At my wits end! Still running lean

I'm not sure what I should do with my carbs. This is my 77 KZ1000 with recently installed 1075 kit. The carbs are VM28's without accel pump. I'm using K&N air pods. I have 20 pilots and 127.5 mains. The needles are the non-adjustable kind.

The bike idles great. Top end is good. The problem is it surges at a steady throttle. The ground straps on the sparkplugs are light tan to almost white. I have a set of adjustable needles out of VM26 carbs that I was going to put in, but the slides are not machined the same way. On my VM26's the clip of the needle rests on top of the slide and is retained by the throttle linkage. On my VM28's the needles sit inside the slide and are held up by a spring. They also have a bushing on top of the clip which prevents the needle from being raised.

I recently changed from 122.5 mains to 127.5 and it helped some, but not a whole lot. Should I go bigger on the mains or mess with the needles?

How do I richen up the needles?? Can I just swap the throttle linkage, slides, and needles from my 26's to my 28's?

Main jets only affect full throttle. If you are getting surging at constant highway throttle it is the needle setting. If the needles are non adjustable they can be shimmed up using spacers. I would shim them up about 1.5mm.

Otakar,

Unless I'm just not getting it, I don't see how to shim the needles. The needles don't rest on the clips like on my VM26's. I wish I had a picture of them. I'll try and describe them. In order from the top, there is a bushing that measures .100", then the clip, a washer, then a spring. All of this fits inside the slide. The spring presses the needle up against the throttle linkage. The needles are shorter in overall length than the adjustable needles in my VM26's. I don't have them in front of me right now, but it's around a half of an inch difference.

The bushing on top of the clip prevents the needle from being raised. As an experiment, I replaced the bushing with three washers that measure .022" each. This raised the needles .034". This did help some, but not nearly enough. Since these needles are so short, I'm leary of removing another washer. At full throttle the needles are very close to pulling out of the needle jet. I could probably remove one more washer safely, but I don't think that it will make enough of a change to be worth it.

I know that he's not popular on this site with some people, but I read a post by wiredgeorge that these nonadjustable needle have such a gradual taper that shimming them doesn't make much difference.

I'm still thinking about swapping the whole slide assemblies out of my VM26's.

Thanks for your advice Otakar. If you think of anything else, please let me know.

fordtruck wrote:

Otakar,

Unless I'm just not getting it, I don't see how to shim the needles. The needles don't rest on the clips like on my VM26's. I wish I had a picture of them. I'll try and describe them. In order from the top, there is a bushing that measures .100", then the clip, a washer, then a spring. All of this fits inside the slide. The spring presses the needle up against the throttle linkage. The needles are shorter in overall length than the adjustable needles in my VM26's. I don't have them in front of me right now, but it's around a half of an inch difference.

The bushing on top of the clip prevents the needle from being raised. As an experiment, I replaced the bushing with three washers that measure .022" each. This raised the needles .034". This did help some, but not nearly enough. Since these needles are so short, I'm leary of removing another washer. At full throttle the needles are very close to pulling out of the needle jet. I could probably remove one more washer safely, but I don't think that it will make enough of a change to be worth it.

I know that he's not popular on this site with some people, but I read a post by wiredgeorge that these nonadjustable needle have such a gradual taper that shimming them doesn't make much difference.

I'm still thinking about swapping the whole slide assemblies out of my VM26's.

Thanks for your advice Otakar. If you think of anything else, please let me know.

I do believe the needles George is talking about are the OEM needles in the OEM CV carbs, not your VM series carbs. He's correct about the gradual taper of those needles. IMO pissing around with OEM needles in CV carbs is a waste of time.

Your 77 model should have adjustable needles. There should be 5 clip grooves. Sounds to me like you've got a rack of 1980 carbs. Are the needles numbered 5CN29?

The length of the needles is suspicious. I don't recall Kawasaki changing the length of the needles in 1980. They did have only one groove and it was in about the 3rd clip position location.

CV carb needles are going to be considerably fatter than the VM series needles would be. I suspect you might have CV needles.

The arrangement you speak of with the spring under the needle is common of later VM series carbs. They'll accept the adjustable needles.

Your problem sound clip position related to me. It's possible your intake boots may be sucking air also. They should get a thin layer of silicone sealer between the boot and the port flange. You can check it by spraying some carb cleaner, Wd40 or BreakKlean around the boot while the motor is running.

What is the number on the needles from the VM26 carbs?

What is the number on the non adjustable needles?

Larry,

From the info I got out of my Clymer manual, the VM28's are off a 1980. I think they are 5CN29, but I'll try and verify that tomorrow. I don't remember the number of the needles in my VM26's, but I remember that they are the same number that my Clymer stated that they should be for a 77 KZ1000A.

