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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 17 Feb 2021 15:55 #843616

  • johnmull
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Thank you for the ideas. I will pre-fit them and see how it fits. Definitely make sure it is not covering those openings. The current pods from the repair guy where simple thin foam and plastic ends. I would have left them alone but they were less than cheap. I am a K&N fan. Had them on my sports car years ago. I will look for 3/4 throttle bottoming out as a guide to change the Moxi filters. Bike owner (son-in-law) unlikely to be using this bike at high speeds to notice. Maybe 65mph at best, I hope not the 155mph top end. There are many other safety concerns on this bike, if he goes that fast. I think his helmet is a 1960's Bell. This is a town cruiser bike.

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 17 Feb 2021 16:11 #843617

  • zed1015
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johnmull wrote: . Bike owner (son-in-law) unlikely to be using this bike at high speeds to notice. Maybe 65mph at best, I hope not the 155mph top end. There are many other safety concerns on this bike, if he goes that fast. I think his helmet is a 1960's Bell. This is a town cruiser bike.


I wouldn't worry too much.
Unless it's got a turbo strapped to it you won't get anywhere near that.
Brand new they barely touched 120 mph.

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 17 Feb 2021 20:57 #843633

  • johnmull
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Many thanks to Mikaw and Zed1015 warning me of the Moxi pods. Pictures attached. Those cover the side ports. The original INA pods have a narrow edge to not restrict the air flow. The Moxi has a thick rim. I tried to cut/trim the edge down on one of them but unhappy with the results. Safer to use the original INA. I was just trying to jazz up this some.

pod on the left is the Moxi and pod on right is the INA with a thin edge. INA was the original podsthat I was saying cheap, etc. Now I'm eating my words and saying....oh they are wonderful.
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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 17 Feb 2021 21:00 #843635

  • johnmull
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Some more pictures. Top view of the Moxi. There is a gap of about 1/4 inch from edge to the back rim but that makes air curve into the port. Even cutting the edge to make it slow had similar

Anyway, lesson learned. $25 could have bought me some beers.
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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 19 Feb 2021 16:51 #843741

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Carbs reinstalled. Previous owner's INA pods used because the Moxi new ones seem to cover the intake holes. Chicago temps cold 20 degrees in the garage/shop. New rubber intake boots. I replaced the Phillips JIS screws with Alan headed screws. Much easier to tighten. Used zip-ties to support the back end of the carbs since it is missing the standard air box.

Engine started with a little priming and work. No gas leaks out the bowls. Gravity fed fuel line. Choke full on at first, then backed down part way. Engine popped a lot. Had a hard time idling when warmed up some with out stopping. After running at 4k rpm (where I could get it) and going through a 1/2 pint of fuel, I used some Mystery oil deluted through the system. Sometimes I use Sea Foam just to "oil" it up some. I knew it had a lot of wd40 inside. Then I go back to regular 87 fuel. Popping stopped/slowed down some. I think cyl4 is too lean. I controlled throttle with the choke lever. If I tried the throttle grip twist, the engine bogged down regardless how slow I turned the throttle.

Engine got hot without much air flow. cyl1-250, cyl2-250, cyl3-300, cyl4-600. Seeing that, I shut it off and check plugs. Plugs 1 and 2 looked pretty good. Not carboned up and a little wet on both. Cyl3 a bit lean (maybe perfect) with the to ground electron wire white on the tip. Rim was white dry. Cyl4 was white across the full top of the ground electron wire. White and dry on the rim. Sorry no pictures.

Think cyl4 was lean (temp high, white on full tip), I turned out the fuel mix screw. "Out" to me is turning-to-the-left. It is a pointy fuel screw close to the engine. So I think that will put in more fuel. Anyone....correct? It was originally 1 1/4, it is now 1 1/2 turns out. I did not change cyl3. Screwdriver doesn't fit under the carb. I have an old one to cut up.

Picture added. The fuel mix screw I turned out is the top one.
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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 19 Feb 2021 19:38 #843752

  • TexasKZ
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Reads like a classic case of clogged pilot circuits.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 19 Feb 2021 21:23 #843755

  • Kaylinator
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Correct. Out to enrichen. Without pictures, I would probably give cylinder 3 a 1/8 turn out to match cylinder 1 & 2.

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 22 Feb 2021 15:42 #843893

  • johnmull
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Made some changes. Pictures of plugs attached.

