- Posts: 23
- Thank you received: 0
Runaway idle but sooty plugs???!
- harmsworthj
- Topic Author
- Offline
- User
Just nearing the completion of my 78 z400A resurrection and having carb tuning trouble. I'm running a 2-1 from a single VM32. It started up right away first time but needed throttle to stay alive. plugs were soaked and oily. But once a little warm then the idle would runaway. turning choke back on brought idle under control. Everything I thought I knew said lean and/vacuum leak but plugs remain sooty. And actually they plugs got slightly less sooty when I threw in a smaller pilot jet. So why does choke help the fast idle but plugs are still gassy???
I've never done a carb tune from complete scratch before so maybe I don't know where to start! I did the things I know: adjusted float, set pilot screw at 1.5 turns out...
Please Log in or Create an account to join the conversation.
- Scirocco
- Offline
- Premium Member
- Never change a running system
- Posts: 4211
- Thank you received: 2072
Some important inner air or fuel ports can be clogged by a long downtime.
The choke enrich the fuel/air mixture and rises the idle for the startup but the pilot and main jet circuit looks like not be fully okay.
This causes a very fat air to fuel mixture that makes your spark plugs.soaked and oily.
My 1975 Z 1 B 900 Project
www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
Please Log in or Create an account to join the conversation.
- harmsworthj
- Topic Author
- Offline
- User
- Posts: 23
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- Scirocco
- Offline
- Premium Member
- Never change a running system
- Posts: 4211
- Thank you received: 2072
Have you adjust the throttle cable right to get the correct slack.? Otherwise the butterflies stay open and rise the idle.
Please upload a picture of your carburetor
My 1975 Z 1 B 900 Project
www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
Please Log in or Create an account to join the conversation.
- harmsworthj
- Topic Author
- Offline
- User
- Posts: 23
- Thank you received: 0
Attachment not found
Attachment not found
Please Log in or Create an account to join the conversation.
- Scirocco
- Offline
- Premium Member
- Never change a running system
- Posts: 4211
- Thank you received: 2072
Are you sure your intake rubber boot and your self made 2 in 1 intake manifold are sealing properly?
Ignition timing and cam timing in spec ?
Valve clearance adjust right?
Normally the engine have to run with the pilot circuit only if all requirements are in spec.
My 1975 Z 1 B 900 Project
www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
Please Log in or Create an account to join the conversation.
- harmsworthj
- Topic Author
- Offline
- User
- Posts: 23
- Thank you received: 0
I tried an even smaller pilot jet and still no change. I have to keep the throttle open to keep it alive. sometimes the idle will hang on its own without the throttle but then if I blip the throttle the idle will come down and bike dies. Lots of backfiring through the carb as well when its dying or starting up after dying. Plugs still always sooty. WTF???!?!
Please Log in or Create an account to join the conversation.
- 650ed
- Offline
- User
- Posts: 15344
- Thank you received: 2829
harmsworthj wrote: I double checked for vancuum leaks. Even added gasket goop to all the intake mating surfaces. Ive never been able to find the exact valve specs for the kz400A but an old kawi mechanic told me to do .01 on intake and ..05 exhaust. timing is good.
Let's start with this -
FIND A DIFFERENT KAWI MECHANIC!
Your "old kawi mechanic" doesn't know what he's talking about!
The spec for the inlet valve clearance is 0.10 - 0.20 mm (0.004 - 0.0078 inch).
The spec for the exhaust valve clearance is 0.15 - 0.25 mm (0.006 - 0.0098 inch)
See www.manualslib.com/manual/849253/Kawasaki-Kz400.html?page=16
Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
Please Log in or Create an account to join the conversation.
- loudhvx
- Offline
- KZr Legend
- Posts: 10868
- Thank you received: 1616
If the plugs are sooty, it's too rich.
Both pieces of evidence agree with each other.
1981 KZ550 D1 gpz.
Kz550 valve train warning.
Other links.
Please Log in or Create an account to join the conversation.
- Scirocco
- Offline
- Premium Member
- Never change a running system
- Posts: 4211
- Thank you received: 2072
If one cylinder blown back into the inlet port, (blow back by burned gas) because of leaking by a bad valve adjustment, will effect the other cylinder and air/fuel mixture flow and vice versa.
Please add some pics of your spark plugs
My 1975 Z 1 B 900 Project
www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
Please Log in or Create an account to join the conversation.
- harmsworthj
- Topic Author
- Offline
- User
- Posts: 23
- Thank you received: 0
One exhaust does seem to puff harder on my had than the other, though both get hot and cylinder compression is even at 150psi each.
I totally have been feeling the rich condition but don't understand how that makes sense with the runaway idle(?) I've dropped to a #20 pilot jet and it's made almost no difference to the #35 I had originally. also screwing the pilot screw in completely or out 3 turns does absolutely nothing to the idle.
The blowback only happens when it chokes out and dies and then when I try to immediately start it. When its running (with throttle held open) it runs great.
i will take photos of plugs
Please Log in or Create an account to join the conversation.
- harmsworthj
- Topic Author
- Offline
- User
- Posts: 23
- Thank you received: 0
Please Log in or Create an account to join the conversation.