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Discussion Starter #1
here is a primer i found about exhausts.

Seven Guidelines in Exhaust Purchase

For the gear heads and mechically inclined, do you agree with what it says?

1)slip-on= low end power
full system = mid to high end power.

2) since our groms are fuel injected, i need something called a power commander to reprogram the airflow? is this like a chip, oris it a computer that gets connected to the grom, etc ???does it need to be done more than once?

3) replace air filter to so that there is more airflow? on my zuma, i would no to replace something called an air box? what is involved with this step. i have always bought drop in KN filters for my cars, but i once had a wrangler. I did add the big KN filter and a new exhaust. so far i havent noticed much about air filters? help

4) what is everyone getting? slip on, full, or stock? i wanted to try the stock so that i would be able to feel the performance boost, but my dealer said he would install it for free and it will be rolled into my payments.

thanks!!!

33 days and counting ( if i get mine on first shipment)...
 

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Sounds complicated. I will just wait and see what others are running and how they like or don't like them. I may stay stock as I really want to keep it quiet.
 

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I want power and clean sound. All the companys have a distinctive tone, i like yosh, termignoni, akrapovic they sound the best not a loud annoying sound like two brothers or the generic megaphone exhuast IMO. Im not sure on Power Commander but time will tell once i put on exhaust.
 

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Here is my opinion, most riders go for the sound and to piss off the neighborhood, I know that from pass experience with my Harleys and my YSR-50.

A really good pipe helps in the weight savings and with the right combo of airbox/filter your engine will be happy.

More junk added such as bigger jugs/cyclinder equals less gas mileage.

Now if you want just the sound I would remove the end caps on the stock pipes and get a long ass drill bit and drill a couple of holes in the can. We have done that when I owned a 1998 TL-1000R and with that mod plus a K&N filter you are set for sound and a little horse power not much but some 1-2 horse power gain. Make sure you vacuum out the junk that you made with all the small metal parts falling into the can.

Any engine needs good compression, good timing spark, good fuel/air mixture flow and good exhaust flow. To increase speed/gas miles etc than work with the gearing, front back sprockets and tire size.

Remember weight is your enemy if you want to go fast so is aerodynamics.

When I had my 1988 Honda VLX 600 I got better performance using high octane gas vers the lower 85-87 octane gas.

Larger cyclinders equals more horse power, a 125cc will not have as much hp such as a 180-200cc engine given all the same variables are the same for EFI and such. Your EFI size might have to change for the bigger bore and so would the fuel management mapping.

If you want to go fast just get a BMW 1000rr, ZX-10, ZX-1400, GSXR 1000, Hayabusa, or any Honda or other brand sports bike.

I learned long ago when I was into Harleys that no matter how much junk you put on your motorcycle it will affect gas mileage and other performance area such as stopping.

The Grom is like a cute puppy it will attract the chicks and other people who never seen one, just go out ride and enjoy the Grom and maybe do some wheel and panel modification, but please no PINK Grom unless you are a Chick or have the fastest Grom on earth. Nothing like being whooped by a PINK vehicle
 

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here is a primer i found about exhausts.

Seven Guidelines in Exhaust Purchase

For the gear heads and mechically inclined, do you agree with what it says?

1)slip-on= low end power
full system = mid to high end power.

2) since our groms are fuel injected, i need something called a power commander to reprogram the airflow? is this like a chip, oris it a computer that gets connected to the grom, etc ???does it need to be done more than once?

3) replace air filter to so that there is more airflow? on my zuma, i would no to replace something called an air box? what is involved with this step. i have always bought drop in KN filters for my cars, but i once had a wrangler. I did add the big KN filter and a new exhaust. so far i havent noticed much about air filters? help

4) what is everyone getting? slip on, full, or stock? i wanted to try the stock so that i would be able to feel the performance boost, but my dealer said he would install it for free and it will be rolled into my payments.

thanks!!!

33 days and counting ( if i get mine on first shipment)...
In general, allowing any engine to breath better will increase performance This involves intake and exhaust. The grom has a catalytic converter in the pipe so if you eliminate that with a full exhaust system that will give you better performance mainly, but not only, in the top end. So if exhaust is upgraded to high flow, then so must your intake. If you don't increase intake air flow, an expansive new exhaust will not show much or any improvement. If you open up one end, you have to open up the other too.

The air box is simply the thing the air filter is housed in. On a carburated engine, most people just replace the stock air box with a "cone" or K&N type filter straight on the carb intake. The problem with changing the Grom EFI (electronic Fuel Injection) air box is that it has an Air Temperature Sensor mounted inside the box that is wired to the EFI computer and if you change or modify the Grom airbox without keeping that sensor in the intake airstream, the engine will not work the way it should.

