New member needs best jet choice for (gasp!) Pods.

Hey guys! I'm new here. It's not my first bike, not my first custom build, not even my first KZ, but certainly my first GPZ! I'm going for the dirt tire cafe-tracker sort of build on this bike, and I'm greatly anticipating being an active part of your community!
Anyhow, I picked up this 82 GPZ750 from a KZR member on Thanksgiving and now I'm fighting with it. For $500, I can't really complain I suppose. The short story is that cylinder 2 was either misfiring, backfiring, an intake valve stuck open or burnt or something; where #2 header was cooler than the others, so I put in a set of smaller intake valve shims to open them back up to spec (2 and 3 had 0 clearance), put it back together, and now it won't even start. During that time I also put on pod filters and rebuilt the petcock (which I suspect are the culprits of my troubles).
If I squirt solvent through the carbs it'll fire right up and run for a bit. There is gas in each of the carb bowls. I've pulled one carb apart just to verify the "rebuilt carbs" claim from the PO, and they look pretty good. New jets, clean bowls, consistent adjustments between air screws, etc. I have found but have not used Patton's cleaning method. Yet.
Since I put the pods on, which I did strictly for the cafe-tracker aesthetics I'm pursuing, I've read about how disliked and finicky they are. Considering that numerous people seem to successfully run them anyway, what size jets are you running to make them work? I have 110 mains and 37.5 pilot jets. Also, where are you putting the needle clips? Mine are on the second-from-the-top notch, which would make it run leaner, right? which is contrary to pod filter philosophy?
Instead of doing all the trial and error, on-and-off of the carb to figure it out myself, I know somebody has the answer!
Thanks so much!!

Here is the backstory of the bike in question: Orange GPZ750

Hopefully, someone will have the magic combination for you.

In the mean time, the video below shows how the CV carb works. Notice the throttle valve diaphragm, which lifts the slide and jet needle, is retracted by vacuum in the throttle vacuum passage when the throttle is opened (times 1:20 and 1:58 show this). So the relationship between the movement of the throttle and the movement of the slide & needle may change if there is any leakage in the diaphragm or if the level of vacuum in the throttle vacuum passage is modified by changing the air intake dynamics by modifying the air filtration system.

You may already understand how the CV carbs work, but others reading this may not, so the video may be helpful to someone. At any rate, I believe the issues mentioned above contributes to the difficulty many have in trying to tune CV carbs for pod filters. Ed

Very cool video! So, with that in mind- the skinny tubes that stick down into the bowl casing are, what, choke tubes? And the plugged/capped pilot jet -for idle- is fed up through the main jet, off to the side, and then up through the pilot? I'm trying to wrap my head around what everything does, and that video was very helpful.

Also, on this bike there are two big unplugged tee fittings- between 1 and 2, and between 3 and 4. Are these simply overflow spouts to keep fuel from the crankcase in the event of a stuck needle?

Is there a preferred vacuum connection for the petcock? Use carb 2, plug the other 3?

If you have a choice, stick with the air box. The video is just an example. Good one.

Sean D - if you are not a carb guy, you certainly will have your work cut out for you!

First, your particular bike, and others like it, are very cold-blooded beasts from the factory, and it is no surprise to me that it won't fire with pod filters on it.

I recommend that you set up the carbs right, carefully remove the caps over the mixture screws, so you can adjust your idle mixture, and up the main jets to 115 mains with stock washable air filter, or the 118.5 main jets with a K&N oiled filter.

Then replace the head mounts the carbs are on if they're hard, put the airbox back on, with soft boots, and then start chasing down your problem with cyl. #2.


You've got 30-year-old coils & electronics, so I'd start at the pickup coil, and work my way all the way down the plug wires. My '82 R1 started stuttering when it was hot last summer - turned out to be a coil.

You're in the right place for help - good luck !

Thanks Eric.
It has new Dyna coils on it, as well as new(er) carb boots. Which is the idle mixture screw? The four on the very top forward of the carbs are exposed, and they are 1.5 turns out. Is there another cap somewhere that I need to drill out?
Before I pulled the carbs again yesterday I did get it to idle with the choke all the way on. I also found last night that all four floats were adjusted almost a half inch low, so hopefully that will straighten something out, I'm going to put some new 91 gas in it today as well because the stuff in there could be A: low and B: as old as last summer.

Thanks!!

The mentioned screws turned 1.5 turns out are the pilot adjustment screws where the "non-tamper" caps have already been removed.

The "clear tube test" method is the most reliable means to assure that float bowl fuel levels are within specs.

Good Fortune!

I think fresh 87 oct would work better for you, it burns quicker at lower compression.
JD

I got it running pretty well! After the float adjust with the clear tube and a good poke of a pin through the choke tubes it seemed to work itself out. Starts easily, idles great without monkeying with the idle knob- Other than the throttle cable being too tight and revving WAAAAYY UP making slow right turns, I was able to ride it back and forth across the yard through a few gears. It ran every bit of good enough... to giver 'er a thumbs up, take 'er apart, and start the cutting and welding!
Thanks guys!

THERE YOU GO AGAIN.
Ronald Regan