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I haven’t ridden my 83 Nighthawk 550sc in about 4 months partly because I am a beginner and didn’t trust myself in the Seattle rain. Now that the weather is clearing up though, I decided it was time to start riding again. My bike has been covered and parked outdoors through the winter.

On my first attempt to ride the bike wouldn’t start and it barely cranked, so I thought a natural thing to do was to charge up the battery on my batter tender junior. Now it cranks just fine but it still won’t start. They are the sounds that may occur when one tries to start a bike on an empty fuel tank. I made sure the tank was full of high octane fuel but still no luck.

In one of my attempts to start it the bike made an extremely loud bang that scared the crap out of me. It seemed to come out of the exhaust area and it echoed throughout my neighborhood. I overcame my surprise and gave it a few more tries to no avail and on the last attempt the bang occurred again.

From previous threads it seems like fuel may not be reaching the engines but I am not sure how to check for this. I am also concerned about the very loud bangs.

Any suggestions?

Update:%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
This is what I have done in this order:

1. Filled the gas tank, made sure starter was cranking
2. Drained the carbs, made sure they are getting fuel
3. Recharged the battery with tender
4. Checked spark in old spark plugs— no blue spark
5. Replaced old spark plugs with new ones
6. Checked spark in new spark plugs— still no blue spark

I keep hearing suggestions that my sparks are flooded, however I do not know what this means exactly or how to troubleshoot this problem. Here is what I plan to try next:

1. Check oil in crankcase, check air filter
2. Connect my car battery to the bike battery
3. Try starting the bike
4. If this doesn’t work, then test the spark plugs again, with the car battery connected
5. if i still dont see a spark, then i am not sure what to check for next. the coils? the bike ran fine before the winter....

Where could I do my homework on flooding troubleshooting and research solutions? Thanks guys/gals.
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Sounds like you just had it flooded and it fired once, igniting fuel vapors in the exhaust pipe. You should be fine.

You may want to pull and clean the spark plugs before trying again. Maybe with only half choke if it's nice and warm outside this time....depends on how cold-blooded the bike normally is.

I wouldn't worry about the bang. Most likely just to be exploding fuel in the exhausts, happens if you keep cranking an engine, the exhausts will be full of petrol. I knew someone who had a Yamaha two stroke with open exhausts. He got flames from the exhaust after starting her up.

As suggested, clean the plugs, and play with the choke. Make sure the plugs work as wel, and that the airfilter is not blocked.

You say it sounds like a bike starting without fuel. Therefore check that their is enough fuel getting through the carbs.

If you didn't put stabilizer in the tank before you parked it, I would say it's likely the carbs are fouled...deposits can form in as little as a couple weeks if the bikes sitting.

Good luck.

misc wrote:ou may want to pull and clean the spark plugs before trying again... clean the plugs, and play with the choke. Make sure the plugs work as well, and that the airfilter is not blocked... check that their is enough fuel getting through the carbs.

If you didn't put stabilizer in the tank before you parked it, I would say it's likely the carbs are fouled...deposits can form in as little as a couple weeks if the bikes sitting.

Good luck.

Ok.... thanks for the suggestions. i will check the filter and clean the spark plugs. But i am not sure how to make sure i am getting fuel to the carbs. also, if the carbs are fouled, how do i clean them?

is there a way to drain the fuel inside the carbs so that fresh fuel can flow in its place? thanks guys.

gerpena wrote:

misc wrote:ou may want to pull and clean the spark plugs before trying again... clean the plugs, and play with the choke. Make sure the plugs work as well, and that the airfilter is not blocked... check that their is enough fuel getting through the carbs.

If you didn't put stabilizer in the tank before you parked it, I would say it's likely the carbs are fouled...deposits can form in as little as a couple weeks if the bikes sitting.

Good luck.

Ok.... thanks for the suggestions. i will check the filter and clean the spark plugs. But i am not sure how to make sure i am getting fuel to the carbs. also, if the carbs are fouled, how do i clean them?

is there a way to drain the fuel inside the carbs so that fresh fuel can flow in its place? thanks guys.

If the carbs are gummed up - you'll need to do a rebuild on them - fairly easy and inexpensive.

If you pull out the spark plugs one at a time (then put the plug wire back on) and hold them with some insulated pliers close to the engine (a 1/2 inch or so) while turning the bike over - you should see a nice blue spark...if you got a good spark - then it's likely that the fuel isn't coming out of the carbs right - thus a cleaning and rebuild is needed.

My carbs (Mikuni's) have a drain plug on the bottom of each float bowl but draining them won't really do a whole lot of good if the jets are gummed up.

Good luck

cruisinflatout wrote: If you pull out the spark plugs one at a time (then put the plug wire back on) and hold them with some insulated pliers close to the engine (a 1/2 inch or so) while turning the bike over - you should see a nice blue spark...if you got a good spark - then it's likely that the fuel isn't coming out of the carbs right - thus a cleaning and rebuild is needed.

I drained the carbs and made sure fuel was flowing to them with the fuel valve open. Fuel appears to be reaching the carbs just fine.

Next I checked the spark plugs. As suggested, I checked each one individually for a nice blue spark when turning the bike over. I observed a minor yellow spark on one for a second, but no blue spark. I then replaced the old spark plugs with new ones and tried again. Still no blue spark, not even the small yellow spark.

Since the yellow spark only occurred once, I suspect a wiring problem. However, before I could troubleshoot further, my battery finally lost its juice. I am currently recharging it again.

Any suggestions?

did you hold them to the block or just try to see it between the gap? To the block works better and you'll have a better idea of how they're doing...

cruisinflatout wrote:did you hold them to the block or just try to see it between the gap? To the block works better and you'll have a better idea of how they're doing...

I just let them hang by the block and tested one at a time. I thought the spark would be obvious. The bike started and ran fine before the winter.

Hold the end of the spark plug wire close to the engine, the spark will be easier to see. Yellow spark means your coil(s) are going, may or may not be an easy fix, depends on the bike