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Exhaust Derestriction

These are the tools needed for this modification:
10mm Socket and Ratchet
10mm Open end box wrench
12mm Socket
3" Ratchet extension
Dremel tool, grinder or screwdriver and hammer (cave man style)
A cool head and a little patience

Exhaust restriction - All Vinos ship from the factory with a restricting washer in the exhaust pipe where it bolts to the exhaust port on the cylinder. Some dealers remove it. If your scooter goes 30mph top speed, you need to remove this annoying piece of metal, believe me, you will never look back!

Removal - Remove the exhaust pipe by loosening the bolts on the right side of the scoot (the ones that secure the pipe to the crankcase [Figure 14 & 15]). After they are loose (do not remove them) you can then remove the bolts on the actual exhaust manifold (under the scooter [Figure 16]). Be careful when you do this, these bolts are made of a very soft alloy to protect the cylinder head and will break if you have to force them. After you remove the manifold bolts you can then remove the bolts that secure it to the crankcase and subsequently remove the entire pipe. When you look down the motor end of the pipe you will see a washer limiting the diameter of the pipe. How you remove this is up to you. I have heard several ways that are effective, from using a grinder/dremel tool to just plain taking a screwdriver/hammer to it, cave man style. Just be careful to not damage the bottom of the pipe, if you flatten out the tube it will be kind of a waste that you are even doing anything to it, since this will restrict it again. [Figure 13]

Reassembly - Once the washer is removed you need to put the pipe back on the scooter. This is the tricky part. The end of the stock pipe has slots as opposed to holes and this makes it a little tricky to reattach. First place the pipe in position and put in the top bolt to the crankcase about halfway, so the pipe is free to move back and forth. Then go to the manifold and hand tighten the bolts to the manifold making sure that you have the threads on straight and that it is not hard to turn the bolts, that they go in easily. If you have to force them or feel like it takes too much force to screw them in, chances are you are cross-threading them. If you do this you may break them off in the head and that is bad news. It is recoverable but you just added about 1-3 hours to your work. Once you have the bolts in the manifold pretty much all the way in (but leave enough room to slightly shift it around if the main crankcase bolts don't fit) then go to the crankcase bolts and replace the bottom bolt and hand-tighten both crankcase bolts. Then you can move to the manifold again and tighten them with a 10mm socket. I don't have the correct torque setting but just past the point where it is flush should be adequate, if you run it a while and get some oil leakage or popping sound from under your scoot, you may need to tighten it up a little. A Yamaha dealer or the official service manual would have the toprque settings if you want to be sure.

If you break it - If you happen to break one of the manifold bolts (don't feel bad, I did it), then you have a couple options according to your situation. If you still have quite a bit of bolt above the surface of the manifold you can use a pair of vice grips to take out the bolt. If you broke it off flush or near flush with the manifold then you will need a drill that has forward and reverse settings and a drill/reverse drill bit set (for removeing broken bolts) from your local hardware store. Follow the directions that come with the drill bit set to drill out the center of the bolt and then use the reverse bit at reverse spin to remove it. You will also have to get a new bolt (I would suggest getting a few) at a Yamaha Dealership. When this happened to me The dealer didn't have these in stock so I just went to the local hardware store and got some normal metric bolts. With these however you have to be extra careful not to cross thread the bolts in the manifold since they are now the same strength you could damage the manifold threads.

Figure 13




Figure 14




Figure 15