TOPIC:

Air screws are on the sides of a VM type carburetor while pilot fuel mixture screws are on the bottom at the front of the bowl. Turning the air mixture screws OUT will lean the mixture. Most plug fouling issues which are due to air/fuel mixture are the result of an improperly adjust mixture in the pilot circuit. I suggest you turn each air screw out 1.5 turns. Then warm the bike and at idle, adjust the #1 air screw for MAXIMUM idle speed. Turn the idle back down using the idle adjust and repeat for each of the the other carburetors in turn. By peaking idle speed on each carburetor you will be adjusting the mixture optimally.


This thread appears to be going in two directions... carbs and plugs... Since you bike is stock, after adjusting the idle mixture and the idle speed, I would operate the bike awhile. I am a tad uncomfortable with using these fancy plugs for the reason that Ron laid out. If there is any fouling, I would consider installing a fresh set of NGK B7ES plugs and see if this resolves the issue. This would be a good subject to report back in on. Thanks to Ron for bringing this info to light...

BeeGee wrote:

Question:
2 -- Ron G - If I went to a hotter plug (NGK B6ES) on all 4 cylinders it would be effecting all cylinders and my problem seems to be only 1 + 2. Are you suggesting that I go with a hotter plug in the 1 + 2 cylinders only?

PS. I was having a problem with sooting on all four plugs this Spring. Finding less than 9 volts to the coils I did the hard wire mod. I've been checking plug #4 since and have seen no sooting as you can see from the picture (3 + 4 may even be a little on the lean side). I thought my worries were over. Little did I know 1 + 2 have been sooting since the mod without me being aware. That's where I am right now. As I said the bike has been starting & running 'Great'. Also, I have not been letting it sit idling for lengthy sessions. Only enough to warm it up and settle down the idle / choke issues inherent with KZs before hitting pavement.

Hotter spark plugs transfer less heat away from the ceramic insulator and center electrode, which promotes burning off the soot. Contrary to popular belief, hotter spark plugs will not make your engine run hotter. The optimum spark plug heat range for a particular engine can vary by spark plug manufacturer. Motorcycle manufacturers tend to specify spark plug heat range on the cool side.

IMO, your spark plug heat range appears to be on the fringe. The insulator should be clean of soot to the base, which is where the mixture strength is read. It would not be detrimental to your engine to try a set of B6ES to determine if the soot will burn off.

Ron

Shouldn't I be leaving cylinder plugs 3 + 4 alone since there is no sooting on those plugs and only change the 1 + 2 plugs to the hotter B6ES ?
See the picture of my plugs at my original post. There is no sooting on plugs 3 + 4 so I shouldn't be changing the heat range of those plugs - should I?

Post edited by: BeeGee, at: 2005/11/03 06:44

Determining the proper spark plug heat range is quite simple, there's no need to make it more complicated than it has to be. The following describes the proper heat range window. The insulator needs to be hot enough to burn off the soot down to the base, but not so hot as to cause pre-ignition or erode the center electrode. An engine will require a hotter plug if it is run at low speed, and a cooler plug if it is constantly hammered on. If a plug is too cold, then the driveway tuneup (revving the engine) or wide open throttle runs are effective to clean the plugs because this elevates the insulator temperature enough to burn off the soot. If my engine were in perfect tune and my plugs appeared as yours do, then I would change the heat range of all four plugs one step hotter. If the change results in a clean insulator on all four plugs down to the base and no pre-ignition or electrode erosion, then I know that I have selected the proper heat range.

Ron

Just out of curiosity...do you park your bike on the centerstand or side stand ?

I always park it on the side kick stand except for when it's stored for the winter. Hmm ... what are you getting at?

Does your petcock leak?

Ron G wrote:

In a waste spark configuration, where one coil fires a pair of spark plugs simultaneously, the spark will leap from the center electrode on one plug and the spark will leap from the side post on the other plug. A double platinum is designed to reduce the voltage required to spark from the side post as well as from the center electrode.



Ron can you sight a source that explains how a spark plug fires from the side post that is the ground side of the system? I have never heard of such a thing.

















Ron

arai59 wrote:

Does your petcock leak?

arai59 ... You're a genius! ... I think you may have just hit, at least one problem, directly on the nose!

My tank has been off the bike for a week now since winterizing. Before tank 'off-the-bike' storage I placed a 6" long clear tube on the outlet of the petcock & plugged it with a golf tee (just in case there was some seepage thru the petcock during winter). I just checked it and the tube was full of gas. Gas is leeking by the petcock just as you suspected! The real amount I don't know since the golf tee was holding it back. Float valve needle leakage may certainly be weeping by (and due to the bike tilt during parking) filling bowl 1 then 2 and progressively - with time - down the line as well to bowls 3 + 4. This may also be leaking gas progressively into the cylinders --- all resulting in an extremely rich start-up condition especially noticable in cylinders 1 + 2.

Now, what's the best fix? Should I simply install an in-line gas shut-off (I never did have full faith in the petcock) or should I rebuild the petcock? Maybe I should do both!

My bike's model 1979 650-D2 has an (ON-PRIME-RESERVE) petcock and an accelerator pump. In the 'ON' position the petcock is only supposed to flow gas when it senses a draw. Besides rebuilding the petcock I'd like to add an 'OFF' in-line shutoff to this setup (Just-in-case).

Post edited by: BeeGee, at: 2005/11/05 22:40

The vacuum petcock can be your best friend or your biggest nightmare. I too experienced this problem and decided to switch over to a Pingel this winter. No more vacuum draw, just need to get used to the manual type again.

Post edited by: arai59, at: 2005/11/05 20:01

Walt,
Lightning often jumps from the ground to the clouds also.

What Ron is saying is that since both plugs are in the same circuit the electrons traveling from negative to positive end up jumping in different directions on each plug. Starting at the coil the electrons travel down one secondary wire, jump from the center electrode to the ground, through the head, from the ground electrode, jump to the center electrode and finally back up the other secondary wire back to the coil. The negative electrode experiences more erosion than the positive one because of the direction the electrons are traveling.

By the way Greg, Good Job on the leaking petcock diagnosis.
KZCSI

Post edited by: kzcsi, at: 2005/11/05 17:38

Here's an illustration.

Ron