Honda CBX/DOHC Petcock Overhaul

Th Petcock on all Honda bikes from the 1970's to the early 1980's fitted to the CBX & DOHC bikes have a tendency to give way just when you don't want it. The Super Sport Shed supplies a genuine Honda replacement gasket and the required screws to upgrade before or even after disaster strikes. Trust me I have personally been there more times than I want to remember. Do this if you are rebuilding any bike or have a bike that has to be upgraded, from experience, mileage or condition makes no difference it will fail.

What you will need;

The good news is the fix is relatively simple and cheap which is available here

You will need to have access to a 3mm tap and a pillar drill with a hand vice and good drill bits.

If you do not have this facility or tools we can upgrade for you here I have done this upgrade many times and have found the perfect way to do it, having refined the process over the years. Taking this approach limits the amount of swarf that can enter the petcock on disassembly.

Step one -

First things first are to secure the petcock in a hand vice making sure it is at right angles and perpendicular to the drill bit. Use a 2.5mm tapping size drill in preparation for the petcock to be tapped Then using a 3mm second tap (taper is not required as it's a soft zinc alloy).

Drill the petcock on both sides down approximately 12mm

Step two -

OK now both sides have been drilled put your tap in the drill chuck. Then start the thread by pulling the drill press handle down to (not too hard but enough to start the thread) the petcock and twisting the chuck to start the thread. This ensures the thread is straight into the drilled hole. Twist 4 or 5 turns, then twist it back to remove the tap. THIS HAS TO BE DONE BY HAND AND NOT BY THE MOTOR, YOU MAY NEED TO REMOVE THE DRIVE BELT.

Start tapping the thread in the drill press

Step three -

The next step is to carefully remove the rivetted material to allow the removal of the faceplate and "innards" of the petcock. Use a 5mm drill to carefully drill the zinc alloy just below the surface of the faceplate, avoid removing material from the faceplate itself (see picture). Once you have done this remove the petcock from the hand vice and tap the 3mm holes (before you split the tap itself) to the bottom taking care not to break the tap off!

Avoid cutting into the faceplate itself with the 5mm drill.

Step Four -

You now need to contain the petcock in a tray to avoid the locating ball bearing going walkabout, along with the spring behind the ball bearing and the pressure spring (see pictures below before proceeding.) Carefully lever the faceplate off with a small screwdriver, start in the middle and lever your way out on both sides, it will give way.

Carefully lever from the middle out

Step Five -

After the faceplate comes free be very careful of losing the locating ( in the side of the tap component) ball bearing and springs as previously mentioned. Remove the old gasket/packer and replace it with the new one (see the wear on the old gasket, this was dripping onto the carbs and engine).

Step SIx -

Now for the fiddly fit! Carefully fit the parts back together in the order they came out. Firstly aligning the base plate (the plate that pushes against the gasket/packer) indent at the 4 O'clock position in line with the locating slot for the ball bearing. Insert the pressure spring and carefully push the faceplate and tap into the slot as per the picture below, hold together with a finger and thumb and with difficulty get the two screws into the newly drilled and tapped holes. Carefully tighten the two screws ensuring they locate over the two existing pillars without catching.

Now it's all done ready for re-fitting to your tank.

If you feel you would like us to undertake this task we will be more than happy to do this for you, the service can be found here

Registration Number: 132 396 97              VAT Number: 372 982 264
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