Forgive me, but I am wondering if it's the iridium spark plug gap at fault. The iridiums come with wide gaps, I think.

I have an iridium in my TTR250 and it runs really well with it, but I did have to close the gap a fair bit.

I've been wondering whether to try one in the Tenere on the strength of the TTR's result. But now you have me wondering!

Regarding using an 8, I will do that this summer as I think the 660 is on the edge with the 7. It doesn't do much town work anyway. Come to think of it, it doesn't do much work anyway! I hadn't ridden it for 3 months until last week. Been away...