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Ok carbs have been cleaned during the rebuild. Starts great on the choke and runs fine. After warming when I try to take the choke off it refuses to run. I also had what looks like a fuel over run from the airbox breather pipe?
The carbs have only been dipped and general cleaning and lubrication, no other work. I do have new end cans though. Would they cause the issue? why am I getting fuel from the breather pipe?
Here is a picture of the exhausts.
My CB650 does NOT get warm enough to run without the choke unless I actually ride it a little with the choke on. Totally rebuilt and synced carbs, stock airbox, stock exhaust.
End cans will have a whole lot less back pressure and usually require a change to jetting. It sounds as if the bike is either cold blooded and needs to worm up more, or the pilot jets are partially clogged. Try adjusting the mixture screws to see if that makes a difference.
It's also possible that the slides are either stuck or lifting too fast. I'd start by adjusting the mixture screws and if that doesn't help, pull the carbs and clean and check them again.
End cans will have a whole lot less back pressure and usually require a change to jetting. It sounds as if the bike is either cold blooded and needs to worm up more, or the pilot jets are partially clogged. Try adjusting the mixture screws to see if that makes a difference.
It's also possible that the slides are either stuck or lifting too fast. I'd start by adjusting the mixture screws and if that doesn't help, pull the carbs and clean and check them again.
Yes, all new plugs, filters and brand new fuel etc. Fuel is in the bowls. Already stripped it down again(sob,Sob) to have a look inside the carbs tomorrow. My neighbour is a bit of an expert in building bikes and he said he would have a look at them once I have removed them. gutted as the airbox is a bastard to get back together. Oh well.
So I stripped it all down again and I found that the float in the left outer bowl was stuck and was only operating a small amount. After a little lube and gentle persuasion it operated freely. As someone mentioned earlier it was probably caused by the ultrasonic bath solution or just got overlooked by myself during the build.
Anyway all back together and running sweet! Went a few streets to give it a ride before it's test tomorrow and it was fantastic! ;DLovely sound and ride,can't wait to go for a proper blast.
Thanks for your help people.
Ok...next problem, whilst the bike seems to be running ok I now have fuel weeping from at least one of the float bowls. The rubber seals are the same ones that where in the bike when I got it so they are probably past there best. Does anyone know where I can buy just these rubber bowl gaskets from? On doing a search I am not having much luck.
Thanks in advance.
Ok after freeing up the sticky float valve it seemed the bike ran almost normal apart from a slightly erratic idle. Now it is worse than ever, I am not getting the overflow of fuel from the overflow pipe anymore. I am getting very slight weeping from the float bowl joins. The problem with the idle speed is back with a vengeance. Starts with choke ok and runs fine, when riding the idle speed gets worse until the last time when it stuck at about 4000 revs and refused to come down. I have now parked it.
Being a novice, why when the float valve sticks does it cause the revs to rise? Is this whats causing the high idle? I want to order new float valves and gaskets this week but I just need to understand whats going on!
Any help people? :-\
Just thought of another thing, when I had the carbs off and was checking everything I noticed that one of the round slides?that the diaphragms are attached to was slower to spring up and down in the carb body than the others. Would this cause the revs to be high? ???
Well, they should be the same, so that is a concern. And yes, a sticking slide could give you the same symptoms.
When dismantling/handling those diaphragms/slides you need to be very careful with them. That rubber is very thin and carb cleaner can weaken and/or bubble the rubber and can result in a tear.
A torn diaphragm needs to be replaced.
Both springs need to be the same when removed and set beside each other. If they are mismatched, a previous owner has botched the job.
The metal slide, jet needle and the carb body can be cleaned with carb clean to make sure there is no gunk or varnish, just be very careful not to get any on the diaphragms.
Carbs need to be extremely clean to work properly. Not just free of obvious gunk, but thoroughly clean of any lingering deposits.
The bike was sat for 8 years so I can understand that maybe there is residue on the slides. When i checked the diaphragms looked perfect but I will check again. I will remove and clean again and give it a try. I am leaning towards just replacing the diaphragms,springs and float valves altogether, but I will try just the slides first. If it makes any difference at all I know I am going in the right direction.
Thanks a lot for your input Bozz
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