Effect of larger jets on GPZ 750

The 82 GPZ 750 is a notoriously cold natured beast. It takes forever to warm up. Is this due to the size of the pilot jets? If I am rebuilding the carbs, is there a better solution?
What would be the effect of larger pilot jets?
what would be the effect of going up from 110 main jets to 115 main jets? I know the main jets come into play at throttle.

I have read the carb specs on both the KZ1000J and the GPZ 750 wich use the same BS34 carbs. The only difference I see are the larger main jets on the KZ1000J. the 1000 jets are #122. The pilot jets appear to both be #37.5

All feedback is welcome on this. I am doing a carb rebuild as we speak.

I had the same cold start issues with mine. What helped the most I think was adjusting the valves. Also, when going thru the carbs pay special attention to the enrichment circuit including the well in the carb bowl.
As for jetting I am at approx 1,000 ft above sea level and run 40 pilots and 130 mains. I also used a Colortune to adjust the fuel screws. It has never run better. It should be noted I also have a Kerker 4 into 1 and a modified airbox with a K&N.
Good luck,
JIm

Also, On the idle air mixture, what is the factory setting? Is it 2 1/2 turns out or 1 1'2 turns out? Thanks

For me, the idle mix screw setting is the one it runs best at, often between about 1.5 and 3.0 turns.

I never thrash these when cold, so a mile or so running a bit lumpy from cold is no big deal. Tolerate it as a common trait of the earl GPz's

Upjetting your main jet two sizes is not the way to go. I'd balance carbs first then and set your airscrews up as best you can, if that and a thorough carb clean doesn't make a change then maybe try lifting the needle a notch.

Not to get overly critical but the adjustment screw is not an air screw rather a pilot screw. They do different things.

Not sure this will hep you any or not but I have access to a GPZ750 FSM and here are the supplement pages related to the carbs on the 82 Mikuni BS34s. They do not indicate what the stock setting is. They do list it for the models that came stock with Kihein CV34s but not the for the Mikunis?????

Thank you for the answers. I am staying stock, as far as the jetting is concerned. I do however want to know the stock number of turns out on the idle/air mixture jet, 1 1/2 turns or 2 1/2 turns.
as far as the change of jetting on the main jet, I simply wanted an objective answer on the effect. REPEAT, I am stating stock, I do not have to be convinced on what jetting I should use in my case. I just want to know what the overall effect would be.

I am now about to reassemble my carbs. The sir mixture screws had a lead cap covering them as per the E.P.A. so that they wouldn't be tampered with. Is it necessary to replace the caps or can I run without the caps. They are a pain to get back in !!

When I rebuilt my carbs I set them at 2 turns. After I put on a ZR7 header with a Kerker can I readjusted to 3. I left the plugs out.

not the gpz, but similar motor i would assume? im running uni individual pods and the vance and hines 4to 1.... mine are set at about 3 turns out each.... i believe stoxk settings can vary, but are normally considered to be around 1.75 tp 2 turns out... hope that helps???

My '83 1100 had 37.5 pilot jets and even at 3 turns open the bike still needed a lot of choke to get going from cold, even in summer. I set the idle mixture based off how much choke it takes to start, much more than a few jabs of choke and it's too lean on the idle mixture. I went to 40 pilot jets and three turns open and the motor is stronger off idle now, noticeable harder pull from a standstill, and needs only a slight touch of choke to be running smoothly after a cold start. All early '80s bikes were too lean stock, and the ethanol enhanced fuels today make that even worse.

DGA wrote: All early '80s bikes were too lean stock, and the ethanol enhanced fuels today make that even worse.

Yep. Even bone stock you will likely benefit from a larger pilot jet. You can leave the main jet alone unless you are changing the airbox or exhaust.
I believe your original concern was cold starting. Check your enrichment circuit top to bottom and make sure that is working correctly. It's easy to miss something.

From my experience, there is not such a thing as recommended turns for mixtures idle screws.
You must start your engine, let it warm for 5 minutes or go and ride a few blocks. Once the engine is fully warm at normal operating temperature; adjust the mixture pilot screw to achieve the highest idle RPM possible. Then turn the idle RPM screw back to maintain 1100 RPM. Do this on each carburetor. Now you are good to go.

If there is no change in RPMs and the mixture screw are out more than 3.5 turns, then your pilot jet is too small. Go up one size and try again.