Justin Posted November 8, 2004 Share Posted November 8, 2004 I'm moving out to CO, which means I'll be going up @ 5000 feet in altitude. So I'm gonna have to re-jet the bird. I have never done much in the way of carb work and just looking for some advise. Are there any good online tutorials for leaning out the carbs. My bird has D-J jet kit, which I think has adjustable jets... is it just a matter of dropping the needles, or is there more that needs to be done? Quote Link to comment Share on other sites More sharing options...
Justin Posted November 8, 2004 Author Share Posted November 8, 2004 actually its a Factory kit on the bike.. it was from muzzys, i thought they used DJ for the bird, but it was factory. Quote Link to comment Share on other sites More sharing options...
Guest rockmeupto125 Posted November 8, 2004 Share Posted November 8, 2004 Hmm.......mine ran just fine in Denver.... :razz: Quote Link to comment Share on other sites More sharing options...
Justin Posted November 8, 2004 Author Share Posted November 8, 2004 Hmm.......mine ran just fine in Denver.... :razz: is yours carbed? Quote Link to comment Share on other sites More sharing options...
Guest rockmeupto125 Posted November 8, 2004 Share Posted November 8, 2004 The one I was in Denver with is. Quote Link to comment Share on other sites More sharing options...
tomek Posted November 9, 2004 Share Posted November 9, 2004 You are gonna have to compromise some how,Colorado has bunch of 11000-12000 passes so,,,,,,,,,,,,,,, There will be a power loss anyway due to thinner air,unless you tubocharge your bike,but on carb motors it is amplified by jetting going rich.Rich jetting kills topend, I would drop mains about 3 sizes down and go leaner on pilot screw 0.5-0.75 turns.If it does not work don`t blame me .What do I know? I`m at 500 feet :wink: Quote Link to comment Share on other sites More sharing options...
bartonmd Posted November 9, 2004 Share Posted November 9, 2004 Correct me if I'm wrong, but isn't altitude changes what the vent tube to the carb slide diaphrams is for?? I know old kawasakis that don't have the vents, you have to rejet for that altitude, but I didn't think you had to do that with any carb that has a vent? Mike Quote Link to comment Share on other sites More sharing options...
RodeRash Posted November 9, 2004 Share Posted November 9, 2004 As a starting point, try dropping the main's 2 sizes, then you may need to richen the needles a little. For what it's worth. After always screwing around trying to get the jetting perfect on previous bikes, I decided to just leave well enough alone with the Blackbird. I have no issues with the stock settings, and I don't have to worry about the bike running lean when I go on rides outside of Colorado. Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted November 9, 2004 Share Posted November 9, 2004 First lets back up a second. Factory pipes, 4 into 1, slipons, or full system? Factory or K@N air filter? How did the bike run at your lower location? I think at the most move the needles and turn the pilot screw in 3/4 turn, depending on where it is now. Maybe not even that. Remember, all Honda wants you to do if the bike is completely stock is turn the pilots in 3/4 of a turn if operated CONTINUOUSLY above 6500 FT. This is more for emissions then anything else. I can't see dropping main jet sizes. For Mike: the carb and diaphram vent hoses are to allow air in and out. They don't respond differently to different altitudes. Just for reference I'm running the factory pipe and air filter. I drilled the carb slide hole slightly larger and pilot screws out 3 turns. runs great. Quote Link to comment Share on other sites More sharing options...
Justin Posted November 9, 2004 Author Share Posted November 9, 2004 I have muzzy 4-2-1 full pipe and headers ... factory Jet kit ... not sure what filter element ... I am going to pull the tank today and check what filter it has .... I didn't get that info when I bought it .. right now the bike runs a bit rich .. but not so much that its a problem .. I healthy dose of dark when I crack the throttle open ... but IMO, thats not un-normal with a high performance well tuned bike.. The bike runs good, has better low-end and mid-range than a stock carbed bird, and the top is still pretty good .. I can get close to 180 and I'm not a shrimpy guy ... I'll have to see how it runs when I get out there ... which will be on Sunday ... maybe I'll get lucky and throwing a high-flow filter on will be good enough. Quote Link to comment Share on other sites More sharing options...
bartonmd Posted November 9, 2004 Share Posted November 9, 2004 Pete, I know they're to let air in and out as the slides go up and down, but I thougth that was so the bike ran well at all different air pressures too, since it knows what's going on on the outside now, rather than just the pressure they were sealed up at?? Not trying to argue, but more trying to learn... Mike Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted November 9, 2004 Share Posted November 9, 2004 Nope the only thing that responds to altitude is FI, and that's only if it's a closed loop system. Quote Link to comment Share on other sites More sharing options...
tomek Posted November 10, 2004 Share Posted November 10, 2004 Nope the only thing that responds to altitude is FI, and that's only if it's a closed loop system. It has nothing to do with close or open loop systems.Fi XX have BARO and MAP sensors ,they take care of changes of atmosheric pressure. Quote Link to comment Share on other sites More sharing options...
