Carb crossover 1-4/2-3 or all4? Ivan's MB with full akra

[Motopsycho87]

Just wondering what your opinions are on the crossover? I made the all4 adaptor up, and fitted it after syncing my carbs (I rode the bike with them blanked first). First though was that the idle was WAY lower, I had to screw in the adjuster a lot. It takes a long time for the engine to get hot enough to idle properly, more like my 2 stroke. And secondly, it did smooth out the power, but also feels like there might be less?

Now the 1-4/2-3 makes a little more sense to me, as when the valves are closed there will be a positive pressure in one inlet tract, while the other is drawing a vacuum... Now, if the carb with open valves is drawing from this positive pressure, surely this reduces the amount of draw through it's carb, in which lower velocity would result in less fuel being delivered to the cylinder, as its the velocity that aids fuelling?

I'm pretty much set on removing the system, but if I'm wrong about 1-4/2-3, it might pose some benefits... Just wondering what you've all found works best?

Cheers!

[Motopsycho87]

Just tried 1-4/2-3, still greatly reduced idle. Capped them off, the idle isn't as consistent, but is much higher, so I'm gonna keep them off.

[Falcon 269]

Any benefit is minimal, mostly snake oil, IMHO.  I tried it and then took it off again - too many potential intake air leaks for my liking. 

[Motopsycho87]

Mine was pretty well sealed tbh, and I used 5mm fittings and hose (what's the point in larger diameter if what's feeding it is smaller anyway??)

[Motopsycho87]

Put it back on, it definitely smooths out the little flat spot at 5k rpm

[PaulSmith]

What problem are you trying to solve?

[Motopsycho87]

Just a mild flat spot at 4-5k rpm, if the kit leans the mixture somewhat, might be worth dropping the needle one click... What you think? Set up as per ivans instructions. MB kit, akra exhaust, k&n filter

[Motopsycho87]

Refitted it, nothing changes, still got the flat spot recommendations?

[Falcon 269]

Just checking.  Ivan's MB kit, modded intake stubs and airbox lid, K&N filter, correct?  Recent DIY installation?  Carbs properly synch'ed?  Akra end can on stock headers?  EXUP properly adjusted and TPS?

I've never had to deviate from Ivan's settings with needle height.  What year is your Fazer?  Did you get the e-clip/nylon spacer/shim permutation correct for your year?

[Motopsycho87]

Full akrapovic, airbox mod, k&n (cleaned), needles middle clip, one plastic shim, one steel per needle (2002 fzs1), slides drilled, 10mm clipped from springs, measured with vernier afterwards and filed sharp ends down. Inlet rubbers ported, as similar as they can be without a gauge (I'm a toolmaker). Bypass jets drilled etc. Did everything exactly to the dot, cleaned out the carbs while I did it, checked for any damage etc...

[Motopsycho87]

To me it feels as though it's slightly lean for that revs (and with CV carbs surely the slide is at a similar position each time?)

I know it's a completely different kettle of fish, but I've jetted my 300 2 smoke perfectly, and it feels like a lean condition on the needle, not the 2 stroke "booowaaaahhhh" noise, but just soft and fluttery I suppose, no crackling or bogging...

[Motopsycho87]

I've found this where someone has had a similar problem,
http://www.yamahafz1oa.com/forum/showthread.php?t=59308&highlight=ivan+flat+spot

But the post ended on a cliffhanger

Looking at dynos they seem to get a little bit rich just as the needle comes into play... Perhaps I should drop the needle half a clip.. Or a clip?

[Motopsycho87]

Even Ivan's own dynos show a flat spot there

[Falcon 269]

I've got the full Akra system on mine and the power delivery does kind of level off in that rev range if you're in the upper gears.  I guess I've just got used to it.

One thing I noticed going back to your thread on the airbox lid is that you appear to have cut the snorkel down in height as well as removing the half facing the intake.  That might be causing a bit of a resonance issue in the airbox at just the wrong rpm range.

[Motopsycho87]

Should have gone pods really shouldn't I since Ivan doesn't sell the pods with the velocity stacks any more, where would they be sourced? Or how long were they? Is the only difference with the kit the main jets or is everything different? Not really considering... But if it's easy I love getting rid of clutter....

[Falcon 269]

Not really.    They offer nothing more performance-wise over a well-modded airbox and performance filter except ease of access to the carbs, possibly at the expense of fuel consumption and some extra set-up challenges.

You can modify the stubs connecting the airbox to the carbs to act as velocity stack inserts if you're really determined to go this route.

[Motopsycho87]

I think I'll avoid it haha.

So there seems to be no record of anyone shimming the needles half a clip lower? As mentioned prior there is evidence on some of the fz1oa dynos that shows it's a little rich at that point. I know dropping the needle slightly will change the fuelling all-over... But by how much?

[Falcon 269]

Honest opinion?  If Ivan couldn't tune out that dip in his bike's dyno chart between 4 - 4.5k rpm, odds are it can't be done.  It will be down to the design of the Akra full system.  There's no way he would have accepted that without trying all permutations of needle height etc.

No harm in you trying, though.

[Motopsycho87]

Had a reply from Ivan, he's said the only way to clean it up is crossover pipe welded onto the exhaust headers . Looks like I'll just have to deal with it!

[Motopsycho87]

Raised the needles anyway big improvement! Might be because sea level, and damn cold atm, may switch back for the summer!