kz750 twin performance upgrades

more like time to download a manual.

gumby prichard wrote: you mean cross over as in 2 into 1? cause that's what i have.

nope. The stock pipe is 2-2 with a crossover at the front and that crosover increases low end torque.

gumby prichard wrote: but wouldnt you get better airflow with a 2 into 1? being that they meet at an angle which both tubes are being forced in the same directing rather than having to turn at a right angle? idk maybe not

A well tuned 2-1 will give better flow at mid and high RPM for a bit more HP, but the 2-2 with a crossover increases low RPM torque.

right on. i just hate the look of the 2-2.

ok when mine idles it sounds a whole lot like this.... is this normal? i though cv carbs kept it at a consistent idle.

It's idling too slow for one thing, supposed to be 1000 rpm. Mine idles a lot smoother than yours. I doubt it will ever run perfectly with straight pipes and pods on it.

but the thing is, mine has stock airbox, but currently no muffler, i plan on putting a supertrapp on it. but basically this idling is normal? my kz400 only idled like that when i had a 2 into 1, mechanical slide carb on it. Any explanation?

it also backfires every now and then while idling and backfires more often when you try to step on the gas while driving.

gumby prichard wrote: it also backfires every now and then while idling and backfires more often when you try to step on the gas while driving.

The sound from listening to the video is consistent with suggestions as to ignition timing and functioning of the timing advancer.

The rather nice sound at idle morphs to something more anemic when cracking the throttle, similar to what might occur if the advancer is hanging in the retarded idle position. Would view the advancer function under a strobe-type timing light. And check alignment of the F mark at idle rpm. Being certain of correctly identifying the F mark, not the letter F, and not the letter T, and not the T mark.

Backfiring under acceleration may result from insufficient valve clearance, especially where an intake valve fails to fully seat, which allows combustion within the cylinder to escape through the intake port and on through the carb.

Good Fortune!

I keep meaning to look up how to check these valves without having rockers, but i forget. im assuming you just check the clearence between the lobes and the valves whaile in top dead center....but i guess it chould look it up to be sure, never worked on a DOHC :S

ok guys, tried to do a little trial and error, messed with the timing advance, got it idling without backfire, then tried to ride but when i gave it gas it immediately began backfiring bad, then would idle good, so i pulled the plugs, tested, noticed cyl 1 plug was not firing, tested in both sides and seems plug was either fouled or just bad. cylinder 2 was extremely lean...idk how. currently i am running stock jets, put the stock pipe on for now and running airbox. so i had a few br8es, threw them in drove down the road and it ran great for the first minute, then suddnly began backfiring, then started running on 1 cylinder, then died, luckily i was able to squeeze some life out of her and didnt have to push her far this time. she eventually died before i got back. then i got back pulled the plugs an now noticed cyl 1 was extremely lean and 2 seemed a little black but not bad. im so confused. i should probably just check valves then go from there.


anyone wanna give me a heads up? are the shims on top or under the buckets?

gumby prichard wrote: so i pulled the plugs, tested, noticed cyl 1 plug was not firing, tested in both sides and seems plug was either fouled or just bad. cylinder 2 was extremely lean...idk how. currently i am running stock jets, put the stock pipe on for now and running airbox. so i had a few br8es, threw them in drove down the road and it ran great for the first minute, then suddnly began backfiring, then started running on 1 cylinder, then died

The plugs on a twin are wired in series. If one fouls, usually both stop firing. If one is firing and one is not, it's more likely a carb problem. That "runs great then suddenly starts backfiring" reminds me of when mine had crud in the tank getting into the main jet. Then it would wash out and run OK for a while then do it again.

Has your tank/petcock been thoroughly cleaned?

Good inline fuel filters?