I mash the gas, once above 3000rpm, it farts and stumbles and feels like it's missing. Stock hitachi carb, only 120K on it. Could this be Valves out of adjustment? Cold or hot, makes no difference, once the secondaries open, it runs like it's running rich, BUT no black smoke from tailpipe. Fuel filter is brand new, carb was sprayed and seafoamed for 2 tanks. It almost feels like a miss, but all wires ohm out correct and are new, just replaced NGK vpower plugs, cap, rotor. timing is an unknown but never looks to be moved judging by condition of bolt and grime on motor.

 

Any thoughts?

 

Have you verified that the secondary circuit is in fact opening? If it idles a little high and not much has been done to the engine, then you likely have a vacuum leak. That may or may not be the problem in question, but it will make a difference since the secondary butterfly and timing advance actuate with vacuum diaphrams.

Yes, secondaries are opening. I've replaced most of the vac. lines thinking it's just a leak, but no joy.

 

Vac advance is working as well.

Yes, secondaries are opening. I've replaced most of the vac. lines thinking it's just a leak, but no joy.

 

Vac advance is working as well.

 

I find most of the vacuum leaks are at the carb itself instead of the lines. Did you keep the orifice restrictor in the choke pull off vac line? Do you know if the carb has it ever been rebuilt? Definitely verify the timing, even if it hasn't been adjusted for a while doesn't mean it was correct.

I find most of the vacuum leaks are at the carb itself instead of the lines. Did you keep the orifice restrictor in the choke pull off vac line? Do you know if the carb has it ever been rebuilt? Definitely verify the timing, even if it hasn't been adjusted for a while doesn't mean it was correct.

 

Choke works correctly. It feels more and more like a misfire at this point.

 

I'm going to adjust valves this weekend as they are kinda loud and hoping it's a valve lift issue causing it to flood out from short lift/duration. I know the valves have not been adjusted in a long time.

Think I found the problem. Pulled cap off last night and saw a TINY crack by #4 New cap and it runs better...not Perfect, but the stumble under high throttle/heavy load is much less.

 

Still thinking the carb is kinda wonky but at least I no longer feel like I'm riding a mechanical bull crossing the pass.

Hey.

 

Like Ferox says, Check igition timing. And yes, check valve clearances.

 

Also you may need to confirm the operation of the mechanical advance. You can do this with a timing light or open up distributor and check if springs are present and correct.

 

If its a points type distributor then you will want to reset points gap too.

 

I would be doing a full tune up before looking into the carb any further.

 

regards

 

Dirk.

Hey.

 

Like Ferox says, Check igition timing. And yes, check valve clearances.

 

Also you may need to confirm the operation of the mechanical advance. You can do this with a timing light or open up distributor and check if springs are present and correct.

 

If its a points type distributor then you will want to reset points gap too.

 

I would be doing a full tune up before looking into the carb any further.

 

regards

 

Dirk.

I did a full tune up aside from timing and valves not 2 weeks ago. New cap was defective out of the box. I have to pick up gaskets today as parts house didn't have them in stock, doing valves tomorrow after she cools off all night. I know Valves need to be done as they clatter away even hot.