Since the weather has been so unpardonably warm these days, I decided to finally get out on the tarp in the empty parking space next to mine and get this expansion chamber / muffler installed and recalibrate the CVT to take advantage of it.
An expansion chamber is a neat little exhaust hack for 2-stroke engines that causes the engine to burn more fuel/air mixture on each stroke, giving you increased power (and decreased gas mileage, but what can I say, I'm a fashion of slavery). Read about how they work here, and look at an informative animation of one in action here.
The particulars should be the same for any late-model (2000 or newer) Jog, and the concepts and procedure should be the same for any Japanese scooter.
More after the jump... (i.e. click "Read more" below!)
1.1: The subject
Fig. 1.1.1: Stock muffler
This is my scooter pre-op. Note the ugly stock muffler. Really, this is just a silver plastic cover for a standard scooter muffler. Big, heavy, inefficient, and ugly. The plastic cover is just there to make it look cooler than it is, and make it cooler to the touch. It has not, however, protected my cover from melting to it at all.
1.2: The players
Now I will introduce you to the various players in our little instructodrama:
Fig. 1.2.1: Silencer
This is the silencer for the expansion chamber. It tries to reduce the whining roar of the 50cc engine so that one is less likely to be pulled over for violating noise restrictions. Zero actually makes a quieter expansion chamber product called the Zeek, but it appeared to me that reducing the noise also reduced the power, so I opted for the more yanki offering.
Zero makes an array of colors for the silencer, and I was torn between blue, which is what I really wanted, but that would mean I'd also need to replace the shock absorber with a blue one (no problem, since I'm planning on lowering the bike anyway), and paint the front brake caliper blue (which would be a hassle), red, which already got along with the rest of the bike, but which is a color I don't particularly like with white, and silver, which is the design equivalent of going "whatever." For these reasons, I went with red. I may look into having the bike repainted to dark gunmetal anyway. Why not throw good money after bad?
Fig. 1.2.2: Bag of parts
This is the bag of parts that came with the expansion chamber, containing silencer springs, installation bolts, a rubber-lined ring for securing the silencer to the chamber body, a small bolt and washer for the ring, and an installation manual. The tube of grease is left over from my pulley upgrade project from a couple months ago.
I will not be using the sticker or the large installation bolts.
Fig. 1.2.3: Slider
This is why I won't be using those installation screws. This package has its own.
This is a slider. It installs at the base of the chamber and the white plastic part sticks out to the side further than the chamber and silencer so that in the unfortunate event of a spill on that side, as the bike slides along, it chews up your ¥4,000 slider instead of your ¥30,000 chromed expansion chamber.
Fig 1.2.4: New muffler gaskets
I read when ordering the expansion chamber that it didn't include a new gasket and took that to mean I couldn't use the old one, so I picked new ones up. It appears I could have used the old one, but, then again, at ¥472 for two of them, I don't see the point of using an old one.
Fig. 1.2.5: New weight rollers
Zero recommends pairing a 3.5g set and 3.25g set for the 2006 Yamaha Jog ZR Evolution with the Corsa chamber, so that is what I did. The "setting manual" in the chamber package recommends a total roller weight of 19.5-22.5 for this bike with the Zero pulley (which I have), which puts me in the lower-middle of this range at 20.25g total.
I may bump this up to try to get a little more torque in the low-mid rpm range.
Fig. 1.2.6: New crankcase cover screws
These are not strictly necessary, of course, but they are handy to have when you have completely gorfed these custom screws in a previous upgrade, requiring you to use visegrips to get them on and off.
Let me say it again: All the screws on the drivetrain require a large Phillips-head screwdriver, even though the rest of the bike does not. Avoid embarrassing screw-ups (Mah-hah! A pun! Top drawer!); use the right tool.
Fig 1.2.7: The chamber
And here it is. I've deliberately saved this pic for the end. Just look at that thing shine. The chrome was worth the ¥5,000 extra, if you ask me. I just don't get the standard steel-with-welding-burn-marks look.
2: INSTALLING THE CHAMBER
2.1: Removing the stock muffler
First we will be removing the stock muffler.
Fig 2.1.1: The stock muffler stay
In this picture we can see the stock muffler stay and the mystery hose. We will need to remove the two bolds attaching the stay to the scooter, and unhook the mystery hose.
I have it on good authority (well, the yanki kid in the parking lot of the motorcycle shop I frequent whose identical scooter was loaded with likely stolen parts, including mismatched body panels) that the mystery tube is unnecessary, so we'll just be disconnecting it.
