Still no increase in power.

[JMcDonald]

I put on the Sportisi VR Black exhaust system, put in the 110 mains with the clips at the 4th position as a baseline, and there is absolutely no increase in overall power. Top speed is still in the low 90s, actual.

I have been troubleshooting this for quite a while, and havent had any imptovements since just removing the snorkel. The top end runs just the same with every jet from 102 to 112, though once below 110 the clip position starts having to get a little ridiculous to keep the midrange strong. The low end and midrange are fine. The carbs are opening and closing all the way. It had been previously concluded that it was previously my stock exhaust holding me back, though neither the custom dual exhaust I made, or now the VR exhaust, made any difference. The valve lash is wishin spec, and all the hoses are connected.

I thought maybe the slides werent opening in the top end, but the top end at WOT gets very rich with 115 mains and will barely go past about 12k. I cant think of anything else except a broken CDI or something resulting in significantly reduced timing, or maybe the cams are off a tooth or something? I dunno.

Any ideas?

Posted via Mobile Device

[ztrack157]

Ya put 96 or the 98 mains in it. Clip in the second groove. If your using my jet kit. I can't remember. Your basically choking the motor with gas.

[kkim]

yep, if you still have your airbox, leave the 98s in there. I thought you had gone to pods, though?

[scotty]

Originally Posted by kkim

yep, if you still have your airbox, leave the 98s in there. I thought you had gone to pods, though?

I thought so too, I remember reading thr past post and could have sworn he was running pod's. 110's are to big I think with the stock air box.

[JMcDonald]

Yeah, I have a pod filter. I forgot to mention that. I have the K&N dual-outlet filter (R-0990) and the Factory Pro jet kit.

With the 102 mains, even with the needle clip in the 5th position with another two washers underneath, the midrange was very lean. Going to 105 mains put it back to normal, and 108 mains only required the needle to be in about the 4th position for a good midrange (before the VR exhaust, at least). However, overall power and top-end performance does not change at all between the 102 mains and the 112 mains. 115 mains give a very rich top end and it will hardly rev past 12k, and obviously 102 mains are too lean with how much the needle needs to be raised. These numbers are from the stock exhaust with the pod filter.

[kkim]

when you say top speed is in the low 90s, what are you measuring this with?

[JMcDonald]

Calculating it based on the speedo reading around 100-102. I have compared my speedo to a half dozen of those radar speed signs, and it was consistently about 8% fast. I've also compared it to my Honda Fit for the same error, and the Fit consistently reads correctly with the signs.

[kkim]

maybe w/ your 16/41 gearing the bike can't pull past the wall with such tall gearing? try throwing the stock front sprocket back on and see if it makes any diff.

dunno... you're top speed sounds about right to me. maybe a bit low, but nothing significant.

do you have anyone in the area that can dyno the bike?

[DaBlue1]

Your sprocket set up is hampering your work. Try 15/41 instead.
A 16/41 set up has a 2.56 ratio and a 15/38 has a 2.53 ratio. As you can see they are pretty close. 2.53 ratio is about the lowest you want to go because of the amount of HP needed to pull that gear ratio for top speed.

http://www.theyeagergroup.com/kawasa...rive_ratio.htm

[JMcDonald]

I think there might be a couple of shops. I'll look for one.

Gearing isn't the issue. My 4th gear is very close to stock 6th, but 5th gear actually usually can get me going a little faster as it puts the RPMs closer to stock power peak (my top speed went up a couple MPH, actually, after changing the gearing and being able to pull in 5th at a lower RPM). In any case, I am definitely in the right gear for pulling (I'm not trying to still do this in 6th gear...). I've heard members here talk about going much faster than low-90s, usually with less mods--hell, someone reported 108mph on the GPS on flat ground with just an exhaust system and rejetting. But, even avoiding chasing internet numbers, that I haven't gained anything is the main reason I am confused and a bit frustrated.

[kkim]

go back to a smaller CS sprocket and see if that helps.

[JMcDonald]

At 95mph, with a 14/41 combo I'd go from either 12100 in my 4th to 11900 in the proposed 5th, OR 10500 in my 5th gear to 10650 in the proposed 6th gear. There is no way 200 RPM is going to give me the 4-6HP difference everyone else seems to be getting with these mods, heh.

