|
Post by unclejack3 on Jan 16, 2016 17:40:01 GMT 10
hi all, i am trying to understand the carby stages setup and i think i understand it so am posting a summary of my understanding of it so here goes. A factory bike comes pre installed with the right air/fuel mixture but if any alterations are made such as the 2 major ones being air filter and exhaust then these could substantially affect the a/f ratio as the bike would generally run a more lean mixture which can cause performance issues such as backfiring and stalling. Fixing this is a matter of adjusting the a/f mixture screws located on the carby and usually set at 2.5 turns outwards(counterclockwise) but to get a richer mix the screw is adjusted out to a max of 4-5 turns,,,if this has no effect then the size of the jets inside the carby must be increased to allow more fuel,,this is known as stage 1 2 or 3, 3 being bigger jets..... Once having replaced these jets the a/f screw must be readjusted ,turned from 4 back to 2 or whatever to get the right lean mix once again.... Am i generally correct? any comments are appreciated.... some questions though... 1- is a stage 1 kit the same as a factory preset or is this already one size up.... 2- how do you determine what kit is needed,is there a calculation depending on what exhaust you put on annd air filter etc,,,
Or is it trial and error meaning taking the carbs off and on which looks like so much fun....
I am sure there are more knowledgeable people out there...
|
|
|
Post by SPINAL on Jan 17, 2016 8:19:39 GMT 10
Pretty much hit it on the head, i put V&h pipes and K&N air filter,plus de-snorkeled the stock air box. so i did a stage 2 re-jet and then to get the best result had it dyno-tuned. ok i picked up 10% torque and power in each gear, my fuel consumption went from about 260ks to the best i have had is 317ks when i hit reserve but average about 290ks and i ride 2 up most of the time, so there is a big difference. as for re jet kits i don't think it matters there's a few [ dynjet \ cobra ] if just aftermarket pipes have been put on and the airbox has not been changed [more air intake ] you will likely not have to rejet. just adj air/fuel mix if it's not running well. stages, Stage 1, 2 & 3 Jet Kits Maximizes carburetor performance. Includes step-by-step instructions. Includes jets for both stage 1, 2 and 3. Stage 1: Intended for motorcycles with a stock engine using the stock airbox, air filter and stock pipe. Stage 1 kits are fully adjustable to allow the use of a well designed aftermarket pipes and stock replacement air filters like K&N. Stage 1 kits are designed to improve throttle response and drivability and in most cases power increases of approximately 5% throughout the entire power range can be achieved. Stage 2: Intended for motorcycles with a stock or mildly tuned engine using a well designed aftermarket pipe with a modified airbox and a stock replacement air filter. Stage 2 kits are designed for applications where individual filters cannot be installed and for applications where airbox modification improves the engine's performance. In most cases power increases of approximately 8% can be achieved. Stage 3: Intended for motorcycles with stock or mildly tuned engines using a well designed aftermarket pipe and individual air filters. In most cases power increases of 10 - 15% can be achieved. However, drivability may be compromised particularly with short stroke, high RPM motors. On some modern engine and airbox designs, individual filters and proper jetting offer no performance improvement yet compromise drivability, in such cases stage 3 kits are not available. Dynojet Jet Kits: Dynojet offers a wide range of kits to fit any application. Several types (stages) of kits are available to fit your specific needs. Whether you run a standard motorcycle, or a tuned sportbike, Dynojet Carburetor Jet Kits can provide you with a simple and affordable solution to all your carburetion problems. Dynojet Jet Kits increase power and smoothness throughout the entire rev range, while maintaining optimum fuel economy. Each Dynojet Jet Kit includes comprehensive instructions which show step-by-step installation and testing procedures to ensure a perfect setup every time. This is backed by free telephone and Internet support to Dynojet customers. I did find a site in the USA that will make up a jet kit for your needs instead of buying a whole kit. you may like to check it out, or just get a re-jet kit off ebay. carbjetkits.com/CJKCalculator.php?num=11&d1=105&d1p=40&maintype=393&pilottype=21&bname=VT750C%20VT750CD%20Shadow%20aero%20Spirit%20Ace%20Deluxe%201998-2003hope this is of some help as to what you want to do. cheers, spinal.
