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Jet needle improves acceleration. 17 Jul 2011 17:48 #463367

  • calvin17d
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I pulled the plug on #1 this morning to find that it was soaked and produced no spark at all. I guess I had it fouled up pretty good. I checked the other plugs and spark appeared uniform on all plugs.

I took the bike out for a ride. and it operated quite and pulled hard with a slight sensation of lean conditions near quarter and half throttle.

Pulling the plugs after a 20 min ride revealed white electrodes with an even turn of light soot on the base ring. While the electrode on #1 was also very white, the base ring lacked this turn of soot and was in some spots wet with no soot at all.

I should also mention that I have swapped coils as a means of troubleshooting with no difference. I was unable to swap the coil wires due to lengths but they checked out with the ohm meter.
Resistor caps also Checked out at 5k ohms
1976 Kz900 A4

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Jet needle improves acceleration. 17 Jul 2011 18:10 #463372

  • mark1122
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can u swap coil wier 1 and 4 since they may be the same length? it would be nice to prove that it is fuel or electrical.
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

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Jet needle improves acceleration. 17 Jul 2011 22:00 #463404

  • calvin17d
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mark1122 wrote: can u swap coil wier 1 and 4 since they may be the same length? it would be nice to prove that it is fuel or electrical.


I rode for about 40 mins after swapping the plug wires. It seems the mixture screw has a slight effect at idle now that the plug is not fouled.

Unfortunately the #1 plug unlike the others will not generate a turn of soot on the base ring. The electrode appears wet and base ring without much change. I also lowered the fuel level by bending the tang slightly. I thought it might be worth a shot that I messed up the clear tube reading on the last ten checks I have done.

The plug is again on it's way to fouling.
1976 Kz900 A4

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Jet needle improves acceleration. 18 Jul 2011 09:57 #463467

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calvin17d wrote:

mark1122 wrote: can u swap coil wier 1 and 4 since they may be the same length? it would be nice to prove that it is fuel or electrical.


I rode for about 40 mins after swapping the plug wires. It seems the mixture screw has a slight effect at idle now that the plug is not fouled.

++++Unfortunately the #1 plug unlike the others will not generate a turn of soot on the base ring.
this indicates lean.

+++The electrode appears wet
this indicates no spark

and base ring without much change. I also lowered the fuel level by bending the tang slightly. I thought it might be worth a shot that I messed up the clear tube reading on the last ten checks I have done.

The plug is again on it's way to fouling.


something is amiss.
if the plug is wet, it is not firing.
if it was black with soot, it would be firing and rich.
76 kZ, frame gusset work,1200CC.Ported by Larry Cavanaugh,This email address is being protected from spambots. You need JavaScript enabled to view it., 1.5mm.over intakes,.ZRX12 rear end,and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg,Ont.Can.

~ ~ ~_@
~ ~ _- \,
~ (k) / (z)

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Jet needle improves acceleration. 18 Jul 2011 10:43 #463475

  • calvin17d
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For whatever reason that carb or cylinder is fouling the plug preventing the spark. Switching the coils and the wires if it were an electrical issue should have changed something.
1976 Kz900 A4

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Jet needle improves acceleration. 18 Jul 2011 10:52 #463479

  • Patton
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Perhaps already covered, but does this issue persist when using a good strong fully charged battery, with clean snug terminal connections and a good ground connection where the negative cable attaches to rear of the engine?

Good Fortune! :)
1973 Z1
KZ900 LTD

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Jet needle improves acceleration. 18 Jul 2011 10:58 #463481

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Patton wrote: Perhaps already covered, but does this issue persist when using a good strong fully charged battery, with clean snug terminal connections and a good ground connection where the negative cable attaches to rear of the engine?

Good Fortune! :)


Worth taking a look at.
1976 Kz900 A4

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Jet needle improves acceleration. 19 Jul 2011 01:10 #463646

  • DoubleDub
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This seems to be the things everyone has to learn at least once...I went through it to.

Carbs will only work as well as the weakest component in the rest of the engine. Carbs will only work properly when all other functions of the engine are in proper working order. Many times people start down the road of carb problems to find weak spark, low compression, valves that need adjusting, air leaks, and so on.

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Jet needle improves acceleration. 19 Jul 2011 15:30 #463767

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I have new pilot jets on the way to help with my lean pilot circuit. In the meantime I put together a plan to pull the bike apart and trouble shoot the issue. Here is what I have so far. I welcome any additonal checks or troubleshooting methods.

ELECTRICAl:
Since I have ruled out that changing the coil nor the sparkplug wire will solve my problem I am going to start by testing the voltage to the coils at the red/yellow lead, checking for 12.5V with the ignition switch on.

I will then check the Dyna S ignition Module by grounding the female terminals of the module leads checking for spark with the ignition in the on position.

CARBURETION:
Since I will already have the carburetors off to install the new jets I am planning to swap carbs number 1&3 so that the fuel inlets matchup correctly. Doing this will help me to determine whether the issue is related to fueling provided by the particular #1 carb or rather Electrical.

VALVE CLEARANCE: I have recently verified valve clearance to be .10 - .15 mm roughly. 2 of the intake valves have slightly more than .15 and close to .17mm. Could this be an issue not allowing the valve to fully open?

COMPRESSION: I no longer have a compression gauge, however multiple tests in the last 300 miles have indicated compression on all cylinders to be between 120-135 psi.


Please add any ideas you can think of to my to-do list here.
1976 Kz900 A4
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Jet needle improves acceleration. 19 Jul 2011 18:17 #463808

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calvin17d wrote: ... planning to swap carbs number 1&3....

Thinking this swap may leave the pilot air screws on the wrong sides.

Good Fortune! :)
1973 Z1
KZ900 LTD

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Jet needle improves acceleration. 19 Jul 2011 18:51 #463816

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Patton wrote:

calvin17d wrote: ... planning to swap carbs number 1&3....

Thinking this swap may leave the pilot air screws on the wrong sides.

Good Fortune! :)


I am thinking you are correct. I dont see how this would hinder anything other than making adjustments to the screw a PITA.
1976 Kz900 A4

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Jet needle improves acceleration. 19 Jul 2011 21:44 #463836

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I put a volt meter on the battery terminals and measured 12.5-13V with the bike off.

I then started the bike and revd to 3000 rpm and measured 15V at the battery

I then turned the bike off removed the tank and the cover to the patch panel. With the switch on and the bike off, I measured 9.5-10V at the red/yellow wire on each coil. Measurements should be 12.5v here as well correct?

I then attempted to start the bike and it did not turn. I went straight to the fuse for the ignition and the fuse block was hot and the ignition side of the fuse lead came flopping out of a loose connection. I guess when I removed the panel the wires came apart and shorted on something.

Thoughts on the voltage readings above?
1976 Kz900 A4

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