90 fzr 1000 needle ID and tune

[kurt112345]

Iam a new fzr owner, I posted in the introduction. I picked up a 90 fzr 1000 with 8600 miles on that obviously been sitting a long time, had carbs off put new boots on old ones just cracked apart. Did a dip on carbs get them looking great, but the bike did come with a vance and Hines super sport exhaust, and has a odd jet kit, the needles feel like there aluminum and have 7 clip positions, maybe a vance and Hines jet kit? And they where set at the leanest possible top clip and all factory spacers, anyone have any info on these needles and where to start base line. Bike is kinda doggy till about 6500rpm. And I have new plugs, and carbs synced with morgon carb tune. Bike idles good and revs nice but between 2k and 3k it has this spot where it sounds like cylinders cutting out happens around 1/8th just enough throttle to hold steady and also does it when first start up bike choked when rpms eventually reach 3k. I do have a video if the issue I can post on face book page, it's really annoying with 25-35 cruising kinda kicks back and jumps around bike runs great other then that, thanks, I posted pics of bike on Facebook page.

[djalbin]

The only baseline I can give you is the OEM specs for 1990 FZR1000

Main jets: Cyl #1 and #4 is #125
Main jets: Cyl #2 and #3 is #122.5

Main air jet: #85
Needle jet: Y-0
Pilot jet: #37.5
Pilot outlet size: 0.85
Pilot air jet: #125
Starter jet: #60
Throttle valve size: #125

Fuel level (floats): 10.6 ~ 11.6 mm (0.42 ~ 0.46 inches) above the float chamber line
Engine idle speed: 950 ~ 1050 RPM
.

[kurt112345]

Can these bikes run good down low with out exup? obviously with proper jetting. around from idle to 4000krpm general light cruising in town?

[djalbin]

Can these bikes run good down low with out exup?

The short answer is "no". The exup valve is in it's closed position (closed is still partial open) until the RPMs reach 2K RPMs. Then the servo starts to open the valve. The servo continues to open the valve, as the RPMs increase, until the RPMs reach abut 8K RPMs ... then the valve should be fully open. The valve provides the necessary back pressure at the lower RPMs for the engine to run good in the low to mid-range RPMs. The additional back pressure isn't needed at the higher RPMs.
.

[Jordan_Ciaramitaro]

My bike had a d&d header when I bought it(no exup)

I just installed a wideband o2 to dial it in, and now fully understand why the exup valve is in place. It's important to note that the carbs are downdraft, therefore the main jet is regulated by the needle which is connected to the slide that opens relative to air flow through the carb.
In short:
When you ask for high acceleration at low rpm, the slides open too far causing an overly rich condition.

The exup restricts air flow through the carbs to prevent the slides from opening too much too soon. This helps keep the afr close to optimum throughout the rev range.

On my bike which also has 1st gen r1 carbs the afr gets really nice around 8k which interestingly noted above is when the exup should be fully open.

I can think of several other ways to compensate, however, the exup is the easiest and cheapest way to do so. As also mentioned above, at wot high rpm, you as much flow as possible in respect to proper afr.

So in short no, but turbo, nitrous.... You have options


Sent from my iPhone using Tapatalk

[kurt112345]

alright dang, hmmmmmm, I ordered new emulsion tubes and factory pro jet kit, when I looked at the old needles in my bike which are aluminum and 7 clip positions, the looked kinda worn one side like you can almost feel it. so with new tubes and the new jet kit and no exup, is it possible to make it ok the live with? right know it kind of misses and kicks back at me on the 40mph below cruising once above 4k its great all around. thanks the info has been very helpfull, might half to source out a exup header and complete servo setup.