Starting a rusty '82 KZ750

Pulled the carbs and swapped out the needle valve. Put back on the bike and no more leak BUT now #3 has no fuel AND only cylinder #2 seems to be firing, (it had the only hot header after I tried starting it for 10 minutes.) I'm no mechanic but I've worked on carbs before CB550, kz250, many small engine carbs. At this point I'm scratching my head. So to recap.

- Carbs are clean. were completely stripped down, ultrasonic cleaned 1:30 simple green (green), all jets and ports were rinsed, blown out and inspected before reinstall
- performed a bench synch
- air mixture screws out 1 1/2 turns
- new o'rings on internal plugs (not oem just hardware store)
- swapped needle valve when #3 carb was overflowing (bike was idling). Now carb is completely dry (no start)
- bike did start and run with idle earlier in the day prior to needle valve swap, HOWEVER I'm not confident all cylinders had been firing even then. #2 header was the only hot header after most recent attempt to start the bike.

Other:
Fuel has likely contaminated the oil in the gearbox (~ 6 oz-10oz)
new plugs (all checked for spark)
exhaust leak in the crossover pipe under the bike
yet to check, compression, timing, tappets (but bike was idling so...)
FYI - when bike was running I put my hand down to the exhaust to feel pressure and temperature or exhaust. At that time left side of bike (w/ #2 carb/cylinder) was warm, right side cool

Most likely the carbs are still dirty. Did you remove the pilot jets and fuel pipes and hold them up to a light to see if the orifice is open? Also, checking valve clearance is critical to assure you have good compression.

I used to have that same bike and had a heck of a time getting those CV34 carbs clean. I actually joined this Forum years ago specifically for that issue, figured no way my carbs aren't clean and there was something else I was missing. Took a lot of carb cleaner and compressed air to get the idle circuits clean on those carbs.

I'd start with mixture screws out 2.5 turns.

jayrodoh wrote: I used to have that same bike and had a heck of a time getting those CV34 carbs clean. I actually joined this Forum years ago specifically for that issue, figured no way my carbs aren't clean and there was something else I was missing. Took a lot of carb cleaner and compressed air to get the idle circuits clean on those carbs.

I'd start with mixture screws out 2.5 turns.

Most likely the carbs are still dirty. Did you remove the pilot jets and fuel pipes and hold them up to a light to see if the orifice is open? Also, checking valve clearance is critical to assure you have good compression.

Thanks guys. I feel better. I'll do a compression check and valve maintenance, pull the carbs again and blast some cleaner through em all with plenty of compressed air. I was trying to avoid that caustic carb aerosol but it's this first time I've ever not used it. First I tried soaking these carbs in a Pinesol dilution. They looked nice an clean so I put them on the bike; It ran but leaked. Then simple green and ultrasonic cleaner to try and clear out anything that may be left in those circuits/jets/etc and put them back on with this result. So, I think your right, it's time for some aggressive, caustic chemical intervention! :evil: Weather is getting nicer, these bastard carbs are effing up my timeline! :S .

You can't clean carbs by blowing air through them. The pilot jets, bleed pipes, pilot screws, etc all need to be removed and the circuits cleaned.

Nessism wrote: You can't clean carbs by blowing air through them. The pilot jets, bleed pipes, pilot screws, etc all need to be removed and the circuits cleaned.

I figured with the length of the first soak and rigor of the ultrasonic cleaning, a blast of pressurized air would have sent the scuzz flying. Mea culpa .

Just take your time and don't short cut. I've rebuilt numerous sets of those carbs and while they are more finicky to deal with than the similar Mikuni's, they are not overly difficult per say.

P1030115 by nessism , on Flickr

"Just take your time and don't short cut. "

Lol. Didn't think I did shortcut. Thought I was being thorough. :dry: I guess you don't know what you don't know.

Went back today and started draining float bowls, suddenly #3 was full of fuel. So, I decided to try and start it up again and she did run rough. Headers 1&2 were hot header 3 was warm and 4 was cold. I pulled the carbs intending to clean circuits with carb spray. Also checked compression. All pistons came back at our above 125.

Still cleaning carbs with spray cleaner but...

I noticed when inspecting an exhaust leak at #3 that the exhaust flange was imprinted with a 2. Each of the other flanges had the proper number designation on them except this one that had the leak. The flanges look identical. Do I have a problem with a missing part or is it just coincidence and I maybe didn't tighten it down on the collars enough??

Tvag06 wrote: Went back today and started draining float bowls, suddenly #3 was full of fuel. So, I decided to try and start it up again and she did run rough. Headers 1&2 were hot header 3 was warm and 4 was cold. I pulled the carbs intending to clean circuits with carb spray. Also checked compression. All pistons came back at our above 125.

So after putting the carbs back on and starting it up, #4 header was cold. I opened the screw valve and, sure enough, no fuel in carb 4. This gremlin keeps jumping from one carb to the next it seems. Finally tired of putting carbs on and off the bike, I wanted to be sure all the carbs were receiving fuel. I rigged up a stand to test fuel delivery to each carb after yes another cleaning and inspection. I drilled holes in the side of the container to have access to each screw valve. After hooking up the fuel, opening the tap and opening the screw valves I confirmed fuel is now reaching every carb. After installing carbs (again), the bike started up easily (less than a second on the starter switch.) I let her run for a bit and all headers were hot (some more than others, 4 was the coolest). It was idling at high RPMs (2000 range). Maybe my carb problem is solved. I plan on moving on to carb balancing and idle screw adjustment.

Meanwhile, I took a good listen and observation of the engine running. Left side of the engine is ticking. Occasionally I will hear a pop from that side and a puff of exhaust will escape the valve cover. Seems to me, and I'm no expert, that the valves may need adjustment and a new valve gasket is in order down the road. Thoughts?

Valve adjustment is critical since the valves tighten with mileage and once all the clearance is gone the valves will hang open and burn, along with the valve seats. It should go without saying that the valves must be checked and adjusted as needed.