TOPIC:

Just got done cleaning the carbs on my '77 KZ650, it's sat for about 13 years inside. The bowls were nasty. Tank has been cleaned, petcock too and flows fuel nicely. Needle and seats stop fuel flow and move nicely with the floats. Floats set to 23mm. I reused all the brass, cleaned up and blown through. Just replaced the gaskets and O-rings.

Bike needed some starting fluid it get her going. I was able to heat her up and idle her down, but she's surging pretty bad. I tried to identify the location but having trouble doing so. It actually seems like the throttle shaft seals may be leaking. I checked the intake/boots they are starting to crack, but I didn't see any evidence the cracks have gone through into the carb surface. They have a nice seal on the head surface. The sync port caps are good and free of cracks. It also seems #2 and #3 are not helping like they should. Header is only lightly warm. Timing light says there's spark. Maybe still a needle/seat issue?

Service manual is on the way, I've got the pilot screws out 1 1/8" from lightly seated.

This is my first trials with a carb setup like this. Where should I be looking for specifically?

Thanks
-Paul

Did you spray carb cleaner around each carb boot? Cracks in the intake boots are the most common source of vacuum leaks, however they are often too small to be noticeable with just your eyes

I did spray some around the intake boots. #3 and #4 seemed to react most. That's when I pulled an inspected. They aren't rock hard yet. Think I'll just order a set and be done with it! I'd bet they're original.

I haven't seen one yet, anyone know of a complete rebuild kit that would service all 4 carbs AND their attaching peripherals? All I can seem to find is individual carb kits or a "pkg of 4" which I'm not sure comes with the shaft O-rings or fuel supply O-rings.

Absolutely order a new set of carb boots. If you see cracks they are done. If you spray carb cleaner and the bike reacts they are done. You will never get anywhere trying to tune with leaky carb boots. Also you should search about adjusting your float heights with the "clear tube method". This gives the most accurate height adjustment which is critical to proper function on these carbs.

With properly functioning carbs you shouldn't need to get anywhere near the bike with starting fluid. Just a touch of choke and no throttle should be used to start a properly sorted KZ.

It sounds to me like your carb holders are shot. What happens is that very tiny cracks form on the mating surface of the holders where they seal against the cylinder head. These cracks can be nearly invisible but still have a huge effect. Here's how to best test them:

Make sure the vacuum caps are tight on the carb holder nipples.

Temporarily set the idle as low as possible without stalling the engine. It should be down below 1000 rpm. The lower the better because when it is set low the carb slides are closed (or nearly closed) and this raises the vacuum level in the carb holders. The combination of the increased carb holder vacuum level and the very low idle amplifies the effect of the leak test.

Once the idle is set low, spray carb cleaner around each of the carb holders where they bolt to the cylinder head and where the carbs attach to them. If there are leaks, the vacuum in the carb holders will suck the carb cleaner in and this will affect the idle. It may even cause the engine to stall. If there is any effect at all on the idle, they are leaking. If the leaks are at the carb holder / cylinder head mating surface you need to replace the holders. If the leak is where the carbs attach to the holders you may be able to tighten the clamps enough to seal the leak. Some folks use starter fluid or other substances for the test, but carb cleaner works best as it doesn’t evaporate too quickly like ether and leaves no residue on the engine like WD40.

If you do need new holders just bite the bullet and buy them. Trying to seal things up with some kind of sealant or goop will only lead to frustration as it will at best only last a short time. Ed

Sounds like we're on the right path. I did spray the boots and she rose. So I pulled them off and just as a check, touched them with some copper coat and reinstalled. Now I was getting more rpm change from the carb side. Clamps are as tight as they're going to get before stripping the jap-Phillips.

I was browsing eBay and saw a clear tube adapter for the flat head brass plugs in the bowl. Is that the way to go, or can something be made from the local hardware store?

Thanks again! Love the great info!

No eBay APP ID and/or Cert ID defined in Kunena configurationThe "jap-phillips" aren't Phillips at all even though they look like it. They are JIS (Japanese Industrial Standard) and they work much better than Phillips because unlike Phillips they are not deliberately designed to "cam out." However, if you try to use regular Phillips screwdrivers on them they don't work well at all.

