TOPIC:

I have a question regarding the vaccume that runs from the fuel petcock to the carbs. Most of my vacuum ports on the carbs are capped off except #3 which goes to the petcock . When I was draining my tank last night fuel was running out of the vacuume port on the petcock. So it has to be sucking fuel, I pulled the #3 spark plug and if was wet. What do you just think? Suggestions comments?

Cracked diaphragm in the fuel tap.

Cap off the line at the carb and the petcock, run it until you get and install a rebuild kit in the petcock.
Steve

Very common for that diaphragm to leak fuel into the vacuum port on the carbs. Rebuild kit or replace the petcock with a new one.

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Steve

the rebuild kits you posted is what i used and it failed. you guys are right, it looks like that diaphragm was split. so i capped off my #3 vacuum port on the carb and capped off the vacuum on the petcock. the bike fired up ok. but that starved for fuel and died, im assuming ill have to run it on PRIME since theres no vacuum in the ON position?right?

it also seems that my #3 cylinder and spark plugs are still getting washed with fuel, the cylinder and plug is still getting wet( sticking float?). i have to change the oil because god knows how much fuel it was sucking.

My #4 also seems to have a popping back fire thing happening.no cracks in the boots.

Bike Specs:
81 kz750e
individual filters
4-1 V&H exhaust
stock keihin carbs
DynoJet stage 3 jet kit
#65 primary
secondary#138
pilot #35
needle is on #4 groove
and fuel mixture should be about 3 1/2 turn out from seated
as instructed by dyno jet

to lean? to rich? i live at 500ft elv.

my float was set to 21 +- 2mm

also tonight after i had the bike running for a while, i could hear a vacuum though my gas cap when the bike was off? like maybe it was still sucking gas?

i really appreciate the help! i under stand carbs but my head scrambles when it comes to diagnosing issues.





cheers
Eric

Clear tube test on the carbs. Clean the vent in the tank cap.
Steve

i will get are around to the clear tube test soon. i've done it once before, id like to know what size jets are commonly run with an 4-1 exhaust and pods, i dunno if its running to lean/rich?

any ideas on what would cause a small back fire in a carb?

with out vacuum i have to run in PRIM right? im thinking as long as the floats are right there should be no problem.

gixxerkidd03 wrote: i will get are around to the clear tube test soon. i've done it once before, id like to know what size jets are commonly run with an 4-1 exhaust and pods, i dunno if its running to lean/rich?

any ideas on what would cause a small back fire in a carb?

with out vacuum i have to run in PRIM right? im thinking as long as the floats are right there should be no problem.

Main jet size governs mixture at WOT.
Negligible influence on mixture at less than WOT.
Would use size that produces best spark plug reading via throttle chop test.
A 1 or 2 size larger than stock main jet is often used with 4>1 and pods.

Jet needle clip position governs mixture throughout mid-throttle range.
The stock clip position may be okay with 4>1 and pods.
Could experiment with richer clip position.

Pilot jet size governs mixture at idle and low throttle range.
Tuning and testing should be done only with perfectly clean "as new" pilot circuits.
If have steady idle and strong pull-away, size is likely okay.
Might test run with 1 or 2 size larger than stock pilot jet with 4>1 and pods.

Backfire through carb may result from too tight intake valve (insufficient clearance), where combustion partially escapes through the imperfectly seated valve.

With perfectly functioning float valves and floats, and fuel level within specs, and no fuel leakage from any other source, running with petcock in PRI position should be okay. Would take necessary steps to stop fuel flow into carbs whenever the engine isn't running, such as when the bike is parked.

If not already done, would install a good aftermarket in-line fuel filter.

Good Fortune!

IMPORTANT; Don't jump around, one thing at a time. Timing correct, valves correct, pilots working, mid range burning well then WOT. The main jet will have a influence on mid range so start with stock settings then work up if needed.
Steve

If you choose to rebuild the petcock instead of replacing it I strongly suggest you purchase the needed parts from Kawasaki. K&L rebuild parts are spotty quality at best.

Nessism wrote: If you choose to rebuild the petcock instead of replacing it I strongly suggest you purchase the needed parts from Kawasaki. K&L rebuild parts are spotty quality at best.

yea K&L is what failed me .

i think my jetting and sync its pretty solid. i rode the bike for awhile and i was pretty happy with the power range. Now weather or not i have a float height issue on my #3 thats another thing . i currently keep the bike at a buddies because its the rainy season here in the PNW and i live in an apt at the moment, so i can just go tinker, which is killing me.

Few things im Think at the moment:

im going to clear tube test the float hight, if it checks out, im going to recheck for spark on that hole, Im thinking i have a fouled spark plug due to the excessive fuel it was getting, maybe thats the reason that cylinder is still getting soaked?

i got new plugs, oil and filter today and tomorrow ill check.

not sure why im getting a little backfire on #4, but im hoping a little tinkering with the air/fuel mixture may smooth that out.

im going to grab a new fuel cap because my seal is old and cracked
and fully charge and load test my 1 year old BikeMaster TruGel battery.
it sounds really weak when i try to start it sometimes (could it be from #3 ,misfiring or not firing at all?)
i recently did the lovely starter clutch job and a starter

sorry im all over the place

thank for the replies guys

Eric