If you have trouble identifying the parts in this picture, there are notes on the Flickr page it links to.
Fig. 2.1.2: The stock muffler flange
Here we can see the stock muffler flange as it attaches to the engine's exhaust port and one of the 10mm/Phillips bolts (of 2) attaching it. Between the flange and the engine is a gasket we can't see yet. These screws are the first we must remove.
I am rather dismayed to see that the engine block is so rusty... Oh well, I guess that's what these are for!
Fig 2.1.3: Socket wrench with extender
I found that the best way to get the flange screws off was by using a socket wrench with an extender. If you don't have an extender, it is very difficult to use the wrench in that tight space, although you can probably do it. You will find it easiest to access both screws from the left side of the bike (i.e. the opposite side from the muffler). You can get one of them fairly easily from the right, but both are easiest from the left side.
Fig. 2.1.4: Muffler flange bolt
Here we can see a successfully-removed flange bolt. 10mm/Phillips. Keep these handy. We'll need them to install the new chamber.
Fig. 2.1.5: Muffler stay bolts
Next we turn our attention to these muffler stay bolts.
These are 12mm. Once again, I found that a socket wrench with an extender was the easiest way to remove these.
Fig. 2.1.6: Muffler stay bolts removed
Here we can see the muffler stay bolts removed. The top one is longer than the bottom and has threads all the way up to the head. This isn't really salient information for the rest of the installation, but it will be if you ever want to put the stock muffler back on.
Fig 2.1.7 Stock muffler partly removed
Here we can see the stock muffler partly removed. The only part which still needs to be disconnected is the mystery tube.
Fig. 2.1.8: Mystery tube clamp
If we look inside the body panelling where the mystery tube leads, we see that it is attached to some sort of mystery nozzle with a tension clamp.
Simply use a pair of needle-nose pliers to squeeze these ears toward each other, loosening the clamp, and just pull it back off of the nozzle.
Fig 2.1.8: Removed mystery tube
After moving the clamp off the nozzle, the tube should separate from the scooter with just a little tugging.
Fig 2.1.9: Removed stock muffler
You may now move the stock muffler away. You will be surprised at how heavy it is! It's clear the Taiwanese Yamaha factory spared no expense-saving corner-cut when selecting the materials for these bikes!
I would recommend keeping this handy in case someone nicks your new muffler or you get in trouble with the neighbors over how loud the new one is.
Fig. 2.1.10: Exposed exhaust port
We have now exposed the exhaust port. Note that it is not entirely round. That's okay.
Fig. 2.1.11: Stock gasket
This is the stock muffler gasket. If you didn't buy new gaskets, you need this. If you did... Well, might as well keep it handy, methinks.
Fig. 2.1.12: Engine sans muffler
And here is our engine, all ready for the new muffler!
2.2: Assembling the Super Euro Chamber Corsa
Before attaching the new chamber to the engine, we need to assemble it. First, find a nice, soft place to work on it so you don't scratch it. I used its shipping box.
Fig 2.2.1: Chamber components
Here we can see all the parts lain out and ready to go: chamber, silencer, and bag of parts.
Next we must attach the silencer to the chamber. To do this, we must connect the springs included in the bag of parts to the ears on the silencer and chamber, respectively.
This is most easily done with a strong pair of needle-nose pliers, a strong grip, and some strong pulling.
Take care not to slip and scratch either parts during this procedure.
Fig. 2.2.2: Attaching the silencer
Here we can see the silencer attached. I have also slipped the silencer band onto the silencer to avoid doing it after attaching the silencer to the chamber, although this is entirely optional.
Fig 2.2.3: Attaching the silencer band
To attach the silencer band to the chamber, I found that a socket driver was the best tool for the job. The bolt for this is 10mm.
Fig. 2.2.4: Close-up on the silencer band stay
The silencer band stay has an integrated nut, so you only need to use one hand.
Fig 2.2.5: Assembled chamber
Here we can see the assembled chamber. Beautiful, isn't it?
Next we turn our attention to the assembly of the slider in preparation for the installation of the chamber.
2.3: Assembly of the slider
Fig. 2.3.1: Slider components
Here we see the parts necessary to assemble the slider. They are the baseplate, slider, slider base, bolt, nut, and--of course--the instructions. (Note the orientation of the baseplate, with the "point" pointing down and to the left. This is how it must be installed on the Jog. Other scooters will require it to be pointing up and to the left.)
To assemble the slider, you will need a socket driver (12mm socket) and a 5mm hex wrench.
