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Float bowl gasket?
- TeK9iNe
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Mikuni BS34's with 130Mains, 3rd clip spot on needle, and 37.5Pilots, stock air box, straight pipe.
I've been having a stumbling and "air leak" mimicking problem.
The bike soesnt idle very good, and worse at 1/8 throttle. When I try to pull away slowly, the power is inconsistant and stammery. Once under way its OK, but not super powerful. I've chopped the plugs at an 1/8th, and Cyl. 1,3,4 are nice and tan at the top with a light carbon ring on the metal. The 2 plug is white and no carbon - so I'm starting there.
I just took apart the #2 carb to boil it, and I've found a complete seperation crack in the float bowl gasket.
Is this the magic air leak I was looking for, for so long?!?
If gasket gap not a big deal, then what next. Spark is good, compression 130 cold. Air screws 1 1/2 outish.
Thanks guys...
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
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- bountyhunter
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The carb holders (rubber intake manifolds) are notorious for having leaks. You can also have leaks around the throttle shaft and various places.
The straight pipes are likely what is making it run lean.
1979 KZ-750 Twin
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- TeK9iNe
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The carb holders (rubber intake manifolds) are notorious for having leaks. You can also have leaks around the throttle shaft and various places.
The straight pipes are likely what is making it run lean.
There is only the #2 Cyl. running lean. I replaced the manifold, and gooped it first too. I've also hosed down the entire intake system with wd40, and cant find anything.
These are CV carbs, are you sure about no vac. in bowl?
Thanx for reply.
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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- gane
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[img][/img] 1977 KZ1000A1
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- Patton
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Floatbowl fuel level too low;
Pilot fuel jet clogged;
Pilot fuel passage clogged;
Pilot air jet damaged or missing;
Vac tube to petcock cracked, torn or ill-fitted (if from #2 carb).
Good Luck!
1973 Z1
KZ900 LTD
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- bountyhunter
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I got bit by that one. The holes or cracks in the diaphragm can be very hard to find. I screwed around with jets and needles for a long time until I realized the problem.Oh Yeah. a holed/leaking diaphram could keep slide from rising, and give lean plug reading. luck g
1979 KZ-750 Twin
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- TeK9iNe
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Other possibilities --
Floatbowl fuel level too low;
Pilot fuel jet clogged;
Pilot fuel passage clogged;
Pilot air jet damaged or missing;
Vac tube to petcock cracked, torn or ill-fitted (if from #2 carb).
Good Luck!
Well, fuel level - OK.
Pilot jet - Clean, same as rest.
Pilot fuel passage - Boiled carb, and blew thru them all.
Air jet - passes air at same rate as others.
Vac tube - plugged off, running on prime.
bountyhunter wrote:
You can also have leaks around the throttle shaft and various places.
hmm... maybe throttle shaft...
Gane wrote:
Oh Yeah. a holed/leaking diaphram or escaped return spring could keep slide from rising, and give lean plug reading.
Would this be causing my symptoms at idle - 1/8th? The bike seems to pull ok from 1/4 on...
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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- bountyhunter
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That's exactly where a tiny hole in a diaphragm gets you. At light throttle openings the vacuum differential is small and the piston rise is small.... but if you have a tiny leak, it doesn't rise enough. At higher vacuum difference (where the piston rises a lot) the tiny leak doesn't have much effect.Oh Yeah. a holed/leaking diaphram or escaped return spring could keep slide from rising, and give lean plug reading.
Would this be causing my symptoms at idle - 1/8th? The bike seems to pull ok from 1/4 on...
1979 KZ-750 Twin
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- TeK9iNe
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At light throttle openings the vacuum differential is small and the piston rise is small.... but if you have a tiny leak, it doesn't rise enough. At higher vacuum difference (where the piston rises a lot) the tiny leak doesn't have much effect.
Ah... that makes COMPLETE sense!
Iv'e got it open again, so I'm super checking for this.
Update soon...
Cheers, thanx.
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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- bountyhunter
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1979 KZ-750 Twin
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- TeK9iNe
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There are no detectable holes in the diaphram.
I've had the carbs off, and tested the vacuum slides, with a vacuum, of all things. All the slides rise to exactly the same height at the same throttle position.
There is still a considerable amount of air in the ratio.
The cylinder fires, but the plug stays almost completely white, but for a few splashes of gray on the insulator tip, and the metal base ring never changes condition. The plug is firing, and the pipe gets finger sizzling hot.
Where is the darn air coming from?!? :S
There are no air leaks in the carb itself, if I cover the end with my hand, open the throttle, then suck on the other end, I can't get any air at all.
this is the only thing keeping me from riding this thing.
Does anyone have any more suggestions???
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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Good Luck!
1973 Z1
KZ900 LTD
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