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Cold Cylinder Causes?
- jonnygorman
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I had followed a model which I found online and as it turns out, not everything on the internet is accurate. Go figure. So, instead of connecting all 4 tubes, I essentially bent two separate tubes, one for carbs 1 and 2, and the other for carbs 3 and 4 and put them on the board. It worked great, or at least according to my readings (which were also done exclusively online). It was a trick to tighten the securing nuts without throwing the synch out of line due to their sensitivity. Other than that, I really have no idea the amount of vacuum that my bike is pulling or is supposed to pull, or how to translate inches of Hg into inches of ATF. At this point I am really only confident that all carbs are pulling equal vacuum. Also, after tuning and a quick joy ride I decided to do the header touch test. All headers were screaming hot, except for #3. It was far to hot to hold your hand on but not as hot as the others. Any ideas regardings causes for this? Carbs were just rebuilt, all carb holders and boots replaced along with air filter. I did the carb float wet test and all levels are equal, plugs are new. Bike runs perfectly in all other respects. The only thing I can think of is pilot mixture screws. I have them set at standard 2 turns out. If the pilot screw for carb #3 is not rich enough, could that cause cooler combustion?
I would appreciate any help.
Thanks
Jon
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- PLUMMEN
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Still recovering,some days are better than others.
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- bountyhunter
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1979 KZ-750 Twin
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- jonnygorman
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Thanks
JOn
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- bountyhunter
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Do you hear the usual idle drop off as you turn the pilot screw in?
1979 KZ-750 Twin
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- jonnygorman
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Jon
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- TeK9iNe
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Pull the carbs off and visualy inspect the throttle slides/butterflys. If you had equal vac on a guage/manometer, and your #3 bore is completely/almost closed entirely compared to others, then there is an air leak downstream throwing off the vacuum.
And this makes the cylinder not fire, yet register equal vacuum.
Seen it many times...
GL.
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- TeK9iNe
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Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering. I set the pilot screws at two full turns out and then synched the carbs. It's possible that the pilot screw might be out for whatever reason and also possible that I bumped a synch adjustment screw/nut after synching. I will report when rectified.
Jon
A change in vacuum corresponds to a change in mixture (either concentration or content), which corresponds to a change in cylinder power output thus you hear the change in rpms.
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- Patton
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Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering....
Bountyhunter has a twin cylinder KZ750.
Good Fortune!
1973 Z1
KZ900 LTD
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- bountyhunter
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I set my pilot screws about 2T out. Fully warm up bike, set to idle. Turn screw in until it just starts to drop off from being to lean (note position) back out until idle smooths out (note position) back out a little more until it gets too rich (it will start to run unevenly). Optimum setting is typically about 1/4 to 1/2T out from where it starts dropping lean. I fine tune in that range to get smoothest idle at highest RPM.Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering. I set the pilot screws at two full turns out and then synched the carbs. It's possible that the pilot screw might be out for whatever reason and also possible that I bumped a synch adjustment screw/nut after synching. I will report when rectified.
Jon
Go back and forth left side to right to get best settings.
NOTE: I bench sync the throttles first using the smooth end of a very thin drill bit to get an accurate butterfly opening position on each one.
1979 KZ-750 Twin
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- bountyhunter
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True, I never tried ear tweaking a four.jonnygorman wrote:
Bounty hunter, how do detect vacuum change by ear? That seems like an art I would be interested in mastering....
Bountyhunter has a twin cylinder KZ750.
Good Fortune!
1979 KZ-750 Twin
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