View Full Version : cylinders #1 and #2 running rich
So I just got this 86 zl900. I am completely in love with this bike. At partial throttle under load it sputters and loses power. It feels like fuel but i'm not sure if it's a lack of it or too much. The carbs are spotless and just synced em with merc sticks. Those two cylinders don't share a coil so that's not it. 3 and 4 plugs look absolutly perfect. It's got pods and a very open exhaust. I'm not sure if the guy advanced timing or not. It feels like it's loading up cause it gets worse till I hammer on it then it "cleans up" a bit. It's real bad with a passenger. Could this be float height possibly due to the bike leaning that way all these years on the kick stand? It has to be jetted because 3 and 4 look so good right? I'm looking for insight. It runs so smooth everywhere else. Thanks in advance for any help. I've already learned a ton about this bike reading and searching this site. Oh, on a side note when I fueled up yesterday, I tried to blow through the breather nipple on the gas cap assembly and it was very difficult to blow through so I'm going to clean it today. Could that be it? But why only one and two?? And why rich?
zlMark
06-17-2009, 05:24 PM
Don't know,, sounds like a lean misfire to me
Hmmm....why would I have 1&2 slowly fouling and 3&4 looking beautiful if I was running lean? The carbs are all synced too. I cleaned the tank vent just because it needed it. That didn't help (I assumed it wouldn't) But it needed to be done.
Are 1&2 maybe oil fouling? You'd probably notice smoke or at least smell it tho...
1 and 2 don't share a coil, but they are right next to eachother in the block, so a blown headgasket, cracked head, or cracked cyl wall could result in them going out together...
Do a compression and leak-down check ...
just ideas to fuel the fires of thinking...
Are 1&2 maybe oil fouling? You'd probably notice smoke or at least smell it tho...
1 and 2 don't share a coil, but they are right next to eachother in the block, so a blown headgasket, cracked head, or cracked cyl wall could result in them going out together...
Do a compression and leak-down check ...
just ideas to fuel the fires of thinking...
No smoke, no coolant on the plugs. It runs absolutely flawless and sounds great aside from this little messed up spot. I'm pretty certain it's none of those things but any new ideas help.
I am taking it apart right now. I took the carbs off and drained them. For some reason I stuck my finger in the #1 carb and lifted the piston. It did not return all the way down on it's own. Hmmmmm......the rest do. The plugs aren't really fouling but 1&2 have carbon on them as 3&4 are nice and tan. Perfect really.
I'm willing to bet this sticky piston is causing my light throttle under medium load blurble.
I'm going to check my float heights, clean the carbs again, make sure all the pistons slide nicely, re-assemble, sync, and see where I stand. Is there any recommended lubricant I could use on the slides?
lowlife
06-18-2009, 04:55 PM
alight polish with a very non abrasive action to it, such as 0000 steel wool. 1000 plus sandpaper, light scotchbrite. etc...You should not need a lube on the slides. Might be a build up too
I was thinking along those lines. I'll report back with the outcome......
zlMark
06-18-2009, 10:43 PM
The only thing 1 and 2 share is the bowl vent, have a look
The only thing 1 and 2 share is the bowl vent, have a look
Keen thinking... Totally slipped my mind.
paulfun
06-19-2009, 04:50 AM
Are the carbs all stock?
Are the carbs all stock?
They are jetted.
The sticky slide seems to have fixed my issue. I've gotta grab a chick and take her for a spin to make sure more of a load doesn't still suck but it feels great !! I'm going to re-sync later too and see how the plugs look too.
SnakeDoctor
06-19-2009, 11:06 AM
As long as she does,,, then it'll be a good ride anyway.
lowlife
06-19-2009, 09:13 PM
They are jetted.
The sticky slide seems to have fixed my issue. I've gotta grab a chick and take her for a spin to make sure more of a load doesn't still suck but it feels great !! I'm going to re-sync later too and see how the plugs look too.
Make "er a biggin!!!!!!!!!
Ok, I've been busy but here's where I am at with this issue. Fixing the stuck slide made it run better. I still have the problem though. I took a girly for a ride (no bigguns ;) this one weighs 130lbs) and I still have the miss under load. For the hell of it, I choked it while it was happening and it nearly cleared the problem right up. So, it's obviously a lean misfire like someone said earlier in this thread. So, How do I remedy this problem. I don't think she's lean through the whole power band. Do I need to go with a bigger main jet or shim the needles??
I'm no carb expert, but from what I understand I think needle height is what pertains to mid range/medium load.
Main - High RPM WFO
Needle clip/height - midrange
Pilot/slow jet - off idle
air screw - idle/off idle?
Am I close guys?
I believe your correct. I think I need to raise the needles.
I believe your correct. I think I need to raise the needles.
Worth a shot, just kind of a pain in a** to do... Are you just running straight pipes/open header or something? Kinda curious if you could let me know what size mains you are running while you're in the carbs, and where you end up setting the needle clip position. I'm going to be in the same position as you, trying to tune carbs this week.
Thanks! :hello2:
I can have the carbs off and stripped in 20 mins. It's not hard. I will post up my configuration when I get it right. I've got pretty much straight pipes with a cross over pipe and little baffles on thge end. It's very loud. It's a mx3 exhaust, Pods, and I'm not sure of the jets yet.
I can have the carbs off and stripped in 20 mins. It's not hard. I will post up my configuration when I get it right. I've got pretty much straight pipes with a cross over pipe and little baffles on thge end. It's very loud. It's a mx3 exhaust, Pods, and I'm not sure of the jets yet.
The carbs aren't that big of pain for me either, pods make it simpler, but my only gripe is the d*** throttle cable. Sometimes I get lucky and get it within 5 mins, one time I bet I spend 20 mins just f***** with that stupid thing...
The carbs aren't that big of pain for me either, pods make it simpler, but my only gripe is the d*** throttle cable. Sometimes I get lucky and get it within 5 mins, one time I bet I spend 20 mins just f***** with that stupid thing...
Yeah, why in the middle? Also, why no hole in the frame to easily access the middle sync screw?
Anyone have any idea where I should be shim wise? I remember there are three in it right now. Two are larger diameter silver ones and the third is a smaller diameter gold one. I'm not sure what stock is.
zlMark
06-23-2009, 04:48 PM
This would take alot of guesswork out of it and give you real horsepower. My next purchase: (maybe, I know someone who just bought one :biggrin:)
http://www.sudco.com/tool.html#005-200
This would take alot of guesswork out of it and give you real horsepower. My next purchase: (maybe, I know someone who just bought one :biggrin:)
http://www.sudco.com/tool.html#005-200
I'll write up a real nice tech doc for ya if you convince him to let me borrow it.... :laughing7::laughing7:
zlMark
06-23-2009, 08:00 PM
I'll write up a real nice tech doc for ya if you convince him to let me borrow it.... :laughing7::laughing7:He's a lurker here,, I'll bet he gets a good laugh :laughing7: :hello:
He's a lurker here,, I'll bet he gets a good laugh :laughing7: :hello:
Well, when I notice him reply to this thread, I'll be sure to PM him my address so he can ship it out... :rotf::rotf::rotf::rotf::rotf:
This would take alot of guesswork out of it and give you real horsepower. My next purchase: (maybe, I know someone who just bought one :biggrin:)
http://www.sudco.com/tool.html#005-200
Tempting ..... I guess I'm going to add a shim. I've got a lot of small washers here at thye shop. Any one care to speculate what a good incriment to start with would be. I've tuned stand alone with a laptop but tuning carbs is new to me.
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