#1-# 4plugs keep fouling,Bad coil??

Ok let me start off with this. My 75 Z ran fine until I added 29mm smoothbores. Hasn't ran since! First I cleaned the carbs and used 20 pilots,120 main jets and needle on the three clip. Bike should run fine. Nope. Instantly fouled plugs. Problem came down to cheap main jets that have a differant size hole were the needle seats. Bought good jets . Still bike not running. Two and three plugs are burning perfect but one and four keep fouling. Looks like I have even spark on all four plugs. Can a coil work and then not work or will it just stop working.

Would test voltage to each coil and compare.

Do ohm check on primary and secondary windings on both coils and compare.

Could swap coils and see if problem moves to 2/3.

Might be non-visible break or frayed wire inside insulation of wire supplying voltage to 1/4 coil.

Given history of running fine until 29's installed, it does suggest the carbs as culprit.

May be coincidence that 1/4 are fouling.

The pilot circuit on my 29's was difficult to finally get as-new clean.

There are several good instructive threads already with details about cleaning the pilot circuit, including 29's. Let us know if you need help finding them.

When properly set up, 29's are very streetable.

Good Luck with 1/4!

Forgot to mention checking service float bowl fuel level in 1/4 carbs to see if it might be too high and thereby causing an over-rich mixture.

You know -- the quick easy "clear plastic tube test" requiring no disassembly.

What is the "clear plastic tube test"

GregZ wrote:

What is the "clear plastic tube test"

Okay -- this part about fuel level and float height probably belongs in the carb forum, but here goes anyway.

Clear plastic tube test

Check real-world float bowl service fuel level.
Quick and easy -- no disassembly required.
May perform test with carbs on or off bike.
Carbs must remain still and level during the test.
Turn petcock off.
Fuel line remains attached to carb.
Remove side-located drain-screw from float bowl.
Use short length of clear plastic tube.
Size of clear tube should match drain-screw hole.
Twist-thread clear plastic tube into drain-screw hole.
Rumor has it some folks prefer using a small plastic barb-style connector fitted into the drain-screw hole with the clear tube attached to the connector.

Hold clear tube against top edge of float bowl.
Keep it steady - don't let it move.
Turn petcock on.
Watch level fill and rise up in clear tube as fuel fills float bowl.
Fuel level visible in tube matches fuel level inside float bowl.
Slight fuel leakage from the drain-screw hole is immaterial.
Repeat test to double-check result.

Smoothbore carb has larger bottom-located drain-screw hole.
I use a tapered rubber grommet pressed or twist-threaded inside the drain-screw hole with the clear plastic tube fitted snugly inside the grommet.

If desired, a "special" tool is available for fitment to side-located drain-screw holes.
It is a thumb-screw affair with clear tube attached that threads into the drain-screw hole.

Special Tool


With CV style carbs having combined function bottom-located nipple for both over-flow and drain, just attach the clear plastic tube to the bottom located nipple.
This does not apply to carbs having separate independent drain-screws and overflow nipples.


Refer to manual for specs as to ideal height of service fuel level.
Usually, the correct level is slightly below the float bowl gasket, say 1/8 inch or 2-4 mm.


Checking fuel level is quick and easy (with carbs on or off the bike).
But adjusting the float to attain the correct level is more difficult.
Don't rely on the upside-down work-bench physical measuring method where results are only ball-park at best (unless you're feeling really lucky).


Adjustment -- carbs removed from motorcycle.
There is a tab or tang on the float whereby the height may be adjusted by delicately and ever-so-slightly bending the tab, noting that seemingly minute adjustments often result in significant changes in fuel level. Usually, bending up lowers the level (closes the float-needle/seat interface sooner), and bending down raises the level (at least for Z1, KZ900 and KZ1000 through 1979). Uncertain about universal application of bending directions, so would inspect working mechanism of the interacting parts to confirm this for your particular carb.


Helpful tip (courtesy of wiredgeorge)-- when re-testing after adjustment, only one screw is needed to hold the float bowl onto the carb, which speeds removal and replacement for testing between adjustments.


Bottom line-- Given good compression and spark, with carbs in as-new condition, synced and pilot adjustments set to specs, no air leaks, and clean air filter. Where new plug quickly soots and fouls from apparent over-rich mixture, a too-high float level is a likely suspect IMO (because that's what happened to me).

Good Luck with the repairs.

Post edited by: Patton, at: 2007/09/23 12:38

Hey Patton . Thanks for the info. I removed the smoothbores and insalled the stock carbs so i can ride and enjoy the last summer days here in NW indiana. I will set the floats and try to install them again soon.Thanks again
gregz

you know my bike had the same porblem. after replacing the coil, distributer and igniter we found out that it was a ground short. my dad tested the wires befor ll this too but then he found out he was using AC instead of DC with his Ohm meter. So befor you go and do all the things I have done just to replace a 10 cent wire check your electrical and make sure you use DC lol. Also maybe your float is bad. I'm still rich in my number 1 cylender and its all because I have a bad float. I need to replace my carb so I might as well when I do my compleat engine overhaul this fall/winter. good luck