Another 400 carb issue

[Wrider]

So wait, I'm still back on one of your earlier posts.
You said you pulled the plugs from Cyls 2 and 3 and it had no effect on the idle?  As in they were out of the cylinder head?
If that's the case your problem is an internal engine one.  As in top end is screwed up.

Otherwise I'm going with that cylinder isn't getting fuel.  Did that plug smell like gas when you pulled it out? 

[OfTheSwamp]

So wait, I'm still back on one of your earlier posts.
You said you pulled the plugs from Cyls 2 and 3 and it had no effect on the idle?  As in they were out of the cylinder head?
If that's the case your problem is an internal engine one.  As in top end is screwed up.

Otherwise I'm going with that cylinder isn't getting fuel.  Did that plug smell like gas when you pulled it out? 

Sorry I should have explained that better.

When I "pulled" them, I just plug the plug cap off to deny it spark, I didn't remove the plugs from the head.  Since I was pretty sure that cylinders 1 & 2 (not 2 & 3) weren't working anyway, I yanked their caps one at a time to see if it impacted idle.  Since neither of them did, it just adds to my evidence that they weren't firing at all.

[As an aside, I did run it briefly with the #2 spark plug pulled out (when I was checking to see if it sparked), and the engine actually ran better with the plug completely out of the block.  This makes me think that its still holding compression, and with the plug removed there wasn't the resistance from that cylinder holding it back]

Since then I've realized that #1 is firing sometimes, but not others.  I can't pinpoint what causes it to start or stop firing.  I'm also shocked that the engine will even run when only two cylinders are firing.

Now that you mention it, the spark plug in #2 wasn't even wet with gas when I pulled it out on several occasions, so you're probably right that its not getting fuel.  I'm pretty sure at this point I'm going to have to pull the carbs out and see what the hell is going on, but I'm not looking forward to it.  I'm first going to call up the mechanic and ask him what he did a couple of months ago.

[Wrider]

Honestly pulling the carbs on these bikes isn't bad.  And once you have them off, check your float level and the needle to make sure nothing is clogged up.  It sounds to me like the fuel is in the bowl but isn't enough to be sucked up in the jets when you open it up.

[OfTheSwamp]

Honestly pulling the carbs on these bikes isn't bad.  And once you have them off, check your float level and the needle to make sure nothing is clogged up.  It sounds to me like the fuel is in the bowl but isn't enough to be sucked up in the jets when you open it up.

I know its not that bad,  I've done it several times before but its just a huge pain to get it apart and back together.  I hope its as simple as the float level being off.  That was also most of the point of taking it to a mechanic was to get all those little details set right so I didn't have to mess with it.

The biggest problem with working on it is that I don't have a good workspace.  I don't have a garage or even covered parking to work it, let alone a driveway.  I would pull the carb out and drag it inside my place, but the apartment would reek of gas for a week and my roommate would kill me.  I'll probably arrange to use a friends garage nearby and hope I can figure it out in an afternoon and ride it home.

[aNiMaL]

I've been having the same problem lately.
Bike broke down , luckly only about 5 mile from home, but took me an hour to get back, in short bursts.
get it running ( all spluttery and having to keep revs high , ) get a short way up the road for itto die again ,and then not start for 5 min.

Did a splash test and #1 did not sizzle,
I changed the plugs and it seamed to be running ok again.
I did test all 4 for spark , as it seamed like it wasn't running on at least 2, maybe more when i last rode it ? .
Did the splash test on the down pipes and all 4 sizzled, got the bike out me back gate and forgot to put it in neutral first befor putting the stand down, so it cut out .shut the gate, started it back up, and now #1 is not sizzling again.
Thing is it sounds like its running fine, revs up and all .
Gonna check the carbs yet again ( had probs with them when i first got the bike .)
Cant take it for a test ride after yet though, as me left fork seal is shot , leaking oil all over the place, which has killed the brake pads on that side :(.
Friggin bike is driving me crazy.
First bike in 20 years, and its spent more time sat in garden in bits than under me,No money to fix it  and im now missing the little amount of sun we get here in the uk .

