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78 KZ400B Tuning Help
- treitz
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Here is where I am at after about 4 hours of tuning, and $150 in parts...
Exhaust: Stock
Intake/filter: Stock
Jets:
Pilot = 35 (stock)
Main = 70 (stock)
Secondary = 95 (stock = 90) Note: This was jetted up by someone else. Not sure why.
The stock petcock is leaky, so the first thing I did was replaced it with a aftermarket non-vacuum type. At the same time I capped off the vacuum nipple on the carb. I replaced both diaphragms because one was sticking ope (Wrong part installed by some idiot). Carb holders were leaky, so I replaced those two. Checked float level and everything looks good.
All of this said you would think the bike would run like stock. Wrong.
Bike starts up, runs fine off of idle for a bit but bogs majorly at anything above full throttle. Maybe that jetted up secondary is the issue here?
Then if I try taking it for a spin it just bogs, bogs, and bogs some more. Acts like it's getting fuel but not any air.
Like I said, I haven't messed with CV style carbs in a while. Could the capped off nipple be forcing the slides to not slide with increased throttle? I forget how the diaphragms actually operate.
My only other thought is replacing the petcock with a stock vacuum style replacement, and jetting that secondary back down. Just don't want to waste my time if neither of those are likely the issue.
Any input at all appreciated.
1979 KZ400 - 2-1 Manifold - Mikuni VM34
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- Cynjut
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Check the spark.
If you haven't done so, check the timing.
Make sure the mechanical advancer is working correctly.
1977 KZ-1000 A1
1982 KZ-1000 M2 Frankenbike
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- Patton
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Good Fortune!
1973 Z1
KZ900 LTD
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- 650ed
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1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- treitz
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Should I put the gravity petcock back on and cap off the vacuum nipple again, or would you advise a replacement OEM style petcock?
1979 KZ400 - 2-1 Manifold - Mikuni VM34
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- Cynjut
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1977 KZ-1000 A1
1982 KZ-1000 M2 Frankenbike
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- treitz
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Cynjut wrote: That's a personal preference question. Both have their obvious advantages.
I prefer the gravity feed. Just want to make sure that capping off the vacuum nipple isn't causing issues. I've done it before without issue, so I don't think that is where my problem lies.
1979 KZ400 - 2-1 Manifold - Mikuni VM34
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- Tyler
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I found with my 440 that those CV carbs are very touchy, but the run very well if you are thorough in cleaning them. 90% of the time the pilot circuit is problem. Also is the air filter intact? If that has been messed with the bike won't run for $hit.
Oh yeah one more tricky point to the carbs, some of them have a plastic plug over the pilot jet with a small cross hole drilled to pick up fuel from the near by main jet, if those carbs were supposed to have the plugs over the pilot jets the bike will flood out. Again Kawasaki changed that a few times too...
Lastly capping the vacuum port for the pet cock will not affect the operation of the diaphragms.
If I knew what I was doing all the time life wouldn't be any fun.
'80 KZ650 E 700cc, dyna ignition and coils, frame up restoration, daily driver
'81 KZ1300 A3 full restoration, custom big bore pistons, 1400cc 6 cylinder super bike
"77 KZ650 B1 - Barn Find, work in progeress
"74 Yamaha DT 400 Enduro
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- Tyler
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If I knew what I was doing all the time life wouldn't be any fun.
'80 KZ650 E 700cc, dyna ignition and coils, frame up restoration, daily driver
'81 KZ1300 A3 full restoration, custom big bore pistons, 1400cc 6 cylinder super bike
"77 KZ650 B1 - Barn Find, work in progeress
"74 Yamaha DT 400 Enduro
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- treitz
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1979 KZ400 - 2-1 Manifold - Mikuni VM34
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- Tyler
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If I knew what I was doing all the time life wouldn't be any fun.
'80 KZ650 E 700cc, dyna ignition and coils, frame up restoration, daily driver
'81 KZ1300 A3 full restoration, custom big bore pistons, 1400cc 6 cylinder super bike
"77 KZ650 B1 - Barn Find, work in progeress
"74 Yamaha DT 400 Enduro
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- treitz
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1979 KZ400 - 2-1 Manifold - Mikuni VM34
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