|
|
|
Post by unclejack3 on Jan 18, 2016 6:41:35 GMT 10
that explains it really well,thx,,,,I got courageous and took the carbies off yesterday to clean them and see what jets i had,,the day before i increased the a/f mixture,,turned screw out to 3.5 instaed of 2.5 and apart from the poping i get in the exhaust whilst decelerating i was also getting backfiring so i assume thats fuel not being burnt up and the new plugs were already looking fouled up, so i returned it to 2.... so my jets are rear main keihin 110,,idle 40s,,,float 24.......front : main 105,idle 40s and 24...these i believe are factory standard so with my jama cutoff baffled mufflers these have remained the same.....i also noticed that the breather pipe that attaches to the air compartment had been taped so that there was now only a small hole 3mm instead of 10mm,,,why??? i am not sure what this breather pipe does.... I find it strange that when i take off the air filter the engine still runs well which would suggest its running rich at 2 turns? what happens if i decrease this to 1,5,,,thats pretty lean,,,,,,SO i am doubtfull that i could possibly go to a stage 2 jet as its already running rich....
yOU SAY stage 1 are fully adjustable ,,how? r u talking about the main long needle grooves that you can set in the diaphram? and what is de snorkeling mean? thx.
|
|
|
Post by unclejack3 on Jan 18, 2016 6:43:58 GMT 10
i also did that calculation and the jets i have are the right ones...so the exhaust i have has made it louder but has not changed the air flow.
|
|
|
Post by unclejack3 on Jan 18, 2016 6:53:17 GMT 10
also i noticed the little black foam filter in the pre delivery air box was torn,,is it worth getting a new one..?
|
|
|
Post by SPINAL on Jan 18, 2016 8:33:50 GMT 10
de snorking air box is only for when you change the stock air filter to a K&N air filter in the stock air box, it allows more air into the air box, which then you would have to rejet with stage 2 kit [ change needle size,spring and jets] having trouble working out what your'e trying to do,was the bike not running good to make you start looking at the carby. my understanding is, you have aftermarket pipes and stock air box and filter, so no re jetting is required you can just alter the air/fuel mix screw to make it run richer or leaner as required. the above post is just a run through of the types of stages the dyno kit has, if you were to order a kit for your model as to the mod's that have been done there may not be a stage 1 kit, there's a lot on utube if you want to understand the rejet part better.
cheers,
spinal.
|
|
|
Post by unclejack3 on Jan 18, 2016 10:12:30 GMT 10
the reason i went thru all this palava is that every now and then it dies of power ,like there is no gas,,usually when cold and low gears and accelerating,,the other day it died for about 3 seconds and i was able to fulll throttle it and still nothing,then came good,,so a bit dangerous in corners etc,,,so i thought dirty jets,a floating bit of shit clogging the jets,,old spark plugs,,,,bad align float,or even petrol pump,inline filter but nothing wrong ,,,,,,,maybe now it could be coils or leads.....i have not taken it for a long run yet since the carbies,,,,,but its intermittant so who knows,,,,it does not happen though while cruising so maybe the coils are having a hard time in producing spark when accelerating ,they would be going into overdrive then i assume pushing them a bit,,,but it can only be one coil which means no power on one piston and it would most likely be more of a stutter like misfiring rather than complete death,,,, what did you think about that air chamber tube that was taped up to make the crankcase hole smaller,,any idea why someone would do that? anyway appreciate your thoughts,,,,what about the pre air filter,is it needed as it goes to that 3 wayy valve,,,
|
|
|
Post by SPINAL on Jan 18, 2016 10:47:03 GMT 10
Don't know why anyone would do what they have done to the air chamber tube, perhaps someone with your model may be able to help you out.as for pre air filter don't have that on my model [ 2006 aero ] so sorry can't help you there. as for your prob with bike , well that could be a number of things, it's just a matter of doing what you doing until you find the prob, i know's it's a dump Question, But have you tried another tank of gas [ bad Fuel ] suppose you have already thought of this, sometimes it's just a simple thing and sometimes not.
hope someone else chimes in that may have a better idea on your model.
cheers,
spinal,
|
|
|
Post by unclejack3 on Jan 20, 2016 12:25:43 GMT 10
got the carbs back in,and a new filter and took it for a spin,,,all okay,,also adjusted the idle a/f mixture out to about 3.5 turns and the popping has improved although most probably would be better to increase idle jet from 40 to 42 that way the a/f screw would be in but means taking the carbys out again,,cant be bothered...anyway thanks for your help ,I now understand a bit more what I am riding,,,,knowledge is power,,,,so they say....
|
|