Modifications & Performance

 

I want to upgrade my exhaust.

What models are available?

Muzzy

How much difference does the Muzzy exhaust system make?

Larry - Wed Oct 27 22:48:33 1999

I have just finished installing my second Muzzy system. The entire system weighs just 5 1/2 lbs on my bathroom scale. The stock mufflers alone weighed 13 1/2 lbs. I didn't weigh the headpipes and centerstand but it's a few pounds more off the bike as well. The stainless steel head pipe looks great and fits perfectly. I can give installation tips if you need them. Less weight + more power = faster, better-handling bike.

The Muzzy is loud but it has a deep tone; I don't think it is obnoxious. A good helmet keeps most of the noise out. I didn't want the noise either but after considering all the available exhaust options, Muzzy is the one. I will probably be getting a third one for my wife's bike when I can afford it. Oil filter and drain plug access is fine.

 

Do I have to remove the centerstand to install a Muzzy exhaust?

Jeb - Fri Nov 16 19:28:49 2001

I too wanted to keep my centerstand when I put on my Muzzy system. Centerstands are very useful, and I do miss mine indeed now. There are a few problems with this, however. First, the spring that holds the stand in place when retracted rubs the Muzzy's larger head pipe.

Second, there is no "stop" for the stand anymore when retracted (since the left canister is gone); there is nothing to keep the spring from pulling the centerstand up into the swing arm and drivechain. I heard once of someone fabricating a bracket to hold it in place, but I imagine that's not all they had to do.

Lastly, the Muzzy is designed to increase performance a bit, sound good, and look good. One way it looks good is by really cleaning up the back of the bike; with the stock exhaust cans gone the swing arm is fully visible. If you leave the centerstand on, it will be quite an eyesore, in my opinion.

Sorry to discourage, but it's probably more trouble than it's worth to keep it. You can buy a nice swingarm stand for about $70 though, which will let you do most of the maintenance the centerstand allowed. The only time I still use the centerstand is when I'm doing rear suspension work; I loosely attach the stand temporarily with two 17mm bolts, and put it back in the parts bin when I'm done.

 

How do I repack the Muzzy?

Mark - Tue Jun 12 07:31:26 2001

I repacked my Muzzy last night using the manufacturer's kit. When I opened up the can, what little fibreglass was left in it had settled to the bottom half of the can so there was no sound absorbing material at all in the top half. It's no wonder it was so loud. I estimate that there was only about 1/3 as much fibreglass material in there as there was in the replacement kit. With the new packing the bike is quite a bit quieter than it was. For my taste, it's still louder than I'd like, but it's tolerable.

The repair kit consists of the perforated inner tube wrapped in fibreglass. I ordered this directly from Muzzy last fall. If you could get the right fibreglass material from a muffler shop or auto parts store, there is no reason you couldn't just replace this bit since the metal pieces were all in good shape. To install this, just drill out the rivets and remove the end cap (sounds simple, but there was the small matter of a broken drill bit and what seemed like a lot of blood at the time...). Only one end cap needs to come off and the engine side cap is easier to get off since the mounting hardware provides something to pull on. I removed both caps because I want to experiment with some additional baffling at the outlet end.

You can go to www.muzzys.com and order the kit. It's about US$25. You'll need a pop rivet tool (about US$10) and rivets (1/8" diameter, ~3/8" length) to put it all back together. The end caps are stainless steel and are reused.

I poked around the web and found packing for glass pack mufflers several places for about US$6. If I were to do it over, I'd just get the packing. I suspect that auto stores or motorcycle shops probably stock this kind of stuff.

I've no idea where the old packing goes. I guess it just breaks into small pieces and blows out the tail pipe. I bought the bike with the Muzzy so I don't know how long it has been on there. The bike had about 10,000 miles when I got it and it's at a little over 16,500 now, so it looks like this is something that needs to be done pretty regularly.

Yoshimura

Daryl - Fri Sep 22 09:11:54 2000

I have a Yosh pipe; it's a complete 2-into-1 system. It sounds about the same as a Muzzy. With The Muzzy you have to eliminate the centerstand but you can get to the oil filter; on the Yosh you can keep the centerstand but you have to remove the pipe to change to oil filter.

Part# GP270SSC, for the 88-01 model year; I paid US$319 dollars.

Cobra

Chris Hughes - Sat Jan 20 01:12:34 2001

There are 2 kinds or slip-ons available: Cobra F1's and Cobra F1R's.