So to put my adjustable needles in, I just move the clip to the position that I want and put the spring under it? Which clip position would you recommend?

I'll try and take a pic tomorrow of the two needles side by side so you can see the difference in length.

Thanks for the info Larry. You've helped me a bunch the last few months.

fordtruck wrote:

Larry,

From the info I got out of my Clymer manual, the VM28's are off a 1980. I think they are 5CN29, but I'll try and verify that tomorrow. I don't remember the number of the needles in my VM26's, but I remember that they are the same number that my Clymer stated that they should be for a 77 KZ1000A.

So to put my adjustable needles in, I just move the clip to the position that I want and put the spring under it? Which clip position would you recommend?

I'll try and take a pic tomorrow of the two needles side by side so you can see the difference in length.

Thanks for the info Larry. You've helped me a bunch the last few months.

You're very welcome. I have needles if need some, pm with mail address and I'll get them to you.

You should be able to put the VM26 needles right into the VM 28 carbs. Assemble with all the plastic washers & spacers just as you would with the origintal VM28 needles.

Most likely the VM26 needles have a "C" first taper. Put them in the 3rd groove.

Generally, with a ported head and big bore it, it's not uncommon to have to lean the needle one clip position from where it was before [assumes previously running pod filters, stock cams].

Reason being is the ported head, if it really flows any air & isn't cut much back by the intake boots,[which it shouldn't be unless you're going to run 34mm carbs] it's cut mostly in the bowls and the throat. That's where the flow gains are to be found.

If you went from 68CFM up to 82CFM and it was cut the way I described, then velocity picks up considerably in the inital port entrance area. This has a tendancy to put a stronger vacuum across the needle jet that can often cause richness where it didn't before. Hope that makes sense to you...

Larry C

Forgot to mention that the 5 in the needle number should mean it's a 50mm length needle. The VM33's had "6" or 60mm length needles.

NEVER RUN A NEEDLE THAT IS IN RISK OF PULLING OUT OF THE NEEDLE JET!!!! EVER.......That could lead to a stuck WFO throttle....not good :woohoo:

Larry,

I pulled the carbs off today. The needles are indeed 5CN29. The needles in my old VM26's are 5CN8. The adjustable needles are about 1/4" longer than the nonadjustable ones.

I put the adjustable needles in with the clip in the 3rd position. I did this on one carb. Then with the carbs on the bench I opened the throttle 1/4 way, reached in with a magic marker and made a mark on the needles where they entered the needle jet. I then took two slides out (one with the original needle and one with the adjustable needle) and measured the diameter at the mark. They were identical to .001". Based on this I moved the clip to the bottom groove (richest).

After putting the carbs back on and letting the motor warm up a bit, I hosed the intake boots with WD-40. This made no changed in rpm. I do have ThreeBond on the boots where they bolt up to the head.

I rode the bike on the highway and interstate when I was done and it definitely helped. I can still feel the slightest surge when the wind is just right. Is that just common with air pods? The bike feels much stronger now when I crack the throttle back when cruising. I think I will turn the air screws in 1/4 turn and see what that does.

Here is a pic of the two needles.

fordtruck wrote:

Larry,

I pulled the carbs off today. The needles are indeed 5CN29. The needles in my old VM26's are 5CN8. The adjustable needles are about 1/4" longer than the nonadjustable ones.

I put the adjustable needles in with the clip in the 3rd position. I did this on one carb. Then with the carbs on the bench I opened the throttle 1/4 way, reached in with a magic marker and made a mark on the needles where they entered the needle jet. I then took two slides out (one with the original needle and one with the adjustable needle) and measured the diameter at the mark. They were identical to .001". Based on this I moved the clip to the bottom groove (richest).

After putting the carbs back on and letting the motor warm up a bit, I hosed the intake boots with WD-40. This made no changed in rpm. I do have ThreeBond on the boots where they bolt up to the head.

I rode the bike on the highway and interstate when I was done and it definitely helped. I can still feel the slightest surge when the wind is just right. Is that just common with air pods? The bike feels much stronger now when I crack the throttle back when cruising. I think I will turn the air screws in 1/4 turn and see what that does.

Here is a pic of the two needles.

You shouldn't need to be full rich on the needle clip position.

1980 carbs, at least the LTD units had O-1 needle jets. They're the leanest needle jet ever run in an OEM Kaw carb that I know of on a KZ1000.

You're 26's will likely have an O-5 needle jet. If you can ge the needle jets out of both racks without damaging them, swap them. Should make a big difference. I would move clip back to 3rd groove and probably go with 17.5 long pilot jets.

