650R pilot jet question

6 replies to this topic
  • motopsycho650

Posted November 22, 2006 - 11:17 AM


I recently cut out the side panel of my '03 650R and did the whole screen & rivets.

The bike has the HRC intake, spark arrestor, and needle jet. I also run a Twin Air Power-Flow kit. The stock carb was jetted with a 68S pilot (2 1/4 - 2 1/2 turns out on the mixture screw), and a 170 Main jet, which way a tad rich, but the bike seemed to like that as far as power.

Now, with the cut out side panel, I had to turn the pilot screw out to 3 - 3 1/4 turns out. The main jet seems okay as it has much more power on the top without and hesitation.

Do you think I would benefit from a 70 pilot jet instead of the 68S?
Is there a 70S pilot jet? If so, does anyone have the part number?

Also, even with the pilot jet adjusted as well as it can be right now, I have quite a backfire POP problem. Is the "plug the hole" in the air cut-off in the carb a good thing to do? I saw that on http://www.xr650r.bo...r_caruretor.htm.

  • eastreich

Posted November 22, 2006 - 12:31 PM


Plugging the hole in the cut-off circuit on the carb works as advertised. If you don't race, or hit a lot of whoops at high speed, you probabaly do not need to do it. But it is a very easy mod to do, and I liked the results when I did it. I was tired of the bogging that I got when going through whoop sections from on/off throttle work. It really helped to cure this. It also made the bike work better in timing jump sections on the motocross track as it helped to rid the bike of some hesitation (but not all).

I never had to change the pilot jet to a setting larger than a 68s. Even with the HRC kit, the recommended pilot is still the 68s. At what position is your needle set?

My jetting with the same setup was 68s pilot, with a 168 main at an average elevation of 6000 feet.

  • motopsycho650

Posted November 23, 2006 - 05:26 AM


My needle is in the 4th spot from the top. I've tried the 3rd spot, but I got a power loss from that.

I know it seems weird because I'm riding in about 6000-9000 Ft. usually. Right now I have to stay at around 5000-6000 Ft. because of the snow.

Being the impatient person I am, I went to the bike shop and they had a 70S pilot jet in stock (gotta love Sun Honda in Denver). I threw it in, and the bike loves it.

I must have cut the side panel holes a bit bigger than the kit you can buy. Or I might have used some higher flowing screen. It doesn't make sense at my altitude, but my bike is running better than it ever has before with a 70S pilot, adjusted 1 - 1 1/2 turns out. A 170 main jet, and the HRC Needle in the 4th spot. The numbers look like it's running too rich, but the power is unbelievable & the spark plug is burning perfect.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • motopsycho650

Posted November 23, 2006 - 06:04 AM


The only thing I can think of is that I don't have a true Twin Air Powerflow kit. It's just easier to type.

Before I knew about the Powerflow kit, I ordered a high flow backfire screen from XR's Only, and a stock replacement Twin Air filter. I then cut out 4 large holes in key spots from the XR's Only backfire screen.

The actual Powerflow filter is a 3 stage filter, right? A layer of white foam, orange foam, and finally a layer of fire resistant black foam.

My setup is basically the same thing, except the stock replacement Twin Air filter is thinner, and only 2 stages. There is no flame resistant layer, but I figure if I burn my air filter, I have some much bigger engine issues going on.

  • Ramcc4x4

Posted November 23, 2006 - 08:42 AM


When I modded my side panel my bike had a huge flatspot that didn't go away until I ran a 70s pilot. I am surprised your bike wants that much fuel at your elevation but if it works, great!!!

  • motopsycho650

Posted November 23, 2006 - 12:20 PM


Ok, so I'm still fooling around here.

With the 68S pilot jet, I had to have the adjustment 3 1/4 turns out with my current setup. (Seems like the adjustment screw is too far out).

I have a 70S pilot jet in there now, but it is adjusted only 1 turn out. I don't have the adjustment to go much leaner next season when I get back up to 8000ft. or higher.

As I understand it, the "S" on the jet represents smaller air holes, which means it's slightly richer than it's non "S" counterpart.

Do you guys think a regular 70 pilot jet would be a happy medium between the 68S & 70S?

Do you think I'll lose the bottom-end power I loved with the "S" jets?

And I guess I'll ask, do you think 3 - 3 1/2 turns out is too far for the adjustment screw?

  • iestrada

Posted November 29, 2006 - 10:20 AM


What about the fuel consumption? does it increase going from 68 to 70?

Related Content


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.