55 mm throttle bodies again !!!

[eddie v twin]

Hi wonder if you can give me a bit of advice, just fitted a set of 55mm injectors to my Mille ( bored out from 51mm with new throttle plates)the bike starts and runs no probs, have set the tps, but when i went to set the bypass screws to sync the throttle bodies, i have ended up with both of them turned right in clockwise otherwise the tick over goes right up to about 1900 rpm as soon as i adjust them out, the throttle stop in backed right off as well. Not had a chance to try the bike yet on the road. The bike currently runs renegade airfilter, aprilia evo can and chip

Any advice would be really welcome

Eddie greig ( eddie v twin )

[Exdukenut]

Check your vacuum lines for a possible split. Mine, 55mm tbs, did exactly this and ran like shite, because of it. After we found it, and sync'd the bike again, I was able to get a very smooth idle at 1500rpm, whilst warming up. When completely warm mine idles at around 1600-1650rpm.

Hope this helps.

You may also find that the Aprilia chip can't quite cope with the 55mm bodies. My Renegade chip ran incredibly rich down low, so I installed a PCIII usb, and had a custom map done. It runs like a scalded cat now, anywheres from 3.5k upwards.

[ken zeller]

eddie,

who bored the throttle bodies for you? was it done on a cnc or manual mill? what tooling & speeds did you run (what surface finish did you end up with)? how were the throtlle blades measured & machined? were they hand fitted in each bore?

[eddie v twin]

Hi guys the throttle bodies were done by a local engine performance company who specialise in classic and rally car racing rebulids, the bores were cnc machined and the throttle blades were hand blended to each bore. The finish in each bore was a smooth matt finish.

Eddie

[Exdukenut]

Hi guys the throttle bodies were done by a local engine performance company who specialise in classic and rally car racing rebulids, the bores were cnc machined and the throttle blades were hand blended to each bore. The finish in each bore was a smooth matt finish.

Eddie

Like mine were, by the Racing manager of the Aprilia Pro Twins winner in OZ. Got them on permanent loan.

I'd check the vacuum lines, and then I'd suspect it's the chip causing the prob. JMHO.

A PCIII will sort it.

As stated above my Rene +2 chip was incredibly rich with the mod, even after adding a EVO pressure reg. You could smell the unburnt petrol, at idle, before the PCIII & custom map. The reason I couldn't use the EVO 54mm TB chip was that my bodies were 55, (D'Oh), as I would've probably gone for it, but ended up with the PCIII, (Chuck B got me a great deal on the PCIII, by the way - half the price, compared to OZ prices, Huge tks there Chuck).

The reason I stuck with the Rene chip and had it custom mapped was that the only 2 chips on the market that offer ignition advance are the Rene & the EVO ones, and because I already had the Rene chip, it made a lot more sense, to go this route.

Check the lines, get it sync'd with a decent set of vacuum guages, not to say the EVO guage is bad, but the mercury ones are far more accurate with this mod, (chalk and cheese, by the way), and then get a PCIII with some dyno time. It will work out in the end, I can assure you. It took me a month or 2 to sort it properly, and as said before, it really is a rocket ship these days! I love the 55mm bodies, as it spins up incredibly easily!

[eddie v twin]

Well took the beast out for a run , about 100 miles, mixture of hard blasting and slow round town speeds, gotta say she ran beautifully , certainly has a real kick to it when you wind it up. But there was no glitchs or lumpy running in fact very smooth. Seem to hold on to the top gears much better, where as before i allways felt it ran out of breath in 6th at about 10,000. Just a bit concerned that she ticks over at 1500 smoothly but with both trim synch bypass screws at about 1/4 turn out each ( anti-clockwise from fully seated)where before I was running 2 1/2 front cylinder and 2 rear.
But she does go well and certainly no flat spot at all at about 4-5k mark

Eddie