Posted January 27, 2005 - 04:36 AM
The bike: - XR650R ' 2000
- Monnier tank with custom graphics/seat.
- Brembo race brakes with Braking Wave rotors
- standard engine
- CRD headers + Leo Vince X3 can (open)
- Air box mod,No Toil filter,no backfire screen
- Mikuni TM40
The plan : - mount a HRC piston,I have a new 680 kit but I don't gone use it because of the reliability issues ( I use the OEM crank)
- clean-up the ports ,intake manifold etc.
- bore my Mikuni TM40 to 41mm.
The questions: - Hotcams stage 1 or 2 ?
- Knibblewhite OS valvekit ?
- lighten the flywheel 300gr ?
I don't want to lose low-end(if possible gain) but I need extra power in mid and upper rpm's.
What's the ticket? the stage 2 cam with OS valves or is a stage 1 cam with standard valves the deal?
I know the the stage 1 Hotcam is a "drop in" but what about the stage 2?Any mods to be done?Clearance issues?
What about the flywheel?
The bike is used on the street as SM.
Where can I get the best deals (over there in the USA) for Hotcams and Knibblewhite parts? Anyone?
Posted January 27, 2005 - 08:09 AM
Sounds like a good setup.
XRMANU you may want to wait and upgrade the crank at the same time...with more horsepower I think that may be your weakest link but if it goes its taking alot with it that is if you were looking at a higher compression piston.
Any other thoughts out there?
Posted January 27, 2005 - 12:15 PM
I know Bruce's set-up,I want something like his bike without the stress of the 680 kit ,my engine is in perfect condition ,no need for a rebuild.
Need extra power but without a narrow powerband....
Posted January 27, 2005 - 12:29 PM
My mistake. sorry
Posted January 27, 2005 - 02:16 PM
Barnums cam, Hotcam, Webcam, or HRC Stage 1 cam.
The larger/hotter stge 2 cams will cause some wear issues, and other problems.
Put in a 10.5 or 11:1 piston with the cam. You will be ok with premium from the pump gasoline.
Do the higher compression and the cam and it will be very fast.
The cam really gives it life!
Posted January 27, 2005 - 03:51 PM
as for the oversize valves--there are different considerations....but i like the OEM even on the 680 motor. others have different opinions...but realy is there much performance difference--i dont think so?
with the big carb, cam, higher compression piston...then you really start to have something.
Posted January 28, 2005 - 03:51 AM
What about the jetting with a bored-out carb or ported head? Leaner?Richer?
Posted January 28, 2005 - 08:47 AM
But to answer your leaner/richer question.
Bigger valves means taking in more air which means needs more fuel to keep the right ratio.
Richer/leaner refers to the ratio of Fuel to air mixture... so if you do not adjust the mixture of the carb and just go bigger valves then it will be leaner (because Air intake increases with no increased fuel until you set it to do so) but to get it to run right you will need to increase the fuel supply to keep up with the air supply (may mean just adjustments in carb jetting). Ultimately I don't know if the Ratio will be the same (it should be close) but it will use more fuel in the long run.
So in the long run it should not be much different as in leaner or richer. Just more air AND more fuel keeping a close to orginal ratio of mixture
Sorry THis doesn't help with the OS valve question but I don't feel qualified b/c I can't say benifits or negs. I can on American V8s but thats different (and older) technology
Posted January 28, 2005 - 09:54 AM
Posted January 28, 2005 - 11:55 AM
btw: I think you run a Hotcams,did you chance the cam chain and sliders to the HRC stuff or still OEM?
I found this about jetting on modified motors:"... Highly tuned engines often require leaner jet
needles as do motorcycles ...."
Posted January 28, 2005 - 12:54 PM
Oversized Valves may end up hurting performance as opposed to helping it, unless you know for certain that bigger valves are absolutely necessary. The larger the valve, the lower the air velocity, but larger valves can handle larger volumes of air. Depending on how big the valves are, you may or may not be able to do future valve jobs after the material has been removed, which is another consideration. Getting everything to work in harmony (intake, valves, cam, porting, exhaust, timing, etc) to achieve a known desired outcome takes a good bit of knowledge, experience, time, money, etc, otherwise you're guessing when you're bolting on or installing performance parts. Sometimes the guess work pays off and sometimes it doesn't.
Bigger valves paid off for me but, I have a 680 with 3mm oversized intake. It is a 2.8 hp gain over a 680 with a bigger cam and everything else being the same and stock sized valves. Going only 1mm larger on the intake would make more sense though. That way you could go 3mm oversized at a latter time. You do use the same stock crank for the 680 kit but, I have a XR600 rod bearing. It's stronger or bigger or something. The stock one works also.
Horsepower madifications for the XR650R Click Here:
XR650R Site Click Here:
Posted January 28, 2005 - 04:47 PM
Yes, I have a HotCams stage 1 cam in one of my bikes. I kept everything else stock in terms of springs, cam chain, etc. I did spec out out my springs to make sure they were still good and they were. The slow running 650r engine isn't nearly as hard on springs as the crf/yzf race bikes that buzz to 13,000+ RPM. If you went with another cam besides a HotCams product, then chances are you'll need to have your rockers hard welded to handle the hard coating on the cam (i.e. web cam, etc), but the HotCams product is designed to work with your stock valve train as long as it's still in good shape. For a little over $100, I was happy with the HotCam upgrade, but you do loose the auto decomprssor mechanism, so you have to make sure and start the bike properly or else risk the remote chance of the kick start lever stabbing back at you very harshly. As long as you start your bike by bringing it to TDC, then pulling in the decomp lever and pressing the kick start lever so the piston just passes TDC before you kick it over, you'll be just fine and won't have any kick back issues.
Posted January 29, 2005 - 01:05 PM
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