Leaky carbs

Hi Rudy here new to KZ rider and aquired a 76 KZ900LTD in great shape. When I got it going it runs great but noticed the carbs were leaking alot of gas from the bottom I think its the drain but can't tell and can't ride it because too much gas is leaking out. Has anybody had this same problem and or know what it might be?

More than likely the gas is leaking from the overflows because the float height isn't correct. Although, I did one time forget to tighten the drain screws on my kz after changing jets and as a result ended up with an awful lot of gas leaking.

Could be crud at interface between float-needle and seat.

Rapping smartly on float-bowl with plastic mallet while engine is running sometimes corrects the condition.

Good Luck and Welcome to KZrider!

Last year I ran into a similar issue with my carbs "leaking". Turns out that the overflow from carb #3 was pissing all over. Rather than taking the downtime I tried adding SEAFOAM (a carburator cleaner and lubricant which was recommended to me by members of this board) to my gas tank. I added per the instructions then took my bike down a bad road to bounce it around a bit. LO and BEHOLD! The trick worked and within a few miles my carb stopped pissing and everything was fine for the remainder of the season.
Since then I add a couple ounces every couple of weeks to keep the internals clean and I have had NO problems since.
Try it, it could save you time and money. Although this is no substitute for adjusting your floats if they really need it, it could save time if all you need is a good cleaning.
Just my 1%
-Dave

rsolano wrote:

Hi Rudy here new to KZ rider and aquired a 76 KZ900LTD in great shape. When I got it going it runs great but noticed the carbs were leaking alot of gas from the bottom I think its the drain but can't tell and can't ride it because too much gas is leaking out. Has anybody had this same problem and or know what it might be?

I doubt there are many people who have NOT ahd this problem on an older bike. Gravity never sleeps and it just keeps pushing. Newer bikes have vacuum cutoffs at the petcock which automatically shut the flow off (if the petcock is good). Eventually, petcocks get leaky too.

Here is the things to do:

1) The interface between the brass seat and the valve in the carb is the first thing to fix. I take the valve out (it's the little metal piece with the cone shaped tip the float tab pushes against) and put it in a drill and polish the cone. It has to be dead smooth to get a good seal with the seat.

2) I also polish the seat where the cone sets into. I use a Q-Tip or similar and polish it with chome polish. You can also chuck it into a hand drill and polish it. The idea is to get the inside very smooth.

3) Adjust float levels to make sure they are right.

4) Always turn the gas off at the petcock when not running.

If it still leaks, one or more of the parts listed above may have to be replaced.

bountyhunter wrote:

I take the valve out (it's the little metal piece with the cone shaped tip the float tab pushes against) and put it in a drill and polish the cone. It has to be dead smooth to get a good seal with the seat.

If I remember correctly, the one in my carbs have triangular shafts, which means that they would fit it a drill chuck just fine..... Hmmmm.... wow. Yea rsolano, give this a shot. (Thanks a lot Mr. Teachmesomethingnew.)

I agree that there are probably no people here who have not had this problem.

Try the sea-foam, I wish I had known about it when I got my bike initially and was fixing a leaky float bowl. (I am going to go look for it now for preemtpive maintenance purposes :woohoo: ) As it was, I got a lesson in rebuilding carbs and setting float bowl levels, times four at only 30 bucks per rebuild kit..:huh:

Also, unless you are going for the pure stock thang, switch out the petcock on your tank. Mine leaked a painfully slow, steady drip through the gas supply line in the "off" position (then leaked out the side of the petcock after subsequent attempts at repairing.) This coupled with the recent carb rebuilds and repeated (and unnecessary) float level adjustments had me chasing Gremlins for a couple of weeks.

I suggest that you really do look into that petcock, and consider getting a vacume cut-off replacement. It is a very easy install, and there are many different options you have in getting one.

Welcome to the site. Post often.

Qdude wrote:

bountyhunter wrote:

I take the valve out (it's the little metal piece with the cone shaped tip the float tab pushes against) and put it in a drill and polish the cone. It has to be dead smooth to get a good seal with the seat.

If I remember correctly, the one in my carbs have triangular shafts, which means that they would fit it a drill chuck just fine..... Hmmmm.... wow. Yea rsolano, give this a shot. (Thanks a lot Mr. Teachmesomethingnew.)

You can wrap a little masking tape around them to protect them in the chuck.

Qdude wrote:


Try the sea-foam, I wish I had known about it when I got my bike initially and was fixing a leaky float bowl. [/quote]

As far as gas seeping while the petcock is in the ON position: I don't think it can be "fixed" completely, because it relies on a metal-to-metal seal between the needle cone and the brass seat.

Notice how brass parts (seats and jets) get dull looking gradually? They are oxidizing and the surface is getting slightly rougher. They will leak gas there. You actually have to polish them regularly to get them to seal reasonably well with the petcock left on.

Most common leak points are fuel tees, cracked overflow tubes, the bike left with the fuel tap on when parked, excessive crud in the tank which gets down to the needle/seat and causes overflowing.

Once you have those things check out, set the float heights using the service fuel level method ONLY. While you are at it, examine the float needle and seat assembly. The seat should be clean and the needle should be smooth with no pitting or deformation.

I have two vintage bikes KZ 650 1978 and KZ 750 1979. The KZ 650 had bent metal flanges on the float. Once I corrected them, and checked their free play, there was no more leakage from any of those carborator floats afterwards. Each one of these floats have rubber pods that rise and fall. My KZ 750 has copper pods. One of them leaks--possible because it may have some fuel in them. (i.e. a hair line crack). To replace one of these copper pod floats cost near $42. I just shut off the fuel when I am parked. Hopefully, I can remember. By the way, there is a tab that can be bent to the up position to limit how much fuel goes into the bowl itself. Keep in mind, by raising this tab, you are choosing to run the bike lean. Anyone know how I can replace this copper float of mine on the cheap?

Also,

Pull the carb drain plugs. It flushes the crud out.

Just have a little container to cath the gas when it comes out.

Also the plastic mallet trick has worked for me in the past.

Just wrap on the carb hard enough to jostle the carb body, but not hard enough to cause any damage.

This is a common problem.

This may be a shot in the dark, my '76 kz900 has earlier Z1 28mm carbs on it and they have 17mm drain plugs on the float bowls. I was leaking from there and discovered my o rings are flat. Don't forget to check the gaskets!