*edit*

Compared to stock gearing, I am at 12100 at 95mph in 4th, vs a stock bike which is at 11700rpm in 6th gear.

[kkim]

people are giving you viable suggestions and you're not even willing to try them out before you discount them? up to you... keep on looking for reasons for the lack of power that may or may not even exist. you asked for suggestions, we gave you some.

[JMcDonald]

I do appreciate the suggestions, and I never said I didn't. Providing solid calculations to show why I don't think those suggestions are my problem is not at all in the same vein as simply shrugging them off, so please don't take it like that. If anything, that I actually went as far as providing numbers to support my reasoning should tell you I am not just trying to be selective about which suggestions I take, and am indeed putting thought into all of them.

I am not real excited about constantly wrenching on the bike just guessing. I've already done that way too much in experimenting with all those main jet sizes, even when I already doubted that was my problem.

If nothing else, what else do you think it might be? If I have time tomorrow I will try the 14t, but waiting for that is no reason to stop brainstorming.

*edit*

Also, I changed the gearing before I made any mods for the power, so this gearset is still applicable as a baseline. Additionally, even before any power mods my 4th gear pulled to exactly the same top speed as my origial 6th (about 93-94, or about 102 on the speedo). So, if I am going up in power, it should still be apparent.

[mrlmd]

Don't hate me, but - With all the time and energy and money you've spent so far, did you ever think to use your bike as a trade-in to get a bigger one? You want more power, get a bigger bike.

[JMcDonald]

I figured somebody would say that, but I don't really want a bigger bike. I like this one, I just wanted a bit more out of it.





I'd be doing just as much tinkering with an R1 :P .

[mrlmd]

Just trying to rag on you. don't mean any harm. Hope you get it figured out to your satisfaction (but the Kawasaki engineers did make it that way for a reason).
Good luck, keep us informed on your progress.

[JMcDonald]

Yeah, I guess I'll have to just poke around myself, if actual brainstorming is out of the question. And no, I didn't take any offense to your post .


I might try the CDI to see if perhaps it is an issue with that.

Is there any other way ignition timing could be off on a carbed Ninjette?

Also, has anyone ever gotten the cams off one tooth? I've done it on cars and it would barely run, but maybe on this bike it would be just enough to reduce power.

[mrlmd]

Seriously, what are you trying to accomplish?
How much more HP or top speed or better 0-60 acceleration time are you expecting or trying to achieve? How much more "power" do you think you can actually get with these mods?
And how much less gas mpg and reliability and engine longevity are you willing to accept?
You may never live up to your expectations and there's just so much you will squeeze out of this engine that's actually measurable before and after on a dyno..And most people don't really get more than 1-2 HP extra out of the engine after all that and spending hundreds to thousands of dollars.
There's nothing wrong with your CDI, it's all about reaching the right match between air in (filter), gas in (jets and clip position), and exhaust out (aftermarket hype), and how much money you want to spend to achieve very little in the way of real gain, like 5-10%. Just my opinion, but you really may be happier with a bigger displacement bike unless you want to spend your time chasing your tail instead of riding. You want significant more power, you need more displacement, very simple.

[scotty]

Have you changed your mixture screws? I didn't see you say anything with that. You have the same set up as me, mods wise. I have my bike set up as:

3rd clip on needles,
110 Mians,
mixture screws 2.5 turns out.

I also have stock gearing on my bike ans it pulls great though all gears. As stated above, maybe try and do stock gearing to see if that will change anything. Its worth a try at least!

[JMcDonald]

The low ens and midrange run great. The mixture screws shouldnt affect top end, or at least they havent for me.
Posted via Mobile Device

[scotty]

Originally Posted by JMcDonald

The low ens and midrange run great. The mixture screws shouldnt affect top end, or at least they havent for me.
Posted via Mobile Device

I'm not to sure. When I was working on my set up, I had the screws out two turns and at around 9,500 rpm's, the bike felt like it was dieing. Didn't want to go past that. So I did a half turn to 2.5 turns total out and ran great.

