KZ750-Tune for redline

Patton wrote:

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.

The baffle is in the pipe, but is about 5 years old. Noticeable louder and I am not sure what effect this would have on performance if any.

I haven't done a plug chop. I can wind the bike out in 3rd, 4th with no problems but not in 1st and 2nd. I get the same "flattening out" as before when I am whacking the throttle, but just less now with the inline filter removed. I can wind out 1st and 2nd if I am slower to twist the throttle. Very annoying.

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

Only if you do the same for me.:silly:

guitargeek wrote:

Are you running Keihin or Mikuni carbs?

Keihins; 2 turns out on the air screws, secondary mains bumped up 2 sizes from 125 to 130.

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

That's my plan.

Now I need some good riding weather. It was 25 degrees today when I left for work!:blink:

Was thinking maybe whacking open throttle is contributing to over-fueling (perhaps inciting a gurgling running condition), and that open baffle better withstands larger mainjet size. If easily removed, might do a test-run experiment without baffle. And another test-run also without air-filter. All with the idea of minimizing effect of a possibly too large main jet. Wouldn't harm anything and might afford some diagnostic clues.

But am pretty sure the high speed plug chop test is best indicator for correct main jet size. As known, black sooty plugs usually indicate need for smaller main jet size.

Perhaps irrelevant, but my 1967 twin-Amal-carbed 650 BSA would scream with unbaffled reverse cone megs; however, with the stock mufflers, would began to "gurgle" (8-stroke?) at wide open throttle positions, which I attributed to same main jet size being too large with the stock baffled muffler.

Good Luck!

Patton wrote:

Was thinking maybe whacking open throttle is contributing to over-fueling (perhaps inciting a gurgling running condition), and that open baffle better withstands larger mainjet size. If easily removed, might do a test-run experiment without baffle. And another test-run also without air-filter. All with the idea of minimizing effect of a possibly too large main jet. Wouldn't harm anything and might afford some diagnostic clues.

Good idea. It would not be too hard to remove the baffle or the air filter. More to try if the cleaning I did did not work out as I am hoping.

But am pretty sure the high speed plug chop test is best indicator for correct main jet size. As known, black sooty plugs usually indicate need for smaller main jet size.

I will have a look next I am out with bike.

Perhaps irrelevant, but my 1967 twin-Amal-carbed 650 BSA would scream with unbaffled reverse cone megs; however, with the stock mufflers, would began to "gurgle" (8-stroke?) at wide open throttle positions, which I attributed to same main jet size being too large with the stock baffled muffler.

This is not the first I have heard of this. Do you still have to bike? Any pictures?

The bike revs great until 8000rpm in 1st and 2nd and to 10K in 3rd and 4th.
Could be rich, could be lack of gas, could be jet size. I won't have another opportunity to test the bike until next week. More then.

Well, I had few minutes yesterday to take the KZ out for a spin. In my haste, I forgot my spark plug wrench so, no plug chops. :pinch:
As for the performance, it is the best to date. The flat spot in only in first and around 9000rpms. It did not make any difference revving the bike up with the petcock on "on" or "prime" with the fuel tap open or closed. So that's great news.

Anyone know how long or if a mechanical tachometer can lag behind actual RPMs? I wonder if my tach can't keep up with the motor spinning. Perhaps I am reaching the top? Or am I dreaming?

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?


If this is the case that it performs better in 4th and 5th, than it makes me feel that fuel restriction is not the main issue.

I experienced the fuel flow problem, and had fine performance in 1st, 2nd, and 3rd; 4th and 5th gears would experience the starving....

This seems to be the opposite of what he is experiencing.

Regardless, it would be a good thing to re-inspect as many components pertaining to the flow of fuel as you have time and patience.

Do you have anyone in the area that might have or be willing to lend for a "test" a set of carbs to see if that changes anything? If you were in the Seattle area and our carbs were compatible, I would meet you and pull them off for a couple of beers. Just a thought.

Could there be another cause that is not carb related? Intermittent spark for instance? Could be an electrical connection that fouls during heavy high torque lower gear acceleration that doesn't experience the same stresses in the higher gears. Coupled with a separate fuel flow problem.