Possibly running on 3 cylinders?

After a 15 minute ride or so, It was running ok, but still not quite right. I decided to make sure it was running on all 4. I let some water drip from my fingers onto each pipe. 3 of them spit like water in hot grease. The middle right pipe just sizzled a little.

Haven't had much time since then to get more into it.

Any thoughts?

If only 3 were working, how would it run and how would it act?

Compression good in all cylinders? Valve clearances been checked? Good sparkplug in the bad cylinder?

I'd do the valve clearances,followed by compression checks.
Another place to check is the sparkplug caps and sparkplug wires(high tension leads for the Brits and our neighbors to the north).

What is appearance of #3 spark plug?

Good Fortune!

Well I pulled each plug to look at the tips. Here is a picture of each that I took. Starting left to right, 1-4.

Plug 1


Plug 2


Plug 3


Plug 4


#3 is supposedly the problem child, yet #4 is the one that looks completely different.

I should also note that #4 was cross threaded into the head, so I will need to get that fixed before I can do anything else with it.

Carb sync in spec?

Actually #4 looks the best out of all of them... The others seem to be burning a tad too rich/oily but images can be deceiving due to flash....

Follow the link for How to Read Spark Plugs... This zipped file also contains Carb theory, t-shooting and calibrations of various Mikuni and Keihin Carbs....

kzrider.com/index.php?option=com_docman&...d&gid=461&Itemid=108

OMR

MFolks wrote:

....sparkplug caps and sparkplug wires(high tension leads for the Brits and our neighbors to the north).

We call'em plug wires here :laugh:

Maybe you mean farther north...



HEY: GET THE MANUAL. You'll love it.

GL!

Easiest fix for cross-threaded spark plug hole may be a reverse tap that starts from the deep end where the threads should still be good. No disassembly required.



Install 4 brand new spark plugs per factory specs -- guessing NGKB8ES.

Okay to experiment with leaner pilot circuit by adjusting #3 carb pilot screw.

Assure correct float bowl fuel level in #3 using clear tube method. Too high level results in too rich mixture causing fouled plug.

As already suggested, assure correct valve clearances, especially in #3, and also do compression check.

Combustion requires these three items:
> Decent compression;
> Good spark (properly timed);
> Correct fuel mixture.

There are various reasons that could cause a problem with any of the three items.

The above suggestions address a few of the common reasons relatively easy to correct.

Good Fortune!

Thanks. I was hoping that McMaster Carr would carry those reverse taps, but no luck. I do have a spark plug specific thread chaser, but my guess is that I won't be able to get that started either, so I have not yet tried. I do need to get a manual.

Unfortunately, I have a few other "honey do" projects going right now, my son's baseball, and my annual con-ed training for the next two weekends so this might end up sitting for another couple weeks before I can put much time into it.

Thanks for the suggestions. I was talking with Chris from Z1E and mentioned my issues. He suggested it was more likely electrical that carb related.

I don't own a compression tester, carb sync set, or any other "specialty tools" so I guess my second cash outlay after the manual will be to fill those gaps in my tool box.