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Discussion Starter #1
Hey everyone,

This is my first post as a member of your group. I just read GREENISBEST’s post about new member’s posting not enough detail, so I’ll do my best to avoid falling in the same trap.

I own a 1981 Kawasaki 440 LTD (twin cylinder, SOHC), which I’ve had for a couple years. I initially bought the bike to tear apart and rebuild for my own knowledge. The bike ran well before I took it apart and at the end of last year, the bike was back together and with some blood, sweat, tears and maybe a little luck, it was running again (not overly well and in need of a tune-up).

So with the riding season almost upon us, I tried to fire it up again a few days ago and not surprisingly, it didn’t start. I’ll try and be as descriptive as possible in detailing what the problems were. The bike turns over fine and there seems to be enough compression (with the plugs out and my thumb over the spark plug hole, there’s enough pressure to push my thumb back off the hole – not by a long shot but should be enough to fire it up I assume). If compression might be an issue, I can get a compression tester if anyone thinks it’s time to get more scientific than the ‘ol thumb over the cylinder hole! As far as spark, I took out the plugs, laid them against the engine block and there’s spark (I set the timing last year, which is done by setting the engine at top dead center and lining up the ATU (automatic timing unit) with the firing marks). I haven’t changed the settings or anything since the bike ran last.

The carbs have been disassembled (not entirely, but float bowls checked for gas sludge) and there are no signs of any issues with the carbs being dirty, obstructed or gummed up. I’ve got the air cleaner assembly set up (I don’t assume this would stop the bike from starting, but I’ve attached it to the bike just to be safe). Unfortunately, I’ve adjusted the knob (to the point where I don’t know where it was at the end of last season) that controls how open the throttle sits at idle. To be safe (or at least, what I think is safe), I turned it completely tight (so the throttle was essentially closed at idle), then backed it off about three turns to open it to where I think it should be, but not sure if this is where it really needs to be.

The carbs should be full of gas, I installed clear fuel tubes to be sure the gas was getting to the carbs. However, when I put the petcock to the “RUN” setting, the fuel doesn’t exactly pour out. It does flow out but not heavily like I’d expect it to. I did check and I think the carbs are full because the fuel was starting to fill up the tube a little from the carb end so I assume if it’s backing up, the carbs have gas. Is there a way to be sure my carbs have gas? There’s no sight glass or other obvious way to tell.

So when I go to start the bike, I put the choke on all the way, and then start to turn the bike over. It’ll just turn over and over without any real fireworks. Every once in a while (maybe, every 2-3 full completions of the 4 stroke process), they’ll either be a pop from the exhaust pipe – like there was a little combustion or a pop back up in the carbs, with gas smoke popping out the side of the carbs, where the air intake assembles. It’s as if the engine is backfiring into the carbs or something. That’s about it. I’ve put “Quick Start” (basically, an extremely flammable liquid that supposed to get your engine going long enough to get the engine running under it’s own power) in the cylinders but nothing more than the ordinary pops happen. I’ve tried pouring gas into a tube that opens up right in front of the right throttle body (essentially pouring gas into your cylinder) but even that doesn’t get any more results.

After trying a number of times, I take the spark plugs out and they don’t seem to be wet, which I would expect them to be but maybe someone could tell me how they should look (maybe they should always be dry). I guess I just thought if gas was getting to the cylinder, they’d be wet. Maybe I’m wrong.

Just FYI, since the bike was running, I haven’t adjusted the valves or the timing chain.

If anyone out there can help, I’d truly appreciate it. This bike has been great fun to work on over the past couple years and I’m just dying to ride it after all this work but right now, I need some help if that’s going to happen. If you would like any more information, I’d be more than happy to provide. If you aren’t sure what exactly the problem might be, if you could even provide ways to trouble shoot (i.e. how do I know if gas is getting to the cylinder, etc.), that would be great too.

Thanks so much.

Kirk
 

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I would look to the fuel supply valve screens as a starting point, clean those and see if the fuel flow improves.

Then, if the carburetors sat for any time longer than just a few weeks with fuel in them, totally disassemble them and clean the internal passages. Pay particular attention to the pilot fuel circuit and the passage from the pilot jet to the pilot air control valve. Also, pull the main jet tube and make sure the holes in the side of that are not filled with the results of electrolysis.
 

