The Honda NTV650 Revere mounts two Keihin vacuum piston carburetors.

I replaced the complete vacuum cylinders with diaphragms the first time after 12 years, at 113,000 km. After another 12 years (24 years and 201,000 km in total) the diaphragms were again to be changed as shown in the photo:

Unfortunately, mother Honda no longer produces the spare part (code 16112MN8014)! There are at least three types of non-original membranes adaptable to the NTV650, which differ in the way they are installed. One type requires cutting the upper plastic ring (the black one) which is then put back in place and glued. A second type requires that the black ring be removed and thrown away (it is the Librane model seen in the following photos), the replacement membrane is held in place with cyanoacrylate glue. The glue supplied is gel type, resistant to petrol and high temperatures. Finally, there is a model that must be installed like the original, inserting it in the space between the red and black rings.

The following photos show the installation of a Librane type membrane.

Before removing the old membrane mark the point on the piston that corresponds to the membrane slot, because the new one will have to be positioned at exactly the same angle. The black ring can be cut with a cutter and removed. The groove can be cleaned and degreased with synthetic thinner. Be careful to spread a very thin layer of glue, so that the membrane enters well into the housing without encountering any thickness.

As soon as they were mounted, the result seemed good: the precision and sensitivity of the throttle was significantly improved compared to the old cracked membranes. In a few months I will check the actual seal of the membrane and especially of the glue. The one supplied reports among its characteristics a maximum operating temperature of 80 °C. Probably the Loctite 454 has better characteristics.

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