Carburation-Situation

[Big-Bore]

Well I have managed to get 100+ miles on the polini kit now and as it was running very rich on the standard airbox I have fitted the pipercross filter that I meant to keep until running in was a little more advanced. With the standard airbox, even running in the extra cubes were apparent, but now with the pipercross---WOW. The running is very uneven around the usual 6000rpm stage but then when the power kicks in WOW. This to me, and bear in mind that I am still running in carefully and not revving the tits of it, this feels to me like my old 350 LC Yamaha. Those of you who know will recollect how the power kicked in on these bikes, instant wheelie yeah? The Aprilia power kicks in hard and forces you back against the seat, the riding position and bars keep the weight forward but the front goes distinctly light and the rev counter needle heads for oblivion. This is fun now and will be great when running in is complete if I don’t blow it up first. The low-mid range is a bit of a pig though, you cant go everywhere at 8000rpm + It feels over rich.
Has anyone got any tips on how to best tune the 34mm carb for mid range use?
Has any one actually removed the environmental restrictor bridge in the management system?
Main jet 178
Needle K57 2nd notch
Mixture 2 turns out

[Craig]

178 Main!

[aReSCXXV]

Originally posted by Big-Bore
The low-mid range is a bit of a pig though, you cant go everywhere at 8000rpm + It feels over rich.
Has anyone got any tips on how to best tune the 34mm carb for mid range use?
Has any one actually removed the environmental restrictor bridge in the management system?

Hi,
leave it as is till you have done the running in.
then you have to locate exactly where, regarding the throttle
position, it is running rich or lean. remember that you have to
relate your findings always on the actual throttle position and
NOT ON THE RPM.
for starters get that bridge off as soon as possible.

[aReSCXXV]

Originally posted by Craig
178 Main!

Hi Craig,
it's a big bore with unrestricted air box. i think he's pretty close
with a 178.

[Craig]

Yeh forgot about the big bore, still sunds big, i wold prolly be at 172 / 175. But then i aint done this yet so cant comment to far.

[aReSCXXV]

Hi,
he'll probably come to those when the weather gets warmer.

[Big-Bore]

Thanks for the input guys. The 178 main jet came with the big bore kit, I have no other info to go on so better too rich than weak, at least for the moment. If summer ever returns i can play about with the jet again. I was surprised that the whole kit ran so smooth with standard airbox "straight out of the packet", as i said all the responses are now more pronounced with the pipercross. The throttle is more on-off and the 6000rpm resttriction is more of a nuisance.
I may do your airbox modifications Croation man and try that as well just for comparrison.
The info i have for removing the restrictor bridge is on the Aprilia zone website, it seems to make sense but more input pleas before I start butchering it. Thanks again!

[PJ ENGINEERING]

You may need a smaller jet than std

Big bore sucks more

The best thing is to run her in then go down a bit on the jet.

[aReSCXXV]

Originally posted by Big-Bore

I may do your airbox modifications Croation man and try that as well just for comparrison.
The info i have for removing the restrictor bridge is on the Aprilia zone website, it seems to make sense but more input pleas before I start butchering it.

Hi, Big-Bore

it's not "my air box mode" but Aprilias, same as the CDI mode...
i just put it up here to inform. we use it, Italians and Germans
use it, especially for big-bore cylinders, so why shouldn't you...
maybe you have more oxygen in you air and don't need it

regarding the CDI, just imagine the ridiculous situation, when
Aprilia, in their own user manual, says that the new bike should
be run, first 800km, till 6000rpm. we all know that the FP version
RS is completely useless between 5000 & 6000rpm, so they suggest
that the engine is run in, effectively, with 1500rpm range !!!

when you do the CDI mode follow those instructions and nothing
can go wrong. when dug out the bridge can be cut off easily.
remember to close the "hole" with some water proof putty.

[Big-Bore]

Thanks again people.
Kef, I have removed the pipercross and refitted the standard airbox now modified. Only just completed that task so will run it tomorrow and see how it goes. I guess I need a happy compromise untill the polini kit is close to fully run in, say 200-300 miles. Then I will take the time to do some full bore plug chops and play with jets and airfilter systems.
The cdi had already been modified. It had a big lump of badly applied silicone on the end. Still I dug it out anyway and found the two ends of the bridge and carefully refilled the hole.

[Big-Bore]

Big bore sucks more



Hey whos been letting out my secrets, and anyway I never inhaled!