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1980 KZ750G (Ltd, twin, whatever) weird lean condition, maybe? I'm flummoxed 20 Sep 2023 07:48 #889560

  • Nessism
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You might want to check the "things to know" thread linked in my signature.  It lists items to check when first purchasing a 40 year old machine. 

This site has the factory service manual for your bike.  You might want to download it.

Then, catch up all the maintenance.  Looking at the parts fish on Partzilla.com, suggests your bike has points.  That would be one of the first things I'd check.  And while in there, make sure the mechanical spark advance mechanism moves smoothly.  

Cleaning the carbs involves a lot more than just replacing old jets.  In fact, there is no reason to replace jets, just clean them and reuse, assuming they are the proper size and type.
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1980 KZ750G (Ltd, twin, whatever) weird lean condition, maybe? I'm flummoxed 20 Sep 2023 09:10 #889561

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Thanks guys.

I've rebuilt the carbs (and top end) of my CB a few times, so I am a bit familiar, i just have a dearth of time lately. Ill face reality and pull the carbs and open them up and do a full clean, then find out if i need to order jets and needles. That video will be a big help.

Anyone know if theres a way to identify needle size? I can save myself some money and only buy what is out of spec instead of replacing everything with known good sizes.

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Last edit: by DustinMyEye. Reason: Clarity

1980 KZ750G (Ltd, twin, whatever) weird lean condition, maybe? I'm flummoxed 20 Sep 2023 09:15 #889562

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Oh, and I'll check the points as well. Might as well verify the timing while I'm at it, if I can find my timing gun.

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1980 KZ750G (Ltd, twin, whatever) weird lean condition, maybe? I'm flummoxed 20 Sep 2023 10:27 #889563

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You might want to check the "things to know" thread linked in my signature.  It lists items to check when first purchasing a 40 year old machine. 

This site has the factory service manual for your bike.  You might want to download it.

Then, catch up all the maintenance.  Looking at the parts fish on Partzilla.com, suggests your bike has points.  That would be one of the first things I'd check.  And while in there, make sure the mechanical spark advance mechanism 
 
far too sensible to be bad advice, man. 

Okay, I made a work list. I'll report back.
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1980 KZ750G (Ltd, twin, whatever) weird lean condition, maybe? I'm flummoxed 20 Sep 2023 14:39 #889569

  • TexasKZ
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The stock jet and needle information is on page 114 of the fsm. The markings on the jets and needles will be really tiny. A magnifier will be a great help.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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1980 KZ750G (Ltd, twin, whatever) weird lean condition, maybe? I'm flummoxed 23 Sep 2023 08:26 #889671

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Several things to look at;
750G has unique, 1 year only pilot screws. They have a step instead of the long taper. Rebuild kits I have seen do not have the correct pilot screw

G uses unique one year only needle 4HL14. If carbs were rebuilt with aftermarket kit they typically use generic needles that are different. I can’t recall but I think the G did not have groves in the OEM needle. 

I have seen the wrong float jet size provided in a rebuild kit as well. OEM is 2.5

The G was jetted quite lean from the factory. Going up on pilot jet and main is recommended.

BS carbs are not the greatest design. The jets are in the float bowl
 

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Last edit: by DoctoRot.
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