Motorcycle's power comes and goes erratically?

Question

Hi, just bought my first motorcycle, a 78 Honda cb400tI aka 400 hawk. I know a little about cars (currently rebuilding a 240z). I'm not afraid to get my hands dirty. Here's the story:

it ran good when I bought it, and I drove it around the driveway to get used to the clutch before I got my temps and it ran good then. Friday I got my temps and drove it 1mi from my house and back and it rode fine, but saturday I went on a longer drive around the bock and this was a bit more "spirited" drive, I was acceling faster and then it started to act up. I found out that I left the petcock on res and I think it was running out of gas. Now once it warms up it dies at idle and while driving the power comes and then it goes erradically it will be at constant throttle and rev's climb slow and then have a hit of power going back and forth while in the same gear. It is a twin engine dual carbs and electronic ignition, I cannot get a reliable compression test until I get a new tip for the tester, thanks

Answer 1

Sounds like a fuel feed problem.

Check for a blocked tank vent.

Look for partially blocked or kinked fuel lines.

If there's a filter, clean it.

Answer 2

First, shine a light into the gas tank and seeif there's any rust. If there is then you will want to fix this soon. Second, remove and clean out the petcock, especially if there is rust in the tank. Third, clean out the carburetors or at the very least the carb. bowls. While your doing all that, changed the spark plugs simply because it's cheap insurance. Lastly, I attached a link on how to sync. the carb.s. It's not for your specific bike but the concept is the same and it won't cost you $50 for a tool.

Good luck.

Answer 3

First, what the other guy said about rust.

Second, you might have bad gas in the bottom of the tank.  Fill 'er up.  While you're at it, buy a little bottle of carb cleaner gas additive, and pour a third of it into the tank.

Third, check the oil level.  If there's too much let some out.  If there's too little add some.

Fourth, inspect your spark plugs.  Clean them, and make sure the gaps are correct, and the same for both plugs (inline twin, right?).

Fifth, inspect your air filter element.  If it's the cleanable kind, clean and oil it.  If it's not cleanable, think about replacing the air filter element.

Answer 4

http://infoforyou.rules.it

you can get much information in this website, If you will check anyone blue link in website.

Answer 5

Everybodys answers cover everything but also check your carb diaprahms, if one of then is perished or broken that could cause problems as well.