The power commander "chip" is simply a small computer that works with the stock EFI computer and can be tuned based on the type of intake/exhaust/fuel delivery but is usually model specific - That is, I doubt if they will make one for a Grom. If you are serious about performance, you can take the bike to a Dyno machine that runs the bike on a treadmill while it is plugged in to a computer and a technician can dial the stock computer to the optimum performance.

Does this help with any of your questions?
 

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Discussion Starter #8
wow! thanks for all of the explanations helps a lot!

if i intend for this to be mainly for a means of commuting, i need to reconsider how far i want to push it.

how do you feel about slip-ons? what i have read, a slip-on doesnt alter the factory catalytic covnertor. i will need to worry about replacing the air box for them?
 

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I plan on getting a slip-on, Leo Vince, now about the CAT, I watched a video that shows the exhaust gas flow and temp. There was no hot spot on front of the CAT, which tells me it does no slow the flow of exhaust gases. The CAT has a much larger dia then the head pipe. And a CAT has a bunch of tiny holes in it and just by looking at the size dia. of the CAT and the Head pipe, I'm willing to bet the total surface area of the CATs holes is equal too or larger then the dia of the head pipe, hence why there is no hot spot in front of the CAT.
 

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Just a slip-on requires no other changes, so if you are unhappy with the putt-putt sound, you can easily change that. As someone said though, all of those are loud even with baffles, and it might be a case of talking the talk, but not walking the walk. After all the Grom has a small engine. I have already said I do few upgrades to my bikes, cause if I want more acceleration and speed, I just buy a faster, more powerful bike....turns out it is generally cheaper to do that. You could easily replace forks, full-exhaust, air filters, do a big bore kit, install a Power Commander, put some better tires on the Grom and verify your enhancements with a dyno test....or you could buy a 250 cc. stock bike and out perform the Grom and save money in the process. I will leave the Grom just the way it is. You can run into warranty issues as well with modifications.
 

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It amazes me how many people just dont understand Honda Minis. They are talking about the Grom as though it is a full size bike. The interwebs are full of links but one good place to start looking at examples of why the Grom will not be treated as an underpowered motorcycle, but as the cult classic mini bike that it is sure to become:

Look at post #38 here http://www.hondagrom.net/forums/27-grom-builds/334-swifty-s-build-thread.html
 

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It amazes me how many people just dont understand Honda Minis. They are talking about the Grom as though it is a full size bike. The interwebs are full of links but one good place to start looking at examples of why the Grom will not be treated as an underpowered motorcycle, but as the cult classic mini bike that it is sure to become:

Look at post #38 here http://www.hondagrom.net/forums/27-grom-builds/334-swifty-s-build-thread.html
I think people take the grom very seriously. Please refer to post #39 in Swifty's build thread.
 

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Can anyone please post detailed measurements of the head pipe on the Grom/msx? I have a pipe that is for a monkey and want to know how much chopping and welding I'll need to do.

Need stock head pipe diameter. Need length of pipe from head to upward bend behind motor. Need outter and inner dia of pipe at head.

Thanks.
 

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Can anyone please post detailed measurements of the head pipe on the Grom/msx? I have a pipe that is for a monkey and want to know how much chopping and welding I'll need to do.

Need stock head pipe diameter. Need length of pipe from head to upward bend behind motor. Need outter and inner dia of pipe at head.

Thanks.
Here you go

Pipe ID at manifold 20mm
ID Where the can attaches 23mm

Pipe OD at manifold 32mm ImageUploadedByHondaGrom.net1376329176.826592.jpg
OD where can attaches 26mm

ImageUploadedByHondaGrom.net1376329333.174967.jpg


ImageUploadedByHondaGrom.net1376329434.398423.jpg hard to see, but its about 27cm

Total overall length is about 78cm.

I know its not the best, but i hope this helps.
 

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Just a slip-on requires no other changes....You can run into warranty issues as well with modifications.
Not always true on both accounts. For the slip-on, depending in how the engine is de-tuned from optimal for emissions (thank you Cali), a slip-on may require a ECU change like my Aprilia Tuono. Aprilia actually recommends getting the Race ECU with either a slip-on or full system to make the bike run right. It depends on the bike and how it is tuned. With the Grom's massive torque and horsepower, probably won't need to change.
As for the warranty, a manufacturer is legally obligated to prove, not just say, that an aftermarket addition caused the warranty claim before denying to cover the warranty. Intakes and exhausts are two of the most popular aftermarket additions people make to cars and bikes, and most won't void a warranty if you install it correctly.
 

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Thanks, that helps a lot. I think the pipe I have will be close. The flange to the head will work. It just about the length. It's close. It could work. Can't wait to post the picture.
 
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