TOPIC:

Hi folks. I recently picked up a 94 kz1000 police bike. It runs well, except when taking off from a stop. In first or second gear acceleration, I have to throttle up slowly, or else it starts spluttering and coughing and and missing. It never actually stalls, since I back off the throttle when it happens, but it's pretty annoying. If I throttle up slowly and smoothly, I can get it opened up pretty wide with no problems. The stuttering seems to be caused by how fast I open it up, more than how wide I open it eventually.

Some background on the bike. The coils are stock--I tested the coil secondaries, and they have the proper resistance. I changed the plugs with the stock NGK plugs, .030 gap. And I changed the wires with short car wires I picked up from autozone. The ends of the wires that attach to the coil are made for car distributor caps, so I squashed them down so they make contact with the pins on my coil secondaries. I tested the spark on all 4 wires with a spark tester, and no problems there.

Any ideas what might be causing this problem? A friend at work mentioned that it might be the engine flooding from over-rich accelerator pump jets in the carbs...

Wasn't aware the BS34s on the cop bike had the accelerator pumps... more likely the pilot circuit is either dirty where there is some obstruction or more likely, the idle mixture is not correct. You didn't mention whether you had the stock airbox/filter and/or stock exhaust. Aftermarket air filters or pipes can lean the mixture and the bike may not have been properly jetted (pilot jets/mixture screw adjust).

Thanks for the reply george.

You are prolly right on the lack of accel pumps...that was just a guess by a friend who doesn't know these bikes.

The exhaust and airbox are totally stock. As far as the mixture screws, I'll definitely check that out. I no longer have my vacuum balancer, but I guess I can go to a shop for that.

Would you say the above symptoms point to "too rich" or "too lean" on the idle mixture?

Edit: since it is the idle circuit we are talking about, I guess I should also check my plugs to see what they look like. I'll do that too.

Post edited by: rpsmith, at: 2006/06/13 18:57

Update: I checked my plugs. They are indeed on the rich side. I found that the idle adjustment screws were backed off about 3.5 turns each. I've backed them off an additional 1.5 turns, but no significant improvement yet.

However, I do think this is on the right track. When I try using the choke a little, the problem just gets worse...So it looks like it needs to be leaner. Also I tried richening the screws down to 1.25 turns out absolute, and then the bike was barely able to idle at all.

Rich = too much fuel/not enough air
lean = not enough fuel/too much air

I believe you lean out the idle mixture by screwing those screws IN, make sure your counting 360 degree rotation, not 180 degree. 5 turns out is way too much. be careful you may loose those screws with this setting!

I've played around with idle mixtures a lot, and I never noticed any huge difference no matter what I do.

There is something strange going on. Since you haven't already, I would completely go through the carbs, you would be surprised what messes others will leave for you in there. Please inform us of your jetting, esp. the pilot jet setting. Also check that your ignition timing advancer unit is working correctly.

Here are my list of suspects
1.) Fuel system not delivering gas quickly enough
2.) obstruction in pilot jet system
3.) Weak ignition system (need more power to light chamber up and self-clean plugs, check coil voltage)

Looking at your post again, I definately think your ign system is suspect. Weak ignition can mask a too rich condition nearly exactly.

Peter

Hi Peter, thanks for your reply. I moved this topic up to the engines forum, because I didn't know if it was carbs. I've got some extra info there, too--check it out, please help if you have ideas:

kzrider.com/component/option,com_joomlab...ew/catid,2/id,55620/

The problem goes away if I remove two spark plug wires--any two wires, so it's not any one cylinder or coil. I can't understand why the problem would stop under these conditions, so I'm at a loss to understand what's causing it. I tried wiring the coils straight to the battery, but no luck there.

I just know I'm going to get scolded for this, and of COURSE I'm going to look like an ass because this is my first post.

I bought a Honda XR100R as my first bike to learn on. I bought her for 700 smackers, and she couldn't handle a hard throttle pull. You had to twist her little bit by little bit and wait for the revs to climb.

I took off the carb and soaked it in carb cleaner. It seemed to lessen the definite lag and lack of umph. Then I took off the carb and took OUT the needles and jets and things, and cleaned it like I was supposed to in the first place (D'oh).


My tentative two cents of help is... Didja clean the carbs...? (ducks in anticipation of projectiles)

No, I didn't clean the carbs. I just pulled them last night and they are soaking in doesel now...I'll be taking them apart soon.

After going through the complete pain in the ass of pulling the carbs out past the airbox, I'm definitely getting uni pod filters. Even if they run slightly more erratically, it is more than worth it. So I'll be rejetting one jet up on the mains (and keeping the pilots the same) as suggested by the "Simple jetting advice" doc in our filebase:

kzrider.com/component/option,com_docman/...d/gid,212/Itemid,45/

I have a feeling you're right about dirty carbs being the problem, but I still can't quite explain why...given the behaviour I described in my other thread:

kzrider.com/component/option,com_joomlab...ew/catid,2/id,55620/

Yeah, I read that...!

My XR100R (air cooled, mind you) did that once. It began splutterring like it was sick and when I pulled the clutch it cut out on me. The next day the bike was fine.
I think it was because the mixture was a bit off (lean?) but what I DO KNOW for sure, was that it just overheated, which I heard a lean mixture would lead to, but I'm not sure about a rich mix. I guess that's yet another thing to look into, lean or rich?

I'm going to guess that, whenever you take away the load of two pistons, they stabilize because you're taking away some of the gas appetite, therefore turning a too-lean mixture to an "about-right" one? I know all you did was pull the spark plugs, but if a gas engine tries to "diesel" combust without a spark, not all the gas is run out of the piston, is it?

Which means it wouldn't try to draw in much gas. (rhymes with "I'm talking out of my ***)

The main differences I see between your issue and mine, is, well, sh**, mine was a 100cc single banger, and yours is a much larger 4 cylinder! That, and my "little dirty" got better when I detented or fully choked the intake. Another clue it was lean. But you said it got worse when you choked it...?



Let's hope it's just the carbs, firstly because then "it was just the carbs!" and secondly, so I'll be right about it

Good luck!

Post edited by: DrewDunnit, at: 2006/06/22 12:50