Fork Oil Upgrade, Thickness & Volume: Ninja 400 Project Ep 6

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The Kawasaki Ninja 400 front fork was pogo’ing right off the showroom floor. Also the progressive fork springs were allowing too much brake dive. Time to upgrade.

2022-01-05T20:58:52-08:00

9 Comments

Darkknight January 6, 2022 at 3:50 amLog in to Reply

Great content on the fork oil change defining mechanical bottom out V hydraulic bottom out and usage of the air spring I have a better understanding of this now and I will put into practice the next time I upgrade or change my fork oil
aaronaleixo January 7, 2022 at 1:22 amLog in to Reply

Amazing vídeo! Really good!
But if is invert suspension like a mt09 with one leg with rebound and the other with compression adjustament is the same method?
Thank you,have Nice day 😊
- Dave Moss March 1, 2022 at 7:56 pmLog in to Reply
  
  Same methodology. Separate function forks balance each other out.
faffi January 13, 2022 at 11:24 amLog in to Reply

Interesting video, as per usual.

I am curious, however, why you use the term hydro-locking on compression with stock level oil volume. Would it not be present oil around the bottoming cone that create hydro-lock, regardless of how much extra oil is sitting above it? In my simple mind, it would be the combined forces of spring, air spring and compression damping that prevent the fork to reach bottom during the bounce travel test, but I am open to being wrong.
- Dave Moss March 1, 2022 at 7:55 pmLog in to Reply
  
  Great question. Thicker oil travels much slower and also takes up more volume. If the volume is greater, the air gap is reduced and therefore the travel may also be reduced. That reduction may be via compressed air or it may be via oil volume when hot.
Alana Spurling January 21, 2022 at 11:01 amLog in to Reply

Thank you Dave, as always very informative video. I’m also in the process of building a Honda CBR250R as a track bike, and I suspect that the forks used on that are nearly identical to these. I’m upgrading the front springs with some 90 kg/mm springs, and changing the fork oil. My donor has 15k miles and who knows when/ if the fork oil has ever been changed. Anyway I’m looking forward to what you’re going to do about the rear damper….
atilla8huno May 16, 2022 at 1:49 pmLog in to Reply

Hi Dave, excellent content on this episode.
I would like to ask you about fork emulators, if I’m going to race on a hot weather, around 38 celcius or hotter, can I use fork emulators and a thin oil like 5w or 2.5w instead? Considering your video about oil viscosity and cst degradation when the oil is hot.
Does that makes sense? or this video’s approach is better?
Thanks in advance.
Hank Wallace August 30, 2022 at 3:28 pmLog in to Reply

Very helpful. I just did this on my Ninja 400 before my upcoming first track day. Is there any process required to align the front forks? I saw one of your other videos on this, but in that one the bike had front fork pinch bolts.
- Dave Moss September 7, 2022 at 7:09 amLog in to Reply
  
  Dave Williams, editor, replying here. He does demonstrate that process in another episode of the project. Sorry, I can’t remember off the top of my head which one, but it’s in there somewhere.