Another Stupid Jetting Question...

70 replies to this topic
  • R_Little

Posted December 18, 2002 - 11:51 AM



I did a lot of things in rapid fashion. IE the BK the E needle and the YZ pipe, so I cannot tell for sure what caused what. What I can say is the combination has eliminated the raising idle as the bike warmed, the "dead" spot just off idle with steady throttle and I can now yank the throttle like a 2 stroke with much better response. The bike hits hard off the bottom now. Everyone says the B/K is a good thing and I won't disagree.

What I have not settled out is the high RPM situation.
Now it may be that the motor hits so hard down low that the high rpm power now feels weak. Remember I have WR timing.
I seem to get different "holes" as I move the MJ around.
I got JD's jetting guide and am looking into that right now.
I see that moving the clip has a big effect on the mid, even more so than the needle diameter. It runs good but I think there is more there.

All in all it runs well all around no fouling (yet!) and no pinging.

My advantage to you is that my bike ran good with stock jetting. I am considering putting the WR can back on and trying to get a baseline on the high RPM power to see if I am getting really anywhere. Maybe it is the YZ can that is moving the power down at the expense of some top end.

Meantime, let me know if you can source Taffy's air jets in the U.S. It's a proven performer and it don't hurt to try.

TC, thanks for the suggestion. Maybe I'll try a EKN on the 4th


  • HaremScarem

Posted December 18, 2002 - 01:49 PM


You can get all the Jets you need right here...
Sudco" target="_blank">Sudco' class='bbc_url' title='External link' rel='nofollow external'>]Sudco[/url]</a>

  • Steve_WR400F_#61t

Posted December 18, 2002 - 03:07 PM



Your crackin' me up now. I know I keep asking stupid questions. Just keepin' myself busy 'til my stuff gets in. Everything else is already in place and not much else to do until then. Don't worry, I'll try and let ya'll know when I'm up and running and what I think of the suggested settings.


Good luck with your changes & keep us up on your findings. The YZ pipe should open you up a little and let the bike rev quicker. The YZ timing helps there too. The two together lets the bike hit a bit harder and accelerate a little quicker out of corners. The WR timing probably leaves a little more low end in the bike though and lets you lug the bike a bit more. Just depends on where you want that power.

  • R_Little

Posted December 19, 2002 - 04:04 PM


Dropped in a EJP on the 4th today left the 162 MJ alone.

Just like the JD guide says, the bottom leaned out a little bit, softened the hit a little. I sense a little bit of the lean noise it used to make. Just a little though.
The clip higher added a little more to the upper mid.

I know there is much more low end as I was able to run 3rd in sandy turns that used to require 2nd or clutch slipping.

Bike ran good on the highway up to 65mph and smooth even in bumper to bumper for 20 minutes.

I'm in the neighborhood now. The top end is a little flatter than I think it used to be. But Maybe the top feels weak because of the stronger low end.

It may be a little lean on top yet. I may try a 165 MJ for the winter, or next valve adj I'll YZ time.

  • Steve_WR400F_#61t

Posted December 20, 2002 - 02:03 PM


This needle crap is just getting crazy now. The parts shop just called and said they cant find an EKN needle. Their Yamaha connection doesn't know what it is either & said they never hear of it. So now I'm ordering the EJP needle instead & they said it should be here on Tuesday. We'll see.

I also started to look at doing the bk mod. With the instructions on here, the stock "squirt" should be between 3 & 5 seconds. Doing the mod should make this adjustable and set it to about .3 seconds. I started measuring mine and without touching anything it's already less than a second long. Stock, nothing done yet. Squirt just misses the slide and I can't tell what is really gonna change. Does it sound like I'm doing something wrong?

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

Posted December 20, 2002 - 03:18 PM



Tell your parts dept to pull their head's out of there A$$, the Yamaha part number is OBEKN P/N 5JG-14916-EN.

They are pretty easy to find as well..

Good luck.

Bonzai :)

  • R_Little

Posted December 21, 2002 - 07:15 AM



If your saying the squirt on yr stock carb is already less than 1 sec and you are not having any snap/bog trouble then maybe you should not bother to drill and tap the carb.

On the other hand if you have the stuff and you have tapped a hole before it only takes 5 min to do it. It's probably not critical if you have no bog trouble. The timing vs-a-vis the slide is adjustable by the screw that is already under the plastic cable cover. Turn out a little to make it sooner.

FYG my squirt was 2 sec and at .8 sec now it makes a big difference - NO more bog.

As I mentioned to you before No County Yamaha gets me my needles in 2 days.

Good luck

  • Steve_WR400F_#61t

Posted December 23, 2002 - 09:53 AM


Usually don't have much of a "bog" problem. I can get it to stall off idle if I crack the throttle quickly & hold it there for a bit. But the conditions have to just right & it's gotta be from idle. Anything above idle won't bog the engine.

  • R_Little

Posted December 25, 2002 - 12:21 PM


Okay then I guess the BK is not critical for you.

I did notice an improvement though.

Did you get yr needles yet.....

  • Steve_WR400F_#61t

Posted December 27, 2002 - 05:26 PM


Nope, no needles yet. The stupid shop is now blaming UPS on the delay. First cuz of the Holidays & second, they say the UPS never showed up today with thier orders.

The other thing i decided to do is check my valves. Found out that they are all tight. Need to downsize all pads/shims by one side to get the correct clearances. Now I have to find a shop to order these too. The shops here don't have any in stock. Great, another 2 weeks plus delays.

  • Steve_WR400F_#61t

Posted December 29, 2002 - 08:42 PM


Ended up having to order my parts online. The shop here cant get a needle for my bike until at least the middle of January now. What a crock! The other shop in town is moving and they can't even begin to help me until they unpack from the move. Another Crock!

Hope to be able to ride again someday...


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.