Hi folks. After much carb work on my 1996 trident 900 with 14k miles...almost all new pieces in the carbs...i am still running a bit of a rich smell and really bad mileage 18 to 20mpg. The bike actually performs very well...feels strong and doesnt really exhibit anything significant...but the mileage is terrible the carbs have a stock set up and I'm almost certain that the issue has to be something beyond any "tweaking of settings etc. I should be getting double the MPG so its cant be something minor. Any advice? Could the petcock be an issue. the dial spins 360 degrees...is that normal? Valves? I also notice that the temp guage doesnt move at all...although it has been cold here in new england...i still would have thought it would come up a bit and am not sure if thats indicative of something. I am really looking for something outside of carb settings to explain this but i also intend to run couple of more tanks to be sure of what i am seeing. thanks in advance for any help
Is the manual choke free and fully in the OFF position ? Check the needles in the vacuum operated pistons are they in the correct setting ? As lifting the needles a couple of clip setting's can affect fuel mileage significantly. Otherwise change the air filter or check inlet side of the filter for blockages...?
Thanks. here are some other data points. The petcock appears to be functioing properly and there is no leaking out of the vacumn hose back into the engine...engine oil appears to not have any oil in it. Also after many days of sitting there is no puddling of fuel under the bike..no drips at all but when i start it the bike starts easily with no choke at all.....perhaps that is a sign that the choke is not in the fully off position...even though it does react when i pull it open and close...maybe its not closing fully? thanks again in advance for the advice!
Btw I meant to any fuel in the oil! Choke seems to be working properly...fully seating....perhaps I do need to focus on the needles setting...I just wouldn't have thought that a tweak would have such a profound effect?....could a change in setting be worth 12mpg or more?
Being as you have done quite a lot of work with the carbs .......... Can you push the choke piston further once you have turned off the choke at the lever at the bars ? Have you checked the float heights ? Are all the jet sizes std ? What have you got the pilot screws set at ? What groove are the needles set at ? Settings changes can make a substantial difference in mpg
hi again folks. here are some additional answers to the questions that were posed 1. We have put in a stage 1 dynajet kit...in the hopes to replace worn needles and jets. Remember it was running rich then as well 2. mains are at 120, needles are at 4th groove, screw is turned out 2.5 times. Does something jump out as obviously not right with these settings? We will certainly try 3rd groove in an effort to lean it out a bit but would like a sense from you folks 3. Choke is seating properly, floats have been checked as well....levels are right on...but we will check again when the carb bank comes out thats about it...thanks for the interest in helping me out!
Hi gasanders Are you counting needle grooves from the top or bottom of the needle ? Std setup with triples is to have the center main jet smaller not all the same. 2.5 turns out on the pilot screw seems a bit high, carb runs on this jet for approx. the first 1/4 of throttle opening so can have a big effect on consumption. Have you checked the thermostat is working ie not stuck open ? After a run does the fan come on if you leave the bike idling ? Edit : you mention valves ? and @14K I am assuming the valve clearances were checked / adjusted @ 12 k as per service schedule ? did you do this yourself ? or someone else ? if someone else did you get a list of the current clearances when the job was done ? If not done recently I would suggest they are checked very soon as your rich running could be the result of / or hiding other issues. plug colour would be another good indication.
Thanks for the advice......not sure on valves.but will check..can you elaborate on plug color.....what clues will it give me. Regarding the thermostat can you help me understand how that effects this issue...I will tell you the temp gauge almost never moves....its always reading cold....and I don't think I've ever heard the fan come on...is there a clue there? Really great help...please keep it coming !
