Hey there Evo riders,

I have been lurking for awhile now and just haven't had a reason to join up and pitch in. I just bought my first Harley, a 1998 FLSTC.

I have an interesting problem that has just surfaced. The last two days when I ride in the morning, when I get off the highway my bike will sputter and die. It doesn't matter if I gently roll off the throttle or come off it quickly, it dies. It restarts easily enough and it only seems to happen when its cold (this morning it was 31F).

Yesterday afternoon in the upper 40s she ran like a champ and had no problems when I got off the highway.

Any thoughts?

 

Hi from the UK and welcome to HDF. 31F?! Good grief, you must still be working for a living! Poor chap.

One possibility is simply that your carb has iced up. When I was much younger I had a BSA Rocket 3 and that would occasionally stop when it was darned cold - despite having three carbs. I learned after a while that heat soak while stationary would soon thaw it out and it would then run fine. It will be interesting to see what our experts suggest. It might be worth draining your float bowl, to remove any water there may be in it.

 

I was wondering if it was a water issue as well but I honestly have no idea.

Oh and no, I don't work for a living, I returned to school 4 years ago so this morning I was on my way to Organic Chemistry Lab.

 

Assuming you do have a carb? Do you know which one? Is it stock? I had a similar experience with my S&S SuperE carb last year. Issue did seem to me more evident in colder weather as well. (Albeit not that damn cold tho!, LOL) Mine turned out to have some debri or blockage in the tube (I forget what its called). But if you pull off your air filter and hold open the butterfly mechanism, then twist the throttle a few times and monitor the condition of the spray pattern. It should be an even fan like spray pattern. Mine was streaming every which way. So I was getting unequal amounts of fuel to each cylinder. This may not have anything to do with your issue (my experience pertains directly to an S&S carb), but it is easy enough to check. Might even be possible you also have a bad Accelerator Pump diaphragm. I am just thinking out loud here, so take it for what it's worth. Good luck!

 

Ahh, organic chemistry. Two the the three B's I received in undergraduate school. And totally useless for a medical education.

Yeah, EFI or carb? What carb? Sounds lean. Any backfiring through the air cleaner? What's the idle set at? Should be at about 1K.

 

Organic chemistry...yup its still evil. I'm holding onto a B at this time, hopefully I'll stay there but it isn't exactly an easy subject.

Yes its a carb'd bike. I guess I should've stated that earlier. As to which carb? Stock? I have no idea, I'm going to pull the air cleaning when I get home this evening and look at the spray pattern like Deputy suggested. While I'm in there I'll try and figure out which carb I have.

As for the backfiring through the carb (I call it coughing), occasionally yes it does do that. It tends to go away as the bike warms up. I have no idea what the idle is set at, I also don't know that I have any way of checking that right now.

 

A common source of problems is leaking intake manifold seals. Check that. Spray a little carb cleaner around the seals with the bike idling. If the engine speed changes one way or the other, you have a leak.

 

I'll add that to my list of things to try.

The previous owner of this bike effectively neglected it. In the last 3 years that he owned it, he only put about 300 miles on the bike. I've done that in the last week.

 

Regarding the accelerator pump spray pattern. Is it suppose to spray a stream or a mist on a stock cv carb? I had this question before and meant to ask. Mine is more of a stream but a blockage would make it spray more of a mist wouldn't it?

 

I was told by an S&S service tech directly that it needs to be a fanned out pattern. This would resemble more if a mist in my opinion. Streams are no good, it needs to be evenly distributed. Best I can describe it I guess. He advised to soak it overnight in carb spray, that take a small piece of shim stock (0.006) thick and slide it back and forth in the grooved opening on the tube stem where the fuel comes out. That should remove any debri or build up of grime and so forth. It helped mine, got me through the rest of the season without anymore real issues. I have it in the works to rebuild the whole carb fairly soon here though, just because. I am also installing a new petcock and fuel line from that to the carb. With all that I should basically have a brand new fuel delivery system.