Ironhead Carb help please

[NJDave]

Let me give you all the back round first. What I have. 78 sporty, S&S super B carb, K&N air filter, Milwaukee twins exhaust, not drag pipes, they have slash cut mufflers on them and an Ultima electronic ignition.

Checked timing with a light. At 3K rpm's I had the timing mark in the center of the hole. Compression on front cylinder is 160 rear 155. Test done with bike warmed up with throttle opened.

She was running a little rich. Ran OK but got some bad mileage and the plugs were always black, not fouled, just pretty sooty. I swapped from a 31 intermediate jet down to a 28. This was a touch lean as the plugs were now white and it felt like she was getting too hot. Went to the 295 and went out for a spin. Mid range and top end were great. Now for the trouble.

She will no longer idle. The inside of the float bowl was varnished. I figured I knocked a piece of it off and it clogged my idle circuit. I took the carb off and soaked it in some chem bath cleaner stuff. Once done and clean I blew every passage out with compressed air.

Put it all back together and now it will only idle with the enricher pulled out. If I back out on the idle mixture screw 3 turns (should be ~1.5) it will idle and take gas with the enricher closed but once I take off under load it dies. If I get it up over 2-3K rpms it will go like hell.

I checked for intake leaks with some carb cleaner and wd40 ( no propane torch) and did not notice any change in rpm. I tried the other 2 jets again but same thing at this point. Pulled carb off 2 more times and blew everything out. Get it into the intermediate or main jets and she runs great but my idle circuit is .

I pulled my ignition module to see if maybe the rotor had come lose but that was fine. Now I have to reset my static timing and I figure I will do the push rods while I have it off the ground.

I don't know what to check at this point. Maybe the on and off with the carb jacked up my intake seals? Does this sound like an intake leak? I do notice a miss on my rear jug. Would an intake leak on that side or an exhaust leak cause that?

Do I have to loosen the heads to get new seals on my manifold?

Sorry for the long post, just wanted to get as much info in as I could.

[IronMick]

I cannot help with the S&S, but as to your last question, you do not loosen the heads when re-installing the manifold and seals. If anything you can loosen the cylinder base nuts, then manipulate the cylinder/head assembly to get the best matchup.

If the matchup was good before then it should be good still so no loosening should be necessary. If loosening is necessary then hopefully the cylinder base gaskets were installed dry on the bottom side, rather than with a sticky gasket sealer.

[jrotten]

Just curious. What are you setting the idle mixture at? How many turns out after seating it lightly? Mine was doing the same thing and it was an intake leak.

[NJDave]

Thanks Mick. It was fine before. I thought loosening and re-torqing the carb might have jacked it.

Jrotten, before the issue I was at about 1.5 turns out. Right now it will not idle at less then 3 turns out. If I crank it all the way out it still runs.

I did replace the O ring that goes between the carb and manifold. Perhaps that is not seating right.

Now that I think of it perhaps the new butterfly I put in the carb is not seating right. I have the bevel the right way however there is some space on either side. Top and bottem seal OK but there is play on either side where the shaft goes through the carb body. It does not fit as tight as the old one did. Perhaps I got a cheap rebuild kit. I will hit indy tomorrow for a new one.

[jrotten]

Good luck and I hope ya get it fixed. Sometimes I just have to walk away for awhile.Please let us know what ya find.

[Hopper]

Originally Posted by NJDave

It does not fit as tight as the old one did. Perhaps I got a cheap rebuild kit. I will hit indy tomorrow for a new one.

Taiwan trash strikes again.
Get a genuine S&S rebuild kit. You get what you pay for.

I would also put back the jets you had in place before the problem developed.
If the problem then goes away, it was jetting. If the problem does not go away, it is something else, most likely that cheap rebuild kit.

[ryder rick]

Going from a 31 to a 28 will not make that big of a change in the plugs.

If you were running an S&S with 1.5 turns on the idle mix screw it was very close (if not) out of range I usually see them around .75 to 1 turn.

Your symptoms shout vacuum leak.

[NJDave]

Once I get the correct butterfly in there I will pick up a cheap torch and double check for leaks.

I have to reset the timing this morning. Will double check the push rods too. Heading to local shop this afternoon to hopefully get new body rebuild kit. Will let you know how it turns out.

Local guy was out of stock on rebuild kit. He ordered one up. It is from S&S so I know it will have the correct parts this time. Will update on Thursday when I get it.

[Ferrous Head]

The reason you install a full rebuild kit on these is the throttle shaft gets worn. If the shaft/carb body wear you'll get an air leak and the bike won't idle. The kits come with bushings for the crab bodys but often it's really just the shaft that wears - it's a brass shaft and fairly soft. Sometimes just replacing the shaft will cure your problem. If you can feel any noticable "shake" in the shaft it's probably a problem.
If it was OK before try just re-using the old shaft. Putting the bushings in is a job for a toolmaker or a good engineer at any rate. If you don't drill/ream the holes correctly the shaft will either bind or the throttle plate won't seat.
You say you can see that the throttle plate isn't seating correctly. You need to sort that out. Make absolutly sure you have the bevels on the right side and that the shaft isn't binding for some reason.
Good luck.

I run a Super B on my race bike and it's a great carby.

[chief]

when my ironhead starts acting up like that i readjust my valves.
a simple pushrod adjusting will help when plugs are fouling and you're shure your carb is ok..

just try it..if it will not work, you have some good adjusted valves..