I have owned both and I recommend the F1's since a) they look nicer, and b) they sound better.

The F1R's are way too loud and obnoxious (remember this is coming from an 18 year-old male here); I got a noise violation ticket for them. The F1's have a lot nicer tone, and of course they are still louder than stock :) .

I believe Dennis Kirk sells the F1's for around US$160 and the F1R's for around US$210.

 

Do I have to rejet when I put in a new exhaust system?

Duke - Mon Jul 3 13:27:42 2000

Just after I got my bike (which had a Muzzy installed, but no jet kit), I ran it at 10K+ for about 45 minutes one time, which did it in... (before I realized I was hurting it) I wound up with one of the exhaust valves about 15% melted away, and the bike would no longer run under about 4,000RPM (which made starting a little difficult).

Before that happened, I had to run it with the choke partially on all the time, which 'seemed' to make it run OK. Once into the upper part of the RPM range though, the choke makes no difference to the mixture as everything is wide open and mixture is being determined by the main jets, which in stock form are way too lean to be running with a non-stock pipe.

If you have to run without jetting, go easy on the heat until you can get the right jets installed. The difference in performance (beyond possible damage) is well worth the cost and time involved in jetting.

 

What if I'm just installing slipon canisters; do I still need to rejet?

Duke - Thu Jul 20 20:44:55 2000

You do not have to rejet with slipons, as they don't significantly change the flow characteristics of your exhaust system.

Rejetting is however always a good idea, especially if you have the time to experiment and get your jetting just right. As we've seen here recently, the optimal jets can change significantly depending on the altitude at which you live. There's no magic formula involved with the stock jetting. They’ve merely jetted it for an 'average'. If you are particular, and want the most from your little engine, splurge for a jet kit and the adjustability it offers.

 

Can I get a better exhaust sound without replacing the stock pipes?

Brent - Thu Apr 26 04:05:08 2001

You can take the canisters off and bring them to a machinist to cut off the endcaps, cut out the baffles and place the endcaps back on. Doing a full debaffling yourself may be difficult.

Other options are to drill out the rivets in the endcaps (little bit louder tone), or to use a long rod, place it down the muffler pipe, and hit it with a big hammer to puncture the inner baffles to allow a more straight-through flow of the exhaust (bit louder than drilling rivets), or you can do both.

 

I want to upgrade my suspension.

Front end

How do I stiffen up the front suspension?

Paul 311 - Fri Jun 2 17:23:06 2000

You can do a few things:

On the rear shock you are limited to getting it replaced or rebuilt. Having it re-worked will make the valving better, but you will also need a stiffer spring. Aftershocks has a lot of options there too. You can call them from 10am to 6pm California time at 650-494-8849.

 

Where can I get some preload spacers?

Daryl - Sun May 14 17:52:24 2000

I use PVC piping from the hardware store. I don't remember the diameter of the tubing, but if you take the fork spring washer out of the top of the fork you can take it to the store and see what size diameter you need.

You need to see how much sag in the front end you have before you take the top off. Measure the front end topped out, and with help measure how much it sags with you and riding gear on the bike.

You want about 1 1/4" of sag, no more than 1 1/2"; if it's 2 inches you need 1/2" PVC spacer or more. The PVC tubing can be cut to size.

A guess with stock springs is that you'll need a 1/2" to 3/4" spacer; with Progressive Springs you need about 1/4" to 1/2". The Progressive instructions don't call for it, but there's too much sag without adding some preload; it further improves the front end dive and control. You put the spacer on top of the fork springs.

 

Will a fork brace improve the front suspension?

Paul 311 - Wed Oct 3 13:15:01 2001

I use a fork brace, but I really can't tell a difference between having it on or off. The main thing a fork brace does for me is to keep the forks from twisting when I crash (4 times this season). Last crash, I didn't even have to straighten the triple clamps.

The fork brace does do something. There was enough flex in my front end that the edge of the tire (17" radials) was cutting a little groove in the fender. When I put the fork brace on, I added a little piece of white duct tape to that spot on the fender, and the tape remained untouched. So the fork brace does something, but I sure can't feel it.

I've been using it since about a year ago when I set a 250 Production track record at Buttonwillow (which, for the moment, still stands). After that, I really couldn't bring myself to change anything that didn't have to change.

