Carburetor Jetting throughout the RPM range - Throttle openings explained!

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Published 2019-11-14
In this video you will learn what adjustments to make to the #carburetor for each throttle opening throughout the rev-range. This can help in fine tuning the #jetting for specific conditions or to diagnose a fuel #mixture problem in the carb.

Check out these supplemental videos for more!
Is your #carburetor to big?
   • Is BIGGER always better?  

Rich or Lean? How to know.
   • Rich or Lean, how to figure it out? C...  

Idle mixture adjustment explained
   • Idle mixture adjustment (air OR fuel ...  

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0:00 - Intro
0:15 - Idle speed
0:59 - Idle speed mixture problems
2:27 - Slow speed 1/4 throttle
3:44 - Medium speed 1/2 throttle
4:17 - Full speed wide open throttle
4:53 - Symptoms of carb jetting problems
7:24 - Further videos & information

All Comments (21)
  • @thejunkman
    If this video helped you considering giving "THANKS" ❤ it goes to help making more videos like this.
  • @mexicanbandito
    Best explanation of tuning carbs I've come across thanks for the visual as well sure earned my sub
  • Great explanation. Many people don't really understand what affects what at certain throttle positions. Even old timers commonly tell me to adjust the idle air/fuel screw because it bogs at WOT lol
  • @Larry-vm9jh
    Thank you junkman great job on your presentation I'm a retired master technician I'm glad to have found your site. It is absolutely correct in every way the information that your sharing with others and that is something not common to.all sites on the internet there's a lot of videos out that if you are not a master technician you might not catch the fact that some of them are lacking in some important details that an average d.i.y. needs to make use of the information successfully
  • @aaronjeffries9617
    Very helpful! Thank you. I've owned a few carb'd bikes and don't understand how that system works, so I'm learning up as I'm looking to maintain them better, or make adjustments with different intake/exhaust changes
  • @SteveHacker
    YAY! Made my day! Thanks for getting back to motorcycles! 😊😊😊
  • @louispeters2105
    Thank you. Well done. I'm writing "logie" into my dictionary just for you.
  • Nice video,HI all I have taking a liking to motorcycle and scooters and really like tuning them and playing with settings to get more performance, better milage, I really enjoy it and feel I have a natural talent in doing so Id like to talk about tuning a CV carb, specifically one bike I own a Honda Helix, its a 250cc 4T, simple design and seems to respond to changes This scooter has a CVT and will go 75MPH on top end OEM, but people complain you cant tune it, and I think its said becasue they dont know how Typically this bike has a 110MJ and 38PJ fuel screw 2.5 turns out, There is a fella who posted vidoes of him tuning this bike on a dyno and by simple adding a K&N free flow filter and taking the MJ to 130 he got 1.5more HP out of a 15HP bike I decided to try this with his setup and sure enough its faster, but the very low end throttle crack there is a slight bog and Im thinking a shim will resolve this, in fact he was using a 1.5mm shim I think I can tune further it further to improve Here are some questions 1. would it be better with a CV carb to NOT run the K&N directly on the carb body and use say a few inch pipe in between? 2. this video this guy is using a lollypop to meter air flow, what you think about that? 3. Any other suggestions for tuning a CV carb in this instance? TY all Heres his video https://www.youtube.com/watch?v=Na6dbH9Mprc
  • @BobbyBasketballl
    Great video, gave me the rxact information i needed to fix my lean issue. I noticed i cant get the bike to run rich at all and now i see its likely because of the aftermarket exhaust and smaller stock jet.
  • @ricnegrete1991
    You're the sh*t broooooo. Suuuupeer well explained, by far the best carb vids!!!! Thxxxxx all the way from Mexico!!
  • @vivekkakkat
    Brother..thank u very much..you solved my headache...my bike missfire on lower rpm...now only i understood its the pilot jet...great help..keep on going....👍👍
  • @Ryan_Carder
    Hoping you can help. I'm using a wideband O2 sensor to take any guess work out of determining the stoic nature of my bike. The chart I'm following says that a richer mixture provides better power, and cooler engine temps. I tuned the idle circuit to a target of 13:1. That was easy. Now, when I took the bike out I was INCREDIBLY way too lean along nearly the entire throttle range. I raised the needle, yet it changed little. So, I bumped up my main jet and it fixed the issue for 1/4 - 3/4. However, I am running entirely way too rich at wide open throttle (WOT.) About 10:1 and less AFR. My needle is at its highest position, and by decreasing the size of the main jet to solve the WOT issue, wouldn't that also lean out the needle jet throttle position throwing it off my desired AFR? Not a whole lot of people I've tried asking help from can give me a solid answer. Thanks for the video by the way. Incredible animations, and I love the truly scientific approach!
  • @user-rz8su6dk4e
    Fuel filter does wonders, I would never run any of my motorcycles without one
  • @gster0101
    Excellent info... appreciate your videos.
  • New subscriber from phillipines god bless your channel AGA CEZAR VLOGS shout out next vlogs
  • @harrybrown4815
    Best Carb animation and explanation ive seen to date. brilliant have shared.....
  • @jdmtechllc6589
    Great video, but I would like to add, If the float height ain’t right your just spinning your wheels