Resonance

[Tony C]

I've recently become aware of some disturbing low frequency resonance at approx 1500 rpm.

 

Bonnet off with engine running I can't identify where it's coming from, but it seems less if I hold and lift-up on the airbox (1.8 K-Series with DTH TB's and Bernard Scouse Cold Airbox).

 

I've only become aware of it since I removed the airbox when I installed an oil catch tank. I've loosened the airbox bolts and repositioned the airbox because I thought perhaps it was touching the trumpets - No difference.

 

Checked the alternator, exhaust, TB's and engine mounts and am about to remove the cam belt cover to check the cam belt and vernier sprockets.

 

Any other bright ideas ??????

 

BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery)

[Grim Reaper]

Is it the airbox touching the chassis rail or the clutch cable outer at the pedal box end?

I have noticed a change in design of the airbox over the past year which has altered the shape of the cutout underneath to account for chassis rail changes.

[Tony C]

I removed the airbox at the weekend and found it had been touching the diagonal chassis member, or at least one of the tie-wraps. When I had repositioned it downward because I thought one of the trumpets was touching the inside, I'd merely made the interference worse. I removed the offending tie-wrap and biased the airbox upward during reattachment and it now seems OK.

 

Being an SV I had to modify the airbox quite a bit because the chassis diagonal cut-out and that for the clutch cable were in the wrong place.

I guess I should have been more radical with the modification, but wanted to make as few changes to the airbox volume as possible 😬

 

BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery)