Different coloured exhaust pipes

Feb 22, 2006
My '73 850 Commando has had a single carbie conversion, it has had a recent engine rebuild (2500 miles ago), it has boyer ignition, it also has two distinctly differently coloured exhaust pipes. The right side pipe is a brilliant blue down to near the bottom bend, the left side pipe is more of a dirty grey colour down to about half way between the first bend and the second bend. It runs very nicely, it doesn't spit or backfire so i am wondering "why is it so", could it be a coil problem or maybe a valve problem, although the valves were all done during the rebuild, or is it just some crappy chrome plating, any ideas.
Nov 18, 2005
Country flag
I had the same thing on my old Mk3. When I asked the guy who worked on it for me, he replied that the amount of time each exhaust spent in the chroming bath could affect the colour.
So i wouldn't be worrying about it.
Jan 15, 2006
Colour=heat=power, so a quick test to point you to chrome issues or running problems would be to measure the actual temperature of each pipe after a blast down the road. Some mechanics nowadays have a non-contact temp sensor unit for troubleshooting. Also used by building maintainance and plumbers.
An additional test to make would be to do a cylinder compression comparison. The temp and compression variations should be similar, since the same carb is feeding both cyls.
If compression is close, but temp is not, then you probably have ignition problems.