Still no increase in power.

[Alex]

J - How are you sitting on the bike during these runs? Helmet velcroed to the tank behind the bubble, butt all the way back, knees and elbows tucked in as much as possible? Are you > or < 200 lbs? If the aero isn't just about perfect, or if it cannot be made just about perfect due to body shape on these tiny bikes, a rider isn't going to hit 100+ very easily. Take the internet speeds you hear from some on this forum and others with a grain of salt unless it's at a timed event.

[JMcDonald]

RacerX, I absolutely believe you are trying to help, and wasn't referring specifically to you. Sorry if it seemed like that .

RacerX, normally I am doing these runs in 4th gear, which puts me at about 12100 at 95mph. I was in 6th gear simply cruising and happened to decide to see how fast I could go, and was really just surprised to find it was making that much power to hit ~94-95mph at such a low RPM RPM, which further supports that it is indeed running great up to that point (about 9-10k it seems), and then just doesn't keep going like most would expect of a modded bike. But, I don't normally and had never attempted to go for top speed in 6th, and don't really have any reason to try again.

There is about a 2.5-mile strait stretch of wide (3-lanes plus two more for each shoulder), flat (without wind, will hit the same speeds going each way) road where I am doing these runs. I've held it at WOT, at top speed for over a mile on some occasions (so, using maybe .5 or .75 miles to get to top speed from cruising speed, and then not getting anything else beyond that). So, I'm definitely not running out of room.

Alex, I weigh about 150lbs geared up, and am typically indeed fully tucked in with my chinbar on or near the tank. For my power comparisons I am largely going by the MCN review of the '08 ninja where they were able to hit about 95-96mph with ~26whp, but it does seem generally speaking (and indeed taking it with a grain of salt) that those who try are able to go much faster than I can with modded bikes.

[Shiloh]

What have you modified that would increase your aerodynamic drag, such as a taller windscreen, etc. Aerodynamic drag increase is non linear, essentially proportional to the square of the change in velocity. A ten percent increase in velocity requires a 21 percent in increase in power from an aerodynamic drag standpoint. Therefore, increases in aerodynamic drag have an exponential effect on maximum velocity. The non-aerodynamic drag is components of drag are in large part linear with regards to velocity.

Just running the gear/rpm numbers you posted and I get the actual speeds to be:

9000 RPM/Sixth Gear = 91.6 MPH, Actual, not indicated,

12100 RPM/Fourth Gear = 94.8 MPH, Actual, not indicated,

Delta of 3.2 MPH or 3.4 percent for a implied power delta of 6.9 percent at a minimum. Not what I would expect the engine to be producing, but not flat either.

[JMcDonald]

The 9k and 12k estimates were rough, but I did later specify that I meant close to 95mph for both gears. Like, within 1mph whether I was in 6th or 4th. The windscreen is only 4" taller than stock, and is about at the top of my helmet with my head nearly resting on the tank. In any case, I have had it on and off on different occasions and never noticed any decrease in top speed. But indeed, Shiloh, that simple principle of fluid drag is yet another reason I inferred that going from ~25 to ~30hp should allow me to at least consistently break 100mph, with all else being equal, and how I derived that my overall power did not actually increase (to almost any degree, really).


I might also run some seafoam through my fuel system, or try to use some other method of cleaning it out. I know the PO didn't use the bike all that regularly after he got his car running again (I think he said he hadn't ridden it in like a month before I bought it), so perhaps there might be minor clogs in the fuel system or even the left carb itself, preventing adequate fuel flow. A simple test could be to put in a 112 main on just the left side, and then perhaps a 115. The idea is that, if the left side is starving for fuel at WOT, then either I will pick up some power (if the larger main is enough to offset some minor restriction) in that carb, OR there will be no change in performance if the restriction is significant enough that the larger mains do not compensate. Just working through various ideas to explain the engine variances.

I checked the valves a few thousand miles ago and they were within spec although mostly all on the tight side (don't remember the exact numbers, though). Though, if they aren't closing all the way, which would be more likely at higher RPM with too-tight valve lash, that could also be a potential source of drag.

[Shiloh]

Well, what I'm left with in terms of suggestions, is not anything new, but I would focus on why the exhausts are discolored in such a different manner. Clearly something appears to be amiss there, and when that is determined, and corrected, very probably your quest for 100 MPH will be resolved (but not in sixth gear ).