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Carb Cleaning 101

By M. Shively

The elements of internal combustion engines are: correct fuel/air ratio, spark at right time, and adequate cylinder compression.

There are many passageways and openings to check and clean. All are important in function and when obstructed or not working properly, have subtle to radical effects on engine performance. Vacuum leaks and carburetor synchronization also effect performance and should be inspected and adjusted following the below procedures.

Warning: Remove all rubber parts before you begin. These parts usually include vacuum diaphragms, needle valves, o'rings, hoses, and other parts. Spray cleaners will damage these parts. Do not disassemble individual carbs from the carb bracket.

Air & Fuel Passageways: Trace and learn individual fuel and air circuits from beginning to end. Machines can only drill straight through the cast passageways. To change direction, another angled passageway must be drilled. The union is plugged with a brass or bronze bead. Inspect and clean each passageway with spray cleaner, brushes/pipe cleaners/etc, and compressed air. Remove any discoloration and debris. Look for spray cleaner to exit from one or more passageways.

Jet Cleaning: Inspect jets by holding to light and look through them. You should see an unobstructed round hole. Clean the jets with one or more of the following: jet cleaning wires, soak solutions, carb spray cleaners and compressed air. Re-inspect jets after cleaning and install when clear of obstructions. Some main jets have paper-like gaskets. Most have metal spacers between the jet and the emulsion tube. Some screw directly into a brass emulsion tube which is machined for a 7mm wrench at its float chamber exposed base.

Inlet Fuel Valve: Inspect the needle valve & spring. Press down the tiny metal rod that protrudes from the butt or float end of the needle valve. The spring should move freely and return the rod to its location. Check the needle valve's seat area for a groove or other wear. It should appear highly polished. Some needle valve seats are rubber and wear may not be visible. Inspect the needle valve jet seat. You can clean the jet seat with Q-tips and semi-chrome polish if necessary.

Carb Body Castings: Blow air through the atmospheric vent holes located on the dome of each float bowl chamber. Air should exit via hoses or brass nipples. Inspect the emulsion tubes and passageways (cast towers that jets thread into) for discoloration and debris. Clean interior emulsion towers with a soft bristle gun cleaning brush. Clean each Venturi (main carb bore).

Needle Jets & Jet Needles: Clean the needle jets, jet needles, and passageway or tower that needle jet screws into. Clean the emulsion tube (pipe between needle jet and main jet) (Main Jet may screw into emulsion tube). Jet needles are part of the throttle slides. See below…

Throttle Slides: There are several types of throttle slides: Mechanical linkage, vacuum, diaphragm, and cable. Disassembling the jet needle from the slide is not always required for cleaning. If you have vacuum piston type throttle slides (large diameter solid metal slide), avoid cleaning the lubrication from sides and caps. If piston type check cap vents and passageways with air. Clean if necessary and re-lube. If you have rubber vacuum throttle diaphragms, inspect for dry-rot, defects, and tears by gently stretching rubber away from center. Do this until all areas around diaphragm have been inspected. Replace any defective part as described above. Clean carb body areas around diaphragm including air passageways and air jets. Diaphragms have a locator loop or tab fabricated into their sealing edge. Observe this locator upon reassembly. Avoid pinching the diaphragm when reinstalling caps.

Fuel Screws: Fuel screws have sharp tapered ends. Carefully turn one fuel screw in while counting the turns until it seats lightly. Warning: These screws are very easily damaged if over tightened into their seats. Record amount of "turns-in" and remove the fuel screw, spring, washer, and o'ring. The fuel screw is part of the enrichment (choke) circuit...clean passageways as described above. When carbs are assembled, spray low PSI compressed air into diaphragm air vents located at intake side of carbs. Throttle slides should rise, then fall when air is removed. Lightly lube external moving linkages. Reinstall carbs and follow through with carburetor synchronization.

Throttle Cables: Lubricate cables periodically. If cables are disconnected from carbs or removed for replacement, etc . . . remember cable routing and ensure proper reinstallation routing. Avoid bread-tying, sharp bends, and pinching cables. Adjust cables so throttle grip has about 5mm of play or throttle slides or butterfly valves may not open completely (full throttle)(wide full open).

