Topic: Plug reading

[XN]

Been a while since I have done any. Sorry I don't have any pictures of the actual plug but I will use these pictures to best describe it. FYI 78 750K.
Had the plugs in for at least 100 or so miles. I have yet to do an actual sync, but I have done a bench sync, stock air box and filter, Mac 4-1 exhaust. I have not dug into the carbs yet so I can only assume the jetting is stock.

Only had time to check 3 out of the 4 on my break at work but all looked the same. I have the perfect spot coming into my work with a hill at the start I ran it up into 2nd gear WOT and chopped it off and coasted in. Engine was nice and warm.

Ground strap looked kind of like this in the picture with a little more tan deposits on the thread side of the strap and the other 1/2 of the strap was a very light tan/ gray (over the electrode)



Electrodes had no signs of erosion and a nice gray color with no deposits

the end of the threads had a light layer of carbon similar to this picture but maybe a little more carbon build up



The porcelain was white on all # 1 had a small spot on one side that was a very faint tan # 2 had a light tan ring about 1/10th of an inch down and # 4 was all white with no tan markings on the porcelain.

EDIT.. I checked #3 before I left and it looked the same as #4.

So you think I'm too lean or ok?

[low-side]

It sounds like your probably fine but if it were mine I might adjust the air screws a little, especially if throttle response seems a little sluggish.  Good luck and have fun!

[XN]

throttle response is a little sluggish. Thanks.

[HondaMan]

throttle response is a little sluggish. Thanks.

If the plugs are that light and throttle response is sluggish, try a 5 size larger jet, or try raising the needles one notch if you don't have the jets. This latter won't work at WOT, but will indicate at midrange if that's where the problem lies. Then, if the needles improve it, install the larger jets and drop the needles back down.

The new gasoline recipes we all received, starting this summer, will make these bikes run a tad leaner than they used to. It's all about 2 things: reducing emissions and stretching gasoline supplies...

[XN]

Do the 78 carbs have more than 1 notch?

[eldar]

No they only have the 1. You need to get a micrometer or good digital caliper and measure the thickness of washers. The washers go between the clip and slide and will raise the needle.

Turn you fuel screws out just a tiny bit, no more than 1/8th turn and try it. The 78s run lean at high rpm which is usually fine as it is all hp and not torque then.

What range is your sluggishness?

[XN]

I have both a micrometer and caliper. How much would I try raising it or shim size?

mid range is sluggish. Say I'm riding around at 4000 rpm with say 1/4 or so throttle when I go full throttle it takes a while for the rpm's to pick up, but once it gets spooling its fine.

[eldar]

Get the bike warmed and try riding below 3000 rpm. This uses the idle circuit mainly. See what the plugs look like then.

[XN]

Get the bike warmed and try riding below 3000 rpm. This uses the idle circuit mainly. See what the plugs look like then.

Here you go... 2100 rpm in second gear down the block

[HondaMan]

Well, if I can make a suggestion: the black outer ring indicates a cold shell, while the white tips indicate a lean RPM range. What I would do: richen it up a notch (or 5 jet size) and get the ND plugs #X24ES-U. These are about 1/2 heat step hotter than those D8E plugs, burn better because of their tip design, and warm up faster. I've used them for all-around riding and (very) long touring trips at (over) Interstate speeds.

[eldar]

How far did you go at that rpm? Was the engine already warm? The tips seem to be slightly more colored than the previous pics do. Could just be lighting though.

[XN]

How far did you go at that rpm? Was the engine already warm? The tips seem to be slightly more colored than the previous pics do. Could just be lighting though.

I went a city block with it at around 2000 rpm. Yes the engine was warm I rode it for about 10 or so minutes before I did that. When you say tips your referring to electrode, ground strap base threads?

Remember I didn't have a camera and the pictures in the first post were as close as I could find.


HondaMan I would want to wait to install them plugs after I jetted up correct? Because a hotter plug can just make a lean situation worse correct?