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81 kawasaki KZ 750 help

Posted: Tue Jun 26, 2007 1:27 pm
by telefunkin
I bought this bike yesterday and am already having a few issues. I had a hunch that I was going to have to clean the carbs as it was sitting in the dealership warehouse since august. They warned me about this before I bought it.

It was cheap, I only paid them a few hundred more than what they spent on parts to rebuild it.

It takes about 10 minutes of playing with the choke and throttle before it'll idle unattended without stalling. It also backfires alot during this process. I'm assuming a carb cleaning will take care of this.

After it's all warmed up, it runs perfectly from gears 1-3. Once I get into 4-5 gears, It doesn't have much pickup. In fact, I can't even push her past 110kmph at full throttle. Is this also a carb issue, or should I be looking at something else?

Also, I had to switch to reserve today after only riding 90kms(55 miles). I started with a full tank and it was mostly highway driving. It's a relatively small tank, but this seems extremely low. Anyone know what kind of mileage I should be getting or is this something else that could be carb related?

Posted: Tue Jun 26, 2007 1:53 pm
by thespirit
Sounds like the carbs need a good cleaning. Is it firing on all cylinders?

I would take it one step at a time. Clean the carbs out first, and clean them really really good.

Posted: Tue Jun 26, 2007 2:04 pm
by telefunkin
thespirit wrote:Sounds like the carbs need a good cleaning. Is it firing on all cylinders?
How do I tell if all the cylinders are firing?

Posted: Tue Jun 26, 2007 2:08 pm
by thespirit
telefunkin wrote:
thespirit wrote:Sounds like the carbs need a good cleaning. Is it firing on all cylinders?
How do I tell if all the cylinders are firing?
Well, the smart way is with a spray bottle of water. Get the bike started and let it run for a minute or two, and then lightly squirt each header pipe. If the water sizzles, then the cyl is firing.

The way I do it, is I just grab onto the header pipe with my hand and if it's hot, it's working. I prefer doing that method because I can start to check immediately after starting the bike. If they are all getting warm at the same time, they are all firing. If one or more are not getting as hot as quickly, then there is a problem with those cyls.

I really don't recommend that because you can seriously damage your hand. So don't sue me if you get 1st degree burns on your palms.

Posted: Tue Jun 26, 2007 2:28 pm
by telefunkin
They're all getting hot, burnt my finger on one of them earlier.

Posted: Tue Jun 26, 2007 2:31 pm
by thespirit
Ok. I would start with rebuilding the carbs.

You can also check for vacuum leaks. Since they rebuilt it, I would hope they put new carb boots on, but check them for cracking or see if they are hard as a rock. And easy way to check for vacuum leaks is with a bottle of starting fluid. As the bike is running, you can spray that stuff on the carb boots and see if your idle picks up or slows down. If it does, you have a leak.

Did you have any black smoke coming out while it was running? Black smoke can mean it's running rich. You can take the plugs out and check them to see if they are black or white. They shouldn't be either. They should be a brownish color.

Posted: Tue Jun 26, 2007 2:46 pm
by telefunkin
No black smoke, there was some white smoke when it was first fired.

Carb boots may be may be bad. I didn't take note of their condition, but when I was adjusting the idle, I thought I could hear a "pop" coming from the carb whenever it backfired. I don't have any starting fluid, but I do have carb cleaner. Would that work to test it?

BTW, thanks for the advice.

Posted: Tue Jun 26, 2007 2:52 pm
by thespirit
The popping could have just been from the backfiring, however if it does pop out through the carb, that is a sign of either running too lean, or a vacuum leak.

Carb cleaner will work as well as starting fluid.

Did you get my PM?

Posted: Tue Jun 26, 2007 3:02 pm
by telefunkin
I'll test the boots with carb cleaner tomorrow.

I just read the PM, thanks.

Posted: Wed Jun 27, 2007 3:30 pm
by telefunkin
Carb boots don't appear to be a problem.

I dumped a few shots of carb cleaner into the gas tank this morning and after a quick jaunt on the highway to work, things are getting better.

After sitting all day in the parking lot, it started with a closed choke and I only had to play with the throttle for maybe a minute before it was idling fine by itself and not threatening to stall out. +1

Checked the pipes this morning and when I left work, and all four are getting burning hot right away, so all 4 cylinders appear to be firing.

It still will not accelerate past 110kmph which bothers me. This bike is rated for 195.

yesterday I stalled out and had to switch to reserve after only riding 90kms, I'm at 70 now so we'll see how that goes.