You have to remove the bowls and slides to remove the needle jets. Remove the emulsion tubes from the bottom of the carbs, then very, very carefully push the needle jets down from the top side.

Use a wood dowel rod. It would probably be best to soak then with some penetrating oil overnight if they don't push right out. You can warp them in a heart beat, then the needle will stick....NOT GOOD.

www.motorcyclecarbs.com/Mikuni_Jet_Needl...nsion_Ch_W121C37.cfm

The tapers on both of these needles are identical. 1.5* on top and 4* at the lower butt the 29 needle is considered much leaner because the tapers are shifted much lower down. That needle was intended for the VM29, 30. Even with the clip all the way down the 5CN29s will be leaner than the 5CN8s. I never had a problem with a shim or few, under the clip to richen the needles. We used to do it for the old police bikes all the time when I worked for the Kaw dealer. Technically we were not allowed to do it for privately owned street bikes.

I know for a fact that my VM26's have 0-6 needle jets, except for one carb. When I bought this bike the number four sparkplug would gas foul. I rebuilt the carbs and it still did it. I swapped everything that I could think of between carbs, and it still fouled number four. Finally pushed the needle jet out and found out someone had run a drill bit through it for some darn reason. I never could find another 0-6 needle jet, but did find two NOS 0-4 needle jets on Ebay for $2! I replaced the damaged jet with the 0-4 and it fixed it. Heck, my gas mileage went from 35 to 45 MPG.

My Clymer only lists one carb for a 1980 and it states it has 0-4 needle jets. I guess I won't know until I knock one out. I'll probably exhaust every other option before I do that. For one, I don't even have four of the same size needle jets. Second, it looks like replacement needle jets are almost impossible to find. The site you posted shows them for $21.95 each! Ouch!

The bike runs a lot better with the adjustable needles in it. I thought mid-range response was good before, but it's much stronger now. I also noticed that I'm using less throttle to maintain a steady speed now. I'll pull the plugs again and check them out when I get more time.

If you can think of anything else, please let me know. Do you know of any cheaper places to get needle jets?

fordtruck wrote:

I know for a fact that my VM26's have 0-6 needle jets, except for one carb. When I bought this bike the number four sparkplug would gas foul. I rebuilt the carbs and it still did it. I swapped everything that I could think of between carbs, and it still fouled number four. Finally pushed the needle jet out and found out someone had run a drill bit through it for some darn reason. I never could find another 0-6 needle jet, but did find two NOS 0-4 needle jets on Ebay for $2! I replaced the damaged jet with the 0-4 and it fixed it. Heck, my gas mileage went from 35 to 45 MPG.

My Clymer only lists one carb for a 1980 and it states it has 0-4 needle jets. I guess I won't know until I knock one out. I'll probably exhaust every other option before I do that. For one, I don't even have four of the same size needle jets. Second, it looks like replacement needle jets are almost impossible to find. The site you posted shows them for $21.95 each! Ouch!

The bike runs a lot better with the adjustable needles in it. I thought mid-range response was good before, but it's much stronger now. I also noticed that I'm using less throttle to maintain a steady speed now. I'll pull the plugs again and check them out when I get more time.

If you can think of anything else, please let me know. Do you know of any cheaper places to get needle jets?

Let me look tomorrow and see what I have for needles and needle jets.

What you really need to do is a design fuel level check on the carbs. If the fuel level is low, they'll throw you curve balls that you will band aid with "out of the ordinary" jetting specs.

The 1980 LTD1000 had O-1 Needle jets. Can't remember what the MKII had but O-4 could be correct.

If I have some 17.5 long style pilots, you can have them. I'll see if I have any 5D needles as well. A set of 5DL31 needles would be very good. They're a good needle for the KZ motors.

When trying to really dial in the bottom end circuits on those carbs, start by riding the bike in 1's gear at 1500RPM. Try to hold that RPM. Then increase to 2000RPM and try to hold that RPM, then 2500...

If at 2000 or 2500 RPM, it has the jerks.....richen up the pilot circuit using mixture screws.

If you get to where you're less than 1 turn out on the air screw and the problem is still there....up on the pilot 1 size.

If it does it at 3 grand, lift the needles.

That throttle position of just barely open is the trickiest part to dial in. You have pilot jet, mixture screw, slide cut away and needle clip / diameter all overlapping each other.

Changing slide cut away is generally out because of cost. So that leaves you mixture screw, pilot jet and clip position to work with [without spending money]

Is it time consuming? You bet it is. You'll also learn a great deal about tuning your carbs in the process though.

There's also a place called carbpartswarehouse in Ohio.