Hello, I've been having this issue for some time now, and tried to fix it in several ways, after no avail I'm now seeking help. First off my bike a is 75 400 that I've opened up to 466 with the cruizinimage kit from ebay. I'm running carb rebuild kit from 4into1 since when I got the bike th eoriginal brass was missing or damaged. I have an electronic ignition from tytronics. I have the original header, but the muffler/tail pipe isn't stock, also I'm running the stock airbox, the rubber intake pipes are failrly new (about 3 years old) and still soft and pliable, the origns from the pipes to the head are new. I originally had hardware store hose clamps on the intake, changed them to honda still clamps I got from several junked mopeds, and currently I'm running hose clamp kit from vitalmotorsports. The carbs have been cleaned and reset accordingly to the tutorials I've found here and the specs from the service manual, I can get them in and out in about 20 minutes now since I've done it so many times. The bike didn't come with a push cable for the throttle and currently it still doesn't. The carb floats are set to 22 mm.
The bike starts up, has no gassy smell from the exhaust an idles fine when cold, after a couple of minutes she starts to die so who have to open the throtlle a wee bit I usually do it from the screw in the carb rack. If you rev it and let the throttle go it stays revving at around 3K and then goes down. The carbs have been vacuum synched, and I currently have the gauges hooked up to the bike, they all pull the same vacuum. I also read in this forum that the tytronics' trigger shaft is a bit on the long side and can cause binding in the advancer mechanism due to thermal expansion, just this morning I took out about .5 mm from the shaft in the lathe to see if this would cause any change, I also cleaned and regreased my advancer which was pretty clean to begin with. I've sprayed carb cleaner all around the intake and have no leaks, so I have no idea on what more to do to the bike now.
