You've all seen my threads about the efi to carb conversion on my 98 Ultra. I appreciate all the help and feedback from everyone.


I finally got to spend some time on tweaking the carb and ignition and the bike starts right up, I have it idling right at about 1k rpms when warm. The problem that I am having is that after I turn it off the bike runs on for a couple seconds. Could I have the timing too advanced?


Just to recap. I put an Ultima 53-644 ignition, and H-D VOES, and an S&S Super E Carb (still has he jets that came in it).


Any advice would be appreciated.


Chaz

 

Hey Chaz, I pretty much run the same setup but with a dyna ignition. I am using curve 3 but I don't run the idle to 1k. I keep it at 850 and no problems at all. Not even on hot days....

 

Thanks. You have lots more hp than me! I'm all stock except for a EV-27 cam and muffler pipes. I think I may be hearing some spark knock in the front jug. Maybe I'll just retard the timing a few degrees and see what happens.

 

Mine does that sometimes when I run regular gas.
It doesn't do it ever when I use super unleaded (93 octain).

 

All I use is 93 octane.

 

If it still runs on after dropping some timing, you may have some carbon build up, a few tanks with some MM oil,
or spray some water in the intake followed by seafoam or MM oil and let it soak, change your oil if you do that though.

 

The running-on is due to something inside the cylinder getting hot enough to ignite the incoming air/fuel mixture. As Schex points out that can be due to a build up of carbon, or more seriously a very hot spark plug or valve.

As for idle, that should be set at the correct speed of around 1,000rpm, not lower. Why? These engines ain't shovels with barn-engine sized flywheels, they need a little extra speed for the crank to rotate at a uniform speed. Lowering idle speed introduces fluctuating crank rotation, with each piston slowing down as it approaches compression, then speeding up as that cylinder fires, etc. If allowed to carry on like that it can introduce damage to the various crank and conrod bearings, as well as making the pistons slap.

 

I had the top end done just before I decided to do the switch. It has new rings, a fresh hone, and the heads were checked and cleaned. Anyone have contact info for Ulitma? Nothing on the web site.

 

I would change spark plugs first to RN12YC's. Set the gap at .038 to .040.

Do this first because it is cheapest route. Then follow grbrown and Schex advice.

You may only need to re-gap the plugs and increase the idle RPM's.

Also make sure the carb is correctly set-up ie: WOT is at the stop, the idle is adjusted properly. This to make sure the engine is using all the circuits in the carb. Start, accelerate, cruse, coast down, and idle. A combined combination of needle adjustment and push/pull cable adjustments. (easy to do and not nearly as complicated as written)

Incoming fuel "cools" the valves, spark plugs; thus preventing "hot spots".

 

Thanks I'll check the carb. I just put in a new set of hd plugs. Had them laying around. They are gapped at .40.