setting up carbs and jetting.

[stevo as b4]

Hi, This is just basically a question for anyone that's bought new aftermarket carbs, and paid for dyno time and expertise to have them set up properly.

What did you do regarding jetting in terms of having a range of jets and needle's and slides available on the day? Did you supply your own range of jets and needles etc, or did the tuning firm stock them?

I've got a carb to get set up, that I've had pre-jetted at purchase to the specs of another engine using the same capacity per cylinder, and then I've gone up a size on everything.

I've got main, pilot and power jets a few sizes either side of this, but no different needles as I wouldn't have known what to order.

I'll obviously be speaking to the tuner/dyno operator before going, but i don't want to waste a few hours of expensive dyno time for the sake of not having the right jets or needle required on the day, and then have to go back again.

Finally what are peoples thoughts on fitting a new carb and then if it seems to run okish, riding to the dyno centre on a base setting, or should the bike always go in a van?

I'm not buggering around with this bike trying to read spark plugs that give misleading results, and trying to self jet a brand new carb, that's too much ball ache for me!

[stirlinggaz]

hi,
I dunno what bike your fitting this carb to, but im sure your not the 1st to do it.
why not ask in forums specifically for that bike? or even a fb users group?
there should be owners who have already tried this mod & should be able to point you in the right direction.
has to be better than going in blind....its something I have done in the past.

cheers,
GAZ

[..]

Hope you didn't buy a Dellorto KEIHIN PWK's are better & miles easier to set up you're 100% correct about not to believing in the plug chop myth. always use the "How far from 4 stroking" method on needle clip position & high rpm full throttle. I just switched from a Polini CP 19mm to the Polini CP 17.5mm on a single cylinder 70cc 2 stroke motard, this carb is even easier to jet than PWK's due to having only 1 needle & Atomiser. it has an airbrake feature for 4 strokes but the largest CP carb Polini do is 24mm...too small for larger displacements.

Here's what i did: stuck the carb on this morning with 10 sizes too large MJ so there's no risk of running it lean, slightly large Pilot jet - which actually turned out to be perfect. it sputtered/4 stroked on full throttle until i went 6 sizes smaller on the main jet & now runs perfect

[Nobby the Bastard]

If you are booking dyno time and have told them which carb you have and they don't have suitable jets I'd be looking at a refund.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[stevo as b4]

TBH, I'm sure they will have plenty of suitable Mikuni jets, as they do this sort of thing all the time. But I've never had a professional dyno tune done before, as was unsure if it's a good idea to supply the jets that you think might be needed to get it spot on.

I don't care how long the set up takes, I just don't want it to be a case of we need the XYZ needle to finish the job perfectly and we havn't got one, so please come back for more bike torture next time.

I've played around re-jetting scooters and bikes before, and with my speedfight I got the main jet fairly close, but couldn't get the other circuits tuned very well, so I can't be bothered with messing around, or melting things.