Northman Posted November 10, 2004 Share Posted November 10, 2004 In a carburetor, changes in altitude and air density are usually made up by less atmospheric pressure on the fuel in the bowl. There will be less fuel entering the engine at altitude, anyway, but there's no question that a good jetting job will help. Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted November 10, 2004 Share Posted November 10, 2004 This brings up my next question. Why aren't ALL FI systems closed loop? Why just follow a map which takes input form the sensors? If the PCM relied on the 02 sensor for it's input like all GM cars and trucks, all you would have to do to get more performance is have the PCM look for 12 to 1 air fuel ratio instead of the "clean air" 14.7 to 1 ratio. Quote Link to comment Share on other sites More sharing options...
Red J Posted November 10, 2004 Share Posted November 10, 2004 This brings up my next question. Why aren't ALL FI systems closed loop?Why just follow a map which takes input form the sensors? If the PCM relied on the 02 sensor for it's input like all GM cars and trucks, all you would have to do to get more performance is have the PCM look for 12 to 1 air fuel ratio instead of the "clean air" 14.7 to 1 ratio. It's cheaper to omit the O2 sensor, and have the map dictate the fuel. GM and otherwise, use a map when on full throttle, decel, etc. The only time that the O2 is used is in steady state cruise or very mild acceleration, to clean up emissions and to better fuel economy. Conventional O2 sensors (non-wideband) are not accurate enough to get within a few tenths of O2, and you want to be there under acceleration. Most of your engines use an O2 to go from rich, to lean, back to rich and so forth. If you have a "AFR gauge" that uses the stock O2 sensor, you can see this in action. The gauge simply goes back and forth when in closed loop. Whack the throttle open, and it goes to the map, sits at rich. Get out of it, and it's back to the oscillation. The high load areas of the map (high throttle position, high manifold pressure) stay somewhat consistent over time. As long as the engine's volumetric efficiency doesn't change (displacement, headwork, cams, manifold pressure change), you don't need a different map. The reason why, is that this system is reliable, works well for most of the time. Lean burn cars, like the Honda Civics that have VTEC-E, and some newer cars such as the VW Golf and the new VW/Audi FSI engines, have a wideband sensor. I don't know for sure, but I believe that they still use closed loop for wide open throttle. That isn't the principal reason they use wideband sensors, the reason is that they can get closer to an accurate lean burn on cruise, and better fuel economy than is possible with a narrowband sensor. When your sensor shits out, (they all will) you're back to the map. The ECU will default to a predetermined value for your throttle setting, manifold absolute pressure (or airflow, depending on system) and inject fuel/adjust timing based on that. J. Quote Link to comment Share on other sites More sharing options...
Justin Posted November 16, 2004 Author Share Posted November 16, 2004 false alarm ... bike is running really well here... not even as much power loss as I feared Quote Link to comment Share on other sites More sharing options...
Guest rockmeupto125 Posted November 16, 2004 Share Posted November 16, 2004 Did you still want that route through Pennsylvania? Quote Link to comment Share on other sites More sharing options...
Northman Posted November 16, 2004 Share Posted November 16, 2004 Nice write-up, Jeremy :cheers: Just to expand a bit on that... An oxygen sensor is a tool used to measure the oxygen content in the exhaust system which is an indication of air/fuel mixture going in. It is not solely used to control the fuel, but can adjust the mixtures accordingly for changing conditions, and compensate for dirty injectors, etc. When the adjustment falls out of a certain window, the ECM detects this as a fault, and reverts back to original preset values. Those preset values are also used for cold starts until the engine & O2 sensor get up to temperature, and for full throttle operation as Jeremy already said. There isn't enough heat in the exhaust at idle to keep the oxygen sensor functioning properly, so it comes out of closed loop there, as well. Car manufacturers came up with heated oxygen sensors to speed up the time between startup and closed loop, as well as keeping the sensor hot during long idle times. Quote Link to comment Share on other sites More sharing options...
Justin Posted November 16, 2004 Author Share Posted November 16, 2004 Did you still want that route through Pennsylvania? no ... thanks anyway lol ... when I return next year we have to hook up and ride some of em .. but when I wen through it was midnight and snowing ... so twisty stuff did not seem as much fun lol Quote Link to comment Share on other sites More sharing options...
Red J Posted November 16, 2004 Share Posted November 16, 2004 Car manufacturers came up with heated oxygen sensors to speed up the time between startup and closed loop, as well as keeping the sensor hot during long idle times. Also, to expand on your expansion, the reason why the O2 sensors need to remain warm, is that they are designed to be accurate when warm, and the heat allows the sensor to burn off the unburned fuel and carbon, which would cause them to clog up. Not sure if this was covered. :drink: J. Quote Link to comment Share on other sites More sharing options...
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