Effect of intake position on piston port motor

[tony27]

What effect does the position of the carb in relation to the cylinder have on power delivery?
I have 2 different ACK intakes for my CZ & I noticed that there is somewhere between 5 & 10mm difference in there length which would move the carb by the same amount. The intake that I've had the longest is the longer 1 & I had to shorten the back of the carb to clear the airbox
I'm considering swapping to the shorter 1 for more clearance but not if the power is going to alter too much

[pokey]

longer manifold better torque

[Bamford#69]

Hi,
Side pipes little and large  have a long inlet manifold ; 77mm top side  , single port motors have a shorter manifold 43.5mm , a 250 twinport has a very long one , too hard to find right now, but ,looks longer than a sidepipe one  , but I do have a new from the "Dave Bickers" shed that is very short about 45 mm
long ones for more pulling power great for European mud , the shorter ones give more top end at the expense of low down tractability ,
cheers 

[OverTheHill]

Joel Robert smashed his off between races once. Maybe that's what started the shorter ones Tony!! Max Morf [swiss wild red head] hooked me off over a jump at Woodville In "63/"64 [lapping me] think i nearly smashed his carb off in the tumble. left me nuts on the handlebars as i kissed the front tyre on Alan Collison's single port 250 [might be your bike--check the cross bar for signs] then bugger me if the swing/arm bold didn't come out of a coffin tank 400 & stop the brake pedal operating at the end of a long straight with a hairpin at the end [panic]---love them CZ's, they just don't love me lol. What bore size are your 250 Z's, i have some 70.25 Yamy DT1 rings on trademe as these are flat sided [parallel sided] sent by mistake, not tapered keystone [which i got in the end].

[tony27]

Mine is a 400 running 1mm oversize now Morley, has the name Max Stafford scratched into the inner clutch cover so I'm assuming that he was a previous owner, as far as I know it's always been a local bike
I might try the shorter intake next sunday at the vintage atv meeting & see what it works like

[tony27]

Surprisingly the shorter intake seemed to give a bit more bottom end although track wasn't seriously tight like some are, couple of good off camber 2nd gear turns it seemed to be pull out better than usual. Think I'll use it a few more times to confirm whether it does actually work better for me
Only problem I had with the CZ was the filters on the taps had partially dissolved in the off season & the taps kept clogging up so I had to clean them between races