[JMcDonald]

Mrimd, I am trying to accomplish the same thing as everyoe else who mods their ninjettes. Just that they are all reporting notable gains while Ive seen absolutely nothing (and its still slower than most stock bikes, even). I am simply hoping to see what ideas others have as to what might be holding my bike back.
Posted via Mobile Device

[JMcDonald]

Hmm, scotty. Tomorow i will play around with it and see f anything changes.
Posted via Mobile Device

[DaBlue1]

I understand what you are wanting to do, however all the HP you gain will mean nothing if the bike is geared wrong. I think you will be hard pressed to find any one running a 250 ninja on a dyno with larger than a 15 tooth front sprocket. I believe Racer X runs a 15/41/42/43 depending on conditions. When he runs all motor with a timing changes, he's running 109+ mph
The gear ratio you have is taller than stock for other big bikes. If you do not have a 15t sprocket. Try 16/45 (2.81), it is close to 15/42 (2.80), which is a great ratio to have.

Bike- Front/Rear

09-2010 R1 - 17/ 47
04-08 R1- 17/ 45
98-03 R1- 16/ 43
06-2010 R6- 16/ 45
99-05 R6/06-09 R6S- 16/ 48
06-2010 GSXR 600- 16/ 43
01-05 GSXR 600- 16/ 45
98-00 GSXR 600- 16/ 46
07-09 ZX6R- 16/ 43
05-06 ZX6R/RR(636)- 15/ 43
03-04 ZX6R/RR(636)- 15/ 40
00-06 RC51- 16/ 40
08 CBR 1000RR- 16/ 42
06-07 CBR1000RR- 16/ 42
04-05 CBR1000RR- 16/ 41
00-03 CBR929/954- 16/ 43
07-08 CBR600RR- 16/ 42
03-06 CBR600RR- 16/ 43


Hope you find that sweet spot your looking for.

[almost40]

Aero is the limiting factor in top end. It takes a huge increase in power to increase your top speed. Weight is another factor but not near as important as aero. The problem with the 16/41 is it limits the bikes ability to use the gearing to increase the speed on the top end. Go back to 14/41 and see if you can redline 5th. That will tell alot.
I run 14/41 gears and my modded bike will pull just past peak power in 6th on level ground. The bike will redline 6th with a good tailwind, draft, or downhill grade. Perfect if you ask me.
Dyno your bike to get some good air fuel numbers for carb tuning and a print out of your hp curve. Change the gearing with that info. Otherwise were all just guessing.

[KELPHYN]

One more thing to think about. What kind of outdoor temperatures are you have down there now? If the temps are little on the cold side it will effect top end speeds. I know up here in the spring and fall when temps start dropping I lose some topend, after running great all summer. There were even times on a couple of road trips this summer, during the same day, altitude was close to the same but there was a difference of 10-15 degrees made big difference. Some days my bike pull into redline in sixth on the flats,some not, just hangs around 12000rpm. Although through the lower gears(1-4) it pulls smoothly right to the limiter. It's just that with such little horsepower it doesn't have it to punch a hole through the denser cold air.
I don't know if you have noticed that looking at larger there is a big jump in horsepower to break over 100 mph mark. If you look, bikes with 60-80 hp usually only have a top speed of 120-130 mph. When you think , they have double, close to triple the HP and are only 20-30 mph faster on the top and breaking the tonne(100mph) on 500-650cc bikes in the mid- 70's was still rare. So pulling the tonne (100 mph) on our 250's on a good day and over 90mph on average is still pretty impressive.

[KELPHYN]

Me thinks we think alike Kevin. You just type faster.

[Flashmonkey]

Originally Posted by JMcDonald

there is absolutely no increase in overall power.

Unless you have taken the time to measure the power output on your bike on a dyno before your mods, then taken the bike to that same dyno for a measurement after your mods, there is absolutely no way you can make this claim.

Associating increased power output to a direct increase in top speed (or lack thereof) is a horrible way to measure gains, and is facetious at best.

How does the bike feel now vs before?

Or if you want to get technical about this, get your butt over to a dyno shop. Until you directly measure the actual power output of the engine and compare to a known stock baseline, you're just making wild assumptions.