Google spark plug colour chart, Black & sooty is rich, brown is still a little rich, most plugs run a light brown /grey colour. Hard to describe a picture is easier to see the differences, if you have a Haynes manual its usually on the back page. A cold engine burns more fuel, the thermostat holds water in the block to help with warm up and opens to the rad as the temp rises to normal, a stat that is stuck open allows cold water to circulate through the red during the warm up phase keeping the engine temp lower and burning more fuel in the process. Was your engine up to normal running temp when you set up the carbs, as you cant set up carbs on a cold engine !!
i think you may have something with the thermostat issue...its the one constant that affected the richness before the carb work...and after...and the bikes temp guage never ever moves...but its been cold here and rides have been shorter..but still I think this is something to look at thanks very much
If it helps, my Trident temp gauge points to around 11 o'clock when at normal running temperature and will rise to around 12 o'clock in slow traffic. It will drop back to 11 o'clock when back up to speed. Very rare for it to get hot enough to trip the fan. I usually get 45 - 50 miles per (imperial) gallon. You will get less because your (US) gallons are smaller than ours. But not by much apparently. Mice love nesting in Trident air filters it would seem, as a mate of mine once found out. Fuel tap should only turn through 180 degrees ... pointy end vertical (up) = prime ... pointy end horizontal towards the back = normal running position on vacuum system ... pointy end vertical (down) = reserve fuel supply, also on vacuum system.
It does help...thanks...the big question is very simply if mine is running so much cooler would that have a profound effect on gas mileage
Hi folks. Two tank of running yesterday...here is what i learned. unburnt fuel smell at idle, black smoke, 15mpg, a stumble and roughness at slight throttle opening...and plugs were black. Simply put its running rich and to the extent that there is no doubt that there would be some benefit to a change to 1.5 turns and the 3rd clip on the needle there is something else going on for sure. here is what hasnt been looked at since before or after the carb rebuild 1. Valves have not been checked or adjusted...perhaps there is a story here...if they were out of spec would that have a profound effect? 2. the temp gauge never ever came up from the Cold line....even after stuck in traffic for a while on a warm day...we will check for a stuck thermostat 3. perhaps something wrong with the airbox...im pretty sure there arent any obvious stories there as we had everything apart but i dont want to dismiss it. not sure what that could be so i dont expect to find anything 4. coils?....I dont think this is an issue since we looked at them early on. Two of these 4 things represent things that havent' been looked at yet..... and based on what you folks are saying if these items were issues it could explain everything by themselves....Valves and thermostat...with a slight tweak of carbs settings do i have that right? thanks again
Ooh eck........ This is not something readily diagnosed over the net without knowing a lot more...... You say it is ‘standard’ but Dynojet stuff is not standard and their numbering system does not correlate to Keihin, Mikuni etc. Moreover carbs are sensitive to changes to the inlet side and exhaust. Airbox and filter mods will impact the fuel/air ratio just as exhaust mods affect back pressure and breathing. Even allowing for smaller US gallons (sorry Texas!) your consumption suggests you are running VERY rich as does the smell of fuel. The question is ‘why’? Assuming standard and clean air filtration the jetting is the obvious culprit and an exhaust gas analyser, better still rolling road, will get you quickly in the ball park. Binding brakes would also impact consumption but you’d notice! Who selected and fitted the Dynojet kit and with what intent? Finally, the old plug charts do not work so well with modern fuels which are less sooty and less obviously rich running. I would be for verifying just how ‘standard’ things are and ensuring clean filters etc. Petcocks simply allow the fuel to flow or not. It will not impact carburation. If it runs ignore ignition and timing for now unless you think it is running the wrong (Dynojet?) timing map. Best advice? Local auto shop with an exhaust gas analyser to verify how far out the carbs are. ......take it from there.
A couple of subsidiary thoughts..... I assume the carb kit was something like this? https://dynojet.co.uk/media/attachment/file/e/5/e5102uk.004.pdf And that you are not running a K&N or similar oiled filter that is clogged by over oiling?
