Carb Jetting Advice

Howdy all,

First of all, I'm new to the site, and this is my first post. Awesome site!

Just bought an '81 KZ1000 CSR from my uncle in KC and trailered it to Ft. Collins, CO last weekend (from 1000 ft elev to 5000). I've gotten it to start with help from a friend (Thanks Zenrider!), but it is not acting civilized in any throttle position at the moment. So I'm thinking I had better start from scratch; completely clean them up and bring them as close to stock as possible, adjusting of course for aftermarket mods and elevation change. I'd appreciate any tips on jet sizing anybody can provide.

Here's the set-up: Mikuni BS34 CV carbs, K&N Individual Pods, Kerker 4-1 Header and slip-on silencer. The existing main jets did not have a size stamped in them, but eyeballing them to be about 160s. I haven't figured out how to access the pilot jet (tips on how to remove the pilot screw plug?). Don't know the needle jet size either. Jet needles are clipped at second from bottom setting.

Correct me if I'm wrong here (I just ordered the Clymer Manual but it hasn't come yet), but I believe the stock set-up was 122.5 Main Jets and 37.5 Pilot Jet. Not sure about stock needle jet size. Not sure where the jet needle was originally clipped. Should I assume in the middle (3 of 5)?

Assuming that I have the correct stock sizes and according the the "Simple Jet Guide" in the file base, I should go up three sizes on the main jet to 130 and one size on the pilot jet to 40 due to the intake/exhaust mods.

I get a "Correction Factor" of 0.93 for 68 F and 5000' according to the "KZ_Carb_Jetting_Troubleshoot" document in the filebase. That results in a 120 main and 37.5 pilot, and one size down needle jet (don't know what size is stock). Also back out the air screw 1/2 turn.

Thanks in advance everybody! This is my first real experience with motorcycle carbs, so wish me luck!

Maverick

You can look in buykawasaki.com for the needle jet type/size or in your Clymer. It should be listed in carb specs.

If operating the bike at 5K with pods/pipes, run the stock jetting... I am not real sure from memory but I don't think your jet needle will have more than one slot. You will have to confirm when you open up the carb tops and remove the jet needle. The #122.5 / #37.5 should be about right at this altitude with your set up... give it a try.

I don't think you can eyeball a main jet and really tell very well what size jet you have so order the jets I suggested and give those a try for start.

The BS34 pilot system has the pilot jet drawing gas from a side passageway into the main jet holder tube. Thus the pilot tube has to be plugged else it will draw additional gas from the bowl itself and run way too rich... To remove the metal plug, just use some vise grips. The plug has an oring that MUST be in good shape to keep the plug fastened tightly. Usually, folks take a hammer and tap the plug into place so it may be tight... When removing the pilot jet, make sure you put LOTS of downward pressure on the pilot jet as it is easy to strip this thing. You might want to spray the pilot jets with some PB Blaster or Kroil and let them sit for a few minutes before trying to remove them as they may have been in there awhile and are real tight. If you find any resistance, you can also heat the pilot jet tube a bit and this will make the pilots jets come out much easier.

Thanks WG.

I have since eliminated the carb as the source of my problem. I've lost compression on the number one cylinder and need a ring job. But once I get that done, I will go back to the stock settings. I tore the carb apart and the jet needles do have more than one clip groove. In fact, there are six! The diagram in the manual shows that the needle should have more than one clip, but the buykawasaki.com fiche shows that only the canadian model came with a needle with more than one clip position. Do you have a recommendation for the clip location? I suppose it may just end up being a trial and error process. What would be your recommended procedure?

Thanks again!

Maverick

George-

Curious, does the plug have to be in place for operating the BS34's? I guess I could try blowing a little air through with mouth and rubber hose to see if any air passes by the screws but I'm not gonna be at the shop for a few more days. Still working on this darn bathroom renovation...

-Duck

your carbs have been rejeted with a dyno-jet kit.

try puting your clip in the next lower notch,that will raise the needles a little and make it ritcher.

turn your pilot screws out(counter clockwise)1/2 a turn at a time until it idles right. the pilot screws are the ones on top between the carb and the head.

the mains should be close,if not try some 145's as a starting point

Typically, the six slot jet needles with be Dynajet as has been pointed out. They are typically clipped to the 2nd slot as a starting point. You might benefit from using stock components as the jet needles in your kit are very likely the same ones used in all Kawasakis, regardless of make and model... not very application specific.

As far as the plugs Duck mentioned, they need to be in place on the BS34 else the pilot system will suck in way too much gas. There is a small cross passage between the main jet holder tube and pilot tube to supply gas to the pilot system and if the pilot tube isn't plugged, it sucks in gas from two sources. Not good.... The small "rubber plug" mentioned is in fact metal with an oring.

wiredgeorge wrote:

...They are typically clipped to the 2nd slot as a starting point...

Does this mean the 2nd slot from the top or 2nd slot from the bottom???

Cheers,

Mav

Slots on a jet needle are numbered from top to bottom. 2nd slot is second from top.