Bernie's timing mod results ! (cue Hallelujah Chorus)
 

Well I got my flywheel back and whittled down the excess weld on top and each side going slowly. This flywheel is not lightened-just has a 3mm extension on the front of the rotor nose. The extended parts looks all ugly and lumpy in this hi-res photo, but it's not as bad as it looks; it's nice and smooth on top blending in with the original nose very nicely. Most important it's right on spec and it seems to be doing something.

http://static.wixstatic.com/media/ba...0_0.00_jpg_srz

The original length of the rotor's nose seemed to come out at 47mm, and this is 50mm, yielding the 3mm extension Bernie recommended.


Going out for a quick spin I see I can hit the rev limiter in 1, 2 & 3rd gear with my 14/48 gearing! It didn't peg the tach like instantly (so to speak-I don't have a tach) meaning not necessarily any 'quicker' , but it revved up to 10,500 without much hesitation. That's as much riding as I did as I have other things to do.

I glanced at the indicated kph in 2nd and 3rd (aprx 73 & 93 kmh) and those speeds match up with 10,500 rpm at GearingCommander.com after plugging in my specs.

I am using the stock 34mm CVK carb. I don't know how the WOT jetting is at this higher rpm. Something to check later with the a/f meter. I did look at WOT jetting a/f this morning before putting on the modded flywheel, and it was a little rich with the 130 reading in the mid to low 11s; if I had a 128 I'd be right where I want to be. But maybe a little rich is safer at these high rpms.

So there may be something to this eh? I haven't had the 34mm stock carb on much lately, so how easy it is to hit the rev limiter with the 34 is something ya'll will have to fill me in on.

If I were racing, I'd probably have shifted before it got near 10,500-but it's hard to say because I was just checking what max rpm was. Even though the revs were quickly climbing steady towards the limiter, I can't say it was making max power all the way up, but on the other hand I can't say it wasn't - if I were running it on a dyno, then maybe ya I'd let it crank up higher just to see if it made more HP etc.

I'll have to investigate this some more looking at the jetting and trying it with the 36mm etc

You've been doing so much testing it may be hard to determine the results without a comprehensive before and after with a carb making about 12.2- 12.5 : 1 WOT AFR ...?

More importantly I haven't been doing any real speed testing with the 34.

It'd be 5 weeks probably before the 128 main gets here. Unless shimming the needle half a notch richer the yesterday caused the 34's WOT a/f ratio to go from 13s and a 14 now and then - to low 11s just by replacing the 125 with the 130mj. Seems like a big a/f change for just going from 125 to 130..


Back to the thread subject:

So what about this hi revving engine? Will 34 CVK equipped bikes see the rev limiter in the first three gears (or more) like I did today? Did this 3mm longer rotor nose let it rev higher? It probably would have hit the rev limiter in 4th if I'd had room to run it that fast.

Well I hit the cutoff by accident all the time in 1st - It revs that hard and fast... I sometimes let 2nd go to cutoff. I can feel the power start to slack off on up there in 2nd , before cutoff.

So why didn't everybody chime in about how all their bikes hit the rev limiter already when Bernie was posting ? Seems IIRC the responses and general sentiment were more about the engine being tapped out at 8500 or so.

Revving higher and making more HP as it did was the point of Bernie's post. Now you're saying higher revs are commonly done?

Nonsense about revving higher would go in one ear and out the other with me - nothing about advancing the initial timing would effect the built in rev limiter/cutoff. So I can't comment on anything about "revving higher". Likewise, the crap about 8500 rpm goes in one ear and out the other - so no comment there either. The engine only drops power in the upper range when you don't have it jetted correctly - too lean kills the upper RPM power and so anyone talking about that goes in one ear and out the other.

I was hoping you'd feel the power curve build more quickly without loosing any power on the top end.

I generally don't bang the rev limiter because there is not much to be gained in the 2000 rpms from 8500-10500, if there was I might use it.
That being said, if passing in lower gears I do hit the limiter trying to get the bike to go sometimes. It's mostly when I'm trying to get the shift point to where it'll drop the rpms into the sweet spot for the final pull passing a car.
Been following all your tests. Keep it up! This seems promising. I'd like to know more...

I've hit the rev limiter in at least all of the three first gears. I'm all for looking for extra power, but Ray Cour's adjustable timing CDI yielded no benefit on the dyno, and the Aussie KLX's with an additional 10 degrees of timing advance stock don't show any more power over base either.

There may be some power to be unlocked with big bores and more aggressive cams matched with timing changes, but it appears to me that without such changes the timing is a dead end.

Ray Cour has not tested the module on a proper motorcycle dyno. He indicated that his results may not be accurate due to that fact.

Us old racers know that an additional 10 degrees of advance will certainly do something. His testing showing nothing is suspect to me.

Combustion chamber design, and camshaft profile and timing will determine how much timing it wants. Everybody used to run 40 degrees total back in the cast iron head days, but nobody does that today. If I recall, GM's Ecotec motors make max power somewhere around 27 degrees total advance. I think you need to do some road testing (top speed) to tell if it works or not. Do you guys think Gtech meter would work on these bikes? I have one that I haven't used in years.