VAC run rough ( about to give up)

[CONSERVATIONMAN]

Got this VAC years ago used it for shows, plow days and some sickle bar mowing. Couple of years ago started running rough could not mow with it.
Started checking it out
distributer bad shaft wobbled, replaced with rebuilt from case 400
Instaled carb kit no change
checked valve lash, found casting tumbling media in oil trough and a worn cam, new ( used) cam installed
( https://forums.yesterdaystractors.com/threads/vac-can-lift.1687153/#post-11268523

Completely cleaned the engine, new head gasket, cam and cam bearings
Compression 105-110
Spark good and on time
new Champion D-16 plugs
Battery strong and charged
Went through the carb again, floats .25 in from gasket, all holes flow cleaner through them
Won't run except on almost full choke, finally got it to idle but any throttle and starves for gas?

Put on a carb from running VAC same problem

 

[Tgrasher]

Leave the gas line off the carburetor and check the gas flow. It should put out a pint a minute when you open the sediment bowl valve.

 

[CONSERVATIONMAN]

Clean tank, clean bowl/strainer, plenty of gas flow

 

[kenbob]

I am no expert and don't play one on tv, but I have heard a lot of talk about coil or condenser problems that only show up under load. Do you have that good spark at high rpms? Just a shot in the dark.

 

[CONSERVATIONMAN]

It's a new coil but I could try swapping it out with another when it stops raining.

 

[JOCCO]

Manifold or leaks on intake? Old school if you are using the choke to keep it running it is probably not electrical. Next up what about a crack in the head or block. What about weak valve springs?

 

[DRussell]

It's a new coil but I could try swapping it out with another when it stops raining.

Change the condenser. The coil is more likely to be a problem after it runs for a while.

 

[CONSERVATIONMAN]

I did not specifically look for cracked heads or intake manifold but I had it all apart and cleaned it up , looked good, new head gasket new manifold gasket but I'll check again.

 

[Hoofer B]

Put in new spark plugs and not champions either

 

[Tgrasher]

Easy to miss is the cavity below the needle valve, where the gas comes into the carburetor. A tiny piece of crude will drive a man nuts. I take a small end brush (a gun barrel cleaning brush would work) and scrub it good.

 

[CONSERVATIONMAN]

Any ideas on looking for a vacuum leak?

 

[DRussell]

Any ideas on looking for a vacuum leak?

Get it running and hold a propane bottle open near the outside of the carburetor and intake manifold. If there is an air leak causing it run rough the propane will be sucked into the leak and will fix the rough running.

 

[kenbob]

Change the condenser. The coil is more likely to be a problem after it runs for a while.

IF you do change the condenser make sure you get a brand name one. The no name ones are junk. Also, I had a 351 that had to be run with the choke out after a carb rebuild that I did. My brother took it apart again and I think he cleaned that little hole mentioned in another post. That took care of it.

 

[JOCCO]

Get it running and hold a propane bottle open near the outside of the carburetor and intake manifold. If there is an air leak causing it run rough the propane will be sucked into the leak and will fix the rough running.

You can use Eather starting fluid, carburetor cleaner to do the same.

 

[JOCCO]

Also look at the carburetor shafts, choke and throttle if they are loose or sloppy it can cause it. on your manifold it could be warped twisted or not seating causing an air leak on one or more cylinder. The only real way to eliminate stuff is to test it like valve springs there is a tester for them. Coil and condenser there is a tester for them. Also as of late I have had more than my share of rotor button problems.

 

[CONSERVATIONMAN]

Thanks for all the ideas, but it's raining today, so tomorrow I'll get to work

 

[olddog]

Got this VAC years ago used it for shows, plow days and some sickle bar mowing. Couple of years ago started running rough could not mow with it.
Started checking it out
distributer bad shaft wobbled, replaced with rebuilt from case 400
Instaled carb kit no change
checked valve lash, found casting tumbling media in oil trough and a worn cam, new ( used) cam installed
( https://forums.yesterdaystractors.com/threads/vac-can-lift.1687153/#post-11268523

Completely cleaned the engine, new head gasket, cam and cam bearings
Compression 105-110
Spark good and on time
new Champion D-16 plugs
Battery strong and charged
Went through the carb again, floats .25 in from gasket, all holes flow cleaner through them
Won't run except on almost full choke, finally got it to idle but any throttle and starves for gas?

Put on a carb from running VAC same problem

 

[olddog]

AFTER you get full flow of gas from the drain on the bottom of the carb, try retarding the spark past factory suggested.

 

[mEl]

What make carb? can you send pics of it disassembled?

 

[CONSERVATIONMAN]

You can use Eather starting fluid, carburetor cleaner to do the same.

Tried both Propane and Either no effect.