new to board...running on 3 cylinders

[Mick77]

Hey guys.  Man am I glad I found this site.  This is my first post, so I'll be as specific as possible about my problem.  I bought a non-running 1991 Bandit 400 (us version) for next to nothing, from a guy I know, that needed a carb overhaul.  I had the carbs rebuilt and adjusted, and it ran ok for about a week or two... It ran really rich, smelled pretty bad like gas, and started making sticky residue at the bottom of the end of the pipe sortof an amber color.  (?)  I ran it out of gas (the speedo doesnt work... I know, you don't have to say it) and after that, it hasn't run the same since.  After getting it running again, replacing ALL the spark plugs, and running some Techron in the tank, it still runs only on 3 cylinders.  So, I took it back to the mechanic so he could check out the carbs to make sure there was no debris clogging any jets or anything.  He checked it out and said that #1 cylinder only has 90psi compression, when its supposed to have like 114 or something like that.  He suggested a valve adjustment, but sent me home with it because I didn't have the money to pay for the valve adj.  It's my only mode of transportation, so I have been forced to ride it to work (again, I know it's prolly a very bad idea).  It seems to do "ok" at highway speed, just underpowered.  The pipe for #1 heats up like it's doing SOMETHING, but not nearly as hot as 2-4... not even close.  This morning, I was on the freeway cruising at 65-70mph, and it started acting like it was running out of gas, so I pulled it over to the shoulder and hit the kill switch and rolled to a stop... Stupid vacuum petcock wont pick up if you run it dry, without a shot of ether or WD40 down it's throat, as I'm sure others have found out.  So I open up the tank and there's still about 1/2 left, so I tried to start and nothing.  Gave it about 1/4 choke (which I never have to do) and it fired right up like magic.  Rode it the rest of the way to work running like it did before.. on 3.5 cyl.  Just for reference, the temp here this morning was about 85, and my commute is approx 35 miles.  Incident happened at about mile 30.  Hope I have been specific enough, and I apologize for the length of this post.  Just wanted to cover all the bases.  Thanks in advance for any thoughts on this problem child B4.

[mademiriam]

Sorry I can't actually be of help to your problem why #1 isn't running right. I have guesses but the others on this board should come to your rescue in a much more professional way.
As for the vacuum petcock not working if you have run it dry, this has never been an issue for me, try setting it to 'pri' for prime position. Just for a bit after you refill the tank, that will make the petcock flow even when there is no vacuum on the line.

[Mick77]

For some reason, mine only has Reserve and On... no Prime.  I'm not sure why, I'm 99% sure that it's the factory part, so maybe mine's just an oddball....which would explain my woes, haha.

[PitterB4]

First...   

Just a couple things for you...

There is no marked PRI position on the petcock.  Functionally, PRI is straight up.  You may have to take out a screw that is blocking it from going up there.

For the valve adj...  if you have ANY mechanical skils, some basic tools and a shop manual, you can do it.  Hell, I only had those last two things and still got through it!  The shop manual should be downloadable somewhere.  Search this forum.  I think someone was talking about it recently. 

HOWEVER... I'm willing to bet you have a carb issue or two going on.  First... read through some of the posts here just from the last couple days.  O-rings are probably shot.  Pulling everything apart to clean the carbs probably made the brittle little things worse.  That obviously allows fuel to go places it shouldn't possibly causing the rich conditon you describe.  Also...  having previously been a non-runner for whatever period of time, your tank undoubtedly has a ton of crap in it.  Running the tank all the way down, even with the petcock filters in there, probably drew a whole bunch of new garbage, including rust that had settled down there, down into your nice clean carbs.  Since it was running OK before running it out of gas, that seems like an obvious place to start.  Techron or Seafoam don't do much on all the little particles of rust that get down into the carbs and block stuff up. 

Just some thoughts...  Good luck!

[Mick77]

  for the welcome.
That would make sense that I couldn't find the Prime position.. I'll have a look at it when I get home this evening.  One thing I forgot to mention about the work done so far was the tank treatment.  It was taken off and stripped down and treated with a 3 part sealant... however, the fuel valve wasnt cleaned out... so i havent ruled out the debris clog.  I need this bike back up and running asap, (and I need it done right, so as to be reliable) so this valve adjustment is gonna be a paid for type job.  If it still doesnt run after the valve adjustment I'm sure you guys will be the first to hear about it, and I'll be stripping the carbs again.  OH, carbs... everything was replaced in the carbs- all o rings and bits and pieces when they were cleaned and rebuilt.  Are all B4's this much trouble??    Thanks for the input, and I'll keep you posted on progress

[mic_c]

Hi mick77, have you solved the 3 cylinder problem?...I just bought my 91 b4 last week and its been running great...I never would have thought it was only running on 3 cylinders, but touched the downpipes and cylinder 1 doesn't get hot...i removed the sparkplug and there's spark...hopefully you can help me out...thanks

[andrewsw]

mic_c, welcome. First, to get the best help, you should probably start your own thread (or new post or whatever we call it here) to improve visibility.

What were you doing when you noticed that #1 wasn't firing? I have found that a bike that runs just fine under acceleration will sometimes not fire one cylinder when idling. Of course, That's not *right* but it happens. If #1 was still cold or cool after some running, then you've got a real problem instead of just an annoying idle mixture issue (for example).

How did you test for spark? (we don't know your mechanical ability, so fill us in on exactly what you did).

The coil that fires #1 also fires #4, so check for spark on #4. If you have spark on one but not the other, the first thing to suspect is the wire. You can pull the end off the wire, cut it clean and replace the end. That may be all it takes. If that doesn't work, then move up to replacing the whole length of wire. If there is *still* no spark then you're looking at a bad coil or possibly (?) a cdi that's giving you fits, but I don't know about that one.

You can swap the coils to see if the problem moves with the coil or stays with the cylinder. That would clue you in to whether it's the coil or something else. Of course you can't run with the coils in that configuration...

hth

A

[mic_c]

thanks andrew...the bike was just idling when I noticed it...I guess I'll try again when I get the tank back on...I'm in the process of painting the tank and plastics...

tested for spark by grounding the plug to the frame...owned a bike before, but always brought it to the shop, this is the first bike i'll be trying to do all my own work on (hopefully)... glad I found this site

[Mick77]

After all the trouble I went through to figure it out, it turned out to be a plugged pilot jet.... it needed a valve adjustment anyway... doh!  You've come to the right place for help and answers, by the way.  Great info, great people, great site.  Hope you enjoy your B4, I love mine.. even though there's always something