Recommended Carb Settings...

tmk7c9 · 02-08-2008, 9:34 AM

Hi all,

I'm sure this has been hashed out here before, but after using the search function, I couldn't find what I was looking for.

I've got a '97 BB, with a BMC filter and a pair of RS-3 slip ons, all else is stock. It falls on it's face between 5000 and 7000 rpm. A dynojet kit is in the mail as we speak, I was just looking for a little guidance on jet sizes.

I've heard rumors that the factory pro jet kit recommends using larger mains in the center two carbs (I'm assuming the keep temps in check for the middle two cylinders?), but the dynojet manual I downloaded made no mention of this. Is this something I should try? or Should I just follow the directions to the letter?

If anyone has a similar setup to mine, i'd really appreciate your final carb settings (jet sizes, idle screw turns, e-clip needle position...). Maybe it will save me some tuning time if it just works great right off the bat!

bullet · 02-08-2008, 10:38 AM

...the dynojet kits i owned in the past but not for the xx used similar main jets ..i cant confirm about factory...known policy of honda's stock setup is using 2- 3 numbers down for the inner cylinders...even on v-2 ( even my old hawk 650 had 2 numbers down main jet for the rear cylinder..).....sure the factory kit should come with the approriate mains for the bike ...kit is also adjustable so even if you find settings you can alter them to achieve best berformance suitable to your needs and circumstances...

tmk7c9 · 02-08-2008, 11:01 AM

My mistake, it does look like the jets for the middle two cylinders are sometimes smaller, not larger. I guess hotter=less dense air=less fuel for the middle two. However, given the choice, i'd rather be too rich than too lean.

Either way, thoughts or recommendations welcome, especially on the mix and matched jets vs. same jets all the way across issue!

bullet · 02-08-2008, 11:22 AM

...difficult to match....different riding styles...weather... ...barometric pressure ...altitude...you have to practice..and the jet kit will work assuming the rest of your carbs stuff are in good condition...in these situations a complete overhaul inspection and carefully rebuild using the jet kit solves many problems that may come afterwards...keep in mind ..i 've asked many engineers here and they claim that bmc filters seem to be best choice for mild tuned /nearly stock setups...just their opinion...try the bike once with the stock filter ..and see how it reacts and how responds in various ranges of throttle openings for example in third gear from 3 to red line or with 4th gear from 6000 to red line....you may find the response peakier at some ranges with the stock filter...

tmk7c9 · 02-10-2008, 8:58 PM

Just an update....the dynojet kit went in yesterday. While I was that far, I went ahead and did clutch/brake fluid, coolant, and valves.

I followed the dynojet instructions, 140 mains all across were the recommended mains, but I don't think that can be compared to stock sizes, I think they're measured differently.

E-clip on 3rd groove from the top, idle screws 2 turns out. slides were also drilled out and had new springs (much softer) installed on the slides.

It was very, very cold today (20 deg. F) but at these temps, the carbs feel perfect. I'll wait to give the final verdict when it gets a little warmer, but so far, it's looking well.

Having the valves in spec sure quited the motor down as well.

For reference if anybody wants to use this as a guidlines for thier setup, i've got a BMC filter and Yosh RS-3 exhausts, with the baffles in. everything else is stock.

bullet · 02-13-2008, 5:15 AM

...although the dunojet mains look the same they don't have the same flow characteristics as any other 140's..they have different venturi tube design..

TigreST · 02-13-2008, 8:11 AM

My somewhat limited research has lead me to believe that DynoJet and Factory Pro have rather different philosophies when it comes to carb tuning. Same applies to the dyno thinking...two different ways to look at the issue of hp output calculations. There is lots of interesting reading on the FP site about the dyno thing.

