I would like to keep my stock exhaust to keep the sound level down but would like an increase in power. Is it possible to get noticable power by just modifing the airbox or going with an aftermarket box and rejetting? Would it make sence to port and polish the head and possibly get a larger head pipe with the stock silencer? It's not that I wouldn't like to get a full system or even a tip but I really enjoy not having the cops called on me and not having to put on the old pipe and rejet if I wanted to go on state land with a dB requirement.
BTW I already have a K&N and outwear. What mods should I make to my airbox? Thanks.

 

Depends where you ride, but I would take the lid right off. If your K&N requires the lid in order to stay in place (haven't seen one), then you may think about going to a ProDesign flange, and filter. With the lid off, you can move the jetting up. You should get a noticeable increase.

I haven't tried the setup with the stock exhaust, perhaps someone on the board has.

RM

 

The K&N does require the lid but I was thinking of just screwing the filter onto the box.
I guess I could get a disk exhaust system but I didn't see spending hundreds of dollars for a minimal gain with the right number of disks installed to keep the noise down.

 

You may see a little gain with Dynojets & airbox mods but the stock exaust is very restrictive so the gains will not be huge but should be noticeable. The disc exaust would be a good idea, the power gain in quiet mode would be noticable & you could add discs when you were somewhere without sound restrictions.
With the stock number of discs in my Sparks X6 It is much quieter than with the mods I've done to it (small washers between the discs) & has much more power than stock but it is much louder than the stock pipe without the baffle. With your restrictions it'll be difficult to get much more than an extra 4HP but at least it's something.
The March issue of Dirt Wheels shows Jetting & airbox mods with a stock pipe & gained 3 HP but only from 5000 RPM up. It's just going to be a trade off because you can't put any more air in than you can get out.

Oh yea In wouldn't screw the K&N to the air box It would be too easy to mess up & get a leak that would let dirt past the filter, go with a Pro Flo adaptor.

 

This is really pi$$in me off! Why can't they make a pipe that is quite and has more flow. The amount of flow you have and loudness of your exhaust does not have to be related. If that was the case all the super sport bikes must be extremly choked because they are not as loud as some of these aftermarket pipes I've heard on some raptors! Screw it! I'll leaving it stock until they make one. Maybe I can pull a stock pipe from a hayabusa and retro-fit it.

 

Keep one thing in mind. Yamaha doesn't want a bunch of lawsuits, but they want to win the sportquad battle. My understanding is that they had this thing ripping in prototype, but they had to tone it down for legal reasons. This benefits us in that it has so much potential. It's kind of funny, you don't have to alter the motor at all and you can get another 10HP from this machine with airbox, filter and exhaust mods. Almost 20% increase without having to go into the motor? Take a look at what you have to do to a 400EX to get another 10HP.

So they put a restricive airbox and exhaust on the machine. Big deal, most guys replace that stuff anyway.

I think the suggestions in this thread are sound. Try the pro flow flange and filter, jet it properly, and leave the lid off. I think you will find you get a noticable gain. Then look into getting a quiet slip on. Rejet, and report back on your findings.

If you don't care about noise, then there are plenty of threads on this board that will give you direction.

Good luck,

RM

 

Get the pro design with K&N filter. This way you still have the K&N (max air flow). Remove the lid and get a dyno jet kit or just buy new mikuni small round jets and go from the 140/145 stock to 150/155 to start. If you don't buy the dyno jet kit then I'd buy a 150/155/160/165/170 mikuni small round jets ($2-$3 a jet) to be able to experiment and find the best jetting for your elevation and new increased air flow into the motor with the K&N and no lid. Also use the outerwear on the filter, it comes in the kit. You should see a decent improvment and keep it quiet.

 

Agreed. Great advice.

RM

 

o.k. since we're on the subject, i dropped down 2 spaces on my clips in the carbs. now it acts like it's running rich. what the heck is going on. first off the 180/190 seemed to be running extremely better with the stock filter back on it than the k+n so i dropped them to get more fuel now there's a little puff of black smoke when i hit it. (sign of too rich right?)and besides that it just feels funny. does dropping increase it that much? this sux i don't know if i'll have time to get it back to the shop before the races. that's right, i get someone else to do it for me. so if anyone has any detail instructions on how to do this i would be very thankful.

 

Run your lid across a table saw and cut the front two inches off. Use this piece to lock your stock filter in place. You can still go up a couple of jet sizes and get a performance gain without switching the the adapter plate and filter.

/NotuRaptor