No Start After New Carb Diaphragms

As my slides would stick until warm and my diaphragms had the consistency of wet noodles, I installed brand new genuine Suzuki diaphragms in my 89 Kat 750 carbs. Now she won't start. I am getting fuel to the carbs and I am getting spark. In fact, she almost catches from time to time, but she will not run. It also gave me a loud backfire out of the exhaust once. I checked schematics and a youtube video and I seem to have everything right. Am I missing something? Is there an issue with replacement diaphragms? Please help me.

Diaphragms will not stop it from starting.

bad plugs (are they black?) will

In reply to bentwrench:

Plugs are perfect, I have spark and fuel in the lines. The bike started and ran before I installed the new diaphragms. The ONLY thing I touched were the diaphragms. Yesterday evening it would try to catch a bit, but I ran the battery down. I charged it up and cranked it last nigh and I got a VERY loud backfire and now it won't even try to catch.

Did you leave the carbs on the engine while you did the diaphragm replacement? Since you mentioned the slides sticking, I'll assume that what you used were slides with the diaphragms attached. Are the replacement slides completely identical to the old ones? Can you put the old ones back in and see if that lets it run again?

Slides are the same ones. Carbs were left on the bike. Let me be clear. The slides would stick when the engine had been off for a few days. After 20 minutes of running, that carbs behaved normally. I asked Sudco and they said it sounds like the diaphragms, I removed the slide (as you must do to change the diaphragms, cleaned them and reinstalled with new diaphragms. I checked the slides move freely. The everything is installed correctly as per the schematic and youtube video. Just tried it. I got one stumble and then nothing. I even blew the carbs out with compressed air just now and nothing has changed.

It was down to 1/4 tank. I added about a gallon to get to half a tank. Now if you cranks it for about 10 to 15 seconds it will let a LOUD backfire out of the right pipe. It would even start to catch. It just goes BOOM. This is frustrating because it ran fine (except for a little slide sticking/ diaphragm issue after sitting for a few days. Now, she just goes boom!

Did you see anything wrong with the old diaphragms? If not, you may want to switch back and see what happens.

Make sure you've got the lids on right. Sometimes they are subtly directional.

What do you mean you blew the carburetors out with compressed air?

Other than they are very soft, the ones were ok. I replaced diaphragms be cause I would get sticking slides if the bike sat for a few days. Once warmed for 20 minutes the carbs would work fine. I though maybe the air hole for the idle jet might be plugged to I blew some air through. Made no difference. The tops are directional and are on correctly. Slides are the same old slides and move freely and smoothly.

Sounds like the slides are not lifting under vacuum so your try it start on a Really LEAN. If you can get a few fingers in the throat lift 2 or 3 while cranking and see if it lights off. if it does re-clean the slides and the bores.

The slides move easily when I move them manually. When I crank the engine, the slides move upland down slightly with the pulses of the engine. There isn't much vacuum at cranking speeds. It should not matter so much that the slides are moving at start up anyway.

Try putting some gas in a spray bottle and shooting it in the carbs. Many perceived fuel issues are really electrical issues.

Good you should see them move with each vacuum pulse so your problem likely lies else where. I would try squirting fuel in as Kenny suggested above and see if you can get it to fire up.