Jetting for a 4 into 1 exhaust.

Hello all. Thanks to all for such a wonderful site. The wiring diagrams have been invaluable in wiring the gpz 750 gauges to my bike. I've recently purchased a used no name 4 into 1 exhaust for my 1982 kz750 E. The bike is equipped with keihin CV carbs (32mm?), With the stock jetting of 125 secondary mains, 62 primary mains and 35 pilots. The exhaust is baffled, and fairly quiet except for higher rpm wot pulls. The airbox and filter is stock, and I'd like to keep it that way if at all possible. The clean air system has been bypassed as well. The bike ran perfect stock but the exhaust was ugly looking so a replacement was in order.

Riding the bike I can tell the pilot screws will need a bit of adjustment. The idle is stable but popping in decel has come about. Mid-range is ok, a little flatter then with stock pipes. High rpm wot is lean, again not by much as I can still hit 9k fairly well, but it takes a bit longer to get there. I should also mention the bike warmed up in about half the time, again due to lean pilot screws settings.

My question is: since the 4 into 1 exhaust is realisticly all I have done, what jets should I be looking at to help get things running well? I live in Arizona and consequently Id prefer the bike a bit rich much more then lean. Should I be looking at different primary mains too or just the secondary (125) replacements?
Thanks.

You may only need to adjust the pilot screws and shim the needles.

How would I go about shimming the needle? I assume I find a small washer and place it between the needle and the slide? These needles don't have clips so it seems I could only enrich with this method. Thanks.

On mine, popping on decel means you need richer pilot jets. Throttle response in mid rsange tells you if you need to adjust the needls. Weak response means too lean.

I will be shimming the needle tomorrow, definitely tuning the pilot screws as well. I have some baby washers that may do the trick. Ive read through the search function only to find that everyone that has had 4 into 1 typically has pods too. I don't want that. I also don't wanna buy a jet kit if it isn't really needed. I will If I must but Id figure id poke your brains first to see what direction to take. Thanks.

It would probably be best to make only one change at a time, that way if no improvement is made, or if things get worse, you will know exactly what to undo.
Try adjusting the pilot screws first. If that does not cure it, then as Bountyhunter says, larger pilot jets will be needed. Once that is sorted, then you can determine if shimming the needles or larger main jets are called for.

Just a quick update. Went on a late night ride after taking my dog to the hospital. Took the pilots out a quarter turn each and it made the idle worse, like the carbs were out of sync. When I get up tomorrow I'm going to take the tank off and tune each cylinder by ear via a carb sync and idle screw adjustment. A wot pull from dead stop reveals a very sluggish ride up to 3 to 4 k, then an ok response to redline. Not fantastic but man the sound of this pipe after 6k is pure gold. I will post when and if I get the low end straightened out.

Oh, almost forgot. Here are some images of the pipe. The opening doesnt look that big to be honest. Jetting may not be necessary since richer pilots made it worse. Also a picture of the dog .

I have my 1980 kz750 E1 for going on 15 years now. It has Keihin CV34 carbs If you are going to play with the carbs then first thing i would suggest is to check the fuel service levels using clear tube method ( search here) and adjust all to the required 4 +/- 1 (?) mm. That was the single best improvement i made with carbs

With a Mac into 1 exhaust mine ran well with 130 secondary main. Cant shim the needles and i never bothered with washers
The #35 pilot is the only size available
Pilot air mix screw was 2 turns out from lightly seated.

I put a new Delkevic 4 into 1 on recently and had some popping on decel. Opened pilot air mix screw to 2.25 turns out and much better. Am keeping an eye and ear on it and if nesessary might go another 1/8 turns out on pilot air mix screw.
Plug colour is now just a smidgen on the rich side of normal

Hope this helps

Thanks to everyone for posting their experiences. I've readjusted the idle by checking float levels (which were still spot on), resyncing using my homemade bottle manometers ( far left cylinder was a bit out of sync), and adjusting each pilot screw until a smooth idle was achieved. I'm happy to say the low end is pretty well perfect, from take off to 3/4 throttle. The top end at full throttle is better now, but since the temp outside is about 105 vs 79 of last night's terrible riding, more tests may be needed at different temps to see if I need to bump up to a 127.5 or 130 main. Responsiveness on anything but the very tippy top is great.

I ended up purchasing 130 genuine keihnin mains after another midnight ride. The bike is in drivable condition, but given the PO's statements of wheelies galore I think more fuel at the top end won't hurt anyone. If the 130s don't pan out (I doubt they won't), I'll post again. I'll try to return the favor by helping. Thanks again.

So, just as a last update, I've installed the 130 secondary mains about an hour ago. Top end cleaned up perfectly. half throttle as well. Idle is still crap. I feel my tuning ability has reached an end, and maybe a colortune spark plug is necessary now? Anyone care to chime in?