 

Rear end / How do I change the rear shock?

DrBoom - Thu May 23 23:27:51 2002

What you need:

1. Put bike on center stand.

2. Remove seat.

3. Remove left side cover with Phillips screwdriver.

4. Move coolant reservoir out of the way by removing (2) 10mm bolts. Turn reservoir

180 degrees to your left and loosely secure it to whatever's handy with a zip tie. Put the 10mm bolts back into the holes they came from to avoid kicking them to oblivion when you get up to grab your beer.

5. Working from the left side of the bike, break the lower shock shackle bolt loose with the ratchet + extension + 17mm socket. Once it's loosened up, use the 19mm wrench to keep the nut on the other side from turning -- you won't be able to hold it with your fingers. Once the nut is off, wedge the prybar under the back tire and gently wiggle it up and down while pulling on the bolt head; it should come out easily without trashing the threads. Let the back tire rest on the ground.

6. Still working from the left side, locate the 17mm bolt at the top of the shock and remove it. There is no loose nut on the other side to worry about, so just take the bolt out and watch the shock fall to the ground.

7. If you are installing a new shock with an external reservoir, this is a good time to find a place for it. If you have a Works shock and followed Jeb's advice when you ordered it ("reservoir hose at 8.5", and the fitting at 8:30 o'clock"), it attaches to the rear frame tube and tucks neatly behind the coolant tank.

8. Slide the new shock into the top bracket and install the 17mm bolt. (torque spec?)

9. Line up the shock's bottom shackle with its matching hole by using your prybar to lift the rear tire + some judicious tapping. The bolt should slide right in. This is not a job for a hammer, folks. Put the nut on and tighten it up. (Righty tighty, lefty loosey, eh?)

10. If you have an external reservoir, secure it. Use a zip tie to secure the reservoir hose to the frame. You're done with your shock.

11. Remount coolant tank. This is a good time to fill it, if needed.

12. Replace side cover and seat.

Shouldn't take more than 30 minutes.

 

How do I adjust the rear preload?

Wolcott - Sat Mar 18 13:58:52 2000

The stock shock is not adjustable for preload. Assuming you have an EX500, SV650 or some other better shock, put the shock on the bike, then measure "sag".

To do this, with the bike up on the centerstand - first measure distance from rear axle to some fixed location on rear, such as bottom of cowl at joint in plastic. Then get it off the stand and sit on it in full riding gear and make the same measurement again. Subtract the second from the first to get "sag." Adjust the shock to get 1 1/4 to 1 3/4 inches sag (1/4 to 1/3 of full shock travel).

You see it all depends on your weight. Also, helps to have someone else measure for you so you can get your feet up to get true riding position. Also, jiggle bike with you on it to get accurate reading after suspension is "unstuck."

You can adjust the preload by loosening the preload locknut or ring, then turn the adjusting nut/ring with a suitable spanner, or tapping it with a screwdriver using a mallet to rotate the piece.

 

What kind of shocks are available for the 250R?

Paul 311 - Mon Jan 3 12:44:37 2000

Fox makes some of the best racing shocks. They are adjustable for rebound compression, preload and sometimes even ride height. Fox won't make them anymore, so there are a limited number of them on the used market. They seem to go for $300-$500 on the used market.

I'm working with "Aftershocks" of Palo Alto to develop an Ohlins shock which will have all of the features of the Fox, and have custom valving by Aftershocks. I should get to try one in the next month or so. I'll report back on the results.

The only high-end shock you can buy for the Ninja right now is the Penske shock. It starts at $700 to $1,200.

I would guess that every EX500 racer in the world has a stock shock gathering dust in his garage. The main difference between an EX500 shock and a stock shock is probably the ride height of the rear end of the bike. When you jack up the back a little, you make the head angle steeper and it makes the bike steer more quickly and also puts more weight on the front end. Another way to get the same effect is to loosen the triple clamps, let the forks slide upwards until they stop against the bar risers, then re-tighten the triple clamps. (be sure to use a torque wrench for this, as the top clamp is aluminum)

For real rear end performance you can send your stock shock off to Aftershocks in Palo Alto CA, 650-494-8849 or buy a Works Performance shock. I use an Aftershocks-valved WP shock on my Race bike (the WP shock will also make the rear end taller). You can get a Works Performance shock for the Ninja for about $300 new. They aren't adjustable except for preload. I use one now on my race bike and it's a decent shock for the money. Aftershocks can re-valve these to make them work better too though.

