77' KZ750 - Leaking fuel, stalling and running on

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12 Jul 2011 18:17 - 12 Jul 2011 18:23 #462499 by Tested
KZ 750B2 - 1977

I bought this bike last week and I love it already. It has some problems. Oil leaks from the tach input, some asshole that had bought and returned it put sugar in the tank, oil leaks a lil from the oil pan.

It's been running after I cleaned the tank and put a shop towel on the tach cable. The oil leak isn't bad so I just make sure it has oil.

But today she almost gave up the ghost on me.

I was cruising at about 75 when she started running really rough. I pulled into a lot and it looks like she is only running on one cylinder and there is gas leaking from the same side carb.

I have driven the bike 500 miles since I got it with no problems. Does anyone have any suggestions on this? I am thinking a carb rebuild kit and an engine gasket set from Z1 as soon as I can afford it. The better half let me buy it cause it is supposed to be my daily commuter.

Here are some photos of the two plugs I pulled out if it helps. The black one is from the side that isn't running right and is leaking fuel.
















2008 KLR 650

1977 KZ 750

_____ Have had _____

1981 KZ 440
1970's CR 125
1982 KLX 175
Last edit: 12 Jul 2011 18:23 by Tested. Reason: Add pics

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12 Jul 2011 19:12 #462506 by 650ed
It sounds like a stuck float valve - no big deal, just pull the bowl and clean the float valve needle & jet and see if it stops leaking. If that's all it is you don't need to remove or rebuild the carbs; you can remove the bowl with the carbs still on the bike. Oh, and buy some spark plugs; what are those things from a lawn tractor? :laugh:

1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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12 Jul 2011 19:26 #462510 by Tested
I pulled the bowl off and it had some sugar in it so it's possible that it got in there and messed things up. Yea I was looking at the plugs and wasn't sure what they were.

What kind of plugs do these things take?

2008 KLR 650

1977 KZ 750

_____ Have had _____

1981 KZ 440
1970's CR 125
1982 KLX 175

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12 Jul 2011 19:29 #462511 by 650ed
If you have the owners or service manual they will show which plugs to use, otherwise maybe someone here with a 750 twin will chime in. I would definitely put a fuel filter on the bike in case there's other crap in the fuel tank. Ed

1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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13 Jul 2011 14:43 #462660 by Rainman
Welcome Tested.
Stock plugs are NGKB8ES or NDW24ES-U.
KZINFO tab at top of page has a list of specs for various models. 1976 KZ750 should be the same as your 1977.

Good luck,
Jim

80 KZ750 H1 - the Kaw calf
79 KZ750 Twin - Miss Nov 2008 KZR calander
79 KZ750 Twin parts bike
78 KZ650 C2 Parts Bike
75 KZ400 Wife's old bike sold
81 KZ440 A2 LTD Wife's new bike
84 Honda 450 Rebel Wife's newest bike
Jim
Quincy,IL

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13 Jul 2011 15:53 - 13 Jul 2011 15:54 #462672 by bountyhunter
Replied by bountyhunter on topic 77' KZ750 - Leaking fuel, stalling and running on
The factory spec for the 1979 750 twins was the hotter NGK B6ES or ND W20ESU plugs. The fours ran the colder B8ES plugs.

1979 KZ-750 Twin
Last edit: 13 Jul 2011 15:54 by bountyhunter.

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13 Jul 2011 23:58 #462750 by Tested
Today I put in new NGK B8ES plugs, a new 3 ohm ignition coil and new wires. I also disassembled the carb (again) and cleaned all the jets and fixed a problem with the diaphragm. It ran great for a little while but it is still leaking fuel from the overflows. Now this is really bad because fuel under the bike is bad.

Is this a problem with the float or with the needle? What happens if I plug the overflow tubes from the bowl until I can get it fixed?

From what I read on the Kawai Twin forum the guys were saying that the B8ES plugs were better for these bikes.

2008 KLR 650

1977 KZ 750

_____ Have had _____

1981 KZ 440
1970's CR 125
1982 KLX 175

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14 Jul 2011 00:28 #462753 by 650ed
Do even think about plugging the overflows! If you do, all that gas will go through the intakes, around the piston rings, and into your crankcase. Bad karma! You need to figure out what's going on with the float valve or floats or you risk a fire. Ed

1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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14 Jul 2011 00:45 - 14 Jul 2011 00:46 #462759 by KZJOE900
Tested, are you getting a flow of fuel from the overflow, or just a drip? If it is a drip it could be your overflow tube is damaged and letting fuel seep out, instead of it being an overflow situation from the top of the tube. If your float level is good then this is what most likely is happening. I just had a crack in my overflow tube which was causing a drip. Thanks to some friends here I was able to find it and solder it (I was careful not to solder the tube shut). On the other hand, if it is flowing out faster then a drip then once again the float needle or float setting is suspect. Just food for thought.

Current project 76 KZ900 (This was a Vetter model)
76 KZ900
81 XJ550H SECA (Current Project)
82 XJ550R SECA
Past:
86 FJ1200
74 Z1900
72 CB450
Last edit: 14 Jul 2011 00:46 by KZJOE900.

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14 Jul 2011 01:04 #462762 by Tested
It's a flow from one tube and a drip from the other. I am really starting to think that it has something to do with the float and or needle.

2008 KLR 650

1977 KZ 750

_____ Have had _____

1981 KZ 440
1970's CR 125
1982 KLX 175

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14 Jul 2011 01:32 - 14 Jul 2011 01:33 #462768 by KZJOE900
I would think a drip would not be a stuck needle or improper float setting. But others here can shed light on that. Therefore, the dripping carb could be a damaged overflow tube. You can take the bowl off and fill it 3/4 of the way with fuel. If it drips you will confirm the tube is damaged. As for the carb having the flow instead of a drip, it is most likely the float setting / needle problem.

Current project 76 KZ900 (This was a Vetter model)
76 KZ900
81 XJ550H SECA (Current Project)
82 XJ550R SECA
Past:
86 FJ1200
74 Z1900
72 CB450
Last edit: 14 Jul 2011 01:33 by KZJOE900.
The following user(s) said Thank You: Tested

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19 Jul 2011 03:31 #463672 by Tested
I rebuilt the carb and over adjusted the floats. But hey it doesn't leak. Now just to set the floats right and I should be good to hook.

Thanks for letting me know what happens if the overflows are blocked. You guys educated me and several of my friends that are new to this stuff.

2008 KLR 650

1977 KZ 750

_____ Have had _____

1981 KZ 440
1970's CR 125
1982 KLX 175

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