yz400f throttle bog

Yamaha YZ400F 1998

28 replies to this topic
  • yz400fmaniac

Posted March 13, 2016 - 10:14 AM


ok right now i am about 3 turns out and have a hanging idle and what i have read said a hanging idle means its running lean, so i need a bigger pilot jet but i dont know what size any help is appreciated

  • grayracer513

Posted March 14, 2016 - 06:20 AM


Do yo know what size you have? 

  • yz400fmaniac

Posted March 14, 2016 - 08:17 AM


it has stock pilot jet in it i ordered a 48

  • grayracer513

Posted March 14, 2016 - 08:37 AM


So you have a #45?  That should really be big enough if it's actually clear. 

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • yz400fmaniac

Posted March 14, 2016 - 04:16 PM


Ok right now when i start the bike up, starts first kick almost always, when its cold. but when it gets warmed up after about 10 minutes i have a hanging idle and the motor is running really hot way hotter than it ran last summer i am not exactly sure what size pilot jet is in it, the guy who rebuilt the carb said he put all stock parts in it. but i can back the air/fuel needle all the way out untill it could fall out and i still have a hanging idle and i already know i dont have an air leak. also when it gets warmed up sometimes it starts first or secound kick and sometimes it starts the 50th and yes i know about the starting procedure so its not that. i am really hoping this 48 pilot jet does the trick anything else u have to add is appreciated.

  • yz400fmaniac

Posted March 14, 2016 - 04:20 PM


this is the kit he used https://www.denniski...&ad=46766398717

  • yz400fmaniac

Posted March 17, 2016 - 04:49 PM


ok i ordered a 48 jet that wasent the right one... even though the listing said it was  :banghead: but the last time I rode the bike before messing with anything I did not have a hanging idle so i think i have an air leak...etc 

  • yz400fmaniac

Posted April 07, 2016 - 06:09 AM


well i have done everything i can to that carb and still have a bog i had a hanging idle because of the idle screw, i had it set to high stock pilot works fine i am just going to live with the bog i have the bike running perfect now and it only bogs at idle and none after about 2000 rpm

  • grayracer513

Posted April 07, 2016 - 06:59 AM


And that's really about all you can expect from the older carbs.  A bog that only shows up at around idle speeds, but not while actually riding, is not worth chasing.

Related Content


Engine acting up '98 YZ400F by bjm904

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 4 replies

Yamaha YZ400F 1998 by ThumperTalk

Yamaha YZ400F 1998
  • * * * * -
  • 10 reviews
  • Last review by BeardedYama
  • On August 26, 2016

98 400 Rear Brake Caliper Question by WrightStuff

Dirt Bike   Make / Model Specific   Yamaha   WR 400/426/450
  • 3 replies

Carb conversion by yz400fproject

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

Happy Birthday ThumperTalk! by Bryan Bosch

Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  48 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.