Edit: Ok try your best not to read that in a harsh tone. It just seems harsh because I'm too lazy to put in friendly modifiers

[JMcDonald]

Top speed is a far more reliable means of measuring changes in power, given equal variables or multiple tests, than the butt dyno. But no, I dont feel and have never felt any difference. And yes, more power at a given rpm range would directly affect the amount of speed a vehicle could reach in a gear putting the engine in that RPM range.

Let me ask this, how are people suddenly able to get 105 to 110 if power mods dont increase top speed? How many of you saw increases in how fast your bike could go after modding your bike for power? Hell, when i first removed the snorkel, my top speed went up several mph (from about 88 to the same 92 or soim seeing now, over dozens and dozens and dozens of trials on a few different roads). If anything, enough of a difference to feel would definitely be enough to change top speed, as I could barely feel what the snorkel gave me but the change in top speed was significant. Mathematically speaking, compared to a bike that makes about 25hp and goes 96mph, my bike at 92mph is making about 22-23, and to get past the low-100s would take around 30. And please nobody way "but that math doesnt apply in the real world," because as a 5th-year Physics major Id love to be in such a universe--but we'not :P . Until I get it on a dyno, though, emperical numbers are absolutely accurate enough for comparisons sake. Perhaps comparing to others' top speeds is less accurate because you never know who has a slight unnoticed tailwind or a slight unapparent decline. But, my numbers have not changed at all despite mods that seem to be netting everyone else 15 to 25% more power. Even a 5% increase in power (for me, going from about 23 to 24.5) would be expressed as about a 2mph increase in top speed, but after several runs I do not even have that.
Posted via Mobile Device

[mrlmd]

I doubt anybody is getting a 15-25% increase in "power" with airbox, jetting, and exhaust mods, and the only way to prove that is with a dyno before and after, not top speed.

[JMcDonald]

http://www.areapnolimits.com/images/...8_dyno_big.gif
25 to 30hp is a 20% increase. Kerry reports that every bike he has tested with his exhaust has seen a 3-5hp gain after simple jetting. Even 3HP from 23hp (going by my estimate) would be a 13% gain, enough for a change in top speed from about 93 to 97mph.

These are also showing gains of over 20% from baseline.
http://www.sportisimoto-usa.com/resources/vrdynorp5.jpg


I'm not saying I am expecting my numbers to exactly match what their graphs show, but I was not expecting to see or "feel" nothing at all when, as I mentioned above, nearly everyone else reports notable increases in acceleration with these mods as well as, when measured, increased top speeds.


And btw, the reason I am actually wanting to brainstorm all possible issues is because I spent $300 bucks on a "fix"--my new exhaust system--based on the flat guess that it was my stock exhaust system holding me back even though I had significant doubts that was the only factor. Obviously, the stock exhaust was not my primary problem, so I don't want to just continue throwing time and money at random fixes, especially when they logically should or, dare I say *could* not be the culprits. It makes no difference if my transmission is in 4th gear or 5th gear for a top speed attempt when the difference in RPM is less than 1.5% between the two final drive ratios. Looking at any dyno graph, the difference in power over 200RPM when looking at the 12,000rpm range is pretty much nothing. A difference of 1.5% in RPM is less than that of simply dropping the stock rear sprocket from a 45 to a 44t, if that helps show how small of a change I'd see by changing my front back to a 14t.


BTW, my final ratios is not anywhere near any of those bikes. The simple sprocket ratios, yes, but not the overall reduction, which is what actually matters. A ZX6R, for example, will be doing 70mph at 13000rpm in 1st gear, while I will only be doing 45. Some of those bikes would be doing over 100mph in 1st gear at that RPM. My sprocket ratio is indeed different than what most use on here (though one person does use 15/38, which is taller than mine), but that neither affects overall thrust capabilities (gear selection, yes, but actual wheel thrust, no) or power output on a dyno.

Again, I am just trying to brainstorm all possible solutions.

[HKr1]

Our top speed isnt any different with mods, than it was stock. It just runs better and gets there faster(TS). I know the older 250's go a little faster top end, they kinda walk away from the new-gen top speed wise. < kinda sucks

But I understand you changed gearing hoping for a bit more speed.... Maybe thats it for these bikes speed wise with the mid range cams installed?

[JMcDonald]

Hmm. Hell, I'd be happy just being able to feel a difference in just getting there :P .

