81 KZ550 bogging out if petcock not on prime??

Never had this problem before. I still have a small drip leak out of the overflow tube on carb 1 but when its running and warmed up, i go to give it gas and it boggs down. i look in the new gasl lines i put in and looks like no gas is going into the carbs. When i have the petcock on prime, constent fluid goes through and bike runs fine??? How do i fix that. I am inexperienced but have a shop manuel so please use understandable terms lol. thx

It's time to drain the gas from the tank,look for rust in the petcock screen(you'll have to remove it from the tank).Also order a rebuilding kit from www.z1enterprises.com for your petcock as the gas/alcohol mix is very hard on the rubber diaphrams.

If rust is found, here's a way to remove the rust:

Oxalic Acid Rust Removal On Gas Tanks(Found On the internet)

Just ordered a few pounds of it this morning, it "should" remove the rust in my Kaw tank and it's great for removing rust on shop tools or whatever too.

I used this stuff while I lived in Florida where the humidity usually averaged 100% and it saved me a lot of labor ... it's Eco friendly too. Our humidity here in Alabama is just about as bad as on the gulf coast ... so even if it won't completely clean the tank rust out ... and I truly believe it will ... I can make good use of it

Don't know why I didn't think about it sooner, mixes with tap water, flushes out easy, it won't harm paint, plastics, aluminum or anything of that nature ... just kills the rust and leaves the metal coated to help prevent future rusting.

The guy's name is Gregg and he has a ebay store but you can buy directly from him, send payment by check or paypal. I talked to him yesterday and told him there would probably be more folks from the forum inquiring about it. He said to have whoever calls or emails to remind him they're from the forum.

It sells for $4 a pound and he can fit 4 pounds into a flat rate priority mail package and ship it for $4.95. So 4 pounds should go along way since it can be used over and over again. $20.95 for 4 pounds shipped isn't bad at all in my opinion. The only way he's making any profit on it is by buying LARGE quantities and selling small.
I'm probably going to set up a large vat to soak tanks and tools in.
This stuff will eventually turn black after heavy use but it still cleans good and washes clean with tap water.
He claims he's had several people use it for cleaning rusty tanks with great results and I know I had good luck with it before too, just never used any on a tank ... but will soon.

Here's his info: Best to try his cell first.

Gregg MacEllven
Sea Shield Marine Products (sales rep)
Mac's Pacs; teak/mahog plugs, flax, oxalic, etc.
macspacs@sbcglobal.net
310-547-2687 (home)
310-547-2606 (fax)
310-721-9667 (cell)

Late yesterday afternoon I mixed up a batch and put it inside my original KZ tank.
The tank had what I would call a medium overall surface rust throughout the inside and a fairly heavy rust build up along the entire bottom surface.

The instructions suggest warm water but I talked with Gregg and he said it wouldn't really matter as long as I wasn't looking for INSTANT results and let it soak so I used unheated water from the hose and about 8 heaping tablespoons of Oxalic acid and let it soak for 24 hours.

I just drained the tank and the water was colored kind of a light brown, I flushed the tank with clean water twice and looked inside as far as I could see with a strong miniature LED flashlight and NO RUST was present ANYWHERE including the bottom surfaces.
The Oxalic acid left behind a off white colored protective coating on the metal surface just like Gregg said it would

Once I got the tank dry I saturated a shop rag with gas and rubbed the white coating with it and the coating stayed put.

But ... I will highly recommend you folks give this stuff a try because it sure takes the work out of removing rust from our gas tanks and it did not faze the paint either where I overfilled it.

This old tank will get repainted and used now that the rust is gone ... but for you folks that have internal surface rust on tanks that still have good paint on them, don't worry ... this is the ticket right here !

I can tell you right now that it works very well, the tanks I cleaned back in November have sat in my shop until I decided to tag & drive my 78 KZ a few days ago.

I looked at all 3 tanks & they still looked rust free inside other than a small haze which may be simply what the metal looks like after sitting so long after being treated. I thru a 1/2 gallon of gas in it, sloshed it around, poured it out, installed the tank with clear gas line & the fuel runs out CLEAN ... no rust deposit showing up in the filter either !

Oxalic acid WORKS better than anything I've ever tried in 30 years of wrenching. Use hot water, mix it up double or triple strength, fill the tank to the rim and let it sit overnight. If you don't get the results you want, do it again, this stuff is cheap and WILL clean the rust out of tanks without harming the paint even.

