Just got myself an ultrasonic cleaner for a recommissioning of an old XJR400. Cleaned an amazing amount of shite out the carbs, look good as new! Just got to rebuild them and try them. Carb cleaner just would t remove the varnish
Yeah it can be a right pain getting all the passages clean. The thing to remember is that you have to clean more than just the pilot fuel jet in the bowl. The idle circuit is the pilot air jet, the pilot fuel jet, the transfer ports and the mixture screw port. This diagram shows it wellAt idle the butterfly valve is closed so air is drawn in through the pilot air jet (PAJ in the diagram), the air then goes to the holes in the side of the pilot fuel jet (PJ). Fuel is drawn up through the centre of the pilot fuel jet and mixes with the air from the pilot air jet. It then comes out the transfer ports just after the butterfly valve and also comes out the port at the mixture screw. So all of those passages need to be clear. If you just clean the pilot fuel jet in the bowl and don't clean the pilot air jet, transfer ports and idle screw port you can ustill have problems.
Yeah it can be a right pain getting all the passages clean. The thing to remember is that you have to clean more than just the pilot fuel jet in the bowl. The idle circuit is the pilot air jet, the pilot fuel jet, the transfer ports and the mixture screw port. This diagram shows it wellAt idle the butterfly valve is closed so air is drawn in through the pilot air jet (PAJ in the diagram), the air then goes to the holes in the side of the pilot fuel jet (PJ). Fuel is drawn up through the centre of the pilot fuel jet and mixes with the air from the pilot air jet. It then comes out the transfer ports just after the butterfly valve and also comes out the port at the mixture screw. So all of those passages need to be clear. If you just clean the pilot fuel jet in the bowl and don't clean the pilot air jet, transfer ports and idle screw port you can still have problems.
To me it sound like the pilot circuit is blocked on carb three. To test if the pilot circuit is blocked try starting the bike on choke. Don't touch the throttle just leave the choke on and let the bike idle for a couple of minutes. Check does cylinder three start to get warm when you let it run on choke. The choke circuit is a different circuit to the idle circuit so if it does get warm on the choke but it stays cold off choke it suggest the idle circuit is blocked. You can test if cylinder three is getting warm up by throwing some water on the headers and see if the water dries.
Brilliant I knew that it was essential that the diaphragm should be in perfect condition and that even a pinhole in it would render it useless, but did not understand how it all worked together.Thanks again Dude for a very helpful post.
Does the diagram and description apply to the FZS 1000 carbs as well?
I have just started on full choke which was not as easy as starting without any. 3 exhaust got hot but not as quickly as the others. When I took choke off, the engine stopped. I then went for a ride. All four smooth for several miles. Short stop at junction OK. Another slightly longer stop at lights where I let it idle 30 seconds and down to 3 and lumpy at low revs all the way home.My bike don't like red lights. How does it know ?