However, I was basing my expectations on statements like these:

Originally Posted by almost40

Mod the bike and it will pull a 14t/41t to 108mph (gps verified)

His only reported power mods are an AreaP Quiet Core and jetting.

Not that I am trying to chase internet numbers, but like I said everyone else who mods their bikes with exhaust and intake and jetting reports either notable gains for the butt dyno or an increase in how fast their bike could go (and regardless of how fast they were actually going, the change would be consistent and that is where my focus lies). I have found neither, which is why I think something must be wrong.

[JMcDonald]

Originally Posted by almost40

Go back to 14/41 and see if you can redline 5th. That will tell alot.

That 5th gear would be a hair taller than my 4th gear (again, by about 1.5%). But, if anything, if I can't redline my bike in my 4th gear (about 101-102mph), going to a slightly taller gear (about 103-104mph) wouldn't make it any easier. Gearing isn't my problem.

[almost40]

Let me help ya here. Physics studies aside. Lets look at what I have done to my bike and my experience. First off, I have never cracked open the motor on my bike. I have alot of experience tuning carbs on my 86 SS drag car. I take into account altitude, humitity,tempature and barametric pressure. All those affect your carbs performance in a 1/4 mile. (where I got my carb tuning experience.) I added a Area P CQ full exhaust. I ground down the weld splatter inside the exhaust at the connections near the flange that bolts to the motor. I port matched and shaved the gaskets in the carb and exhaust. I took apart and carefully polished the inside of the carb (and ported a weeee bit) along with the top part of the header. I slightly modded the stock airbox by pulling the snorkel and slightly increasing the size of the hole that held the snorkel. I also added a K&N. I preped my bike to be track ridden. Shaved a few pounds and increased areo by pulling the mirrors and turn signals. I pulled the whole rear fender and tail light assembly and made a coustom bent aluminum cover plate to cover the gap. Removed the whole headlight assembly and bought a used plastic cover to fill in the space. I also junked the chain gaurd and rear pegs. I bought my bike new and broke it in myself using a motoman method and a presonal variation.(why is this important? its all about the rings) I weigh less than 150 lbs totally geared up for track. I can tuck behind the windshield better than most (due to my stature) and my clip-ons have been shaved to bring my hand in closer to minimize the wind drag. I only ride in full gear therefore I dont have a pair of jeans of t-shirt flapping in the wind as I am trying to top end my machine. As stated before Aero and weight are the 2 major factors to top speed. Not the only factors but 2 of the major ones. Take a look at a pic of Racer X's bike. All the extra plastic in the rear is for aero. I would bet that if given the chance to run his bike at his top speed event I could get another mph or 2 out of it due to my smaller size and weight difference.
Dyno your bike (on and avg temp/humidity day where you live) and make carb adjustments base on the air-fuel ratio. I didnt go with the pod set-up because a 250cc motor doesnt need that much air.(in my opinion) Too much air only wastes fuel it doesnt make more HP unless its a ram-air set up. (and I have my doubts about that) 108 mph was on a cool-non humid day if I recall. I also hit 120+ on the speedo and bounced off the rev limiter in 6th repeatedly with a 40 mph tail wind once. On the hot humid summer days here in corn country there are times my bike would only run 100-104. Enviromental factors are huge for a 250 cc machine and vary from day to day. Try to test and make changes all in one day. That will help eliminate or at least minimize the enviro-effect.
As far as my gear choice goes I picked was the best for the 1/4 mile for me (weight) and the avg weather conditions at the dragstrip. It turns out that they work really good for top speed too. I used a 43, 42, 41 at the strip and avg my times to pick my gear.(avg to try to eliminate the lauch factor and 60 foot times a little) The difference between the 42 and 41 were slight but the 41 was faster. 43 to 42 was a big difference in 1/4 mile times.
You havent stated how much you weigh but if your 170 ish Id run a 42 rear. 200 Id try a 43. From my experience any more gear than a 41 is a waste of time. The motor doesnt make enough tourqe. Physics may tell you a diffent story for your gear choice but are you taking into account everything??? There are way to many factors in top speed than can be put in a math formula.
Test, tune, test, tune, test, tune, avg. test, tune, avg and repeat until you find the "magic" your looking for.