Fig. 2.3.2: Assembly of the slider
Feed the bolt through the baseplate, through the slider base, and into the small hole in the slider. Then put the nut into the large opening of the slider, onto the bolt.
Use the hex wrench and socket driver to tighten.
Set the slider aside. We won't need it until we install the chamber.
2.4 Installation of the chamber
Finally, we are going to get the chamber on!
Fig. 2.4.1: Installation tools
What you will need is a socket wrench with a 12mm socket for attaching the slider/flange to the engine, and a 10mm wrench for attaching the flange. You could try a socket wrench with an extender for the latter, but I still found that I was hitting the exhaust pipe more than I would have liked.
Fig. 2.4.2: New muffler gasket
The first thing to do is to fit one of the new gaskets (alternately, you could also use the old gasket) to the Corsa's flange, as pictured.
The next step is one that needs to be done no matter what, but I think I could have done it better. You will need to attach the new chamber's stay to the engine before you attach the flange to the exhaust port. The way I went about this is pictured below.
Fig. 2.4.3: Temporarily attaching the chamber
I used one of the original muffler stay bolts to hold the chamber on as I attached the flange. I found that this made it difficult to get the new stay/slider bolts in after I hooked up the flange and had to loosen the flange and tighten the stay and flange bolts incrementally.
This is how I would recommend doing it, since you'll probably end up doing it this way in one way or another anyway:
By working back and forth like this, it should be pretty painless.
Start with the slider, pictured below.
2.4.4: Slider and bolts
Mount it on top of the stay, using the bolts and washers that came with the slider. The Jog uses the shortest ones.
Fig. 2.4.5: Attaching the flange
Once again, the easiest way to work on the flange is from the left side of the bike.
(Note: Be careful of tightening this too much. It can bend surprisingly easily.)
Fig. 2.4.6: Chamber installed
After working back and forth between the stay and the flange, this is the glorious sight you should see!
Congratulations. The chamber is installed.
But wait... There's more! (And this isn't the optional kind of "more.") Next we need to re-calibrate the CVT, so it's time to turn the bike around...
3: RE-CALIBRATING THE CVT
To re-calibrate the CVT, follow the procedure outlined in HOWTO: Upgrade the drive pulley on a 2006 Yamaha Jog ZR.
The only salient difference between that process and this one is that you will not be putting a new pulley in. You will, however, be changing the weights, as illustrated below:
Fig. 3.1.1: Installation of the 3.5g rollers
Since we will be using a mix of two different weight rollers (3.5g and 3.25g), where we put them is important. As we look at the pulley here, it turns CW. Heavier rollers always go in the forward positions of the "V" troughs.
These are the installed 3.5g rollers, greased.
Fig. 3.1.2: Installation of the 3.25g rollers
Here are the 3.25g rollers, also installed. They go in the trailing positions.
Now simply put the pulley back together, reinstall it, and close up the crankcase as described in the pulley how to.
Fig. 4.1: Super Euro Chamber Corsa Installed
And here is what you get when you're all done: a mean street machine that threatens to put you in the pokey over noise or speed violations!
"How fast," I hear you ask? Well, to be honest, I don't actually know. The former top speed of this bike was about 70kmh, which it got to very slowly. The fastest I've gotten it to since the chamber installation is a little over 80kmh, which it got to very quickly and didn't show signs of backing off. I'm waiting for a good chance to really get out on an empty road with no cops and see how fast it goes. At that speed, I'm not only way over the 30kmh speed limit on 50cc bikes, but I'm also way over the 50kmh normal speed limit! And I understand Japanese speeding tickets are none too pleasant.
I'll update this page if I find more.
Oh, and "how loud" you want to know? Well, this video really doesn't do it justice, but...
The only complaint I have is actually viewable in that video. The CVT doesn't actually engage until you get up to a ridiculous RPM. This makes it kind of sluggish at the stoplight and hard to control at low speed. But as soon as you get to that critical RPM when the expansion chamber starts doing its magic, you suddenly get a second burst of power and the front wheel lifts off the ground if you're not paying attention. It's great fun to ride, but I think I need to work a bit more on the ignition timing and/or CVT to get it a little smoother.
Top speed before upgrade: 70kmh
Top speed after upgrade: 80+kmh
Total time: 5 hours, including photo documentation and test ride
EPILOGUE: Super Euro Blister!
That bastard gets hot! I just brushed up against the bend in the back after riding it for no more than 10 minutes and leaving it sit for about 5. Yikes.
Don't think that my cover is going to get along with it... And there's no way I'm going to disfigure this shiny pretty thing with lumps of melted plastic!