1998 superhawk, stops running at operating temp.

[erik lange]

1998 honda superhawk 996 5k miles. Runs perfectly until engine approaches operating temp. As engine warms up a slight spark rattle can be heard and then seems to be only running on one cylinder until it dies and cant be restarted until the engine cools off. I am thinking coil but wanted to see what other oppinions may be.

[Johnj]

Fuel tank vent.

[erik lange]

Thanks Johnj. How would I go about checking that to see if that's what it is. Could I try running it with the fuel lid open? Are you thinking the vent is just clogged or is that something that can be replaced.

[Johnj]

The easy check is run it till it dies, then open the fuel tank lid. Did it make a sucking sound? Will it start right up? I really don't know about how the tank vents on that bike, but if that's the problem you need to clear it.

[erik lange]

I will give that a try and let you know how it works out. Thanks, Erik.

[erik lange]

Ok Johnj, I ran it till it started cutting out and opened the fuel cap and heard nothing. No sucking sound or anything else. Any suggestions on where to go from here?
I replaced the regulator/rectafier a few days ago and it ran fine for about 25 miles and then started the same thing. Thats longer than it had been though it only took about 2 miles/5 mins. to do it today. Didn't even seem like that was long enough for it to heat up.

[GS_in_CO]

The question is whether it's running short of fuel or heat is causing the ignition system to quit.

Seems to me a simple way to tell after the trick of opening the tank was indeterminate is to see if there is fuel in the carb bowls when it quits.

Opening the tank might take a moment for more fuel to get to the carb. So retry that and see if it will restart after opening the tank cap and giving it 2 minutes.

If you can't tell from that, find where the carb bowl drain screws are. My Hondas had some tubes running down below each carb bowl and a screw each to open a drain that will go into those tubes. Tubes were clear so by opening the drain you can watch the tube and see if fuel runs out. Try this first when the bike is cold and not running to be sure you're using the right tubes and screws. Then ride. When it quits, repeat the drain procedure and see if fuel comes out. If not, it still could be plugged tank vent and you could also add plugged petcock, plugged inlet valves to the carbs to the things to check.

Engines only need fuel, air and spark to run. But it has to be good clean fuel in proper proportion. And strong, correctly timed spark.

[erik lange]

Thanks for the input Ron. When this problem first reared its ugly head I asked the mechanics at my local dealer and they said my particular bike was notorious for blowing the reg/rec. They told me to bring the reg. to them and they would check it n/c which I thought was nice of them because you usually don't see that level of generosity from them. So I took the part to them and after about five mins. the mech. returned and told me the unit was shot. I went and picked one up from a salvage yard, installed it on the bike and what do you know...still the same problem. I decided to check out the regulator myself and after finding some good instruction determined that it was good. I am moving on to the stator now as it is the next logical part to be bad as my charging system is only showing 11.5v at the battery. I would have checked the stator before I replaced the regulator but my Honda dealer was insistant that it was the regulator. If nothing else it has been a great learning exp.
I will let the forum know what the verdict is as soon as it comes in. Thanks to everyone for all the help. Erik.

[BRUMBEAR]

With the bike running it should show 13-13.5 volts then you know your charging system is good. With all power off disconnect the neg terminal see if there is a spark when you touch the cable to the terminal NEG ONLY if so no matter how small you have a drain. My guess is an ign module bad this unit probably has an early solid state ign and the transistors break down with heat. Especially if fuel is not the problem and when it cools it works again. If it were a coil USUALLY not always when it goes it goes or it will only run POORLY when it expands.

[erik lange]

I replaced the stator and the voltes are at 14.3 and it was only charging 11.5v. I took it out and again it started missing. I could tell I was only running on one cylinder so when I got home I checked both exhaust pipes and the rear one was not hot at all. I am going to swap out the coils front to back and see if the problem followes.