Aftershocks may be able to re-valve your stock shocks. I have seen people racing on a re-valved stock shocks and they seemed to work ok too.

 

Why should I upgrade my suspension?

Wolcott - Fri Nov 19 20:10:55 1999

Suspension makes your cornering possible. With a lousy suspension you never feel comfortable enough to really lean it over and get on the gas. With good suspension you can lean way over, get on the gas, do mid-turn swerves to avoid obstacles, and stay stable through bumps. How much faster? - light years.

How? Spend money ($$$$$) on shocks and forks. The stock 250 Ninja is comfortable but sloppy, so it's easy to improve.

 

How does modifying the steering geometry help?

Paul 311 - Wed Feb 9 23:11:53 2000

On my race bike I have found a set up that works really well. Whenever I make a change which has a side effect, changes the ride height, I always try to make a change to counteract it and get things back where they were.

There are two things that change when you change the height of one end of the bike or the other:

a. fork angle

b. weight distribution

Making the fork angle steeper (closer to vertical) makes the bike steer more quickly. This can make the bike feel twitchy and unstable if you take it too far.

Getting more weight on the front end is a good thing. The Ninja 250 is pretty light on the front end and will tend to push the front end with the stock ride height. Raising the rear a little or dropping the front a little helps cure this.

Unfortunately ride height is a relative thing, so set up is difficult to translate from bike to bike, and will be affected by things such as:

a. sag (which can be adjusted by changing preload)

b. position of the forks in the triple clamps

c. tire profile

d. longer or shorter rear shock

Preload is what you change to set the sag. Checking sag is one way to determine if you are using the middle of the available travel on your shock/ forks. The middle range in the travel tends to give the most even damping from what I hear, and it will also help keep you from topping out or bottoming out if you have the sag set correctly.

 

What good does reducing unsprung weight do?

Wes - Thu Jan 11 14:22:01 2001

 

I want to improve my carburettor jetting. / Why would I want to change my jetting?

Duke - Thu Jan 13 06:10:55 2000

You will need to rejet if you make any changes to your exhaust or intake. If you add a new pipe and/or filters, your carbs will run lean so you'll need to richen things up. A carb kit will do this by giving you larger main jets and adjustable jet needles. The jet needles also have a slightly different taper than stock which will smooth out throttle response through the whole RPM range, and add quite a bit of power in the 3,000-6,000 RPM range.

If you don't rejet and run your bike lean, it will a) not run without the choke being partially on, and b) may burn (melt) your exhaust valves if you run it hard lean.

If you are going to spend the $400+ to add the pipe and intakes, go ahead and spend the other $90 for the jets and do it right.

 

How do I improve my jetting?

Duke - Tue Jan 11 15:39:41 2000

Carburettor jetting is the fine art of adjusting the jets inside your carburettors to provide optimal fuel flow into your engine. A couple different companies sell jet kits that include 2 adjustable jet needles and [4 sets of 2] different sized main jets to allow you to accomplish this goal.

If you modify your exhaust or intake you will need to also adjust your mixtures in your carbs due to the increased airflow, which will cause a lean mixture. Depending on what mods you make, you'll use 'Stage 1' or 'Stage 3' (Both are included in the kit; the 'Stage' business is just marketing hype). The carb kit may also improve your stock performance by smoothing the low and mid-range response.

With a Muzzy exhaust system, the Dynojet kit in my bike makes a very noticeable difference. Instructions for installation and adjustment are included in the jet kit, plus they have a 1-800 number for help. If you have a little mechanical aptitude, you can install it in a Saturday afternoon.

However, plan on taking the time to make a few adjustments to get it just right.

For $90, it's worth a try, and you'll have everything you need (carb-wise) to add a hi-flow pipe or intakes in the future.

 

How do I install a jet kit? (GPX250)

Jeb - Fri Mar 31 17:05:50 2000

The instructions that come with the package are concise and assume you have some technical ability; if you have a Kawi service manual, it will clarify a few things.

There is a bit of an art to this; you'll see that after putting the carbs back in after the first rejetsession.

You may have to pull the carbs out several more times before getting the results you really like.

There are four main steps to this process:

 

Where can I purchase a jet kit for my bike?

For the ZZR250 there is no Jet-kit available and the reason is this.

