Total Motorcycle Community Forums

I have a 20 year old Honda Nighthawk "S" with very few miles on it that I am trying to get running again. Its been idle for a while (years). I'm sure I'll have more than one question.

The pistons are moving, the oil, filter, air filter, and spark plugs have been changed, the carb has been cleaned and a couple of carb parts have been replaced. I have a charged battery. Cleaned the tank and petcock.

All systems look good. It turns over and with starting fluid it "almost" catches. Note: There was a dead spot when I started turning it over and when it stopped on that spot I had to move the pistons to get it to turn over again. Does not do this anymore but it might be a clue. I checked and at this point there was gas in the carb bowls. Frustrated I went back to square one.

I put a clear tube with inline filter in the gas line. I drained the carb bowls of gas and checked there was a spark. Vague smell of gas on the plugs but not much of a smell. I'm also I'm not sure how much of a spark there is supposed to be. I assume its a good spark.

I tested the petcock and it works when disconnected from the carb. BUT when its hooked up to the carb it does not work the air out of the fuel line (not enough suction?).

Suggestions on where to go next?

The suction thing sounds about right... Like there's not enough. It might be the piston rings. If it's been sitting for so long the piston rings might not be sealing well against the cylinder walls anymore, so you might be looking at a top end rebuild too...
Wrider

Do you know how to do a compression test?

+1 on compression...

If you have spark, and you have fuel, and you have compression, you SHOULD have GO

When starting my nighthawk after its been sitting for a while I know that it does not like any throttle applied at all. Choke it and turn it over till it starts. Don't give it any throttle tilll its warmed up a bit. If you throttle it and it dies. Start it up again without any throttle leaving the choke on. Hope this helps!

+2 on compression.

Exhaust valve stuck open? It's happened to me

--Dave

Thanks for the replies. Very grateful for your help and advice.

I played with the gas line and I have fuel in the carb bowl now. I do not have anything on hand to test compression. I will find borrow one as soon as I can. I pulled the two left hand side spark plugs and there is compression. How much? I do not know. Too much for me to keep my finger over the plug hole, not enough for it to suck my whole finger in. Didn't want to get my finger sucked in either

I read somewhere that you can put carb cleaner in the cylinder to clean out the gunk. Is that true?

Next clue (while I search for a friend who has compression tester). With gas tank disconnected and the plugs reinstalled I hit the starter (choke off) and it fired for a second or so. There does not seem to be any real gas getting to the plugs. The smell is the lub I've been feeding it to keep the cylinders from locking up.

After writing this reply I went outside and tried to start the bike again. With choke on and fuel on, there was a hint of firing. I let the bike sit for another ten minutes and again the same thing. Just a hint of firing, and then back to just the noise of the starter motor.

Thanks again.

I would check all your cylinders with your finger for compression. Its not the best of options, but you will be able to tell if there is a suck valve causeing a complete loss of compression.

I think you said you checked for spark... did you check all plugs? How did you test for spark?

I'll check again to see if there is spark on all four as well as a finger compression test on the other two.

I was just out for an hour and when I got back I tried again to start it again. Choke on, gas on. When I hit start it caught for a tiny bit and then died.

I'll wait an hour and try with choke off.

I checked and there is spark/compression on all four cylinders. I can not hold my finger over the plug hole. The outgoing pressure is too much. I guess this means there is a fair amount of compression.

I took each spark plug out one at a time, connected it to the plug wire, and clamped it to a good ground on the bike. There was spark on each plug.

I have not found a real compression checker yet. I did make sure to check each spark plug to see if it smelled like gas and none of them really smelled like fresh gas. (I had the clean up the work area to get all the spilled gas/chemical fumes out.) Each plug smelled more like the fluids that have been used to keep the pistons free than gas.

Any suggestions on how to check the carb? There is gas in the bowls. I can easily reach the drain. How high should each carb bowl be filled? I can check using a long clear tube and see how much each bowl is filled. At the moment it not filled very much. Only about 1/4" of fuel in the bowl. Should it be filled?

I pulled the cover off the top of the carb and checked the throttle valve. Should it smell like gas? I assume it should. If it does not smell like gas, where/what to check next?

Again if I let it sit for a while and then try to start it catches for a few cycles and then dies.