New here, need help! 92 Katana 750 - Motorcycle-Journal Forums

phatroksek · 10-08-2006, 04:17 PM

First of all, brand new here, just got my 92 Katana 750.

Now come the explaination of the problems.

After first getting the bike, it ran just fine. Was out riding one day and when I came to a stop after about 20 minutes, the bike stalled on me. I didn't know what happened; I thought I might have released the clutch by accident, but it managed to start right back up only in neutral. Rode it again for another 20 - 30 min and everything was fine. A couple days later was riding for only about 10 minutes and when I stopped the same thing happened; started up again no problem, so I turned it off and let it sit for about 1 hour. Starting riding again and in about 10 minutes, noticed the throttle would not respond while coasting with the clutch in, then it sparked up again after a couple of cranks on the throttle. Eventually, after about 15 minutes of riding the bike stalled out and didn't start again for another 15 minutes. While it was stalled, if I were lucky it would start with the choke on (revving to about 5.5K RPM), but once backed off the choke it would stall.

Ended up cleaning the carbs and right after the cleaning the bike seemed to start somewhat consistently. Still, however, it would rev extremely high with the choke on. The problem this time however was that there was a delay between the time the throttle was cranked and when the engine would rev. Basically, you could hear the intake open once the throttle was cranked, but it would take a second to get the revs. Also, when the revs were up, it would idle at around 2000 RPM. Playing with the idle screw was also a strange thing; after about one revolution of the idle adjusting screw, the RPM's would suddenly drop to around/below 1000 RPM.
Also, while the RPM's were low, the bike would stall if the throttle was cranked. Only sometimes if the throttle was lightly moved it would respond by not stalling.

Ended up correcting the pilot screw positioning (1 5/8 revolutions from seated) the throttle seemed to respond somewhat normally above 2000 RPM. Again, however, at low RPM the bike would stall if the throttle was moved. After some trial tests it seemed like the engine was not getting any fuel. The bike would stall and restart after choking; die when the choke was released; not rev up when the throttle was touched; yada yada yada same thing until the bike wouldn't start.
The trial tests came in when I turned the petcock to prime and waited a couple minutes and the bike started up pretty normally. The throttle responded pretty much like new, even the choke reacted somewhat normally (it would not rev so high). After a few minutes of idling, the bike began acting as it used to, high revving choke, then high idle, delayed throttle response...
Set the fuel to prime while it was running; after a few minutes started reacting normally again!

Just opened up the carbs again for more cleaning thinking it was the pilot jets, but they were clean. Noticed while cleaning however, there was a lot of brown liquid. Flipped the carbs back upright and removed the cover. This is when the I found out that the diaphragm / gasket was stretched! I believe the diaphragm was stretched because it was not seated properly during reassembly. Pushing the gasket down, it was being pressed in on it's side, not fully down into the ring.

After all of this, I have to wait until Monday the earliest to pick up new diaphagms. In any case, what is my problem? If this gasket is stretched is it keeping the fuel from flowing properly? HELP! THANKS IN ADVANCE!