The valves will get tighter over time, but if they were within specs 2k miles ago, they shouldn't be the issue. And I'm sure the air cleaner is clean, and it being completely blocked would affect both carbs equally, so back to the carbs, for the difference.

Noticed that you are using an after market ECU. Have you tried using the original ECU to check for a fault in the after market unit?

[HKr1]

I would think if the passage is clogged, jet size wouldnt have any effect. Also the other passsages would be worst off than the main.

You have one of those laser thermometers to check header pipe temps?

Still kinda think playing around on a dyno would be helpfull. After having one of our bikes on there, was interesting seeing what it really took to get nice hp #'s.

[Shiloh]

Originally Posted by HKr1

Still kinda think playing around on a dyno would be helpfull. After having one of our bikes on there, was interesting seeing what it really took to get nice hp #'s.

Really probably your best option, cheapest and certainly quickest, provided you have a shop with a dyno and good people available to you.

[JMcDonald]

Yeah, I only swapped in the aftermarket TIS later on, and it generally helped.

[Shiloh]

Originally Posted by JMcDonald

Yeah, I only swapped in the aftermarket TIS later on, and it generally helped.

Oh well, just hoping.

[JMcDonald]

Haha yeah, trust me I was hopeful as well when I first installed it :P . But it didn't make any more of a difference than it should have on its own, so the problem couldn't have been the stock CDI.

Sorry I didn't see your post, HKR1. Unfortunately, my thermometer doesn't go high enough to tell, though the colors indicate actual header temps of around 800*F on the left side after the flange, and about 600*F on the right side at the same point. Im not sure what range I would expect, though I have seen bike header's glow which doesn't happen til about 1000-1100*F (depending on ambient light). In any case, it is really the apparently drastic difference that has my attention.

As far as the fuel flow issue, I meant more that the inlet to the carb itself might have been clogged enough that IT is the limiter of maximum fuel flow to the cylinder, rather than the main jet. It is somewhat of a long shot Im sure, but seafoam isn't really expensive. If it weren't my only transportation, I'd be less hesitant to fully disassemble the carbs beyond the caps and bowls. But, as it sits most days I have to have it back together in a few hours, and don't want to risk tearing a seal or something.

Probably the next couple of things are re-checking the valve lash, maybe trying to flush the fuel system, and then taking it to a dyno.


What is a good, simple method of flushing the fuel system? Is there something potentialy better or safer than Seafoam?

Thanks, guys.

[Shiloh]

Have you checked the float height on the carbs, a miss set float could cause the symptom you see on the headers. Could just be, maybe.

Anyway,

You might want to pull the carbs and strip them completely, and then use some product like Gunk or Berryman Carb cleaner, to clean them fully. You can get a gallon of this type cleaner at most auto parts still, and it comes with a basket for dipping the carbs into the gallon can. They will look like new when done. Compressed air is handy to have for blowing the passages.

[JMcDonald]

Will float height (or some malfunction) affect overall fuel flow? If they are only effective at the lowest flow ranges I wouldn't imagine there is enough fuel burning to cause the headers to get that hot. I'd think it was definitely full-power EGTs that caused the color changing.


I do actually have some chem dip, heh. I'll be sure to remember to bust it out if I have to pull apart the carbs.

[Shiloh]

Originally Posted by JMcDonald

Will float height (or some malfunction) affect overall fuel flow? If they are only effective at the lowest flow ranges I wouldn't imagine there is enough fuel burning to cause the headers to get that hot. I'd think it was definitely full-power EGTs that caused the color changing.


I do actually have some chem dip, heh. I'll be sure to remember to bust it out if I have to pull apart the carbs.

Incorrect float height can cause insufficient fuel flow at high RPM which could explain the the lack of power at high RPM. One cylinder being starved at WOT once the RPM is high enough. An easy thing to check. Should be set at 17 mm.

[JMcDonald]

Hmm. Never knew that, and didn't consider it as the FP manual only explains its benefits at small throttle openings. I'll look into it for sure!

[Shiloh]

Have you been able to solve this?

[thomason2wheels]

Originally Posted by Racer x

The top speed is going to be 104 to 107 regaurdless of gearing. The air wall will hold the 30 hp bike at the top speed .then wind and grade will help or hurt. Just remember 5th gear is 1to 1 in the trans and
6th is over drive.

Doont forget the losses are most likely less at the 1:1 ratio than in overdrive...mechanical losses vary according to which gear you are in.