'92 Ninja 250 Running Slow

[slamminsammyb]

Hey everyone, I just recently bought this bike for $600, and I'm extremely new to everything about motorcycles and everything related, so please be patient with me. Below is a rundown of the issue that I'm having. Any and all help is appreciated!

1992 Ninja 250 with 4000 miles on it. The bike sat for about 3 or 4 years, was ridden for maybe a month, then sat for at least another year. The bike starts fine, and usually has no real trouble idling once the engine is warm. It does run, and did make a 50 mile trip from the place of purchase back to my residence. My friend who rode it back got it up to 55-60 mph on occasion, but it took an incredibly long time to get it to that speed.

The problem that I am having is that the bike is lacking power, and lacking a lot of it. The bike takes forever (at least 5-10 seconds) to even get up to 20 mph. At low and high RPMs, the bike doesn't accelerate anywhere near what it should. We did the easiest thing first, which was changing the spark plugs, and this did not help. However, the left spark plug was black, while the right one was a reddish color, possibly indicating an issue with the left valve or carburetor. My friend who helped me do this work said that the left valve is running rich.

We took the carbs off and sprayed them out with carb cleaner as much as we could without completely disassembling them. They did not look like they had been sitting for years on end, and did not have any sort of gummy build up or residue. I think the last owner may have put new ones on when he purchased the bike a little over a year ago, so we did what we could with cleaning. The only "adjusting" that we did was to try and make sure that each carb was symmetric with the other as far as the adjustable settings go. Sorry that I cannot go into more detail, but I do not know enough about it or the terminology to properly explain in any further detail.

After we put the carbs back on, the bike started fine, and still ran. However, it still lacked just as much power as it did before, and now it stumbles on occasion as well.

Things that I have done so far, but have not fixed the problem:
Changed spark plugs
Changed oil/oil filter
Cleaned the carburetors (to the best of our ability, but is probably still the issue)

Thanks in advance for all responses!

[StarGate]

You really can't clean the carbs without taking them fully apart. Some of the passages in the carbs are so small it only takes a very small amount of varnish or trash to block them or the jets. Since you have it running you may gain a little better performance by putting in a new air filter and running a tank or 2 of Seafoam in your gas to help clean the carbs. It would be a good idea to check/adjust the valves also.