KZ750-Tune for redline

Here is the UNI website. It seems like mostly dirt bike and off road stuff. Below is a graphic showing the increase in power from stock to there foam filter. Of course, we don't know the bike this is on or the conditions as well as whether this is universal or just for this bike. The website does say that rejetting will be necessary for high air flow.

UNI's Filter Website

Anyone know what the "Twin Air" filter is?

cafekz750 wrote:

Here is the UNI website. It seems like mostly dirt bike and off road stuff. Below is a graphic showing the increase in power from stock to there foam filter. Of course, we don't know the bike this is on or the conditions as well as whether this is universal or just for this bike. The website does say that rejetting will be necessary for high air flow.

UNI's Filter Website

Anyone know what the "Twin Air" filter is?

By eye, it looks like the difference is less than one HP. I wonder if that big improvement is still there after you soak the foam in that gooey red stuff you need to run to trap the dirt? That will affect airflow a lot, probably more than the open cell foam itself.

cafekz750 wrote:

I rode the bike today to work so on my way home I will try to rev the bike to up to 10000rpm slowly and again by whacking the throttle. This way, I will know for sure that this is what is happening.

It was pouring rain as I left work so perhaps tomorrow or next week.

If you think you have a fuel flow problem, it might be a good idea to check that your gas cap is venting properly.

I was able to take the bike out last night to check the flow vs jets issue.

I was able to rev to 10000rpm in 1st, 2nd and 3rd if I went slow and steady with opening the throttle.

If I yanked the throttle open, the bike would flatten out around 8000rpm and not run on all cylinders.

I removed the fuel filter (an alloy bodied Russell brand) and cut a new piece of fuel line. The line now runs straight from the petcock to the carbs. I won't have opportunity to test it out until tomorrow evening at the earliest.

On a side note: the bike had the original fuel line on it until I just replaced it. Does the "T" on the carb where the fuel flows into supposed to be able to pivot front to back?

cafekz750 wrote:

On a side note: the bike had the original fuel line on it until I just replaced it. Does the "T" on the carb where the fuel flows into supposed to be able to pivot front to back?

Yes the "T" should pivot.

Well, last night I was able to take the KZ out for a spin. I installed brand new 5/16" fuel line without a fuel filter .
I revved the bike up to 10000rpm slowly in 1st, 2nd, and 3rd with no problems.
I whacked the throttle and 1st went to 10000rpms but 2nd flattened out around 8500rpm then kick in and out.
So, better than before, but not where I want it to be. I tried again a few more times with the same deal happening in 1st and 2nd but not as bad with the filter removed.
I opened the gas cap and launched the bike. The same thing happened as before (except a large whiff of gasoline being directed at me).
So, it's better now but I am not quite satisfied with it.
The flattening out phenomenon only happens in 1st and 2nd. 3rd, 4th and 5th are fine. I am guessing it is a matter of gearing allowing the engine to spool up faster, ideas?
I was able to get to 9200rpm in 5th, but no further. The throttle was pinned. When I began to release the throttle the bike picked up another 100rpm. What's the deal?
All of this "testing" is leaving its mark on my rear tire (though I should get good mileage out of the front).
So, jets? What jets? Or is it the stock petcock? Suggestions appreciated (I have a new back tire in the garage for when testing is complete).
A picture of how the bike sits as of last night, cooling off from "testing".

So, better than before, but not where I want it to be.

Then it seems we're on the right track

Have you checked the inside of the petcock itself to see if there is any buildup in the out port? How about the carb inlets? I have seen buildup in the carb inlets that restricted fuel flow. It seems to me that the float bowls are emptying, as in not enough fuel getting to them at the rate you are using it.

I have not inspected the petcock since last year in May. It was clean looking, but at the time I was removing it for other purposes. I will have to check that out.
And varnish on the carb inlets. Do you mean were the fuel flows into the carbs from the fuel line or the needles and seats?

You know what I did, right...I filled the fuel tank after the ride, so I have 1.5 miles on a full tank. I really dislike draining the tank but the weather here is going to be non-riding weather for about another week and half so...

Do you think that my jetting is okay for what I am running?

This weekend I drained the gas from the tank to inspect and clean the petcock.
I noticed that when I had the fuel cap open, gas flowed faster from the petcock in the "Prime" position. So, I decided to clean the fuel cap as well. There was a little varnish but not much in the cap/vent. The petcock was clean, screen in good shape and no debris in the tank. I cleaned up the petcock anyway and reassembled the bike.
My plan is the following stopping with what works:
1. Test with the petcock in the "On" position and the fuel cap closed. (Normal riding)
2. Test with the petcock in the "On" position and the fuel cap open.
3. Test with the petcock in the "Prime" position and the fuel cap closed.
4. Test with the petcock in the "Prime" position and the fuel cap open.
If none of this works, then on to the carbs (which appeared to be clean when I put the new secondary mains in about month ago).
Now I just need the weather to cooperated with me.

Maybe I overlooked it, but are baffles being used or open meg? And has a high speed plug chop test been done, and if so, what plug readings are seen? Could be thinking backwards (no surprise there :lol: ) but if plugs are real sooty, performance might improve with a smaller main jet, especially if exhaust is baffled.

And tell the men in white suits you haven't seen me.

I think you're on the right track, looking for fuel flow issues. You want to take the gas cap apart periodically to clean and lube it anyway, so this gives you an opportunity to make sure that's not part of the problem.

Are you running Keihin or Mikuni carbs? When I switched to Mikunis I took them apart to give them a good cleaning and noticed that they have little screens at the fuel inlet to the float bowls, and three of mine were full of trash.

Also (obviously) once you've gotten this problem sorted out, be sure to put that filter back inline!