The carbs on the ZZR are already larger than that of the GPX (despite them both being a parallel twin 250), so when you get the jet-kit for the GPX you are essentially installing ZZR carb pins etc into GPX Carbs.

However I have left jetting information on this page because it's always good to know.

If anyone have any further information let me know: paws11@hotmail.com

 

Can I improve carb performance without buying a whole jet kit?

Paul 311 - Sun Jan 23 22:44:30 2000

You can get about 90% of the performance of installing a jet kit by installing new main jets. Main jets are available from better motorcycle shops. You just bring in your old ones and tell them what size you want, or even tell them you want one size larger (richer) or one size smaller (more lean). Believe it or not my CB-1 jet kit came with jets that were a size smaller than stock, and the bike makes more power. A lot of Japanese bikes come jetted a rich on top and will make more power if jetted more lean (the needles will then need to be raised a bit to richen them, as they are usually on the lean side to start with). My race Ninja when I bought it had been jetted with size 98 main jets (stock is 105), and it had lots of power. The reason I suggest buying main jets without the jet kit is that a set of main jets for a Ninja is about $8. A jet kit for a Ninja is about $70.

The nice thing about jet kits is they come with instructions and they are based on a lot of actual dyno research, so they get you in the ball park right away. That's what you're really paying for. I did some ass-dyno jetting on my Ninja last year. I later duplicated the dyno testing (same jets) on a real dyno. The old ass-dyno picked the same jets the real dyno picked.

One thing to watch out for if you buy jets on your own: DynoJet brand jets have their own sizing system that doesn't correspond to Keihin jet sizes.

 

What components are needed to rejet without a jet kit?

Leon - Mon Jun 23 19:54:45 2003

I wouldn't advise spending the money on a jet kit. If you change the main jet size, you can buy the jets from Kawasaki for about $5 each.

If you adjust the needle settings, you can do it with #4 flat washers (4mm washers for the metric world) for a dime per washer.

You can drill the slide holes with the biggest bit that will fit down from the top (I think that's how Dynojet decided what size bit to include in their kit).

And you can remove the plugs from the idle mixture screws with another small drill bit and a wood screw.

Just put two or three washers under the needles for pods and another one or two for an exhaust pipe and you're 90% of the way there. It's that last 10% that can be difficult.

 

How do I adjust the idle mixture?

Jeb - Thu Apr 18 23:43:33 2002

Pull the carbs, drill a small hole in each of the mixture screw caps (carefully). Screw a machine screw into each cap, and use pliers to pull the screw and cap out together. Once the screws are exposed, turn them in (gently; not too tight!), then back out 2 turns each.

Put the carbs back on the bike; go for a ride. Come home on with a warm engine, park and leave it idling. Put on a jersey glove or something to protect your hand from the heat. Use a small screwdriver to turn in each screw until the cylinder for the screw being adjusted starts to miss, then turn it back out 1/4 to 1/2 turn.

Same deal for a K&N'd bike, only the screws will be opened a little more. 1.5 to 2 turns out should be plenty for a stock machine; mine are set at 2 turns out now, and I have the full Muzzy/K&N package).

The factory setting is a little over 2 turns out, I think.

 

How does weather affect jetting?

Duke - Sun Jul 14 18:52:15 2002

Here's the skinny on weather:

So... dry cool air is more dense, moist warm air is less dense.

Your carburettors mix a certain amount of fuel with a certain volume of air. There is an ideal ratio of fuel to air called the stoichiometric ratio, which is about 14.7:1. At this ratio, theoretically, all of the fuel will be burned using all of the oxygen in the air. In reality (your bike/my bike), the fuel to air ratio varies from 14.7:1 quite a bit. More air = less gas (lean); more gas = less air (rich).

Your job when jetting your bike is to get as close to this ideal 14.7:1 ratio as possible, (which also produces the most power). The problem is denser air (Cold/Dry) produces a leaner condition and thinner air (hot/wet) produces a richer condition. The other problem is that the weather is constantly changing. So in the end, yes you can constantly chase the perfect mixture (thus the advantage of fuel injection which is constantly adjusting for weather) or you compromise and set up the jetting to work well at about 70 degrees... a happy medium.

A lean condition can hurt your engine over time, but you would certainly know it's lean (spitting, sputtering, etc.). I ran 92 mains in my carbs for a long time and had no problems until I pulled my airbox top (allowing more air to flow - thus creating a leaner condition) and I could immediately tell it was too lean. 105's (stock) are in it now and it runs very well. Why did I pull my airbox lid? Why do people use K&N pods? More air in = more O2 in = more gas in = more power.