I'll be doing a Factory Pro carb tune at some point and have the kit here,..just not next to the puter so i can't check the spec's. If you go to the Factory Pro site you'll find the following:

Subject: CBR1100XX kit

Date: Wed, 15 Mar 2000 10:41:10 -0600
From: "Backus, Daniel" <Daniel.Backus@Laureatexxxxx.com>
To: "'factory2@ix.netcom.com'" <factory2@ix.netcom.com>

re: CRB-H75-1.0 carb recalibration kit and RTR-HON=8=02 +2 advance kit.

Thanks, Marc for your kit for the XX. The install was simple and what a relief to not have to drill out the slides AKA dynojet install.

The performance improvement has shocked me, especially since the exhaust and air filter remain stock. Based on my initial results, I am nixing plans to change the exhaust system (noise preference) since I already have a hard
time hanging on under WOT.

I followed the recommended specs exactly, changing the outside jets to 142, and leaving the inside mains at 142, and setting the needles to the second slot from the top. I then seated the pilots and backed each out the recommended 2 1/2 turns, and reassembled.

Have you ever dynoed this configuration (stock pipe, air and kits) - and what was the delta? We do not have the Eddy here, only the dynojet deceiver.

P.S. the gasket that came with the ignition advance did not fit. I used Hi-Temp RTV copper successfully, tho.
Note: The supplied gasket is for the cbr600/900. You need to supply your own XX gasket. Cheers! Marc

Paste ends.

I'll be running a Ti Force pipe with my jet kit..so the numbers will be changed. Factory Pro do not drill the slide nor change the springs. It is simply jet changes, needle changes, and pilot needle valve adjustments. They supply a range of jets depending on your intended application,...pipe change, airfilter change, etc. I can check and relate this info to you if you like.

I did read one report where a customer was going from a DynoJet to the Factory Pro kit...FP advised that the drilled slides could be plugged with epoxy and then redrilled back to stock sizes holes. The info on the site is convincing,..but of course I'll get to see for myself at some point.

Tony

tmk7c9 · 02-13-2008, 8:39 AM

I've only done one FP jet kit in my life, for a '95 katana 600. I had terrible results with it. The bike came with a full yosh system and k&n filter in it. After the carb work, it had a terrible flat spot around 6K rpm, it simply fell on it's face. I tried every needle position...nothing. Then I switched mains, and tried every needle position with the larger mains. Still no good.

I found a fantastic set of stock pipes for it on ebay, and now it has the stock pipes, and the stock carb settings, and it runs better than ever, almost perfect, with just a slight hint of that flat spot at 6k.

I know I should give FP another shot, I've heard nothing but great things about them. But every dynojet kit i've ever installed (including MANY on other peoples bikes while I was a mechanic) have always worked the very first time. Follow the directions....done.

It worked out great with the BB, although I'm still waiting for the weather to rise above the freezing point so that I can give it a thourough thrashing. Initial impressions from a 1 hour, 20 deg F ride are looking great though!

Pete-in-PA · 02-13-2008, 10:29 AM

I had bad results with a Dynojet kit on the XX and went back to stock. Never tried the Factory Pro kit. (wish I had instead of Dynojet)

The dynojet needle had a steep step in it instead of the gradual taper this part needs.

I'm now at 142 mains on all 4, have the Honda needle raised 20 thou. and pilot screws out 3 turns.

I'm still playing with needle height, I can tell the difference with and without ethanol in the gas. I try to buy without but sometimes have no choice.

I do have the Factory Pro ignition advancer, like that a lot.

TigreST · 02-14-2008, 1:15 PM

Factory Pro info: see attachements.

Tony

bullet · 02-15-2008, 9:11 AM

...FP produces amazing stuff....they also sell aftermarket gear selector drum of astonishing quality and quieter operation of the gearbox....the have also an amazing portable efi managing unit called teka available only for zuki's and kawa's....

TigreST · 02-15-2008, 9:37 AM

I'll be putting a selection of their products to the real world test. Shift Star Improver Kit, Ignition Advancer and Jet kit. So far my purchase dealings with Marc at FP have been very good.

Tony