The needle jet is where the jet needle slides into. Depending on the inside diameter of the needle jet, it will affect the jet needle. The needle jet and jet needle work together to control the fuel flow between the 1/8 thru 3/4 range. Most of the tuning for this range is done to the jet needle, and not the needle jet. The main jet controls fuel flow from 3/4 thru full throttle, fig 5. Once the throttle is opened far enough, the jet needle is pulled high enough out of the needle jet and the size of the hole in the main jet begins to regulate fuel flow. Main jets have different size holes in them and the bigger the hole, the more fuel that will flow (and the richer the mixture). The higher the number on the main jet, the more fuel that can flow through it and the richer the mixture. Carburetor troubleshooting is simple once the basic principles are known. The first step is to find where the engine is running poorly, fig 7. It must be remembered that carburetor jetting is determined by the throttle position, not engine speed. If the engine is having troubles at low rpm (idle to 1/4 throttle), the pilot system or slide valve is the likely problem. If the engine has problems between 1/4 and 3/4 throttle, the jet needle and needle jet (most likely the jet needle) is likely the problem. If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem. FIG 7 While jetting carburetors, place a piece of tape on the throttle housing. Place another piece of tape on the throttle grip and draw a line (while the throttle is at idle) straight across from one piece of tape to the other. When these two lines are lined up, the engine will be idling. Now open the throttle to full throttle and draw another line directly across from it on the throttle housing. At this point, there should be two lines on the throttle housing, and one on the throttle grip. Now find the half-way point between both of the lines on the throttle housing. Make a mark and this will show when the throttle is at half throttle. Divide the spaces up even again until idle, 1/4, 1/2, 3/4, and full throttle positions are known. These lines will be used to quickly find the exact throttle opening while jetting. Clean the air filter and warm the bike up. Accelerate through the gears until the throttle is at full throttle (a slight uphill is the best place for this). After a few seconds of full throttle running, quickly pull in the clutch and stop the engine (Do not allow the engine to idle or coast to a stop). Remove the spark plug and look at its color. It should be a light tan color (for more info on reading spark plugs click here). If it's white, the air/fuel mixture is too lean and a bigger main jet will have to be installed. If it's black or dark brown, the air/fuel mixture is too rich and a smaller main jet will have to be installed. While changing jets, change them one size at a time, test run after each change, and look at the plug color after each run. After the main jet has been set, run the bike at half throttle and check the plug color. If it's white, lower the clip on the jet needle to richen the air/fuel mixture. If it's dark brown or black, raise the clip to lean the air/fuel mixture. The pilot circuit can be adjusted while the bike is idling and then test run. If the engine is running poorly just off of idle, the pilot jet screw can be turned in or out to change the air-fuel mixture. If the screw is in the back of the carburetor, screwing it out will lean the mixture while screwing it in will richen it. If the adjustment screw is in the front of the carburetor, it will be the opposite. If turning the screw between one and two and a half doesn't have any affect, the pilot jet will have to be replaced with either a larger or smaller one. While adjusting the pilot screw, turn it 1/4 turn at a time and test run the bike between adjustments. Adjust the pilot circuit until the motorcycle runs cleanly off of idle with no hesitations or bogs.
Terrific advice. I wonder if I am over looking the airbox?...despitethe fact that there are no nests in there I cant say that we have really analyzed it. I question it for this simple reason. When i first got the bike with what looked like stock carb settings it ran rich with the exact same issues i am describing now. We went to the kit thinking that some of the needles and jets might be worn and freshened up gaskets etc....and still have the same issue. So unless we failed to resolve the settings when stock...and further failed with the kit i presume its something else. The bike starts after being cold for a week without choke...and it initially runs up the revs before setting down to a nice idle. I do question float heights but beyond that i wonder about the things that havent been really looked at 1. air 2.valves 3. thermostat Are there any caps or issues with a stock airbox that could be a story?
The fact it starts with no choke is a big clue. All petrol engines employ an enriching device to compensate for poor fuel evaporation/atomisation in a cold engine. Subsequent rough running and excessive consumption can all be down to an over rich condition. Sprinter had posted an informative piece about the interaction of jets, needles etc., at differing engine speeds without going overboard on air pressure differentials. Suffice to say, if everything else is ''standard and serviceable" I think you have compounded the previous owner's errors with the carbs. I will not attempt to guess at whether slides have been drilled too large but assume all else has been checked and the complete dynojet kit fitted - otherwise you will have mismatched parts...... With only 14,000 miles the original set up was about 15% through its service life! I think you need to bite on the bullet and either rebuild carbs etc., to oem spec or get thee to a rolling road with a box of needles, jets etc., & fix it scientifically having wandered so far off track.
