Manifold and jetting question


3 replies to this topic
  • wildchubby

Posted February 14, 2006 - 04:02 PM

#1

How can you tell if you have a stock manifold or the HRC manifold part number (16211-MBN-640)? I recently bought a slightly used XR650R and the original owner said the complete uncorking job has been done. The bike has a small lag at 1/8-1/4 throttle so I want to make sure all jetting is correct and the HRC manifold is installed.

Just to verify jetting. I live at about 300' with temps typically between 70 and 100. With a cut out exhaust and assuming I have the correct manifold the main should be 172, 2nd to 4th clip position and the pilot should be a 68s?

Thanks for the info.

  • snaggleXR650

Posted February 14, 2006 - 06:29 PM

#2

No way to know without pulling the carb and looking up in there. Unbolt everything necesary (support your pipe, don't remove it from the header) and just swing up your rear subframe until the airbox boot comes off the carb. Easy peasy.

Throttle response in the 1/16 to 1/4 throttle position range is the needle jet (the brass jet that the needle slides in and out of, not the needle itself). There is an HRC needle and needle jet than you can get. However, you will never get the stock carb perfect. The Mikuni pumper and Edlebrock pumper carbs are what you need to look at if you want instantaneous throttle response.

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  • wildchubby

Posted February 14, 2006 - 06:53 PM

#3

I figured the edlebrock response would be common. After the bike purchase and DS kit I'll have to wait till more funds find their way to my pocket before I go for the carb.

Is it true that with the Edlebrock the bike will be easier to start?

  • motopsycho650

Posted February 15, 2006 - 06:56 AM

#4

However, you will never get the stock carb perfect. The Mikuni pumper and Edlebrock pumper carbs are what you need to look at if you want instantaneous throttle response.


I agree that a pumper carb will be a big improvement, but I disagree that you can't get the stock carb perfect. Mine runs pretty damn flawless. I ride at 5,000-10,000 Ft., and the stock carb only needs a 1/4 turn pilot adjustment at around 8,500 ft. AND, my bike with the stock carb starts within 3 kicks, hot or cold. I might get a pumper carb one of these days, but for now I'm happy, and 500 buck richer.

Wildchubby, Your jetting sounds pretty good. I would REALLY recommend the HRC exhaust tip over the cut out stock one. The HRC tip is around 160 bucks, but WORTH it in my opinion. With the HRC tip, you'll want a 175 main jet though.





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