[mark 69 912]

I had the same problem with the idle running very high. If I put the clutch in and acted like I was starting off I could get the idle down. I have the origional distributor and solexs. The mechanic found a plate warped in the solexs causing the idle to stay high. Now it runs perfectly, no back fires and great idle. Wish I could remember the name of the part replaced but much cheaper than replacing everything else. Good luck.