Port timing assistance VSP Road Pipe

[habibi]

Good morning Everyone 

My Mechanic is in the Process of rebuilding my Small frame motor in a new casing and he asked me if i have a suggested port timing for my Exhaust 

The kit we have built is as follows 
Polini 130 Worb 5 tuned with GS piston and head

VSP Road exhaust

Vape Race variable electronic ignition

PHBL 25b carb with malossi manifold (or should I try match with a polini CP carb and manifold)

DRT Sport clutch

Racing Crankshaft MAZZUCCHELLI RACE

can someone please assist and advise best port timing recommendations for above. 

Thank you in advance 

[henri]

i'd aim for around 180-182 exhaust duration , an 28 blowdown with that set up .H

[habibi]

Good Morning Henri

thank you very much for the response there is another thing I would like to know from you if you dont mind with regards to the Malossi intake manifold is a reed set up and the crank is a cut away crank disc pad set up


should I set this up with the reed manifold with out the reeds or should I replace with a straight intake manifold with out the reed box? 

[henri]

ok if the sealing pad isnt removed or damaged why the reed manifold being used . if pads still good you dont need a reed set up. it will just constrict the flow an cause problems .you could just remove the reed petals ,but be better just getting a straighter manifold .H

[jonnysnatchsniffer]

rotary induction will like a bigger carb than a 25mm, contrary to popular belief i had more low down grunt with a 35mm carb than i did when it was a 30mm carb
polini do a nice 30mm manifold
180 degrees is the optimum for pipe resonance, that equates about 190 geometric degrees, not just about blowdown degrees, more important is blowdown angle area. which
will change depending on stroke and rod, i now go 190/130 for all and let the pipe dictate power delivery
suffice to say do not alter the exhaust port below the transfers opening as its not needed for blowdown
you will need inlet timing sorted too id go up to around 180-220 butl only the later if you have the large pad motor 42mm long
i always prefer area on the inlet rather than the cutting of the creank but to get decent inlet timing you will need to do both
you can get away with about 0.5mm seal on the pad but id play safe with 1mm all round, but no trumpet into the inlet, from edge on manifold to edge of inlet pad needs to
be straight walled, and bow inwaerds and you may as well fit the 19mm carb, to do this properly even with a 24 manifold you may break thru the back of the case of the inlet.
infact if you dont break thru it will cost you hp where you need it, up to 5hp can be made here low down
good luck and have fun, oh and buy a proper fucking carb, why use a 40 year old round slide dellorto when the rest of yr motor is modern

[habibi]

Hey Jonny

this sounds amazing I do want to know this system you describe here would it still be ridable as a daily or does it become more Peaky? although I want a quick bike I am happy to loose some HP and speed for rideability this is not going to be a track bike

[habibi]

Oh and thank you for the response these changes sound spectacular

[jonnysnatchsniffer]

well the worb 5 is a tuned polini 130, what i would say is is that mine with a franz pipe was like a p200 under 6000rpm then when on the pipe behave accordingly which was just pull till 9500 so really torqey even with 225 degrees inlet and 35 carb
thing is as the worb 5 cylinder has been shortened and yr using a 51mm crank the port times has already been determined by worb5 maybe with a 0.5mm deck height the port times may be what they are, i dont have any idea of what port times the vsp road likes but i suspect that it will tame your scooter somewhat with that barrel
tho