[almost40]

Originally Posted by JMcDonald

That 5th gear would be a hair taller than my 4th gear (again, by about 1.5%). But, if anything, if I can't redline my bike in my 4th gear (about 101-102mph), going to a slightly taller gear (about 103-104mph) wouldn't make it any easier. Gearing isn't my problem.

I beg to differ about gearing and Ill tell you why. Acceleration and top speed for the most part, go had in hand. When you shift from 3rd to 4th what is the rpm drop?? does the bike drop out of the power band below 10000 rpm?? The whole point of a 6 speed transmission is to keep the bikes tiny 250cc motor singing in between 11000 and 12500 all the way to the point where there isnt enough tourqe to turn the gear anymore because of aero and weight factors. I think I know what your trying to accomplish, but to get what you want you need to have the 4th 5th and 6th gear cogs in the transmission changed. Not the sprockets (Kinda like a GM 6 speed manual where the motor will never turn 6th for top speed but makes enough tourqe to turn the gearset to return good fuel economy, less vibration and engine noise)
Better yet, try this.......... Find a streach of road that has signs or tar strips or take a paint can and mark off a distance (roughly a 1/4 mile is good) Start in 1st while rolling 10 mph and run it thru the gears WOT and check your speed on the speedo at the mark you made or picked. Run the bike as it is today. Go home and swap the gears back to stock and try the same test. Next swap only the rear to a 41 and compare the 3 tests. Tell us what you get. That way we have some numbers to play with not just a butt dyno. Using all 6 gears to get to your top speed greatly increases the bikes ability to use what little tourqe there is to maximize your speed.

[JMcDonald]

Thanks for the post!

Originally Posted by almost40

I ground down the weld splatter inside the exhaust at the connections near the flange that bolts to the motor. I port matched and shaved the gaskets in the carb and exhaust. I took apart and carefully polished the inside of the carb (and ported a weeee bit) along with the top part of the header. I slightly modded the stock airbox by pulling the snorkel and slightly increasing the size of the hole that held the snorkel. I also added a K&N. I preped my bike to be track ridden. Shaved a few pounds and increased areo by pulling the mirrors and turn signals. I pulled the whole rear fender and tail light assembly and made a coustom bent aluminum cover plate to cover the gap. Removed the whole headlight assembly and bought a used plastic cover to fill in the space. I also junked the chain gaurd and rear pegs.

I'm sure all of that helped, but I'm also sure you'd agree there is no way you would have gained nothing had you simply installed the exhaust, removed the snorkel, and tuned the carbs, right?

Originally Posted by almost40

I can tuck behind the windshield better than most (due to my stature) and my clip-ons have been shaved to bring my hand in closer to minimize the wind drag. I only ride in full gear therefore I dont have a pair of jeans of t-shirt flapping in the wind as I am trying to top end my machine. As stated before Aero and weight are the 2 major factors to top speed. Not the only factors but 2 of the major ones. Take a look at a pic of Racer X's bike. All the extra plastic in the rear is for aero. I would bet that if given the chance to run his bike at his top speed event I could get another mph or 2 out of it due to my smaller size and weight difference.

That is all correct, for sure. But, take this example. Say someone gets on a stock bike and does a top speed run on the highway, sitting perfectly upright, and makes it to 90mph. Then he goes to AreaP and has them install their exhaust and tune the bike, and dyno it to make sure there a few more HP as they would expect to see. Now, if he went out and did the same run again with the same body position, it would make absolutely no sense that he would not pick up any MPH. My point is not that there aren't other factors affective aero and such, but that it makes no sense that my bike has no picked up any more power at all (either directly measurable through top speeds, or more subjectively through perceived acceleration), unless something is wrong.

I will try to get my bike on a dyno sometime soon if something obvious doesn't present itself. However, as far as tune goes, nobody else has reported that a seemingly well-running engine would make no more power than stock. Like, in experimenting with jets, Kkim reported that the 112s, while later discovered to be rich, it still ran significantly better than stock. The 110s turned out to be better, but it wasn't like going to 110s from 112s is what gave him all of the ~5hp he might have gained from his mods.

