KZ650 float settings and tuning problems

1979 KZ650 B3

Have been trying to get the carbs sorted out. Have completely dissassembled carbs, cleaned them in a chemical carb cleaner, and thoroughly gone over them with a set of bore brushes. New carb kits and accelerator pump kit.

Can't get the bike to run right. I've taken the carbs back off and re-checked/recleaned everything several times. No good.

I'm setting the floats by the service method wiredgeorge posted. I'm having a problem with the #2 carb (the one with the accelerator pump), however. On that carb the overflow tube is not connected with the drain port. I'm having to use the bowl from another carb (without the accelerator pump)to set the float level. I'm wondering if this could be making a difference in the float setting.

Also, these carbs have air bleeds. I currently have them set at about two turns out. What is the best way to dial them in?

There is significant fluctuation at idle. There is often significant hesitation on takeoff, I'm as yet uncertain whether this is caused by too much fuel, or too little, and haven't as of yet figured out how to determine which it is.

Amd then there's the needle and seat. My understanding of how to adjust the needle and seat is through clip settings on the needle, starting at the second setting ftrom the bottom. I've disassembled the needle and seats, however, and can find only one setting. I've dissassembled a set of 81 KZ650 carbs I have, and it's the same story. On the diagram, it's part # 16. On the diagram, it looks like there are several notches for the clip at the top of the needle, but there is only one notch on both sets of my carbs. Where am I going wrong?

Post edited by: jccwall, at: 2007/10/30 19:54

I zoomed in on the diagram on Kaswasaki.com, and I was right. There are clearly a number of grooves on top of the needle (PN 16) for the clip adjustment, but, neither set of my carbs have those grooves. There is only a single groove for the clip

Post edited by: jccwall, at: 2007/10/30 20:03

The only symptom I see here is that at idle the engine speed is not steady and it increases and decreases on its own. This may not be a carb problem at all. :dry:

The main cause for this is usually an air leak. The leak can be:
1) Into the vacuum line or,
2) Into one or more of the carb mounts (rubber)
between the carb and the engine block or,
3) Past the vacuum caps on the carb mounts.

If you can, get the carb close to its adjustment before you started adjusting. Spray WD40 on each carb mount one at a time to identify the leaky mount or mounts if any.

Also, could be an ignition fault. Have you done the WG Coil Re-powering Mod?

Finally, could be a compression fault. Check your compression.

Actually this is all in reverse order. :pinch:
Should be:
A- Compression check.
B- Ignition check (WG Mod).
C- Carb leak check.
D- Carb adjust.

Best of success.

Not too familiar with your specific year, but I wonder if you have a California Model that doesn't come with an adjustable needles? The Canadian Model is another choice for your replacement needle.

Post edited by: CoreyClough, at: 2007/10/30 21:54

I have a '79 D2 with the accelerator pump and the drain screw worked for me for checking the level.

I have done three sets of '650 carbs and on each carb the static float level is 25 mm from the bowl gasket surface. I used a stainless steel rule and with the gasket in the body and the body upside down I measured the height of each float. Sometimes I needed to twist the floats to even them up or adjust the tab that contacts the float needle to move them up or down. One should be careful so that the float rests lightly on its needle.

I made a jig with a pair of carb holders to temporarily mount the carbs onto a piece of plywood I put in a vise. Then I use a pair of small C-clamps to get them level fore and aft and adjust the board in the vise for left to right level. Then I check the fuel level and in every case it was spot-on.

As for the jet needles, yes, there should be five grooves. Stock setting is the middle (3rd) groove. Putting the clips 2nd from the bottom will flow a bit more gas than stock.

I hate to address stuff in one of those point for point style blatherings but since you shot-gunned soooo many questions into one email, I am sure I will forget some point otherwise. Sorry... wg

"1979 KZ650 B3"

"Have been trying to get the carbs sorted out. Have completely dissassembled carbs, cleaned them in a chemical carb cleaner, and thoroughly gone over them with a set of bore brushes. New carb kits and accelerator pump kit.

