1994CBR900RR 41mm FCR Tuning help - Honda Motorcycles - FireBlades.org
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post #1 of 6 Old 06-05-2017, 1:44 PM Thread Starter
 
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1994CBR900RR 41mm FCR Tuning help

Alright, so did a bit of work on a bike I bought in Florida and brought up to Wisconsin. Carbs are cleaned and tuned somewhat close, bike starts up and idles fine. Full throttle isn't exactly what it should be, and higher rpm's above 8-9k it bogs bad. I think it is running too rich. I don't know off hand what the jet sizes are, I do know what the needle height is adjusted at and I tried it at the 2nd, 3rd, and 6th notch from the bottom of the needle. Not a whole lot of difference in any position. Bike has a lot of porting and polishing done to the head, cams, full two bros exhaust, adjustable TBR ignition advancer, V&H power pak, velo stacks with filters on top on the carbs and I think that's about it. Weather ranges from 50-80 up here for when I ride.

What are some recommended jet sizes and fine tuning?
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post #2 of 6 Old 06-05-2017, 6:23 PM
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Re: 1994CBR900RR 41mm FCR Tuning help

For what you just described there is no baseline, or anything close to a recommendation.

That motor is so "built" and tweaked that it would be tough for Mike Velasco to figure a good all around setting. If your looking to street ride it I would say you'll never find a happy medium.

Is the bore stock? I can only assume that with 41's it would have to be at least 5mm over (1024cc), otherwise they're a waste. 39's would more suit a standard 893cc or a 945cc overbore. There is such a HUGE selection of needles for FCR's. Where the taper starts, ends, diameter, length, clip position, etc it's mind boggling.

Don't get me wrong, I love the sound of everything you described, it's just trying to dial that all in is an old art that isn't done anymore because of FI.

I know I didn't help, but you'll need to contact someone that has a similar set up and pick their brain.

Good luck!

My 99 900RR Track Build Link:Track Build 900RRX

My Red Rocker 93 Build Link: Café 900RRP
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Re: 1994CBR900RR 41mm FCR Tuning help

Sound like you need to invest into a wideband 02 sensor/guage/meter. You'll never know if you're truly lean or rich without a wideband 02 gauge/sensor. You don't necessarily have to to have a bung welded into your exhaust im sure you can find a sensor designed to get stuffed down your exhaust. Either way I highly recommended getting one.
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post #4 of 6 Old 09-15-2017, 2:54 AM Thread Starter
 
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Re: 1994CBR900RR 41mm FCR Tuning help

Tried multiple jets, here's what's still happening....

Hello everyone, I have a question for you all. My 900 seems to hit a false redline, lose spark, or sputters out at about 8500/9000 rpms. I have tried re jetting the carbs multiple times and no difference. Anyone have this same issue? Little background, '94 model 893 10k miles, fcr 41mm carbs, head port & polish, cams, full tbr exhaust, stock ignition rotor, and v&h power pak.
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post #5 of 6 Old 09-15-2017, 3:54 AM
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Re: 1994CBR900RR 41mm FCR Tuning help

Quote:
Originally Posted by jman2000 View Post
Tried multiple jets, here's what's still happening....

Hello everyone, I have a question for you all. My 900 seems to hit a false redline, lose spark, or sputters out at about 8500/9000 rpms. I have tried re jetting the carbs multiple times and no difference. Anyone have this same issue? Little background, '94 model 893 10k miles, fcr 41mm carbs, head port & polish, cams, full tbr exhaust, stock ignition rotor, and v&h power pak.
Hi only thing I can suggest (which you've probably already looked at)is the Patrick Burns write up
http://www.litetek.co/docs/Flatslide_Tuning_Guide.pdf
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post #6 of 6 Old 09-15-2017, 8:17 AM
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Re: 1994CBR900RR 41mm FCR Tuning help

Have you tried the set up without the power pack?, or found a set of stock carbs to rule out fuel or spark issue?

Also, with the FCR's aside from moving the needle up and down, there are replacement needles that have different diameters AND tapers.

Does the bike power through the 8-9k rpm stutter and then pull like a raped ape?

Does the Power Pack have an adjustable red line setting? Maybe it's set too low?

It might just be something you need to bring to a really good dyno guy and see what the A/F ratio is at that RPM.

I'm curious to see how this turns out. Please keep us updated on what you've tried/ruled out.

I did a coil on plug mod to my 99. It was very simple to do, and I'm more confident in that set up than the old 2 coil set up. Something you might want to try to rule out a spark/coil issue.
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My 99 900RR Track Build Link:Track Build 900RRX

My Red Rocker 93 Build Link: Café 900RRP
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