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Honda NTV650 Revere - Fuel petcock restoration
During the restoration of my second-hand Honda NTV650 Revere, I come across the fuel petcock severely damaged. The thank itself were corroded by rust and needed a deep restoration (see this article, in Italian: Restauro con Power Tank di un serbatoio arrugginito).
The original Honda spare part
The original Honda part has code 16950MS9005 COCK ASSY., FUEL, but it is no longer produced by Honda. The body of the petcock is closed by two rivets, so no maintenance is planned. In my case some rust from the tank accumulated into the holes and damaged the 4-holes rubber gasket.
| Tank petcock thread diameter | 22 mm |
|---|---|
| Hexagonal nut | 30 mm |
| Fuel pipe connection outer diameter | 10 mm |
| Distance between rivets | mm |
| Screws to replace rivets | 3 x 16 mm (1) |
| Reserve tube lenght | 100 mm (protrusion from the petcock-tank contact surface) |
| Reserve tube diameter | 7.5 x 8.5 mm (inner x outer) |
| Filter base outer diameter | 14.2 mm |
| Filter full height | 180 mm |
- We drilled two passing holes, the screws were provided with self-locking nuts.
The brass tube of the reserve were severely corroded; I suspect that the previous owner used some sort of acid to clean the inside of the thank, producing even more damages!
Drill the rivets to disassemble the petcock
I drilled the rivets hand-free; first I removed the rivets heads using a 4 mm bit, so that the petcock can be disassembled. Then, using a file, I smoothed out the parts of the rivets that were protruding from the body of the petcock. I completed the hole using a 2 mm bit, finally I enlarged the hole till 3.2 mm, with the idea of using two 3 mm bolts with self-locking nuts.
| Tap inner diameter | 28.75 mm |
|---|---|
| Tap knob outer diameter | 28.72 mm |
| Tap knob pin | Square section 8 x 8 mm, height 13 mm |
| 4-holes gasket | 27.10 mm diameter, 2.70 thickness(1), 8.60 mm holes |
| O-Ring (rectangular section) | 25.64 mm inner, 28.80 mm outer, 2.10 mm thickness |
- The thickness was measured on a very old and squeezed gasket, probably a new gasket is more thick. The maximum acceptable thickness (calculated upon the available space) should be 2.95 mm. Because the original gasket has a raised outer border as well as raised borders around the holes, an overall thickness of 3.00 mm, that includes the raised borders, is plausible.
According to this forum post, it seems that the rubber parts (the 4-holes gasket and the o-ring) are the same mounted into the petcock of the Honda quad TRX350, years 1986-1989. User Goober published some nice photos and drawings with the measures of the gaskets; he succeeded to restore the petcock using a kit, despite the measures were slightly different.
Non-original petcock spare part
As the original spare part is no longer in production, it is possible to buy a non-original one. Unfortunately the quality is by far worse than Honda, and it seems that none of the available items fit perfectly the NTV650, even if the part is advertised for that model.
In my case the dimensional difference were on the knob pin, wich is shorter than the original. This means that the knob does not fully engage because it contacts the body of the petcock, the contact prevents the knob from rotating.
| Tank petcock thread diameter | 22 mm |
|---|---|
| Fuel pipe connection outer diameter | 10 mm |
| Reserve tube lenght | 95 mm from the base of the hex nut. |
| Reserve tube diameter | 7.0 x 8.0 mm (inner x outer) |
| Tap inner diameter | 28.95 mm |
|---|---|
| Tap knob outer diameter | 28.65 mm |
| Tap knob pin | Square section 8 x 8 mm, height 5 mm |
| 4-holes gasket | 27.10 mm diameter, 2.50 thickness, 8.50 mm holes |
| O-Ring (round section) | 26.34 mm inner, 28.82 mm outer, 1.42 mm section (1) |
- The knob o-ring fits very loose into the tap inner diameter, probably it will leaks if the 4-hole gasket leaks.
Customize the knob pin
The original knob pin is 13 mm, while the non-original one is only 5 mm. In the following photos the small extension I built to fit it. The collar made of brass sheet allows for good resistance, but it required to slightly enlarge the hole in the plastic knob.