 

I want to upgrade my intake.

Do K&N pods provide a significant improvement in horsepower?

Jeb - Sun May 14 13:41:32 2000

K&N filter pods (part #RC-1822) pull in more air than the stock airbox does. Combined with the proper jetting, this can help to increase peak horsepower by up to 10%. However, you also lose a bit of low-end drivability in the process, because the pressured air of the box is gone, and the added resonance it provides as well.

Still, I would recommend this upgrade if you do a lot of work on your bike (makes removing/replacing the carbs much easier), and can afford to spend the $$. With newer, more advanced bikes, taking out the airbox would not be a good idea, but with the relatively low-tech engine of the Kawi 250, you can tune it to achieve an improvement over the stock setup.

Also, note that the stock intake is more restrictive than the stock exhaust. This means, if you have to choose one or the other, the intake mod is more effective, not to mention less expensive (about $50, instead of $300 for a full-system exhaust). Taking out the old airbox will be a pain in the ass; putting in the pods will take 3 minutes. The K&N's do amplify intake noises (or, I should say, do not muffle them like the airbox does). You'll also get a little more underseat storage and a slight drop in weight as a bonus.

 

How do I get the airbox out to install these?

Jeb - Wed Oct 25 05:13:33 2000

If you're going to take the airbox out altogether, it should be for good. You need to remove the 10 or so screws that hold the two halves of the box together. Remove the battery, and the two bolts that hold the back of the box to the frame under the battery, then start to work on those screws. When you've got them all out, you should be able to break the two halves apart (if you have trouble doing this, then you missed a screw; trust me, they're hidden all over the perimeter of the box). Remove the plastics and filter element at this time from inside the box, then work the left half of the box out of the frame, then the right.

It is possible to do this carefully, and not damage the box. The problem is the box is bigger than the frame space it occupies, and is tricky to work out. This is a frustrating job, and can require a lot of grunt work. You can make the job a little easier by removing the two bolts at the inside front of the rear fender, and pulling the fender back a bit.

But with no airbox in the way, and the modular filter pods in their place, removing the carbs is as easy as loosening a few intake screws, and popping them out.

 

I've got the filters in, now what do I do with the battery?

Jeb - Thu Jul 20 21:10:19 2000

Drill two holes through the bottom of the rubber 'sheath' that the battery sits in, then use the two bolts that held the rear part of the airbox to the bike to bolt it down; it may not seem like a very sturdy method, but I've had mine like this for months with no trouble. Some thin washers can be used to improve stability. If you have a '94 or earlier model, then you don't have the sealed-type battery and rubber sheath, you have the larger, maintenance-type battery that sits directly in the box. In this case, you can cut the rear part of the airbox off with a dremel; works just as well, just not quite as clean a job. Or, you might be able to more easily build a small cage for it out of aluminum brackets or something.

 

What do I do with the crankcase vent hose?

Jeb - Sun Sep 9 22:18:20 2001

The crankcase breather tube is an s-shaped tube that sticks up from the crankcase below the carbs. It is normally routed to the airbox, so case gasses can be taken back in through the engine intake, and blowby oil reabsorbed to the sump when the mist accumulates and drips back down into the case.

With the airbox gone, this vent is unchecked, and the crankcase has no protection from the elements, except for the s-shaped hose. Also, if the hose is not otherwise dealt with, then the oil mist from the engine will cover the top of the case and the bottom of the carbs. The hose could be plugged, but then the case would be pressurized; not a good idea.

There are two practical filter options: buy a permanent, cleanable filter (looks like a small K&N pod), or get one with a replicable element. I chose to do the latter, since cleaning the crankcase filter needs to be done much more often than cleaning the carb intake filters.

I selected a compact filter with a good-sized surface area, part number B23124 (Purolator), or BF305 (Deutsch). This filter has a terminal connector of 1/2" O.D., just like the breather tube; I used a 1" length of 1/2" I.D. hose to couple the parts. The filter has a low profile and fits beneath the carbs. The part is $2.50 USD, and the element can be replaced as well for a little less; I replace mine with every oil change.

Alternatively, you can install a 14" or so hose, and point it at the drivechain; then your blowby will lube your chain!