Prior status was cyl4 extra hot and lean. I started over and pulled the carb off and boots. The rubber covering cyl4 vacuum test brass was loose and likely leaking. I removed the boots, changed the rubber vacuum covers to new rubber, used RTV on the brass that inserts in the boot. Should be no leaks now. Picture of cyl1 boot. All boots got new rubber caps.

I did not change the needle height or the main jet of 97.5 but I reset the fuel mix screw. cyl1, now 1 1/8, cyl2 now 1 1/8m cyl 3, now 1 1/4, cyl4 now 1 1/2 . Carbs 1 & 2 were carbon and wet last time, so I leaned then 1/8. Carb 3 was my goal, left it alone. Cyl4 was lean and I make it richer at 1 1/2.

I ran the engine for 10 mins, hard to find a solid idle but cyl temps were very close to the same 425 degrees. Pleased the temps were similar on each cyl, measured several times during the run.

Also pleased was the throttle twist. When running at 3k RPM, the throttle did not bog down. Multiple tests in the 5k range and 4k range. So...I guess the needle position #4 and using main jet 97.5 ok so far. Changed nothing.

I had a hard time getting a 1200 RPM idle. I had to leave the choke on at 1/8 open. Picture attached. I would adjust the thumb screw idle to increase the RPMs in the 2500 range and gently tried to close the choke. Engine would die. To start, I had to use throttle twist or more choke to run again. It should have just started.

No sure how to fix this. The choke should be off and the idle screw control the idle speed. Any ideas on how to fix this?

I run a pint of 87 fuel directly to the engine, when low, I sometimes add Sea Foam or Mystery oil as my break in these new carb parts.

The engine does bog down using the throttle twist if I am around 500 RPM trying to save it. Doesn't bog down if the RPM is 1500-2000 range.

Thank you for the ideas.

Regarding plugs with black on the ground electrode, I have been cleaning these. The blackness is from prior runs. I likely will turn back cyl4 1/4 leaner to match cyl3's 1 1/4. I sure would like to fix the choke issue though. Plug pictures 1-4 are in picture order. I am running Champion N4C. And try NGK B7ES when the right ones arrive.

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Last edit: by johnmull.

KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 22 Feb 2021 16:29 #843897

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I am reading articles that to fix the choke needing to 1/8 open, I should enriched the fuel mix.

I am at 1 1/8, 1 1/8, 1 1/4, 1 1/2 right now for cyl1-4. So....maybe change the fuel mix out a bit. Maybe 1/8 on each. Maybe set all of them to be 1 1/4 and retest.

See if the choke can be set OFF with the thumb screw controlling the RPMs. Get that first and then recheck plugs to adjust later.

Advise if you have other ideas. Thanks.

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 22 Feb 2021 17:20 #843901

  • Mikaw
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Running with choke 1/8 on indicates an air leak or pilots are to small. With the choke plungers off their seat your adding fuel. No carb “new Parts break-in” required. If the o rings are good, ALL passages clear, floats set, and a minimum bench sync done, they will run correct the first run. Stop adding stuff to the fuel.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 22 Feb 2021 17:23 #843902

  • Mikaw
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1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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KZ650 VM22 carb sync question. Do you use the air mix or the adjusters? 22 Feb 2021 19:01 #843904

  • johnmull
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Hi Mikaw, Thanks for the reply and also the plug reading reference. I

will stop adding Sea Foam/Mystery oil to the test runs to remove it as a possible issue. My concern on the chokes is that I can't easily improve the choke plunger mechanism. Replacing the plungers on all 4 are expensive. Hopefully, I am not drawing in air there. I will look again for more air leaks.

I have the choke 1/8 up from totally off, because the engine dies. It needs the fuel to keep running at idle. Also, when off, I can't start the engine. I tried with a warm/hot engine when it died. I even checked to see if I lost spark, but that was good. Thought I had the kill switch wrong. I opened up the choke and the engine restarted fine.

So knowing this, if I allow more fuel in the fuel mix screw won't that compensate what the choke is doing? My next approach is to add more fuel on fuel mix screw ( say out 1/8) turn. Are you telling me, wrong idea....won't work?

Main jet and fuel mix screw had O rings. They are replaced. Old ones brittle/cracked off. The idle jets have two. A #15 and a second pilot #50. No O rings on the idle jets. My rebuild kit has the secondary idle jet but it is a #45, so I didn't change that.

Thanks for the review.

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