Engine hanging at 4000RPM

[singlecoillover]

Hello, I guess this thread will serve as a sort of intro as well as a question. My name is Barak; I just bought (Am picking up this week) a 1987 EX250-E2 from craigslist. I got it for pretty cheap as a bike to learn on. It has a few issues, the most notable of which is the fact that after the throttle is released from say 6000 RPM the engine will hang at 4000 RPM for about 30 seconds before falling to idle speed. This poses a potentially dangerous situation when trying to maneuver slowly. After riding my brother's EX250-J yesterday I know that the engine should smoothly fall to idle as soon as the throttle is closed. I've googled the problem but couldn't find much helpful/ex250 relevant info. This seems like a pretty quality forum so I figured this should be my first stop to find out how to fix the problem.

Thanks in advance!

[Betlog]

Maybe something is getting stuck. You are not running with the choke on are you?

[singlecoillover]

Thanks for the reply.

The choke lever is closed, could the choke be stuck open even with the lever closed?
Posted via Mobile Device

[Momaru]

Sounds like your idle mix may be a bit on the lean side. If the bike's still stock after 20+ years, they do come lean from the factory for fuel economy.
http://faq.ninja250.org/wiki/How_to_...e_your_jetting

Might also have some gunk in the carbs that's built up over the years. Probably worth running some Seafoam thru as well. If neither of those help, may need to pull the carbs for cleaning.
http://gallery.darladog.com/v/motorc.../carbcleaning/

Regarding the choke possibly being stuck, I think it's unlikely. IIRC if just the choke was stuck open a little, the bike wouldn't fall to a normal idle RPM once warmed up, even after hanging for a while. However there's a couple ways to check just to be sure.
1) Get the bike warmed up (with or without choke, as necessary) then start turning on the choke a little at a time. There should be 2-3mm of rotation in the choke lever before the RPMs start to rise as the choke is engaged. If the RPMs rise immediately, the choke cable may be adjusted improperly, sticking the choke open.
2) With the bike off (just easier that way), follow the choke cable down to where it meets the carbs. Move the choke lever a bit to see exactly how the choke operates. On the newer generation it pulls a brass pin out the side of the carbs. See if the pin is returning all the way to a resting position when the choke is closed/off.

[2WheelGuy]

Sounds like the carbs are gummed up and/or out of sync.

I'd pull the carbs and give them a good cleaning. Don't spray carb cleaner on the slide diaphragms! Make sure the idle screw o-rings are intact. After you put them back in sync them.

While you've got the tank off check the valve clearances. I'd put money on them being too tight. This could also be part of your problem.

[singlecoillover]

Thanks for the links. The bike has been sitting outside for the past couple of months so it could be getting gummed up. I really hope I don't have to manually clean the carb though. Pulling the carburetor off seems like a daunting task that's a little bit beyond my technical abilities.

Related Question: Do you have to pull the carb completely off the bike to unplug the idle mixture screws? It seems like a lot of bother, for such a relatively simple task.

I googled seafoam and found this video:

http://video.google.com/videoplay?do...0865726229173#

It says to pour the stuff into the carb throat, crankcase, and gas tank...is that safe?

[Jakester9500]

if you don't want to do the carb work, i'm sure you could take the bike to a place like Don's Kawasaki and have them do a tune up, or look to fix the problem.

Its always cheaper to do things yourself, but if you get overwhelmed, there are dealerships out there too. Just saying.

And no, I don't work there or anything.

[Humblephilosopher]

I have had this problem on a couple of bikes and both times it turned out to be a lean carburetion situation. It will probably help to adjust your idle mixture. It is possible to remove the plugs and adjust the idle mixture screws with the carbs in place. First find the four plugs - each carb has one sticking straight down directly under the carb to engine outlet - check your Clymers or other manual. There isn't a lot of room, but you can tap a nail into the plug to make a little hole, then screw in a screw until it is pretty secure. Now get a pliers and pull the plug out with the screw. Once unplugged, a 2 inch stubby screwdriver can be seated on the adjusting screw. Carefully turn the screw clockwise until it just seats - make sure you count the turns. You will want to turn the screws back out a little more than they were in order to richen up the idle circuit. I recommend 1/2 inch increments until you find the sweet spot (where the engine idles most strongly. Be sure all carbs are adjusted the same amount.
Good Luck!

[singlecoillover]

When I took the carb off (other post) to clean it, I noticed the screws were already exposed so I decided to leave it for now assuming they were adjusted by a previous owner.

I think the problem stems from some sort of choke problem...not really sure. Sometimes when I start the bike I have to crank the idle speed up to get it to stay running at 1300 rpms, but then once it warms up it will idle at 4000 and turning the idle screw back will bring it down to reasonable levels for the duration of my ride. Kinda wierd. I think I need to leave it low and then use choke on startup, unfortunately the choke lever is kinda messed up on this bike and may need replaced.

As of now it no longer falls to 1300 after hanging at 4000, cleaning the carb probably helped some.

[mrlmd]

Have you lubed up your throttle cable and choke cable? Maybe after all these years, they're sticking.