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Exhaust & Clutch
When installing a performance exhaust it is absolutely
critical that the roller weights be changed. These
are usually supplied with the exhaust system. This allows the engine to be in
the engine rpm band it needs, to be efficient. Some brands of bikes such as the
Yamaha Vino and Zuma the clutch springs must be upgraded also. A typical symptom
of having the wrong roller weight is that acceleration will be weak up to 20-25
mph and then start pulling strong. Symptoms like this are the rollers are too
heavy and need to be 1 gram lighter. Clutch springs affect the initial
take off only. The first 10 feet of movement is controlled by the clutch.
Either an aftermarket clutch can be used or the original clutch springs can be
replaced with stiffer ones that allow the clutch to engage at higher rpm’s.
Sometimes the clutch shoes are so heavy from the factory that the only choice is
the aftermarket unit. The ETON and CPI brand is a perfect example of this.
Rider weight also affects the rollers that should be used. The ones from
Tecnigas are based on the average rider of 150 pounds. For every 50 pounds of
rider weight the required rollers may need to be varied by ½ gram. Rollers are a
tuning aid and the “golden” weight varies.
Carburetion jetting should not need to be changed
if just the exhaust /clutch are replaced. If installing a larger cylinder kit it
is critical that more fuel is supplied. Never install a larger cylinder kit
without changing the jetting/carburetor also.
When installing an exhaust always mount to the
exhaust flange first (loosely) then to the rear mounting bracket. Everything
should be aligned first then
tightened. Some minor fitting might be required but is
rare. If brackets do not line up it is possible they are reversed.
To install the rollers remove the clutch cover. With the cover
removed squeeze the belt to get some belt slack. Using an impact wrench remove
the front variator nut. Remove the outer variator half. Slide the belt off the
shaft and out of the way. Now slide the inner half with the back plate off the
shaft. Remove the rear back plate and you will now see the rollers. Pay
attention that the 3 plastic guides do not fall off the rear plate. Now replace
the rollers with the ones supplied and assemble in reverse order.
With all the different brands out there today some share a
common engine design .
It does not mean it is the same engine.
Again the Vino and New style Zuma share common parts but the drive belts, reed
blocks and engine cases are different. To get the correct parts call and confirm
the model and brand.
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