Bandit wont idle... lags... -1991 400cc

[halamadrid]

Hey everybody Im really excited that I found this forum.  This is my first post, it will be a long one but I should introduce myself. I am 18, I have been riding a scooter for 2 years and I did basic maintenance on that and then early February I bought a 1991 bandit 400cc.

When I bought it it was running what seemed fine to me and my uncle made note that it sounded like the carbs needed to be cleaned and it all made good sense. (it had sat all winter in a farm guys garage). So I took it home and he showed me how to work on it and I caught on very quickly. We cleaned the carbs lightly, not thoroughly, and it didnt do much to help it run. When trying to run it we noticed that we couldnt get it to idle without stalling and that it lagged a lot. At times it was slightly responsive and others it wasnt.

  So i worked on it on my own for a while, charged battery, lots of small things, ran seafoam, and finally decided to pull out the pilot jets. I cleaned these and noticed a huge difference. The bike ran pretty well (I thought, it probably wasnt peak and I couldnt tell because of my inexperience). I rode it for about 30 miles over several days. The only mod i made in this time was a repair to the muffler, i wire fed welded a crack where the header met the pipes. THe next day I rode it to school and it was great. I got on it that day after class and it just...i dont know.. Is very hard to start, have to hold the throttle or turn the idle way high to get it to start, almost always with the choke on. With the choke it will rev really high and with the choke off it comes down slowly and dies. Impossible to set the idle anywhere below 2500rpm.   I dont know if this is relevant but a punk kid at school that day saw me with my helmet and told me "Im going to tip over your motorcycle."  Maybe he screwed with some wiring?

From here (about a month ago), Ive done several things.  Replaced the rubber plugs that cover the pilot jets, Ive done a pretty deep cleaning of the carbs, and Ive checked spark plug wires and spark plugs. None of them look bad although they are CR8EK Type R plugs, with double elctrodes. The only clue I have right now, seeing that the carbs are clean, is that the left coil+plugs 1 and 4 will cause a screwdriver in the cap to create a great long spark, and the right coil 2 and 3 will hardly do anything and very seldom. Ive checked the resistance on the coils and through the plug caps and Im not sure if I am reading the right values, but i do know that the measurements from both coils match each other. I am wondering if a coil could still not function right while still having the correct resistance?   The only other information i can give you is the compression in the cylinders: left to right it is  170, 135, 170, and 170. Oh yea, and it backfires now quite frequently.

Ive had a ton of fun with this bike even though its been in my garage for 3 months. I want to ride it so badly :(   But at the same time i enjoy doing the work on it, Learning TONS of stuff. I love it.  But now I am becoming impatient.  

What can I check now? am I on the right track assuming that the coil is bad? I found one on ebay for $25. Or is it possible one of the electrical components behind the coils in the circuit?   CDI, or that other thing...?

People have mentioned possibilities of it being valve adjustment issues,  carb balancing... Im still leaning towards electrical but i dont know the specifics on what it could be...
 thank you guys!  



Also, what are these two black boxes? The one by the helmet lock looks pretty grimy to me. How can I check these and their performance?

http://i121.photobucket.com/albums/o220/nicksteckler/CIMG2891.jpg

[halamadrid]

Hey everybody Im really excited that I found this forum.  This is my first post, it will be a long one but I should introduce myself. I am 18, I have been riding a scooter for 2 years and I did basic maintenance on that and then early February I bought a 1991 bandit 400cc.

When I bought it it was running what seemed fine to me and my uncle made note that it sounded like the carbs needed to be cleaned and it all made good sense. (it had sat all winter in a farm guys garage). So I took it home and he showed me how to work on it and I caught on very quickly. We cleaned the carbs lightly, not thoroughly, and it didnt do much to help it run. When trying to run it we noticed that we couldnt get it to idle without stalling and that it lagged a lot. At times it was slightly responsive and others it wasnt.

  So i worked on it on my own for a while, charged battery, lots of small things, ran seafoam, and finally decided to pull out the pilot jets. I cleaned these and noticed a huge difference. The bike ran pretty well (I thought, it probably wasnt peak and I couldnt tell because of my inexperience). I rode it for about 30 miles over several days. The only mod i made in this time was a repair to the muffler, i wire fed welded a crack where the header met the pipes. THe next day I rode it to school and it was great. I got on it that day after class and it just...i dont know.. Is very hard to start, have to hold the throttle or turn the idle way high to get it to start, almost always with the choke on. With the choke it will rev really high and with the choke off it comes down slowly and dies. Impossible to set the idle anywhere below 2500rpm.   I dont know if this is relevant but a punk kid at school that day saw me with my helmet and told me "Im going to tip over your motorcycle."  Maybe he screwed with some wiring?

From here (about a month ago), Ive done several things.  Replaced the rubber plugs that cover the pilot jets, Ive done a pretty deep cleaning of the carbs, and Ive checked spark plug wires and spark plugs. None of them look bad although they are CR8EK Type R plugs, with double elctrodes. The only clue I have right now, seeing that the carbs are clean, is that the left coil+plugs 1 and 4 will cause a screwdriver in the cap to create a great long spark, and the right coil 2 and 3 will hardly do anything and very seldom. Ive checked the resistance on the coils and through the plug caps and Im not sure if I am reading the right values, but i do know that the measurements from both coils match each other. I am wondering if a coil could still not function right while still having the correct resistance?   The only other information i can give you is the compression in the cylinders: left to right it is  170, 135, 170, and 170. Oh, and it backfires quite frequently now, it didnt do it before.