I kept several gallons of used mix in a large plastic container & constantly throw stuff in it like a set of rusted boat trailer wheels, impact sockets etc. & it cleans them like new, may take a while but it works.


Some tanks may require more acid to do the job but this stuff is cheap & easy to use, won't even burn the grass when poured out.

I did a Honda tank for a buddy that had some ridiculous rust along the inside bottom flat areas & top part of the hump. I tripled the recipe & let it sit a couple of days and it came out CLEAN.

Would rather NOT use a tank liner product that may or may not peel away ... oxolic axid won't hurt the paint either, so that's a huge plus.

RobQ wrote:

Never had this problem before. I still have a small drip leak out of the overflow tube on carb 1 but when its running and warmed up, i go to give it gas and it boggs down. i look in the new gasl lines i put in and looks like no gas is going into the carbs. When i have the petcock on prime, constent fluid goes through and bike runs fine??? How do i fix that. I am inexperienced but have a shop manuel so please use understandable terms lol. thx

So you do have the vacuum line for the petcock hooked up to one of the vacuum nipples of a carb of your choosing right??? If not there is your problem. I think factory is on carb 2 on inline 4s.

If it is hooked up, then maybe it died they do that sometimes, or your not getting good vacuum off the carb it's hooked to. Put a long piece of hose on it and add a little suction (it requires very little) to the hose and watch to see if you get fuel like you do on Prime. If it isn't allowing fuel to flow, or fuel comes into the hose when you add suction, then the diaphragms are ripped. (note: if it does allow fuel to flow when you add vacuum to it, then try putting it on a different carb.)

If the petcock needs a rebuild the kit was $20.00 Canuck, last time I bought one and it came with new everything.

Sorry, i meant the reserve. I can now only ride the bike when it is on reserve. When it is on prime, i can see the fuel going down to the carbs. On the petcock, there is the top nipple and the bottom nipple. The top one is going to the first carb, the bottom is going to the three way joint. Im guessing thats right because the bike runs

RobQ wrote:

Sorry, i meant the reserve. I can now only ride the bike when it is on reserve. When it is on prime, i can see the fuel going down to the carbs. On the petcock, there is the top nipple and the bottom nipple. The top one is going to the first carb, the bottom is going to the three way joint. Im guessing thats right because the bike runs

On 550's petcock, the top pipe, which is the smaller one, is vacuum. It goes to a port on the #4 carb only. #4 is on the right as you sit on the bike.

The fuel pipe is the lower pipe on the petcock. It goes between the 2 and 3 carb to a T which feeds the rack.

This is for the KZ550 A, C, and D which use the TK-22 carbs.

If it flows gas in prime or reserve, but not "on", then you'll have to investigate the petcock. You can take the lever off without taking it off the tank. If the feed tube in the tank is blocked, you'll have to remove the petcock and clean/fix it.

There is also manual in my signature, you can download if you want.

As CA said, you can still get rebuild kits for the petcock. It'll have the gaskets, orings etc, but it won't have the screen that is inside the tank. If that's messed up, you'll have to get an ebay one or salvage yard.

got it, ill try cleaning it tonight

And you need to address that drip. That's usually a sign that the needle and seat are not sealing. Likely due to a small piece of crud.

RobQ wrote:

...I can now only ride the bike when it is on reserve. When it is on prime, i can see the fuel going down to the carbs....

Perhaps the fuel level is too low inside the tank to run with petcock in ON position. That's the way it's supposed to work, flowing fuel in the petcock ON position until fuel level inside tank gets too low, which requires turning petcock to RES (reserve) position and hopefully providing enough additional range to reach a service station (perhaps 20~30 miles on RES position) until tank runs completely dry.

PRI (prime) petcock position flows fuel like an on-off valve, regardless of whether engine is running or not, as PRI position doesn't rely on vacuum from a running engine to flow fuel. Riding the bike on PRI risks running dry without warning.

Would fill the fuel tank and test ride with petcock in the ON position.

Good Fortune!

damn patton ur so damn smart, one day i wana be like that

I hate to say it, but I've gone on many trouble calls to help friends get their bikes going, and they were just low on gas. Now I just tell them on the phone to put in a gallon to be sure (if they're not already full).

ill have to check tomarrow. but when i first got the bike started i put a gallon in and it never happened and i ride it about 4 minutes per day. And it just up and happened so i changed the fuel lines because i think they were put on wrong and im going to add gas tomarrow so more than likely that was the case. Its fine that its an 81' but a gas gauge would be awsome