oldfrt613 said:I read the same thing somewhere - greater crank inertia than the '01. Installing the '01 is supposed to make it rev quicker. Sounds reasonable - would explain the dyno numbers - engine looks good on paper, but lacks snap. Speaking of which, wouldn't it be cool to see a rpm vs time to show engine accelleration rates ? This would probably relate to how a bike "feels" when you ride it.
Dino Y said:The Weight on a crank is always ballanced on its axis. Keep in mind that crank weight works about the same way as heavier or lighter flywhees, and a lighter crank would defenetly rev faster in time but lower in rpm. heavier cranks rev higher and can keep their revs easier and again the placement of the weight relative to the axis of rotation affects reving. The Further from the axis the weight is the slower it can rev
SQUIRLEYMOFO said:maybe I don't need to install that flywheel weight after all..........
I agree that the moment is the relevant piece of information. However, the very close physical similarity (they both use the same crank bearings - 91008-KAE-731) between the cranks coupled with the observations of a heavier crank in '02 coinciding with a perception of slow revving (classic symptom of increased moment) bears further examination. I'm not aware of any published info on Honda crank moment numbers and an accurate calculation seems difficult (??). I'd be willing to experiment with a lighter crank when it's time for the next top end...Rider 007 said:since the moment is what is important
One last thing - how does the fact that Gorr and Varner agree that the porting has limitations (and I believe EG has said that the CR will never be a YZ or KTM due to the limitations of its PV design) support or undercut the "heavy crank" theory?
I''ve ridden my CR back to back with my friends '05 YZ250. Where the stock CR seems lacking is in the responsiveness down low. As said above, when the CR comes on, it is at least as strong as the YZ and seems to be stronger. Now that I have my Boyesen ported cylinder, my CR is silly fast compared to the YZ. But the YZ still seems more responsive down low.Rider 007 said:One last thing - how does the fact that Gorr and Varner agree that the porting has limitations (and I believe EG has said that the CR will never be a YZ or KTM due to the limitations of its PV design) support or undercut the "heavy crank" theory?
john3_16 said:My buddy called up Varner before he got his engine work and asked him if a ported CR would still not be able to match a stock YZ like EG mentioned....Varner was like "What?? It can be made faster than a YZ".
Now I have ridden the Varner motor and I cannot see how any stock motor could match a Varner CR...It is hands down the fastest 250 I've ridden...
skipn8r said:The original observer of the weight difference said that an older (lighter) crank will bolt into the later engines. He went on to say that the heavier cranks are better for oval tracks and the lighter crank is better for MX; hence, he has presumably observed a performance difference.
skipn8r said:BTW, if the bearings are the same, and the cranks interchange and one is lighter; it is reasonable to presume a priori that the lighter crank may have a lower MoI.
skipn8r said:That being said, I'm not claiming that a lighter crank will solve the observed low RPM CR "problem". I am saying that given two otherwise equivalent engines, the one with the lower MoI will feel (and will be) more responsive to the throttle. It's at least worth a try....
Partly in a PM response I got from the original poster as well as other inputs I've read:Rider 007 said:I missed this... is it in another thread? I'd like to learn more.
Not the first time I've heard of a fast modded CR (not that a stock one is slow) but have never heard of anyone getting the breadth, flexibility and ease of use of the YZ power out of it. Is that the case here?
Does it still run on pump gas or does it now require race gas?
Now that's what I'm looking for whether I need it or not!john3_16 said:The bike runs on race gas.....It's not like a YZ with an easy to use and flexible powerband...Maybe that's what Eric meant by saying a CR can't be made into a YZ...
The Varner bike is not a YZ....No the Varner bike is just flat out ferrocious and pulls so hard it's rediculous...It's definitely a pro motor and has a nasty top end bark...I got off that bike wondering how my buddy raced that bike with the throttle to the stops because it was just too much motor....Coming out of corners in 3rd gear and wick the throttle open and the bike is revving like it's burning nitro... Definitely stronger than any stock bike out there.
Waiting for a full report.....john3_16 said:We are supposed to finally get together again tomorrow and test the two motors(mine is modded by EG) back to back...And we're going to sample each motor with the SST pipe and shorty silencer...
Sounds like my Boyesen-ported cylinder setup; it's broad, smooth (no nasty "hit") and insanely powerful. If I change anything, it'll be to have Wes make the power come on at a lower RPM.oldfrt613 said:My current cylinder has decent bottom, but gets with the program in the midrange and revs to the moon. You really notice the power in 3rd and up - it flat halls azzzzzzzz !
Still waiting on the ride report....john3_16 said:We are supposed to finally get together again tomorrow and test the two motors(mine is modded by EG) back to back...And we're going to sample each motor with the SST pipe and shorty silencer...
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