Can't get the bike to run right. I've taken the carbs back off and re-checked/recleaned everything several times. No good."

"I'm setting the floats by the service method wiredgeorge posted. I'm having a problem with the #2 carb (the one with the accelerator pump), however. On that carb the overflow tube is not connected with the drain port. I'm having to use the bowl from another carb (without the accelerator pump)to set the float level. I'm wondering if this could be making a difference in the float setting."

wg

---

The volume of fuel in the #2 float bowl is the same as an ordinary bowl. You should be able to set the fuel level with an ordinary bowl and then install the pump bowl. There is no reason why you couldn't use the pump bowl as I am pretty sure the drain screw is a drain screw... the 6mm steel flat-head screwdriver type screw is the drain screw. On a VM carb, you have to insert a 1/4" vacuum fitting into the hole where the drain screw goes to check the fuel level. Set the fuel to 1/8 below the gasket mating line.

"Also, these carbs have air bleeds. I currently have them set at about two turns out. What is the best way to dial them in?"

wg---- This will be a tad lean. About 1 1/4 turns out from seated for the air screws. First get the bike running and then adjust each air screw about 1/2 turn in either direction for max idle speed on that cylinder and adjust idle back down as you go... that is about as close as you can set the idle mixture without an Exhaust Gas Analyzer. The air screws just are not that fussy.

"There is significant fluctuation at idle."

wg---- Air leak in pilot circuit. Check carb holders, vacuum line to petcock, Air Suction System fittings/lines, vacuum caps, orings in air screws, rubber pads on choke plungers... any of these will cause idle fluctuation if air is leaking in at any of these places mentioned. You may also have a timing or mechanical timing advance issue... both are known culprits but the air leak is more likely since you worked on the carburetors.

" There is often significant hesitation on takeoff, I'm as yet uncertain whether this is caused by too much fuel, or too little, and haven't as of yet figured out how to determine which it is."

wg---- Idle mixture is likely lean... adjust air screws in; you didn't mention factors that might affect air/fuel mixture... what type air filters, what type pipes, how clean air filter is, what altitude... may need pilot circuit rejet if adjustment is inadequate.

"Amd then there's the needle and seat. My understanding of how to adjust the needle and seat is through clip settings on the needle, starting at the second setting ftrom the bottom. I've disassembled the needle and seats, however, and can find only one setting. I've dissassembled a set of 81 KZ650 carbs I have, and it's the same story. On the diagram, it's part # 16. On the diagram, it looks like there are several notches for the clip at the top of the needle, but there is only one notch on both sets of my carbs. Where am I going wrong?"

First, you are calling this a needle and seat. This terminology refers to a float needle/seat assembly. You have a needle jet and jet needle. The jet needle is the bit that LOOKS like a needle and the needle jet is the brass bit with a hole that recieves the jet needle. It is press fit into the venturi bottom and has no adjustment and the main jet holder tube (aka emulsion tube) retains it. Your 79 model carbs have pretty much eliminated adjustable jet needles with 5 clip positions by 1979. You should have orange spacers sandwiching a single clip and the jet needle inserted through a spring. There is an addition plate over the jet needle (under the sync actuating arm mechanism) on this type assembly. I suggest you clean them and put them back without any modification. I doubt your tuning issues will be resolved by messing with the jet needles.

Dissassembled carbs again.

Both left-side air bleed screws would not fully seat without what I considered excessive force. The threas and seats in the carbs looked good, and I couldn't see anything wrong with the screws, but I replaced them with the screws from another set of carbs I have and they are now seating properly.

There are no o-rings on any of the screws in either set of carbs. I see them in the diagram I posted earlier (PN 42), but, they are definitely not there. I guess the previous mechanic, who installed the new kits, left them out, but, I find it strange that they aren't in the set of '81 model carbs I have, either. Can I get replacement o-rings, only, or will I have to buy full kits?

