Finally Started up my Project...A few Questions.

Well, I finally started up my 1981 KZ750E2. I did get it to run, but there are a few issues.

First off, my #3 cylinder is not firing (although there is spark and the float bowl has fuel in it). I will check all my coil connections, etc, to make sure I get a strong spark and I will need to look at that carb again. No real question on that until I do some investigation.

My question is with another cylinder that runs at idle and then seems to shut down when I give it gas. I think this, because I have an exhaust leak at the head that is pretty loud at idle, but goes away when I give it gas. Is that possible?

Also, it seems that when I try to rev it, the engine kind of goes flat and doesn't want to speed up. It must be carb related, but an not sure.

I think I may be in over my head. maybe I should start parting it out!

Mid life crisis wrote: Well, I finally started up my 1981 KZ750E2. I did get it to run, but there are a few issues.

First off, my #3 cylinder is not firing (although there is spark and the float bowl has fuel in it). I will check all my coil connections, etc, to make sure I get a strong spark and I will need to look at that carb again. No real question on that until I do some investigation.

My question is with another cylinder that runs at idle and then seems to shut down when I give it gas. I think this, because I have an exhaust leak at the head that is pretty loud at idle, but goes away when I give it gas. Is that possible?

Also, it seems that when I try to rev it, the engine kind of goes flat and doesn't want to speed up. It must be carb related, but an not sure.

I think I may be in over my head. maybe I should start parting it out!

No.. don't part it out... you can do it bro!!!

First off, do a compression check (throttle wide open) hot or cold, I don't care.

Then tell me the history of the bike.

Post them both in the same post and we can probably help you solve your problems.

Recez...I will keep trying!

I will be away for a week or so, so I will get the compression checked as soon as I get back and will post the results.

Unfortunately, I don't have any real information on the history of the bike, other than it has been sitting for a few years. I believe the owner has passed away and no one else knows about it.

I have checked the values and cleaned the carbs.

I will post the compressions as soon as possible.

Thanks.

You've already checked the valve clearances? Good job!

Have you checked the carb diaphragms on all the carbs? Checked for tears and holes?

Yep! I read through a fair number of posts before I started, and lots of people suggested the valves as a good start. They are all within spec. I also looked at the timing (just by counting the links on the chain and using the sprocket markings) and that was correct as well.

I really should have checked the compression as well, but I just figured I would give it a shot and see how it worked as is.

The diaphragms all looked good. I went over them very carefully to be sure there were no tears or holes. The jets, etc. all looked clean as well (looks like they were drained before they were stored), but I gave them all a good clean anyway.

Since my last post, I put in a different set of coils to see if that was the problem. There was no difference and the #3 pipe was still cold. It has a new and fully charged battery, a new igniter, and new regulator (I have a second KZ750 that I got off of a friend that was moving and he was replacing all the electronics at the time).

I may have some time before I leave tomorrow, so I may go borrow a compression tester and see if I can't get the values to you.

Thanks for your time.

I was able to check the compression (stone cold with throttle wide open):

#1 = 110
#2 = 125
#3 = 130
#4 = 125

It looks like #1 is a little low, but it is firing. #3 has the highest compression, and that is the one giving me issues.

I know there are some carb issues, as some are over flowing. I will have to look into that.

Could it be something as simple as a bad plug or plug wire?

Gary

I have all new plugs and the I tried two sets of coils (with different wires). Same results each time. I wish it were that simple! Thanks for the thought.

I have another set of carbs that I am going to try. That way, I will see if it is a carb setting.

If that doesn't make a difference, I will start changing components (igniter, etc.) to see if that changes anything. I will also clean up all the grounds to see if that is an issue.

I just want to ride it! maybe I will get my wife to push me down the road on it.

Over the weekend, I polished up the float needle seats and checked for cracked overflow tubes in the bowls. Well, 2 of them were cracked, so I have fixed those (I have a second set of carbs, so I only needed to fix one with JB Weld).

Once I was done that, I set the service fuel level using the clear tube method. The fuel levels are now where they should be and the flat needles all work well.

I then turned my attention to the electronics. I took the newer igniter and regulator off and put on the originals that came with the bike (remember I have a parts bike that had some newer components on it).

I started it up and bingo! I am running on all 4 cylinders. I still have a mean exhaust leak (I have new exhaust gaskets on the way), but I am now able to rev it it seems to run and idle well.

Here is my new issue: The bike seems to run really well with the choke on, but I can't rev it up with the choke off. It is like it is staving for gas when i turn the throttle (but it will idle nicely with the choke off). It just seems flat when I twist the throttle.

Are these bikes normally cold blooded and take some time to warm up and run well off choke? Could my exhaust leak at the header cause this issue?

Thanks again for all the help on this. I will start a new thread over in the carb section if that seems to be the problem.

I started it up and bingo! I am running on all 4 cylinders. I still have a mean exhaust leak (I have new exhaust gaskets on the way), but I am now able to rev it it seems to run and idle well.

Here is my new issue: The bike seems to run really well with the choke on, but I can't rev it up with the choke off. It is like it is staving for gas when i turn the throttle (but it will idle nicely with the choke off). It just seems flat when I twist the throttle.

Are these bikes normally cold blooded and take some time to warm up and run well off choke? Could my exhaust leak at the header cause this issue?

Sound like you are making great progress
Within an minute or 2 of firing it up you you should be able to reduce the choke to about half. At that point revving should not be a problem. The last 1/4 travel of the choke lever is really just a high idle. These bikes do tend to be somewhat cold blooded and I find it will take 5 - 10 km before fully warmed up.
I dont know if an exhaust leak would cause the latest issue although I kinda doubt it.

My dumb question would be - do you have the airbox on it at the moment and or do you have an air filter in it?

Yes, I feel I am making progress as well. having it on all 4 cylinders is always a good place to be!

I do have the airbox with all the connections and a brand new filter in it. I will have to let it warm up for a bit and see if that makes a difference. I was in a poorly ventilated garage, so I didn't want to run it for too long.

I am assuming the air/fuel mixture screw on each carb has an impact on the pilot circuit only? I have each set up at 2 turns out. I also did a bench-top sync of the carbs, so they should be somewhat in sync.