Topic: Sparkplug confusion CB550F

[stevey]

Not been on the bike for a few weeks (1978 CB550 F2), (helping my old folks move from England to sunny South West France) and not had it that long anyway, so returned to it with fresh eyes. It was a b....rd to start, over 20 kicks but having warmed it up at 2000 revs, shut it off to get it out of the garage, it then started really easily on the button. During the run I noticed a slight lack of power over 7000 revs in 5th and lumpy running when idling. So back at base I whipped out the plugs for 1 and 4 and they were really sooty. Too rich I thought and then I noticed that the plugs were NGK D7EA whereas Clymer says they should be D7ES. Thought I had the answer until I checked the excellent USA NGK web site (the european verson is rubbish) and found that the recommended plugs for the 550F were indeed D7EA. So is Clymer wrong and does it make any difference anyway?

Any comments welcomed.

The previous owner had just had the carbs tuned and synched plus new points and coils so I'm going to check the timing as my gutfeel is that it needs advancing. Any more thoughts from people who really know what they are doing would be appreciated.

Steve

lost in France

[Bodi]

The plugs are pretty much identical. If you have one beside the other you can see a slight difference in the electrodes. This doesn't seem to make any difference to the performance in my experience.

[TwoTired]

The Clymer simply copied what the Honda manual said and published when the bike was first manufactured.

Since that time, NGK discontinued the D7ES and replaced it with a D7EA, which is a nearly identical plug, intended for use it the CB550, as well as other bikes where the D7ES was previously specified.

My Cb550F2 (still in stock configuation) will also carbon foul the plugs if I spend too much time operating with the choke on, at low throttle settings, and don't take it out on the freeway to get the bike and combustion chambers up to full temp for a good long duration (about 15-20 minutes).  Then all is well, plugs come out tan.

It will also foul plugs with greater frequency when the air filter is dirty.

The air screw settings for the F2 are different than other CB500/550s, and they are more sensitive to setting changes.  They should be close to (or even a bit more than) 1 1/2 turns insteads of the 1 turn that other models have as settings with similar carbs.  This may also account for your sooty plugs if the mech that did the carbs looked up the wrong data for the carb setup.  Of, course if this is wrong on your bike now, who knows the extent of other changed made to the "tuned" carbs you have now.

Lastly, changes to stock exhaust and air filter may have a greater effect carb tuning.  Since you didn't say, I assume you still have the stock configuration.

[stevey]

Thanks Two tired and Bodi. The air filter is stock, the exhaust is still 4 to 1 but it has pattern slip on. Guess I'll check everything over. All I know about the mechanic who worked on the bike previously is that he was strong! Good fun bruising the knuckles trying to undo things.

Thanks also Biffta for the advice but I kinda like the 550 (and also the challenge).

Steve

[bryanj]

IF you can find them, and more imortantly afford them, fit D7EV I did only that years ago on a 500 and got an extra 3mph and 4mpg. BUT you will pay for one what a set of standards cost!!