Newbe Jetting Question


4 replies to this topic
  • Joseph Byrd

Posted August 12, 2006 - 07:05 AM

#1

I have just changed my jetting for the Power Up Mods. There was some difference of opinion about the necessity of changing the pilot from the stock 65s. Well, I did all the mods and changes, the pilot is hugely lean. I can't get it to come out of it with the fuel screw. I ordered a 68s and a 70s. What are your opinions for 800 feet altitude, has any one tried the 70s? This thing is way cold blooded, dies and boggs with the 65s, go to the 70s? Or is the universal 68s going to make enough difference? Thanks, Joe

  • motopsycho650

Posted August 12, 2006 - 07:42 AM

#2

That is quite an altitude difference for where I am. I am at 5000 ft., but mostly ride in the 7000-9000 range. I run the 68s pilot jet and a 170 main jet, and I have way less air than you. I have the pilot adjustment between 2 and 2.5 turns out, but I run custom air filter setup than is really good flow.

1st off, there is a difference between a 68 pilot jet, and a 68s pilot jet. To my knowledge, there is no 70s jet, it is simply a 70. Just FYI. Hopefully, you ordered the 68s pilot jet, Honda Part # 99105-MBN-0680.

But anyways, The 650R should be pretty easy to start, hot or cold. I would try the 68s pilot, with a 175 main at you altitude. I would start with around 3 turns out on the pilot adjustment. If you have to adjust out more than 4 turn out, use a 70 pilot jet. Get the bike warmed up, and snap the throttle quickly. The 650R will naturally have a "Dead Spot" where the engine chokes. You'll want to adjust the pilot adjustment to minimize that dead spot. Another trick is to go for a ride, and listen to the de-acceleration pops, (engine braking). Too lean will be loud, non-rythmic pops. Too rich will be more muffled, very rythimic pops.

Nothing intended here, but I'm suprised it even ran being uncorked with a 65 pilot jet.

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  • Joseph Byrd

Posted August 12, 2006 - 05:22 PM

#3

Thanks for the reply, has anyone tried a 70s? Joe

  • HawkGT

Posted August 12, 2006 - 07:39 PM

#4

They'll run at that altitude with a 65s--just not well. And there are a whole range of "S" type Series 21 pilot jets available from Honda.

I run a 68 at 1300ft (corked Moriwaki exhaust). I don't care for the "S" jets myself. My take on "S" jets? Internet lore has continually reinforced that "S" jets should be run on the XR650R so that's what most people use. I believe the difference in the emulsification holes has everything to do with emissions and nothing to do with performance. The "S" jets work but there is no reason to use them over a standard Keihin Series 21 pilot jet. JMO

  • captb

Posted August 12, 2006 - 10:27 PM

#5

I run a 75 pilot, no problem, starts easy, no hesitation, runs cool, steady idle, my sidecover (airbox) is cut out, a 70 will probably be fine for most, I don't remember my pilot screew setting but it's turned in a good bit.





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