RE: Horsepower question on Uncorked 650r

9 replies to this topic
  • MountainMax

Posted January 12, 2007 - 10:34 AM


What gains in HP will the normal uncorking do to this bike, and what HP did it start out with? i have heard many stories regarding different numbers...................

  • Zapp22

Posted January 12, 2007 - 10:46 AM


googly boynack BRP

  • xr650rkyle

Posted January 12, 2007 - 12:27 PM


Try: "Borynack xr650" Search

  • MountainMax

Posted January 12, 2007 - 01:19 PM


WoW, thanks guys, what a $**T load of info there, everything my buddy wanted to know and more, he's out for more mods now to reach the top 64 HP they say is possible........ :lol:

  • loufish

Posted January 15, 2007 - 11:35 AM


Normal uncorking(open airbox, re-jet main, pilot and needle, open exhaust and replace restricted intake manifold) will net you about 10-11 hp which is a bunch!
The best thing is you are getting back the HP it's supposed to make, so your not sacrificing reliability.

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  • InternalCombustion

Posted January 15, 2007 - 12:40 PM


If he hasn't uncorked it yet he should do so and then ride it in that state before he spends beau-coup bucks on more power. The mighty Pig is a real butt-kicker, just uncorked.

Yeah, "more is better" but once uncorked, the low-end torque of the 650R must be experienced to be believed. Awesome.

In any case, have fun!!!

Ride safe.

  • MountainMax

Posted January 15, 2007 - 01:21 PM


actually i have two buddies (im a yammy man) with 2005 xr650's and they both just done the uncorking mods you mentioned and removed some of the baffle material and drilled out tailpipe 2". they wondered what power gains they would have, as my bike stock could not keep up with them, (2006 wr450f) but after i done my free mods (uncorking) I could take them in a 1/8 mile drag race, now they want to get even, they will end up with very similar HP as me but they will have more torque now, so im getting worried, lol

  • BWB63

Posted January 15, 2007 - 01:35 PM


WoW, thanks guys, what a $**T load of info there, everything my buddy wanted to know and more, he's out for more mods now to reach the top 64 HP they say is possible........ :lol:

The 64bhp number you hear about is at the engine For an Honda HRC Piston, cam, timing chain, This is not at the rear wheel. You will hear tons for different numbers because of the two different ways of messuring horsepower. Honda (Manufacture's) messure at the crank/flywheel consumers (that is us) messure at the rear wheel with a dyno. Stock uncorked bike on a dyno is about 44rwhp Honda would say 55bhp different number same horsepower, The difference from Breaking horsepower and rear wheel horsepower will be about 24% and it is very reliable tested 1000's of times and it still comes out about 24%. uncorked bike 44wrhp +24% = 55bhp
HRC fitted bike 51~52rwhp+24%=64bhp, tricked out 680cc 55~58rwhp+24%=68~72bhp and that is about the limit. There are a lot of dyno's out there that corect for the difference and give you SAE corrected horsepower right off the bat making lots of confussion. Some change the dampening to make the numbers bigger to make the costumer happier.

Posted Image

  • RC30

Posted January 15, 2007 - 02:05 PM


.......The difference from Breaking horsepower and rear wheel horsepower will be about 24%........

Sorry BWB63, if breaking horsepower means the power at the crankshaft then the difference from rear wheel horsepower will be about 10%, not 24%.

.......Stock uncorked bike on a dyno is about 44rwhp ........

I confirm this number, it's like mine dyno-diagram.......

http://www.thumperta...=421904&page=13 the crankshaft the horsepower becomes about 49.

  • BWB63

Posted January 15, 2007 - 03:33 PM


Drive train uses 24% of the power. Do the Math, 44rwhp uncorked (stock where you live) on the Dynamometer for the XR650R's. Honda shows 55bhp (messured at the crank)for the same setup. 44 X 24% = 10.56 + 44 = 54.56 am I missing something or are we trying to shead a few oz here to save weight? Same goes for the cars we dyno, engine said to make 360hp from GM we get 284rwhp on the dyno. Not one dyno but three different dynamometers come within 7hp. My XR650R uncorked 43.7, with XR's Only header/R4 muffler, UNI air filter, holes in the side cover, Mikuni TM40 pumper, 48.6, With a 680cc bore; with cam, and 3mm bigger intake valves, Moriwaki full system and 42mm Edelbrock it is just over 58rwhp and that comes out to 72bhp. Honda claims that an XR650R with HRC kit (11:1 piston, cam, timeing chain) makes 64bhp but, there are tons of guys here in the US that will show you there 51~52rwhp charts for the same bike. Like I said, a strickly stock uncorked bike is 44rwhp, with header/muffler/TM40 carb 49rwhp in the USA. You get 48rwhp on a mod'ed bike on your DYNAMOMETER charts you put up today and 44rwhp on a stock bike do the math?? (That would be 44rwhp=55bhp and 48rwhp=59.5bhp) Am I mising something? A DYNAMOMETER reads rear wheel Torque and calculates Horsepower from Torque and RPM. Breaking horsepower is messured at the crank and uses a a totaly different machine then the Dynamometer that most use to get horsepower.
Here is some more math that might work for you.... If you are running 20 pound of air pressure in your tires, lower them to 10 pounds and your bike will be 20 pounds lighter :confused: :lol: (that was a funny) Your bikes come stock uncorked, we have our bikes here in California coming corked up and only putting out 34rwhp.

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