VM28 w/pump, needle jet swap

  • KzEnormous
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VM28 w/pump, needle jet swap

13 May 2025 13:45
#912404
I have 1980 kz1000 ltd with Makuni VM28's with accelerator pump. It's a California bike, which means the original needle jet's are not adjustable(only 1 clip position) 
I picked up new needles (5d131) adjustable, and new needle jet sleeves(bleed pipes) Besides, possibly the main jets, are there any other parts that I would need to change for this to work correctly ?
1980 Kz 1000 Ltd -
Currently in resurrection
1980 Kz 440 Ltd -
Waiting for attention, possible sale or part out.
1982 Kz 1000 -
Part donater, sale or scrap metal
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  • asphalt900
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Re: VM28 w/pump, needle jet swap

14 May 2025 04:46
#912418
If memory serves me correctly, ALL 1980 VM28 pumpers had non-adjustable needles. Not just California. Adjustable jet needles ceased after the 1979 model year, at least US models. I believe Canadian/other countries still used adjustable though.  

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  • KzEnormous
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Re: VM28 w/pump, needle jet swap

14 May 2025 12:28
#912436
After a little more digging, I believe you are correct. Looks like there were a few changes in 1977, then again in late 1979. The 1980 models were the first non adjustable needles. Canadian models however, as you said still had the adjustable type. There's so many crazy policies in California politics, emissions being on the list.
California - the only state in which you can legally change your gender but not your muffler.

 
1980 Kz 1000 Ltd -
Currently in resurrection
1980 Kz 440 Ltd -
Waiting for attention, possible sale or part out.
1982 Kz 1000 -
Part donater, sale or scrap metal

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  • gd4now
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Re: VM28 w/pump, needle jet swap

14 May 2025 12:37
#912437
I agree with asphalt regarding non adjustable needles, washers can be used to make them act like they do have some. But beyond that what is it that you are wanting to do. Do you intend to set the carb set up like a non pump set, by turning its function off? You ask what else if anything needs to be changed for this to work correctly. Did the stock settings not working correctly? 
1977 KZ650 B1
Pods and Denco header


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  • KzEnormous
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Re: VM28 w/pump, needle jet swap

14 May 2025 13:13 - 14 May 2025 13:15
#912444
Back in the late 90's, on the hunt for the "free lunch" I removed the airbox from my 1980 Kz1000 ltd and switched to pod filters hoping to get a few more hp from the bike. I already had Kerker header and pipe so along with the pod's I did some jet changes and added a nylon washer to raise the needle. It all worked out pretty well. I later removed the vm28's and ran the  33mm smooth bores I had my Gs1100 while it was non-op while doing work on it. The smooth bores really woke the Kz up. I took apart the 28's for a rebuild..... time goes by and bike sits for 15+ years. I recently got back on the project. When I found the carbs in a box, still dismantled,  the needle jet sleeves were missing. Don't know how or why. Following asphalt900's advice I was able to locate new sleeves. Then I thought might as well get adjustable needles also. Which I got from the same source as needle sleeves. All good. 
My question, (not clearly stated) was/is,  what else, if anything would need to be changed with needle, sleeve swap? I didn't know if I was overlooking something. 
For example, a different o-ring because the sleeve was different. Etc.
1980 Kz 1000 Ltd -
Currently in resurrection
1980 Kz 440 Ltd -
Waiting for attention, possible sale or part out.
1982 Kz 1000 -
Part donater, sale or scrap metal
Last edit: 14 May 2025 13:15 by KzEnormous.

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