 

How do I make use of the extra space under the seat?

Jeb - Sat Sep 29 15:52:18 2001

I've spent the last few weeks looking for a storage box of the right size that could be put under the seat between the battery and K&N's, to use the space made available from removing the airbox.

I finally found the right item at a K-Mart, after checking a few hardware stores (looking at mailboxes, plastic box planters, small parts bins, etc); it's an ordinary $2 file box for 4" x 6" index cards. The box is just the right size (well, it could be an inch deeper, but it works well enough). I simply removed the flip-top lid, drilled a hole in each top corner, and used some zip ties to suspend it from inside the frame of the bike, just below the bracket at the rear of the gas tank.

A 4" x 4"x 6" box isn't huge, but every bit helps. There's not a lot you can do with the space otherwise, since the drive chain and rear suspension are directly beneath that spot.

 

I want to change my gearing. / How do I change my gearing?

Gazoo - Sun Mar 5 19:26:22 2000

For about $50 you can get some new sprockets for the Ninja 250 that will lower the RPM's at highway speeds (better mileage). On a stock Ninja the front sprocket has 14-teeth and the rear sprocket has 45-teeth.

Replace the front with a 15-tooth sprocket:

JT Sprocket, Part# 24-8637 or PBI Sprocket, Part# 456-15 (Special order from a dealer) and/or

Replace the rear with a 42-tooth sprocket:

Sunstar, (Denniskirk.com Part# 80-017-42S)

 

Does installing a new front sprocket make a significant difference?

Jeb - Thu Mar 9 14:24:16 2000

Changing the countershaft gear from a 14- to 15-tooth sprocket is the most common gearing mod, and it does make quite a difference. At first I thought the bike seemed sluggish after changing mine; the torqueyness I was used to wasn't really there. As I rode around town for awhile, it seemed the bike just wasn't revving as quickly as it used to- this of course was to be expected since the countershaft was working harder. But I soon realized that the change in acceleration was marginal; though the bike was taking longer to rev through the gears, each gear was putting out 7% more travel per revolution.

So the twist on throttle has to be a little greater now to get a satisfying 0-60 run, but the high-speed cruising has been improved noticeably. Twice today I thought I was already in 6th, when I was still in 5th.

It wasn't too difficult a task: loosen the rear wheel, remove the countershaft housing, remove the 14-tooth sprocket, put the new sprocket in, torque the retainer bolts, replace housing, set correct tension to chain and torque rear wheel, and clean/wax the chain. The sprocket switch took about an hour overall; just followed the process as outlined in the service manual. Popping the old sprocket off was a snap; putting the new one on took a bit because the countershaft teeth are cut to very close tolerances. Cost= $15.

 

Is there any advantage to installing a smaller front sprocket?

Paul 311 - Tue Dec 11 20:49:30 2001

I tried a 13-tooth front on the track for a little while. It makes it harder to keep lube on the chain because the chain is turning a tighter corner. Also, the chain eats into the keeper, even if you file it waaaay back.

The only advantage is a) lower first gear b) puts ratios closer together. Aside from that, it's all the same because you end up in 3rd when you would normally be in 2nd... etc.

 

What drive ratios are attainable?

Paul 311 - Wed Dec 15 07:20:34 1999

I have a few sets of gearing for my race Ninja. Using 14/47 works well at the three tracks I race. This weekend I'm heading to Willow Springs raceway to do some off-season racing/testing. I'll probably use the 15 tooth front sprocket, since I hear you spend a lot of time WFO at Willow. Changing the front sprockets is easy and doesn't take a whole lot of chain adjustment. The rear sprocket, on the other hand may require links to be added or removed from your chain.

Here are some gear configurations and their respective final drive ratios:

15/42 = .35714 14/42 = .33333 13/42 = .30952

15/45 = .33333 14/45 = .31111 13/45 = .28889

15/46 = .32608 14/46 = .30435 13/46 = .28261

15/47 = .31915 14/47 = .29787**** 13/47 = .27660

 

I just want more power.

Leon - Thu Apr 27 13:31:01 2000

How much HP do you want?

1-5 : Exhaust pipe, intake and jet kit

3-8 : Porting, compression, cams

20+ : trade the Ninja 250 for a bigger bike.

The most economical of these is the trade. You can get a good used 600 or a superbike in fair condition for the price of a new 250.

However, if what you really want is to be able to go faster, then learn to ride better.