Getting my 71 1.8L ready for Spring driving; replaced the spark plugs today. Here are the ones just removed. #3 looks really good; #2 a bit sooty but not too bad. The other two sort of in between. They've been in there maybe 5k+ miles of leisurely driving; cleaned them off last spring.
Car is running fine; it has its original injectors.
What are they saying about their living conditions? Happy?
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I think they look great for 5k+. I wonder about 2 though, it isn't terrible but it is not like the others. Could just be the vagaries of the whacky intake runners and plenum.

Check the #2 wire. Does it look any different than the other 3?

The spark plug connector wiggles a bit more than I think it used to. I have a spare I'll put on and compare.

It was the #4 connector that was a bit wiggly; replaced it and changed out the #2 connector. Otherwise, weak current through the wire? weak plug (now changed out)? a sign that that injector is now off a bit?
Otherwise, running fine so not going to dwell too much on it (pun intended).
Next up - confirm dwell and finish prep for a wee bit of metalwork.

Check the gaps on all 4. See if they differ at all...

I just bought some BP7ES for my car and the plugs I pulled out were all dark brown. But I also have those new matched injectors. The color on a plug is only reflective of the last time the engine ran. That's why when you would tune old two stroke dirt bikes, you would run it up, chop throttle and hit the kill switch. That was the only way you could assess rich/lean at WOT.
So, what I see here is that the last time you drove, you doodled around at low RPM part throttle driving... assuming there isn't significant variance in the plug gap.

What is this 'low rpm part throttle driving' you speak of? That's just crazy talk.

Dude… I could not agree more!

True story:
Years ago when I raced superbikes in Texas, I was visiting a dealership that sponsored me and a customer who was there started a conversation about his new bike and how fast it was. I asked him if he was taking care during the break-in process. He said he was and in total seriousness he said, “I can’t wait till I’m done. I know when I can rev it high enough to make the pistons go all the way to the top, it’s gonna be SO FAST!”

Somehow I kept a straight face when he said that. But I think the funniest part is that what he said stuck with me so much that it has been a saying of mine for 20yrs!

For example:
-That guys pistons definitely don’t go all the way to the top
-*engine won’t start* Well I don’t think these pistons are able to make it to the top
-And my personal favorite is when I take my wife for a drive and then haul ass a bit, I tell her, “you gotta stretch these pistons or they won’t be able to go all the way to the top.”

Good idea. Will pull them after first drive. Have never had to change gaps on NGK BP6ES. Put in the resistor type this time.

more evidence that texas was influential in the settlement of australia in covert operations against british imperial forces despite what the history books say.

Back when we used to read spark plugs on our motorcycles (long ago), we were told to only read them after a full throttle run, then hit the kill switch and pull in the clutch and coast to the pits. Any other method produced dubious results.

Manual says .6mm for the original W 175 T2 Bosch plug. I gapped my new plugs at .635mm just to account for the new Pertronix ignitor I got. I’m sure I’d be fine at .7mm but I’d rather do that kind of tuning when I have everything else sorted.


I would do two runs, steady half throttle and full throttle. Half throttle runs were used to adjust the needle and full throttle for the main jet.

3 out of 4 look great, is it possible the injector for the dark plug is leaking? Either way, if she is running good just make sure the pistons are getting to the top with an Italian tune up, if such can be performed on German machines.

That’ll be my initial guess. Original injectors but have one proven replacement. Mileage has been so-so, but mainly doing town casual driving so somewhat expected. Highway driving in it scares me senseless.

A quick and easy couple of trouble shooting steps would be to touch nothing and move the spark plug or touch nothing and move the injector. See if it follows.

The faster it strokes, the longer it gets.