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TOPIC: Basic tuning help for Mikuni carbs

Basic tuning help for Mikuni carbs 28 May 2020 20:36 #826794

  • Gorf
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My carb tuning skills is pretty weak. My 1980 KZ1000 LTD was really having problems with the stock carbs. So I upgraded to mikuni RS flat sides. The motor has been gone through top to bottom and I'm really happy with how it turned out. Because I bored it out a bit I went with the 36 mm carbs at the recommendation of KZzone.com. I put them on and the thing idled perfect. But as soon as I apply a little throttle it sputters and dies. I'm a little lost on where to start. Like I said my carb tuning knowledge is a bit limited. The documentation from mikuni both makes it even more confusing and only slightly helpful. :cheer:

Is anybody willing to give me a little hand-holding advice?

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Last edit: by Gorf.

Basic tuning help for Mikuni carbs 28 May 2020 22:23 #826799

  • Scirocco
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I can offer you a basic setting diagram to start with.

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Basic tuning help for Mikuni carbs 28 May 2020 22:37 #826800

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Cool! So is this settings that I should have to get started? I'll pull jets and stuff and compare to this.

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Basic tuning help for Mikuni carbs 29 May 2020 07:30 #826835

  • Rick H.
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I don't know anything about the carbs you have, but wait for a little bit and I am sure others will jump in with some pretty darn good advice for you.

Rick H.
Rick H.

1977 Kawasaki KZ-1000A1

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Basic tuning help for Mikuni carbs 29 May 2020 10:09 #826841

  • racerx311
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Personally, I would call APE Racing and speak with them. They sold them to you and will/should provide customer support.. They should have "notes" on what jetting should be for your particular motor set up .

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Basic tuning help for Mikuni carbs 03 Jun 2020 12:40 #827224

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So I got out my handheld AFR meter and welded a bung into the 4:1 collector that is on the bike. At idle it was off the chart lean. Like greater than 25:1. I'm surprised it started. I got on the pilot screw and reset them all to the same place. For reference these are the RS36-D3-K's. So starting to back out he pilot screws, it didn't get down into good range until the screws were 3 full turns out. That seems like a lot especially since the documentation seems to suggest it should only be about 1/2 turn. Do I need to be adjusting the pilot screw and the pilot air jet? Is it this just how it is?

Getting the pilot screws down into a good AFR fixed all the reving problems for sure. But now my upper RPM's are super lean. We'll fix that next.

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Basic tuning help for Mikuni carbs 03 Jun 2020 17:05 #827245

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I don't know much about those carbs but in general I think it's a sign of too large a pilot jet when they have to be screwed out much farther than normal.
I have a couple of Z1B's restored, an '80 KZ1000LTD restored, a 1981 KZ550 restored and a 2008 KLR 650 for off road fun. My wife has a 2019 Suzuki DR 650 for on and off road.

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Basic tuning help for Mikuni carbs 03 Jun 2020 20:32 #827261

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Changed carbs from factory BS34's to a set of RS36's based on the Mikuni sizing chart. But according to fellow member recommendations, the 36's were "too big" for my engine, so I swapped them out for RS34's when prices were right on ebay.
I'm happy with that decision, but the variety of jetting options have nearly driven me cra...Z!

:woohoo:
1982 KZ1100A-2 (sort-of)
1135 since 10/25/19
January 2016 BOTM

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Basic tuning help for Mikuni carbs 04 Jun 2020 18:21 #827322

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Yeah so if the jet that comes stock is a 17.5, which direction do I need to go? To a 15 right?

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Basic tuning help for Mikuni carbs 04 Jun 2020 20:19 #827329

  • Funtimes
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Hello what size pistons , cams are you running. ? Ported head. ? I'm having the same problem. I have newly built engine , 1075 12.5:1 . Ported head . Oversize intake & exhaust valves. Open Kerker header. Seems have to choke carbs for about minute before engine will idle , then around 4k rpm , engine pops and seems doesn't want to take the gas . Hard to run it over 4k rpm . Did you have to reset your carbs. My engine builder told me the carbs shouldn't need syncing or jetting.
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Basic tuning help for Mikuni carbs 05 Jun 2020 02:46 #827340

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Funtimes wrote:
My engine builder told me the carbs shouldn't need syncing or jetting.


So why he didn´t do the carb tuning right? If your engine pops and doesn't want to take the gas your engine is running very lean.
What´s your pilot and main jetting set-up?

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Basic tuning help for Mikuni carbs 05 Jun 2020 04:07 #827341

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Hello , I guess the jets are the same ones that the carbs came with . I don't know a whole lot about carbs . I may have to take my bike to a good carb person . Thanks for your reply .

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