Before reaching for that Phillips screwdriver to do a repair or maintenance PLEASE do yourself a big favor and visit the following link. It explains the fact that Phillips screwdriver tips will wreck the crosshead screws on your bike and tells how to easily deal with this issue so it will not be a problem.

kzrider.com/forum/21-tools/532335-budget...ewdriver-tips#532335

Consider buying a can of Kroil penetrating oil and use it to soak stubborn fasteners for a couple days before trying to loosen them. Remember, the original screws and bolts were installed on your bike when Jimmy Carter was President, so many of them may be hard to remove. Kroil can be bought online (www.kanolabs.com), at guns shows, and at some other venues.

Regarding the carb tool, the one shown in the eBay listing below looks to be a very good value. You can make a tool like I did (see bottom for pics), but if the one on eBay was available when I made mine I would have just bought it and saved time and money. Some folks just jam a piece of tubing in the hole, but I would be afraid of leaks. Ed

Alrighty! Back from the dead here.

Found cyl 3/4 carb holders leaking causing a large vacuum leak.

Bought a set of new OEM carb holders, and new vacuum nipple caps. I adjusted the cam chain slack, per manual. Adjusted the float levels for all 4 carbs. They are on the high side, but within the window in the manual. Bench synched the carbs and installed. I may have burnt myself here, but I reused the bowl gaskets.

Once I got her running (which wasn't easy and the starter isn't grabbing all the time now), cyl 2 is weak. 1/3/4 headers burn off a drip of water real fast, cyl 2 it takes a few seconds. If I cover the carb mostly with my hand, she revs up. Looks like I have a vacuum leak there now. A little carb spray around the holder for #2 and she rises.

I cleaned the head well with scotchbite pads. No signs of warping or cracks that were obvious. I thought it might be a stuck needle from manipulating the carbs so I tapped the bowl with a hammer and the engine responded, but it didn't wake up right. Actually kind of wanted to stall. I adjusted the throttle cables per the book. Turning the handle bars doesn't change speed, but leaning the bike does. This doesn't make sense with properly adjusted float levels.

I'm so confused now. Maybe this is why Diesel Tech's shouldn't work on carbs.

Have you checked compression? may need valves re-shimmed.

I'll look for my old compression gauge. With the starter inop, I'll have to check it with the kick start.

I do have a fuel filter inline from the tank, but today I'll pull the carbs back off, pull the bowls and make sure there isn't any hidden junk. I'll check valve lash also today.

Any detriment to using conventional hose clamps on the carb holders? Mine originals are pretty worn it seems. One (not the cyl in question though) isn't quite round, and they are all tightened pretty easily to their maximum and still seem a little loose.

Thanks,
-Paul

Wow, fuel in the PNW really screws with carbs over the winter. These were spotless last summer when I started this thread.


That was for my dead cylinder, the others are bad but still have some holes clear! I'm getting a set of gaskets/O-rings coming for all of them.

Cold kicking compression: #1/150psi, #2/150psi, #3/145psi, #4/142psi
A little low compared to the book's hot spec, but I think it's acceptable yes? 23,000miles.

Starter issue: Idler has 1/8-3/6" lateral play on the shaft. Starter when turning by hand is very gravely. I'll take it apart and see if a rebuild kit will work or if I need to source another.

Valve Lash:
#1 i-.15mm, e-.22mm
#2 i-.13mm, e-.10mm
#3 i-.05mm, e-.18mm
#4 i-.10mm, e-.20mm

So those are all over the place. Pulled the cams and got the shims out. Starting a file to determine which all I need. Not a difficult job, just annoying I guess. Technically only 1E, 3I, and 4E are out of the 0.08mm-0.18mm spec.


And I'm ordering new throttle cables. Can't seem to find a good source for the carb holder clamps though. Maybe just hose clamps? I'm hoping that's all the leak was, that maybe It wasn't so much a vacuum leak, but rather fuel delivery? The engine definitely changed with some spray around the holders though. :O(

"Wow, fuel in the PNW really screws with carbs over the winter. These were spotless last summer when I started this thread."

This is true of fuel anywhere, not just the PNW. If over the Winter you start your bike once a week and let it run for 10 - 15 minutes your carbs will stay clean, the cylinder walls, cams, etc. will stay lubed, the battery will stay charged, and when the first warm day arrives you'll be ready to ride. Ed