Originally Posted by almost40

You havent stated how much you weigh but if your 170 ish Id run a 42 rear. 200 Id try a 43. From my experience any more gear than a 41 is a waste of time. The motor doesnt make enough tourqe. Physics may tell you a diffent story for your gear choice but are you taking into account everything??? There are way to many factors in top speed than cant be put in a math formula.

I weigh about 155 or so, fully geared. I have little interest in drag racing this bike, and didn't select my sprockets to excel in that.

And while you are correct that it is difficult to predict outcomes with pure math, even the simplest formulae would successfully conclude some difference when changing power with all other factors either staying roughly equal or being averaged out over several tests. I mean, you could ask any Salt Flat racer if adding power to their machines would increase top speed potential and they would say yes.

[JMcDonald]

Originally Posted by almost40

I beg to differ about gearing and Ill tell you why. Acceleration and top speed for the most part, go had in hand. When you shift from 3rd to 4th what is the rpm drop?? does the bike drop out of the power band below 10000 rpm?? The whole point of a 6 speed transmission is to keep the bikes tiny 250cc motor singing in between 11000 and 12500 all the way to the point where there isnt enough tourqe to turn the gear anymore because of aero and weight factors. I think I know what your trying to accomplish, but to get what you want you need to have the 4th 5th and 6th gear cogs in the transmission changed. Not the sprockets (Kinda like a GM 6 speed manual where the motor will never turn 6th for top speed but makes enough tourqe to turn the gearset to return good fuel economy, less vibration and engine noise)
Better yet, try this.......... Find a streach of road that has signs or tar strips or take a paint can and mark off a distance (roughly a 1/4 mile is good) Start in 1st while rolling 10 mph and run it thru the gears WOT and check your speed on the speedo at the mark you made or picked. Run the bike as it is today. Go home and swap the gears back to stock and try the same test. Next swap only the rear to a 41 and compare the 3 tests. Tell us what you get. That way we have some numbers to play with not just a butt dyno. Using all 6 gears to get to your top speed greatly increases the bikes ability to use what little tourqe there is to maximize your speed.

I haven't claimed my combo would be better for acceleration, and have on multiple occasions happily admitted it is surely worse. In fact, that conclusion is based on your previous reports on drag runs with 41-45t gears. The RPM drop is the same despite the sprocket ratios. A shift at redline from 1st to second, regardless of the sprocket ratios, will always result in an RPM drop from 13k to 9k. A shift at redline from 3rd to 4th will always land at about 10,700rpm. These drops are determined by the transmission ratios, as the differences between gears stays the same regardless of the final drive ratio.

In any case, none of this refutes my point that if a bike doesn't have the power to redline a gear that goes to 101mph, making the same gear longer couldn't possibly make it any easier for the engine to pull it.

And again, I am not interested in all-out acceleration through the gears. The only time I ever go WOT through more than 1 gear in a strait line is if I am getting on the highway, and I am still perfectly happy with how it accelerates. My disappointment lies with the fact that it still both accelerates at the same rate and reaches the same speeds as it did before, despite all the changes which, for everyone else it seems, give marked increases in power.

Question:
Can ignition timing be physically altered in any way on this bike? Like, is there an adjustable base timing or something? If so, I would want to make sure the PO or some maintenance guy didn't set it incorrectly.

[Flashmonkey]

Originally Posted by JMcDonald

My point is not that there aren't other factors affective aero and such, but that it makes no sense that my bike has no picked up any more power at all (either directly measurable through top speeds, or more subjectively through perceived acceleration), unless something is wrong.

I'm going to avoid going into the fact that expecting a 25-30% increase in power over stock from exhaust/intake mods is overly optimistic at best. I'll also overlook the fact that you can't seem to accept the idea that top speed and engine peak power output have, at best, an indirect relationship, and that exhaust/intake mods don't actually create power, but increase the efficiency of the engine at a different point(s) on the powerband.

What I will get into, however, is your methodology. The bottom line is that you're still not measuring anything consistently...and relying almost entirely on top speed performance to measure the success of your project. Whether you take the dyno tuning approach or go with almost40's suggestion of timing yourself on a marked road, you need quantitative data in order to draw conclusions. Otherwise we'll all just be waxing philosophical.