I did a compression check:

#1: 120

#2: 105

#3: 120

#4: 120

Clymer says a 10% variance is ok, the #2 cylinder is slightly more than that, but Clymer also says they should be at 170. Could this be part of the problem?

How did you perform the compression test? Did you remove the carbs or keep the throttle wide open? The compression seems a bit low for a 650.

carbs removed. on initial test. added oil to cylinders, rechecked and all went up to 180.
jim

wg---- Idle mixture is likely lean... adjust air screws in; you didn't mention factors that might affect air/fuel mixture... what type air filters, what type pipes, how clean air filter is, what altitude... may need pilot circuit rejet if adjustment is inadequate.


air filters are pods, exhaust is 4 into 1 with no baffles. altitude, tulsa ok.

You need to use #110 mains, jet needle clipped to 4th slot (if slotted) and #17.5 pilot jets. Start with air screws out 1.5 turns and at idle, turn the air screws back and forth about 1/2 turn in either direction looking for HIGHEST idle speed. Air screws are not very touchy and you may not a change. If you don't leave that screw at 1.5 turns out. If you do have a small idle rise, that is the correct position for the screw... turn the idle speed back down and do the other cylidners in turn. Once you have the idle mixture set for all four cylinders, you might re-sync.

If you checked compression with the carbs off and found what you did, the bike will start and probably run fair once you get it tuned but it won't run nearly as well as it should. If you did drop the oil in and found that compression bumped considerably, this, of course, indicates ring seal issues. To determine what needs to be done, you MUST remove the cylinder head and block and measure the cylinder bores. The correct method is outlined in your manual... 3 different angles at three depths in the cylinder. The point is to check for ovaling of the bores. To measure, you need bore gauges which allow transfer of the diameter of the bore to a measurement tool such as a caliper. You then measure the pistons diameter under where the pin fits in on the skirt. Your manual tells you where exactly. Anyway, once you have diameters and take the difference between the bore diameter and piston, if the difference is beyond the spec, then you need oversized pistons and will need to bore the block. If you find the piston/bore clearance in spec, you just need to re-ring.

The new piston situation can be expensive. It is sometimes less expensive to look for a new block/piston set from a low mileage donor bike and just re-ring the donor pistons rather than boring and new pistons for the old block. The difference will be about $200 for a good set of used block/pistons and new rings with some honing compared to $750 or so for new pistons/rings and boring your old block.

Returning to the o-ring issue. I checked the "Carb Parts" diagram on Kawasaki.com for my '81 KZ650H-1 CSR. I can't get it to post on here because it is too big, and I don't know how to shrink it, or how much to shrink it.

The diagram for the '79 model shows both air bleeds, coming into the carbs at 45 degrees, and pilot jets, coming in from the bottom. As I understand it, on that model, it's either air bleeds, or pilot jets, and the '79 I'm working on has air bleeds.

The diagram for the '81 model is different. It does not show the pilot jets on the bottom. Instead, it shows two assemblies, both going in at 45 degrees on the side of the carbs, as the '79 diagram showed.

One assembly is the same as the air bleeds on the '79 model:

PN 16014: Screw, air adjusting ("CN" is in remarks; Canada?)

PN 11009D: "O" ring ("CN")

PN 92081A: Spring, thr stop screw

The other assembly shown is:

PN 92066: Plug, pilot screw ("US")

PN 16014A Screw, pilot adjusting ("US" is in remarks)

PN 92081A: Spring, thr stop screw

Even though the bike I'm working on is a '79, it has the second "US"-style pilot jet assembly shown on the '81 model; exactly the same as on my '81.

It does not, however, have the PN 92066 pilot screw plugs. It looks to me like they may perform the same function as the "o" rings, sealing the pilot screw assembly to prevent air from passing by. Are these plugs necessary? If so, can anyone tell me where I might find them?

Post edited by: jccwall, at: 2007/11/01 16:07