2005 450x jetting woes
  • Igeekedyou
    Posts: 3
    Joined: Mon Jul 25, 2016 8:37 pm

    2005 450x jetting woes

    by Igeekedyou » Mon Jul 25, 2016 8:55 pm

    Just bought a plated 450x, it's my first carbed bike. I have searched high and low for answers and nothing has seemed to help. When approx 1/8-1/2 throttle somewhere in there. The bike seems to have a slight sputter. I'm rejecting it because the previous owner had it incredibly rich. He had a 190 main, 50 pilot and a NCvs needle with the clip second to last from the bottom. The bike has a full fmf exhaust, top of the air box chopped, the print mod was done along with the a filed down ap diaphragm. Right now the bike has a 48 pilot(it dies of the fuel screw is turned to much so I figured it's a good size) the main is a 170 and the NCvs needle it at the 4 clip from the bottom. I have tried both extremes of the fuel screw to try and get rid of the sputter. Also the bike has brand new fluids, spark plug, the hot start doesn't have a leak ( I sprayed carb cleaner around it and on the carb joints to check for leaks) also the hot start is properly adjusted. Tomorrow I'm going to play around the needle jet again. But some help would be much appreciated I have been at this for 3 days. Also I'm around 1000ft elevation. Also I figured to jets were clean since I just bought them and also sprayed cleaner through them before I put them in just in case
  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    by Leardriver » Wed Jul 27, 2016 6:02 pm

    A dirt bike doesn't meter fuel for steady state cruising quite as well as a car, which is set at 14.7-1 air fuel mixture. It will sputter if you try to put it on cruise control.

    Dirt bikes are jetted to go full blast for a bit, slide a turn, get back on the gas, etc.

    You need a 165 main, 45 pilot at 1 7/8 turn out, and a stock, JD, or NVCS needle at the third clip from the top. That will work on a bike that is stock, ported head, different cam, exhaust, etc. You will be close enough to rule out jetting as the problem.

    If that doesn't work, there is another problem, like a chunk of gas debris plugging the top of the fuel screw or pilot jet orifice.
    Last edited by Leardriver on Thu Jul 28, 2016 4:02 pm, edited 1 time in total.
  • Igeekedyou
    Posts: 3
    Joined: Mon Jul 25, 2016 8:37 pm

    by Igeekedyou » Thu Jul 28, 2016 2:10 pm

    I figured it out, the NCvs needle clip needed to be in the 4 position from the top. No more sputtering with constant 1/8 turn throttle. Spark plug is also a great tan color.
  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    by Leardriver » Thu Jul 28, 2016 4:04 pm

    You can't judge jetting with modern fuels by looking at the spark plug. A 450 will also run pretty good with the jetting 5 sizes off.

    I have measured and tuned them on a dyno, and it will surprise you with the difference between what you though was a great running bike, and one that has been truly optimized.
  • Igeekedyou
    Posts: 3
    Joined: Mon Jul 25, 2016 8:37 pm

    by Igeekedyou » Fri Jul 29, 2016 12:16 am

    I figured I was pretty good but I will give it a shot when I have some time to mess with the jets. Is there anyway beside power difference I can tell I'm on the spot? Like I said I haven't had a carbed bike before and it also my first 450, so I'm not exactly sure where the bike is performing the best at. I have a street bike and a 250 both with fi
  • Back2-2
    Posts: 1148
    Joined: Tue Jan 04, 2011 3:31 pm

    by Back2-2 » Fri Jul 29, 2016 9:36 am

    With all due respect to Mr. Leaddriver, - Without A/F ratio and exhaust equipment available or a dynamometer you have two means available to jet any motorcycle. You have both your seat of the pants and spark plug readings. While I do agree that modern fuel [ pump gas] makes it tougher due to variances in fuels between stations and additives you still can use the spark plug as a good measure of what is going on inside the engine. What you will be trying to achieve is the following : These are based on the 4 stroke engine.
    Clean crisp starting
    Quickly being able to close enrichment / choke at above 50F OAT.
    Nice idle at operating temperature
    No evidence of overheating quickly
    Smooth acceleration from off-idle throughout the entire acceleration to top RPM.
    No popping on deceleration.
    No surging at steady throttle
    No flat spots when throttle is backed off and quickly returned to acceleration.
    The spark plug should have a uniform tan or slightly dark tone with modern pump fuels.
    Deposits are usually a result of additives and or burning oil.
    The exhaust pipe / muffler end can also be a sign of the engines burn characteristics.

    Be aware that items not covered here are air flow through your intake and carburetor that can produce all kinds of problems. If you have a OEM air box and no modifications from the inside of the filter and on this should not be a problem. I have seen many things disturb air flow causing many issues with jetting.

    Having an understand of what is going on inside the carburetor and the areas each circuit is in control of is required if you really want to be able to adjust jets to get that perfect balance of air, fuel and burning of the combination.
    There are many guides out there than can give you information and help the understanding. Some motorcycle manuals even have pretty good descriptive diagrams of each circuit and what influences them.

    I have been jetting motorbikes for many, many years and truly enjoy it – I know it’s weird.
    Hope that helps at little.
    8)
    Neil
    Black Hills of SD
    Life without Motorcycles would just be boring, really boring
    Honda 450X. Yamaha Tracer GT900. HD Fat Boy. Triumph Bonneville. Yamaha Majesty 400. Yamaha Grizzly. Yamaha Wolverine. Yamaha TW200
  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    by Leardriver » Sun Jul 31, 2016 6:13 am

    I agree that you can get it close by feel.

    The benefit of a forum and people sharing information is that someone out there has done the precise tuning with a wideband and is willing to share that.

    These bikes have been out long enough that accurate jetting is widely available and the info is free. Why use the standard of "close enough" when you can get it spot on?

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