Thumbs up. I think you have basicly gotten to the bottom of your problem. Before now, I thought when I had gotten the chance, I was going to tell you that it appeared that your flat top-end was associated with your hanging idle situation you asked about in your other thread. Both of these problems really lean towards a lean condition, heh,heh pardon the pun.
The whole talk of a hotter cam and such is not the solution to what you have had going on with your bike. A cam would certainly give the bike more pull and topend power over what the bikes current potential is but as said is not the solution to what is/was currently going on.
What made your lean condition even more pronouced is that you were using a K&N. I have used the K&N myself for awhile along with a UNI. I have found that the click adjustment setting needed with use of a K&N can be required to be richer in comparison to a foam filter if you have holes in your sidecover. Some bikes and mod setups may vary.
In short, it appears your needle click adjustment was set too lean as well as a freerer flowing K&N filter contributing to an even leaner condition. These two factors together could very well be your bikes problem.
As a side note to what Thumpmeister brought up;
It has been said by the Baja Honda team,(from what I have read) that in their experience, the higher comp piston does not allow the XR650R to rev out as much or maybe as cleanly versus the stock compression piston when both are used with the HRC cam. Honda was reported as using the HRC cam and stock piston for longer, higher top speed races for rev out and used the HRC cam & HRC high comp piston for desert races where the course was a bit more transitional in speeds. It appears the high comp piston does add additional power pull but I guess does not provide the same kind of over rev.
As an additional note, when the top speed wars took place a few years ago out at the dry lake beds, the Honda team switched from a full HRC kitted bike to another one of their bikes with the HRC cam and stock piston. That was the bike that ran better/faster on flat out speed runs. I still have that magazine article tucked away somewhere.
I agree: getting the bike to run as cleanly as possible is the first order to getting the most out of the motor. I am not one to throw money at problems expecting a solution.
I'm one of those guys that can feel the difference in gas brands/octanes, when all around me say I am crazy. When I started with two-strokes, I matched, ported, and polished motors for me and my friends, and learned quickly that everything has a compromise when you try to go with 'more'. I know that getting the Edle dialed in will give me the most of what i want right now: 'better' power, opposed to 'more' power.
Having said all that, getting a bit more top end without having to gear up would be nice. I really like the stock gearing for dirt, but would like to accelerate to 80 mph as quickly as possible, as LA fwys are nutty to be on without superior power.
So, I plan to do these things, in no specific order, to get the bike 'better' before I go 'bigger':
- learn the edle's tuning and go as rich as is practicle
- replace my rear blown shock, and go with heavier springs
- get the front and rear shim stacks redone by ESP
- replace plastics as they become (cheaply) avialable on ebay
- find a reasonably priced full exhaust
(I really think the stock header is part of the problem with over-rev)
- get a comp/speedo (I want to see revs)
- new chain and sprocket
- get the valve train freshend, do a bit of home port/polishing, and while I'm at it, try a new hotte cam.
I ride the thing almost everyday right now, and do an occasional 'questionable' trail ride near my Chatsworth home. I don't think I will have the confidence to do a 'real' ride till the rear boinger is fixed (pretty boingy now).