[rider123]

I know this sounds weird but I had an old GS650 that had a coil go bad. WHen the bike was colder it was fine but as soon as the engine heated up enough to get the coil hot it lost spark. When the bike goes tits up do you get spark on all cylinders? My suggestion is wait for a day which is super nice drive the bike around your house until it dies. Then check every cylinder for spark. If all spark fine, great you just eliminated that type of problem and can concentrate on fuel/air. For fun I would also check to see if your breather hose to your fuel tank is not clogged. When the bike dies next try opening the fuel cap. IF you hear a whoosh or a pop than what is happening is that there is not enough air to displace the lost gas in the tank and vacuum is starving the bike of fuel. You could also run around with the gas tank cap open a bit to see if that goes away. Also that plug you pulled looks pretty rich to me or is not getting a strong enough spark.

[OfTheSwamp]

Sorry to resurrect my thread, but I've finally had time and good weather to work on the Bandit.  I also lost a little motivation to work on it because I bought a '98 Bandit 600 back in April and have been having a blast with it.

Anyway, I'm basically back to where I was in my last post from the previous page.  In the last few days I have:

- Recharged the battery, it was a little low from sitting too long.
- With no gas in the tank, I sprayed some carb cleaner around the air intake and it fired right up.  It only ran for a few seconds so I wasn't able to determine which cylinders were/weren't running.
- Replaced all of the spark plugs with brand new ones I had from awhile back.
- Drained as much gas as I could from the carbs and gastank, then added fresh gas.
- Removed the carbs yet again, check for obvious blockages and then put them back in place.
- With bike fully assembled, gastank restocked, battery charged, and ensuring gas in the carbs, I got it to fire up pretty easily.  At most it was only running on 3 cylinders (1,2,3), and dropped to just 2 (2,3) after idling poorly for a minute or so.  After that it would not stay running for more than a few seconds and was still only firing cylinders 2 and 3.

To do:
- Find adapter for compression tester, I didn't research thoroughly and mine doesn't fit in the plug holes.
- Find better way to determine if the plugs are sparking.  I can pull them out and watch, but I'm never sure whether they're going or not.

Questions for y'all:
- I've got the pilot screws set to that ridiculous 5 turns out the previous mechanic left them at, is there a way to determine a more optimal setting?
- Same goes for the idle adjustment screw, I left it set to basically zero throttle opening.
- How accurate are the resistance tests on the ignition coils?  Both of them are well within spec.
- How long would it take with the bike running for a spark plug to get fouled if it were receiving gas but not firing?  I only had the bike running for a minute, maybe 2 cumulatively, but when I checked the #4 cylinder, its plug was clean as a whistle.  The carb attached to it had gas in it.

[Red01]

You can verify the plug is getting the voltage to spark with an inductive type timing light.  Just put the pickup over the plug wire in question (when running) and if the timing light will strobe when the trigger is pulled, that plug is getting power.

[strykersbane]

This sounds like a ridiculous question, but it happened to me so I'll ask. Did you check to make sure that the connectors at the coils are good? I put my 400 away for the winter and when I went to get it running in May (with SeaFoam in the gas and a fresh oil change) it was running worse then I've ever seen it, and since I basically rebuilt the bike at this point that's saying something. I resynched the carbs, replaced plugs, checked over the whole bike and basically couldn't find the problem. My dad happened to reach around the tank while we were synching and bump on of the connectors on the left side coil and all of a sudden she ran great. I checked and the connectors were all gunked up. Some sandpaper and some contact cleaner as well as some dielectric grease cleared up the problem, and aside from a couple hicks (I'm pretty sure one of the PO's damaged the top end a bit, and just don't have the money or time right now to take down the top end and check it out) the bike runs like a top. Got rid of a hesitation around 6k as well. Just a basic thought that I'd overlooked. Worth checking.