Float Bowls: Inspect float bowls for sediment, gum or varnish, crystallization, and defects. Clean all pipes, tubes, passageways, and embedded jets with cleaners and compressed air. Remove and clean the drain screw and area. Inspect bowl gasket and replace if necessary. Clean and inspect overflow pipes and tubes, look for vertical cracks.

Floats: There are several types of float materials: plastic, brass, black composite, tin, and others. Handle floats carefully. Avoid bending, twisting, denting, or other means of mishandling. Most floats are adjustable by bending a small metal tab near the float axle end. Do not change the float adjuster tab unless tuning fuel service levels. Clean metal floats by soaking or by spraying cleaner and wiping clean. Other material type floats may require replacement if cleaning is necessary. Inspect the needle valve (float valve) and seat. Check needle valve's spring loaded pin. It should depress and return smoothly and without resistance. Check the needle valve's tip for a worn groove. Replace needle valve and seat if either symptom exists. These parts wear together and must be replaced as a set.

Synchronization: This is a fine adjustment performed usually and preferably with the carbs installed and the engine running. The unusual part is performed with gauged wire with the carbs on the work bench. Carburetor synchronizing balances Venturi vacuum at the exhaust side of each carburetor, resulting with smooth idling and optimized performance at all throttle openings. Synchronization is checked using a set of gauges which are either air vacuum type or liquid mercury type. The gauges are connected to vacuum ports on the intake manifolds via nipple tubes or if sealed with screws, sync gauge adapters will be needed. With the engine running at temperature, and with a fan or means of forced convection aimed onto the engine, the carbs fuel screws and idle are adjusted, then the synchronization is adjusted via adjustment screws on the carbs. A reserve fuel tank is recommended for convenience of accessing carbs during this procedure. See gauge instructions and repair manuals for detailed use of synchronization gauges.

Notes: While carbs are apart, record the jet sizes. Look for a very small number imprinted on the body of the jets. Verify that numbers are the same for all jets on models with in-line cylinders. A few transverse-4 models and V-engines, the inner and outer carbs use some different size jets and it's important to not mix them up. If you have dial or veneer calipers, measure and record float heights. Perform measurements with floats just touching needle valves, though not depressing the needle valve rods. Replace fuel and vacuum hoses. Be sure to use fuel rated hose for fuel. Install or replace in-line fuel filters. It's a good time to remove and clean interior petcock fuel filters. Inspect carb manifolds for dry-rotting, inspect all clamps and air ducts. Inspect, clean, lube, and/or replace air filter(s).
 

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And: Lemon Juice Carb Cleaning(Found on the internet)

If it was me, I'd pull the top covers off, pull the slides out, drop off the bottom bowls, remove pilots/mains. Then with the rest of the carbs still assembled boil them in some lemon juice. You'll need a big roaster pan, a little over a gallon of lemon juice (cooking supply stores), and an understanding wife/girlfriend cause the sh*ts gonna stink a little.

Boil them for about 15 minutes, then rinse them really well and blow them dry with compressed air (make sure all passages are clean). You'll be amazed at how clean they come in that short of a time.

I just did a set yesterday after hearing about it from a buddy who's used lemon juice on a couple dozen racks of carbs. After a couple of minutes at slow boil the lemon juice starts to foam up a little (careful not to boil over) and you can see all the sh*t just dissolving.

After boiling them for 15 minutes (might have to roll them around once to make sure you get the entire carbs) rinse them really well and blow them dry with compressed air. The carb bodies will be kinda chalky looking at this point. I used a toothbrush and PB blaster to put a little luster back into them and then put my internals back in.

I had pulled the bowls off, removed the floats, float needles and seats, jets, and air/pilot screws as well as the top covers and slides just to make sure no crap got itself wedged inside those passages.
After putting the carbs back together and bolting them up not only do they look great but the bikes running MUCH better with all the jet passages finally cleaned out.
 

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Discussion Starter #6
Thanks for all the help guys, I'll give this a whirl. Any more advice would be greatly appreciated, like how to know if I'm getting fuel to the cylinder, is there an easy way to tell?

As for the question about the spark, I'm not sure how to tell if it's fat, but it's definitely blue and seems strong (I'm not an experienced mechanic, but to me, it looks strong and steady).

Thanks again!

Kirk
 
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