SHIGGSY
Expert Class
Posts: 128
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posted September 08, 2007 11:26 AM
Idle bottoms out at 1000rpm
Fiddling with the bike today I noticed that the lowest my idle speed will drop to is 1000rpm, which in itself is not a problem but I'm curious as to why it is as it never used to be. Checkng the throttle body plates, they all seemed to be completely shut and unobstructed, TPS is set and throttle bodies are synched. The vacuum on the throttle bodies does read around 26cmhg when the manual says it should be around 19.5, but I don't know what I can do about that. If i wanted to set the idle lower, how would I go about it given this situation ?
Incidentely, regarding the TPS setting, if anyone asked me what the standard range was I would have replied 1.084-1.086 volts at 1000rpm as per the manual. But thats the First Edition manual (the one that floats around the internet), I have the Third Edition manual and it's different, I never noticed before because I always knew what the setting was and never referred to my manual. Standard setting for the TPS is a calculation dependent on the input voltage. My input voltage is 4.98 so the calculation is 1.07 x 4.98 / 5 =1.065.
  
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ninja12
Needs a job
Posts: 3310
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posted September 08, 2007 05:31 PM
Don't know what's causing your problem, but I'd be careful idling the zx12 that low even testing. Put a oil pressure guage on it and you won't care if it never goes below 1200.
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shiggsy
Expert Class
Posts: 128
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posted September 09, 2007 11:32 AM
 Edited By: shiggsy on 9 Sep 2007 12:35
Well, I got the ability back to set the rpm below 1000rpm. Pulled the throttle bodies and drilled all the bypass caps to check the turns on the screws as I have read in the archives they can be variable. Mine were all closed, even though I knew it would raise the rpms, the opposite of what I required I opened them up 2 turns for a look see.
I then backed off the 3 adjustment screws fully. This leaves throttle plate 1 fully closed, plate 2 slightly open, plate 3 slightly more open and plate 4 open further still. Screwing in adjustment screw 1 closes plate 2 untill its fully closed at which point it starts to lift plate 1. The same all the way down, screw 2 closes plate three and the starts to open plate 2. I set them all so that the moment the neighbouring plate started to lift I backed off 1/2 a turn.
Below each adjustment screw is a smaller adjustment screw. I couldn't really work out the purpose of these. When a main adjustment screw is turned in enough to meet one of these screws then all 4 throttle plates start to lift in unison. Hence why I couldn't synch below 1000rpm. I backed all these out and left them.
Put it all back toegether and fired her up. Tickover was 1200rpm and there was a loud hissing sound. I screwed the bypass screws back to the fully closed position, hissing dissapeared and the tickover dropped below 1000rpm. Synced the throttle bodies (which were pretty close) and reset the TPS and put the idle back to 1100rpm.
Result. tickover seems to have developed a bit of a harsh knock which mostly dissapears when the clutch is pulled in. Out on the road she fine, really smooth apart from the 1800 - 2100rpm range which is really jerky on a closing partial throttle, but that seems to have reduced a tad. She still backfires, and blows back up the inlet pipes and compression locks on start up if given any amount of throttle (i.e. enrichment lever).
Think I have a clutch issue and maybe the cams are out by 1 tooth or something because the compresion locking thing must be a timing issue ? Still, gives me something to do next weekened.
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entropy
Moderator
Posts: 8671
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posted September 09, 2007 01:44 PM
quote:
Don't know what's causing your problem, but I'd be careful idling the zx12 that low even testing. Put a oil pressure guage on it and you won't care if it never goes below 1200.
BIG 10-4!!!
having the capabilty of idling below 1000 may be cool, but i would NEVER let a 12 idle that low.
As Ninja says, the oil pressure goes thru the floor. Bad ju-ju, indeed.
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shiggsy
Expert Class
Posts: 128
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posted September 10, 2007 12:11 AM
Yup I would never have the idle below 1000 rpm, I usually have it minimum 1100rpm. On my 15 mile ride across the city this morning the stu-stu-stuttering I get at 1800-2100rpm has greatly reduced, still there but nowhere near as bad as it was. Just feels like a twin at tickover at the moment though, especially with the clutch out.
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shiggsy
Expert Class
Posts: 128
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posted September 12, 2007 12:07 AM
quote:
Just feels like a twin at tickover at the moment though, especially with the clutch out.
Next day tickover got worse but the bike ran better. In the evening I spotted the tubing going back to the seperator wasn't connected to the #4 throttle body. Pushed it back on and tickover is back to normal, but the stutter has come back and on the move it's like I have plugged a choking restrictor on to the engine, it span a hell of a lot better with that hose disconnected. I need more air ?
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