many things needed as far as tuning on a KZ550A1.

I'm wondering where to start on the tuning up of a 1980 KZ550. It has 12k miles on it. Here's what I have done so far.

-new plugs
-seafoam ran through gas
-new vaccum lines (except 2 lines from exhaust tank and
2 large lines to the air recirc valve)

-new air filter
-new rubber caps on vacuum gauge ports (I think thats what they are for)
-new boots from air intake box to carbs
-used dwell gauge for setting points. they are set good.

I guess thats it. Here's what's been happening. Before I did all this, I did take it for a ride after I changed the oil. (this bike sat for 4 of the 6 years my buddy had it). It ran so-so. It has a back fire issue that I read has some thing to do with the air recirc system. I did blow into the chambers with the reed valves and could only go one way. I'm not sure if that's a valid check or not.

It also has a knock when it idles very low, like 500 RPM. Goes away instantly when revved to 1200. I read a couple things about that being possibly carb resyncing.

So, that was all before I replaced parts. Now after the fact, the bike will idle only with the choke on for quite a while. After it's warm it I can't give it a bit of gas or it kills it. Almost like starving gas. I was thinking of the petcock maybe.

I'm not sure where to start. The bike could probably have a really good once-through but I'm not a bike mechanic. I get all my info from the clymers book and I just do things. I work on my own cars but thats it. I read all about syncing (never have tried it), I'm kinda afraid to pull apart carbs fear of messing something up. I also read about the cam chain tensioner that seems to go bad. I'm wondering if I should go to a manual.

I know it's a lot to read, but any help is appreciated. Thanks!!

I noticed you said nothing of cleaning the tank other than running seafoam through it. I would start there and work my way to the carbs replacing the fuel filters and draining the tank and pulling the petcock to clean it to. You will probably have to pull the carbs if you sucked up some trash.

Idleing at 500rpm will cause a knock so just adjust it up a notch. These bikes run very low oil pressure so a low idle is not good for the internals

GET A MANUAL, you need it, and you will love it.

Bring that idle up to 900rpm minimum for an old bike like that.

If the bike has all the stock stuff (airbox/filter stock carbs and jetting), the carbs probly need a good going thru.

Make sure your timing and the spark advance is correctly set and lubricated.

You should be able to go off choke completely within 1 minute for an air cooled engine of any size/configuration if it is jetted/setup properly for its environment.

Set your mixture screws to stock, usually about 1 1/2 turns out from lightly seated.

GL!

Thanks for the help. I do have a Clymers manual which is where I've been gettin all my "schooling" from. And everything is stock. I will start with all the cleaning from tank first, right on down the line. My mixture screws are sealed I think. Can I just pop out the crap that's in it?

well it's running great!! I didn't take apart but one of the bowls. I was to afraid to mess anything up. So I replaced the 5/8" hose that goes to the reed valves for emissions, I put a new gas line and vacuum line to the petcock on, I also found I had some vacuum lines messed up. (yea...I know).

So, it's all running great except for I think the petcock is messed up. Now that I can see the gas in the line (it's clear), the "ON" setting is not working. I checked for proper pulsing on the vacuum line to it and i did disassemble it. THe diaphragm looked good. What happened is I was riding it and the bike just quit. I saw no fuel in the line when i looked. I turned it to "PRI" and I saw gas start to flow.

www.metrovationinc.com/christemple/KZ550.pdf

here is a manual:)

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Good Fortune!

ehhh, you wont mess anything up by removing the float bowls and main jets....its pretty much just screws, when you take the bowls off be carefull not to rip the gaskets, as sometimes they can be resuable. clean the bowls out.

Get a little mirror and look at the bottom side of the carbs and whats under the float bowls, there is a brass flathead screw with a tiny hole in it, take em out....soak em, blow em out with some air, maybe even poke them out with a small guitar string or something, just dont damage the brass or make the hole any bigger...

that usually helps with some issues that shit in your tank would cause.... you could also take carb cleaner and spray it up into the main jet hole where you took the screw out....take the idle screws out at the same time the main jets are out and blow them out as well, you could put em in at 1 1/2 turns as TecK9iNe said....

reverse procedure to assemble...


i would suggest carefully removing your petcock, you will be able to any crap in your tank that gets caught in the screen.

ehhh, im rambling, but this is what it takes to keep these old bikes alive...your definetly on the right track bro.

Ride On.

-Luke

gutter wrote:

well it's running great!! I didn't take apart but one of the bowls. I was to afraid to mess anything up. So I replaced the 5/8" hose that goes to the reed valves for emissions, I put a new gas line and vacuum line to the petcock on, I also found I had some vacuum lines messed up. (yea...I know).

So, it's all running great except for I think the petcock is messed up. Now that I can see the gas in the line (it's clear), the "ON" setting is not working. I checked for proper pulsing on the vacuum line to it and i did disassemble it. THe diaphragm looked good. What happened is I was riding it and the bike just quit. I saw no fuel in the line when i looked. I turned it to "PRI" and I saw gas start to flow.

Hi, I might be stating the obvious, but are you sure you have enough gas in your tank? If the gas level is to low it can't pick up in the on position. Res and Pri have a lower pickup point. Pri position lets the gas flow freely, no vacuum needed. Here's a way to check if your petcock is working properly.

On is also off and vacuum from the engine turns it on.
One way to check it is to disconnect both lines from the engine in the on position. Gas should not flow in the on position because when the engine is not running, this is the off position.Then suck on the vacuum line. This simulates the engine running. Gas should flow through the other line, which is the gas supply line. Simple little test.
Hope this helps. If you already knew this then disregard.

Actually I did that exact thing with the petcock. I sucked on the vac line and watched gas run out on the ground when i had the tank removed. But it seemed to not work when the motor was running. Well it worked at first but then I had to put it on PRI to keep motor running. Maybe I didn't have enough gas in. I did only put a little in it and then went fr my drive.

And thanks for the links to the manuals.

I agree with Tony, did you try the "res" reserve position on the petcock? (As he said) the "pri" prime position takes from the reserve port in the tank so you get gas when the tank is low. The "on" does not.

gutter wrote:

...was riding it and the bike just quit....

A clogged vent on fuel cap can cause this to happen due to fuel starvation resulting from vapor lock inside the tank.

The carb float bowls get emptied.

Sit at roadside for a few moments, float bowls gradually refill, the bike starts right up again, and runs until the bowls run dry.

A quick easy test is to run with the fuel cap ajar to determine whether the problem recurs.

Similar fuel starvation problem may occur from other caused, such as crud suspended inside tank, clogged pickup screen inside tank or otherwise clogged petcock, kinked fuel line, clogged inline fuel filter, etc.

Fuel tank may be flushed by removing it whereby it may be fast-dumped out the filler hole, add a little fresh gas, shake, re-dump, repeat several times if necessary until all grit and crud is removed from inside the tank.

Good Fortune!