Ive had a ton of fun with this bike even though its been in my garage for 3 months. I want to ride it so badly :(   But at the same time i enjoy doing the work on it, Learning TONS of stuff. I love it.  But now I am becoming impatient.  

What can I check now? am I on the right track assuming that the coil is bad? I found one on ebay for $25. Or is it possible one of the electrical components behind the coils in the circuit?   CDI, or that other thing...?

People have mentioned possibilities of it being valve adjustment issues,  carb balancing... Im still leaning towards electrical but i dont know the specifics on what it could be...
 thank you guys!  



Also, what are these two black boxes? The one by the helmet lock looks pretty grimy to me. How can I check these and their performance?

http://i121.photobucket.com/albums/o220/nicksteckler/CIMG2891.jpg

[interfuse]

It's not an electrical problem. It's carb related. Check o-rings, float height, etc.

fyi one of the black boxes you mention is the turn signal relay. If you're turn signals flash, it's working... the other one escapes me at the moment.

[tomacGTi]

If you've gone over the carbs and replaced all the o-rings as well as cleaned the jets with a piece of wire and cleaner, then it's not them. Just make sure to synch and that the mixture screws are at an equal number of turns.

Make sure the spade connectors are both tight onto the coils and that the spark plug wires are in good shape. Check the condition of the battery and run Stormi's test for the RR to ensure it's not cooking the battery (which will cook the CDI).

None of those items you have in your picture will affect how the bike runs.

Since it has been sitting, I would do all the basic maintenance to ensure all bases are covered before trying to thoroughly troubleshoot. Generally, dying on idle is a sign of a rich mixture but since the bike has been sitting it could be more than that.

[stormi]

He means the one in my Sig,....
down there
    |
   \/

[Red01]

Have you checked for vacuum leaks?  What you're describing sounds like it's a good possiblity... won't idle, runs better with the choke/enrichener on.

Check all vacuum hoses, nipple caps & fuel petcock diaphragm for condition and security.  Also check the carb to manifold clamps, manifold to head connection and the manifolds themselves.  With a bike that's pushing 20 years old, these could be dried out and cracking, allowing extra air in.  To check the manifolds, with the engine running at whatever minimum smooth "idle" you can sustain, spray them with WD-40, starter fluid, or similar combustible.  If the rpm's change, you've found the leak.

[halamadrid]

Yes Ive checked for vacuum leaks. Im not sure which o-rings exactly you are referring to, but the gaskets around the float bowls look good and the o-rings on the pilot needles looked good. Thats about all I saw. I replaced the pilot hole rubber plugs. Because of a split spark plug cap, I just bought a used one from a 92 bandit from ebay for 40$, got both of them. I hope that it works. It seems like that break between the plug cap and the wire could be a problem. I try putting it back together but it doesnt fit real well anymore, doesnt sta together. Oh and I wanted to ask,   The wires coming from the harness to the coils, Its very possible that they are mixed up. How do I know which goes to which post on the coil?

[halamadrid]

HEy guys! I have an update. Its been a month or two but I have made some progress. I replaced the bad ignition coil (whether it was the coil or just the frayed wire Im not sure), and its running much better already. THe bike doesnt die anymore and has a much easier time purring at 1200 rpm right where I want it. It has TONS of power now and only very seldom lags for a second.   The reoccurring problem is the idle hovering at 4000 rpm. Im pretty sure that the screw is in the right place because when I first turn it on it sits right where I want it. And even for a while and the first few stop signs it drops down perfectly. But it seems that after it heats up it is much more prone to having the idle stick really high.  I am happy because it is now much more responsive and no longer dies on me at stops. But Im not sure what the possibilities are on this hovering. Is a vacuum leak the only one? and if so, where could the vacuum leak be besides the carb intake boots?

Thanks a ton

[halamadrid]

Its over, the bandit runs great. It was the ignition wire like someone had told me. Thank you! It runs really well now Im so happy. Listening to it now it sounds like it has a lot of tap tap tap meaning it might still need a valve adjustment but its a lot easier to listen for small problems when it stays running

[stormi]

Yay! Congratulations!

Give that old girl a good bath to let her know how much you appreciate her new good behaviour (watch the ignitor box though! )

[halamadrid]

so how do I care for the ignitor box?

[stormi]

so how do I care for the ignitor box?

Don't spray it directly with a blast of water.   
It's under the seat on purpose, treat it like the ignition part of your car. 
Spraying it directly is asking for trouble.  As long as you leave the seat on, and don't direct spray directly between the seat and the frame, you should be fine.   No need to anyway, it's not typically the dirtiest part of the bike. :)

[cadwell14]

 :congrats:Mines been off the road recently (intermitently only firing on 3 cylinders).  Carbs changed=no improvement. Coils changed= no improvement. Mechanic in desperation cleaned all the relevant electrical connections (some corrotion present). Success!! Luckily I recently started working at a dealership and the mechanics only charged me beer money.

Been riding it now every day to work for the last 3 weeks. Just love this bike when it's running well. Seriously thinking about upgrading the suspension now.