Swapped coils still same issue, carbs are back off now going to see if I find anything this time

 

Swapped over coils same issue,pulled carbs and changed float and needle checked jets and gave it a good blast of carb cleaner, refitted and just the same ...argh

 

Removed/cleaned the pilot jets as well right? Item #6 here. Not #39 the slow jet. Just have to ask...

 

Hi yes the pilot jet was replaced and then changed again as part of fault finding (not today though) I have set them all to 2 1/2 turns out I could try adjusting it while it's running ?
I've just replaced the float and fitted a new float valve but that didn't work either

 

Have you revved it and seen all the slides rise?

 

Hi Mark yes all the slides rise ok im beginning to think its a fuelling issue carbs have been on and off again checked sparks on all 4 - 3 looks weaker than others. reassembled and now 3 and 4 headers are colder than 1 + 2 but now respond to easy start.
took carbs off bench synced them set pilot jets to 3 turns open on all. bike now ticks over and revs better but 3+4 not as hot as 1+2. got my synchroniser fitted and all pulling the same vac just slightly in the header intake leak zone. so im getting somewhere now lol

 

@tommoturbo That's great news. I wish I could be there looking over your shoulder and helping. This seems like a fun one. Will be satisfying to get it resolved. Try to verify all the passageways as far as where air should be going and where fuel should be going. Although this is for the 600F3, they are essentially identical to the 900RR. Might be of some help.

https://cbrforum.com/forum/stickies-...cation-124026/

 

Wow you know your stuff alright! that's a superb write up and thanks for all your advice. I almost got it spot on earlier it was idling great and revving perfect but on my synchroniser no 4 was down slightly so i made a slight adjustment then it all went wrong ...sigh. Im coming to the conclusion im trying to fine tune each carb individually to compensate for cylinder / piston wear etc. I should just try and get decent baseline and be happy with it. haha

 

Just an update ive figured partly why im having issues synching them, the return cable is preventing the the throttle from seating correctly, i force the throttle shut the revs drop off. Ive disconnected it for now while i tune it again. No matter what i seem to do the best outcome is 3 and 4 synced perfectly and 1 and 2 synced but i cant synch 1+2 to 3+4, 1+2 are running lean. Ive set the mixture screws to 2.5 turns from lightly seated and also bench synced. the bike idles fine without choke or idle adjustment and just misses slightly when blipping the throttle. Ill take them off and bench sync them again as i need to start from a known baseline. ive attached a quick video to give an idea of where my vac is at. ive checked for leaks with easy start and theres none?.

 

@tommoturbo So based on what I see there, Ive got some questions. Are the lengths of the vacuum hoses the same for each of the gauges? Are the hoses, where they attach to the brass portion of the gauge easy to remove? Did you synchronize each of the gauges to 1 cylinder?

Here is the reason for the question. First, I see you turning the brass **** on the gauges while the engine is running. Like you said, you have to start from a baseline. How do you know that each of those gauges will read the same thing if they are presented with an identical vacuum load. Well you don't unless you check and calibrate them to the same source. So here is what I would propose you do. Disconnect all of the gauges except from cylinder #1 since that's the easiest to get to. Remember to plug the ports on the other 3 cylinders. Start the engine and look at the gauge and how it's reading on the first cylinder. Disconnect the hose of the first gauge from the port on the intake, and connect gauge #2 to it. Does it read the same? If not, then adjust the brass **** on gauge #2 until it reads the same as #1. Put gauge #1 back on and verify it's still reading the same as it was. Put gage #2 back on again to see it's still the same. If all ok, then disconnect #2 and connect gauge #3 and adjust it to read the same as #1 and #2. Then do the same for #4. Once you do that, now you know that all gauges read the same if they have the same vacuum. Then go back and connect to all the intake ports. If the readings are different, then it's the engine and carburetors that are different and not the gauges. Don't adjust the gauges anymore from this point.

Let us know how it goes.