Technical Engine surging issue

[rawill]

My 88 60s (with a 1300 carb) surges/hunts annoyingly at approx 50kph.

My 84 70s does the same thing. The carbs are cleaned out, the timing is set at 10deg. The carb on both cars is the Solex C30-32 (CIC/1)

Is this a common fixable fault?

The car tune of both cars can't be too far off the mark they both do about 36-27mpg on mixed running.

Both cars have done just over 205,000km.

 

[Chas Uno]

I assume that at 50kph you are in a high gear and only using a light throttle? If so, then it sounds more like an air leak to me :idea:

My 70SX with the Weber 30/32 DMTE runs fine at all speeds (touch wood) so maybe it's a fault specific to the Solex :shrug: Then again, I was lucky in picking up a brand new carburettor for £1!!! The original carburettor did run ok but was flooding a lot. Far easier to swap carbs than to rebuild one so I never did find out what was wrong with it.

 

[rawill]

I assume that at 50kph you are in a high gear and only using a light throttle? If so, then it sounds more like an air leak to me :idea:

Yes you assume correctly, it is in high gear, but it still happens in 4th or 3rd, but the surging is slightly different.