Vortip to PMB insert change and performance impact

Today I switched from the Vortip to the PMB quiet insert. Surprisingly, the bike's mid-to-top end suffered. It felt a little starved, like a lean condition. With the old tip, I got a nice burst of accelleration in the mid-top rpm range.

I looked at the volume each tip can flow, and I estimate that the PMB can flow appproximately 20% more. If this is accurate, I probably need to make a tweak to the jetting to compensate. Can someone give me a guess based on my current settings what should change?

I'm thinking needle from c-4 to c-5, but what about the MJ?

By the way, the sound level between the two is pretty comparable and very tolerable.


I would go up (raise the needle) on the needle first and test, then up to a 160 on the main. See how that works before getting any crazier with it. I would bet you will see some improvement with the needle but the main AND the needle will probably be the answer.



Did you ever do any testing with alternate jetting?



I've now tested PMV vs VOR with these settings:

158MJ C-4 (original and great with Vortip)

160Mj C-4 (not much different)

160Mj C-5 (running a little rich at top)

With all these, the vor still has better top end.

So, now I will start going back towards the lean side and see what it does to the top.

We need to get together sometime soon and compare notes. We are running the same pas and maj with different needle. Your main is way larger than mine.

I'd like to ride both bikes back to back and see how different they feel. I'm not sure when I'm going to have time though.

I'm going to drop my needle by raising the clip one notch and try riding it again with the insert.


If you are weaker on top (MJ) why don't you stay at clip 4 and keep going up on the MJ until its gets better or worse. When you find the ceiling it will give you a hint of which way to go.


Looking this over further I am having second thoughts on my previous post. You sig. says EMP4. I ride the same bike in Michigan, less than 1,000 feet and have a BD Vortip. I had the privelage of having Taffy work through my jetting with me. I am currently running the JD jetting and very happy with it. After 50 plus combo's I ended up 38PJ, 160MJ and EMP3. I tested several E-- needles and EMP3 was the best. While testing the EKN needle clip 2 was the best, clip 3 terrible, clip 4 better and clip 5 not bad at all, but not as good as 2. So my findings indicate that a little rich on the needle is terrible, very rich is pretty good. So I wonder with your higher altitude what EMP2 would do?

Thanks TC,

I'm only trying to perfect it at this point. I bought the PMB hoping to get even a little more our of it.

The best jetting I've ever run is basically Taffy jetting, he helped me too.

150/160 38/65 EMP-4. Only went richer on the main because the plug was way too white and I was a little worried about running too hot, but it probably was fine.

You do see why I raised the needle and MJ, more exhaust= air through the motor? Anyways, the seat of the pants tells the real story and we'll see if I can get any more out of it. I will first just test mains then needle position vs both inserts.

BTW, after running a new plug with 160/160 and C-5, the plug was sooty. So I'll probably end up close to where I was originally, but hopefully with the other insert!


I played with my bike on Saturday and in the end, all I did was drop the needle 1 notch so I'm now at on the 2nd clip. I tried going to 1 1/2 turns on the fuel screw but this did not let the bike come back to idle quickly when chopping the throttle so I knew that was too lean.

I got a call late on Saturday night about going to Rampart and my buddy picked me up at 5:00 am and got in 45 miles in 2 1/2 hours.

The bike ran great with this change. It had good low end, strong mid and excellent top end. I'm done for now with the changes. I think Rampart is about 7000-9000+ feet so for that area, I'm very pleased with the changes.

I am YZ timed so if you still don't get the hit back that you wanted, you should try this mod.


Look at the previous post by Vmax. He is running an open pipe that should need richer jetting than your Baffled pipe. Are the two of you at similar altitude? He is running 152MJ, EKP2. The EKP is one clip richer than the EMP you are running. So EKP2 = EMP3. Your jetting is quite a bit richer than his. When I ran the E taper the best I found was 160MJ, 38PJ and EMP3. This was at sea level with a Vortip. Based on this it would seem that you are rich on the needle and MJ.


I'm only about 10 miles away from Steve (Stefe9999) and we've gone riding together. We are close to 5,280 feet above sea level. Most of our riding is at 7,500+ feet.

I have a PMB in now and all I've done is raised the clip one notch (dropped the needle). My next step is to try a 150 or 148 main jet.

I am YZ timed which I think helped a lot. I did not change my jetting after I changed the timing.


You and Sefe need to get together for a ride, swap bikes, swap Baffles. Should be easy to get them dialed in, sounds like you are very close if not there.


Yeah, I'm richer than him, I went up from my original 150Mj just to experiment, and found that I could use anything from 150-158 and still really liked the overall powerband with the Vortip. I thought I'd need a little richer jetting when I switched to the PMB anyway. BTW, V-Max is also running the PMB insert.

But, I'm going right back lean again. This Friday I'll test of C-3 (equal to John's C-2) and a variety of Mj's. We run at the same altitudes and it looks like we will probably end up with my original of 150/160 C-3. Maybe even C-2.

John, I really want to ride sometime so I can check out the YZ-time. Do you have any plans in the near future? I haven't been to Rampart yet this year.

Thanks for the input.


Are you still running the Michelin M-12's, I thought that is what you had? Either way what are you running and how do you like them? I'm due for some new feet. My current plan is a set of M-12's unless I hear something else for this rocky stuff we have to ride in.


Hey Steve,

I may be riding next on 9-27-03 which is a Saturday up at Seven Mile with a bunch of guys. I doubt I'll have time to mess with jetting there since everyone will just want to get as many miles in as possible but we could try and meet there.

I put a Maxxis IT on my WR recently and I'm very happy with the traction and durability. The thing hooks up great and has worn much better than the D739's do. Plus, they are cheap from Rocky Mountain.


Did you put that on front and rear? If not, what front?

I put that tire on the rear. I had a brand new K691 which I know is a crappy tire but I decided to use it anyway.


I should be up for the ride on 9/27. I decided on the Dunlop 739FAJ for the front and will probably get the Maxx Cross IT you have for the back.

Will have jetting refinements done then, so it should be all just riding. Had a blast last time at 7-mile.


I only had time to test one setup. Moved the needle back to C4 and the Mj down to 155. The PMB insert now performs at least as well as the Vortip. The hit on top is back!!


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