One would think that changing a spark plug is a simple manner. However, after I have changed the variator belt and rollers, oil, hub oil, air filter, I cannot figure out how to remove the plug!!!

The spark plug cap needs to turn to be released from its clip holding it. But there is not enough cable to allow for this. Haynes Manual says to unclip the cable from the oval clip down by the battery wall to offer the slack.  Do you think I could figure out how to unclip that cable holder?

I tried and tried and did not want to force it. I even removed the battery to gain access through a small hole in the wall. No Luck.

So a new post at www.modernvespa.com proved once again to be fruitful (thank you Cheekythomas). Cheekythomas wrote:

“Haha.. Yeah the newer ones are proper tight on the HT cable…
Look at the main wiring harness from under the seat, and you’ll see the same type of clip used where the wires cross onto the engine, so you can see how it works…

Basically it opens from one end, once open you’ll have just enough Freeplay in the lead to get the cap off the plug…”

That was great. I found the clip to the main harness and I undid it and clipped it up again. However, once again, the place where you cannot see while your hand is reaching into the belly of the beast proved yet again to be challenging. After a bit of tool searching, I found the perfect tool. A paint can opener! It fits in the palm of your hand and can be easily manoeuvred to release the clip  while you are working blind from touch alone.

I removed the cable from the clip and immediately the spark plug cap was able to turn a full 90 degrees that allowed me to pull it off. There are no screws as was suggested by some other people. I replaced the plug with a new one (NGK Laser Iridium). The plug was clean, unlike the one that came out of the GTS 300.

If anyone knows why the plug from the GTS 3900 is so black with soot, I would appreciate some insight here. For the record, I had removed the plug two weeks ago for inspection and it was the same. I cleaned it with a wire brush and after two weeks (not much running) the plug is black again. I changed it to a new plug and will check it again at the end of this long weekend.

So, another challenge solved and never again to be an issue.

Thanks again to Modern Vespa!