Extension tubes carb to power filters

[Nicky]

Norbo mentions these if fitting power filters to prevent flat spots. I've also spotted a set fitted to an inline four diesel. Does anyone have a spec for these? Basically, how long? I'm running standard ignition, pipes, and carbs the only deviation is 170 jets and 4th needle clip - and no airbox obviously.

[steven]

Hi,
I have never tried them, but I think they are called Velocity Stacks ?
Steven.

en.wikipedia.org/wiki/Velocity_stack

[dusty350]

I had them on an Rd400 years ago. Used in conjunction with pod filters and Ledar tubes. Just long enough to clamp to the carb and then the filter clamped in a position touching the back edge of the carb, so a couple of inches probably - sorry I cant be specific, it was 20 years ago. Never ran great with them to be honest, and unless you get it properly set up I think you will always be chasing problems, imo

Dusty

[mikee]

I have fitted these to yam twins for years
They work well enabling you to set the induction length properly so you can dial the carb in to run very smoothly
You need a big filter 56mm ish bore works best so your tube needs to be stepped in diameter
I originally discovered this on an aircooled r5 I had a million years ago , I used the carb to airbox tubes , cut to 3/4 their original length and some filters I had kicking about
It all fitted together nicely ( bit of a fluke) and you could move the position of the filter relative to the carb
The ram air full foam filters work well with this too

Mike

[Nicky]

Thanks all! Interesting. This sounds a bit techy for me, but I suppose it's the fettling that keeps us smokin'. If I have a bash at it, I'll let you know how it hangs.