Need advise. Due to galled cylinders and compression problem, I just did complete top end rebuild (oversize pistons and valve job) on my stock 1991 FLT with 72,000 miles. Was running fine before teardown. Put back together and it will only start when cold with enricher on and run for about a minute, then dies. Will not start or run without enricher. I did not change anything on timing or cam and marked push rods to get them back in correctly. After not starting other than with enricher, I took apart carb and checked float and checked to see if carb was getting gas from tank, both good. I did check rubber gasket between carb and maniford and it is fitted propertly. I have not removed manifold from heads to check the swedge type gaskets at heads yet. I am almost positive I have the rubber gaskets between manifold installed properly and manifold is tight to heads. Seems like starting with encricher only is a manifold leak. Going to take out gas and try new gas tomorrow, however runs with old gas with enricher. Any suggestions what to look for other than possible problem with installation of new rubber gaskets between heads and manifold. Any help appreciated. Thanks!!

 

I would remove the carb to check the intake seals, and while it is off disassemble and clean it.

Make sure the low speed circuit is clear.

Remove the idle mixture screw (don`t lose the tiny washer or o ring), and give it a shot of carb cleaner.

Make sure you haven`t installed the needle guide collar incorrectly (the thing that guides the needle where it goes into the throat of the carb).

Don`t bother changing gas, that is not the problem.

 

If you have a vacume operated petcock, make sure the diaphram is opening the valve. Those things can fail or diaphram leak when it wants to

 

My bike does'nt have vaccum petcock, I checked to see it is getting gas from tank line at carb. I noticed that after the manifold was bolted to heads, it will not swivel up and down with resistance like it did resistance before I took bike apart. I though this was simply due to new gaskets. Could be manifold is at slight angle and carb not lining up exactly to manifold opening. Only other thing I can think of is leak between manifold and heads. Going to drain gas today and take back apart first of week. Since it runs for a while with enchicher, seems like it has to be a air leak problem. Anyother ideas, let me know. Thanks!!

 

Manual petcock, then it sounds like you and Dan have a plan

 

Sounds like a carburetor or intake issue to me. If you’ve not replaced the intake manifold seals at both heads I would certainly do that. What are you using to align the intake manifold to your carburetor? Asking because I just replaced the manifold seals on my Springer, and found using the stage 1 back plate (HD Screamin Eagle) to be a total PITA. So I purchased an Arlen Ness Big Sucker back plate on EBay. This made alignment of the intake manifold very easy. On my Sportster I used a chopped down stock back plate to get things aligned.

 

The old harley manifold to head gaskets I took off let the manifold move to line up with carb. The James manifold to head gaskets fit tight and do not allow manifold to move to align with carb. I took gas tank back off today, but will be day or so before I go further. I think it is a manifold to carb alignement problem and air leak. I will loose manifold at head to allow it to swivel and install carb and air filter mount to heads, before tightening manifold to head gasket. Seems to be quite a difference in head to manifold fit with the James gaskets. This was never a problem with the OEM harley gaskets, but the James gaskets do seem to seal better at manifold to head.

 

I just want to +1 Dan on that. But I am assuming you adjusted your idle mixture screw to suit the rebuild? I just have to ask since it will run with the enrichment circuit out.

 

Idle enrichment screw is 2.5 turns out. It will not run at all with throttle twisted open, just at idle and enricher used. Took gas tank back off yesterday but had to quite and haven't had chance to get back into this yet, hopefully tomorrow. I really think I have intake manifold alignment wrong, especially since the manifold will not swivel (like it did with the old HD gaskets) with the new James manifold to head gaskets. The manifold used to automatically align with carb when you installed carb, but not now. I thing carb is inserting into manifold at a slight angle. Thanks!!

 

How long was the carb sitting during the top end rebuild? I just ran into the same exact issue with my Dyna after it set for a while. The gas they are selling these days gums up is a very short time frame.. Most likely, the Carb needs to be disassembled and cleaned... or swap itout for an S&S Super E...LOL