Fixing A Carburettor Fuel Leak on My Kawasaki Z650

I'm in the process of getting my Z650 back out of winter hibernation, and inevitably I've found an interesting variety of issues since putting it away while the weather was bad.

Most annoying and important of these is a series of fuel leaks and carburetion problems. Ethanol-based fuel has a LOT to answer for !

I've got two workable sets of carburettors for the bike. The ones that were on there were leaking from several of the float bowl drain screws, and number 3 cylinder on the bike wasn't working, which I suspected might be due to a blockage in the pilot circuit on that carburettor.

So I swapped them out and put the other set on. All the drain screws were nice and sealed, but there was a significant leak from the fuel feed. The feed consists of a "T" piece with the fuel intake pipe that sits between carburettors 2 and 3, and then two pipes linking the inner to outer carbs. It was the pipe linking carburettors 3 and 4 that was leaking, quite profusely.

The photo below shows the issue; I wrapped the blue tape around just to try to isolate the issue. It proved that it was where the leak was, but after 5 minutes the fuel dissolved the glue on the tape and that was that.

To solve the problem, I had to take the carbs back off. My goal was to replace the o-rings on the leaking pipe while doing the minimal disturbance to everything else. I didn't want to create any additional leaks !

With the carbs removed from the bike, the first step was to remove the tickover adjuster screw and then the four caps. The adjuster has to be removed because it blocks one of the cap screws. Poor design !

Then I loosened the 8 screws holding the bank of carburettors to the mounting plate. It's best done at this stage, because once other parts are removed or loosened, it can be a real pig to get them loose.

Nest step was to remove the four 8mm bolts holding the throttle slide arms to the control rod, together with the one holding the throttle pulley, and the two rubber bungs at each end of the control rod.

The photo blow shows what I did next, which was to use a metal chopstick to push the control rod out just enough to remove carburettor number 4. I didn't want to push it past the pulley, because getting that back on and lined up again is incredibly fiddly.

With all that done, I was able to remove the 8 screws I'd loosened earlier and swing the bank of carbs back from the mounting plate. A lot of wiggling and cursing later and carb number 4 came away as I wanted. You can see below the pipe and it's blue tape.

This is the culprit ! It's hard to see on the phot, but the four o-rings were badly cracked and perished. It's the effect of the rubbish high-ethanol petrol we get in the UK nowadays, it just eats most types of rubber.

I replaced the o-rings with new viton ones, supposedly more durable and fuel-resistant, although my experience is that nothing survives ethanol for long. I also added a little bit of blue Hylomar gasket sealant, being careful to put it only on the outer o-rings to avoid contaminating the fuel going through the system.

With all that done, it only took about 10 minutes to put everything back together and get the carburettors back on the bike.

The good news is that there are no more leaks so far.

The not so good news is that number 3 cylinder still isn't working - I use the technique of flicking a few drops of water at each exhaust header pipe. If it sizzles and boils away then it's all good, if the water just sits there it tells me the pipe isn't as hot as it should be and something is wrong.

That can be next weekend's problem to investigate ! What I know is that carb cleaner sprays cleanly through the pilot circuit, and the fact it's only number 3 rather than 2 and 3 together means that timing and ignition problems are unlikely. My suspicion is that the rubber boot connecting the carb to the cylinder, and/or the rubber plug that stops up the vacuum gauge port have been eaten by ethanol.

All photos are mine