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Effect of larger jets on GPZ 750
- Jrider
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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.
1982 Kawasaki KZ 750 R , Stock
2007 Harley Davidson Police Electraglide
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- ThatGPzGuy
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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
Jim
North GA
2016 Yamaha FJR1300ES
1982 GPz750 R1
1974 Kawasaki H1
1976 Kawasaki KZ400
1979 Yamaha XS650 cafe'
2001 KZ1000P
2001 Yamaha YZ426
1981 Honda XR200 stroked in an '89 CR125 chassis
1965 Mustang
1967 Triumph GT6
1976 Bronco
"If you didn't build it, it's not really yours"
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- Jrider
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1982 Kawasaki KZ 750 R , Stock
2007 Harley Davidson Police Electraglide
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- Tyrell Corp
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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.
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces
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- gd4now
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- Denco where did you go?
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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?????
1977 KZ650 B1
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OLD KAW OWNERS SMILE ALOT
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- Jrider
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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.
1982 Kawasaki KZ 750 R , Stock
2007 Harley Davidson Police Electraglide
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- Jrider
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1982 Kawasaki KZ 750 R , Stock
2007 Harley Davidson Police Electraglide
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- GPzMOD750
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- Randombeat
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1980 KZ750H LTD-- pods-- vance & hines 4-1 --speedo/tach/blinker/switch deletes -- brat style
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- DGA
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"83 KZ1100 Spectre, '81 Yamaha XV750 Cafe, '74 Kawasaki H2B 750
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- ThatGPzGuy
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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.DGA wrote: All early '80s bikes were too lean stock, and the ethanol enhanced fuels today make that even worse.
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.
Jim
North GA
2016 Yamaha FJR1300ES
1982 GPz750 R1
1974 Kawasaki H1
1976 Kawasaki KZ400
1979 Yamaha XS650 cafe'
2001 KZ1000P
2001 Yamaha YZ426
1981 Honda XR200 stroked in an '89 CR125 chassis
1965 Mustang
1967 Triumph GT6
1976 Bronco
"If you didn't build it, it's not really yours"
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- undiablo
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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.
Kawasaki KZ 750/4 LTD 1981
Kawasaki KLR 650 2011
Argentina - Buenos Aires
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