I have a 900rr and it runs like crap... i've done the following:

Changed Plugs
Cleaned Carbs (Chem B12)
Changed fuel diaphram
Tested the petcock
drained the fuel, put new fuel
Tried Seafoam in the fuel tank
Changed coil for 2/3 (the one on the left) and verified the wiring.
Tested spark and am getting spark on 2/3
cleaned out subair filter

bottom line, only 1 and 4 are firing (because the headers are hot after it runs). 2 and 3 are not hot... i've messed with the fuel mixture screws with no success... still the same thing.. im lost...

Any suggestions are appreciated.. attached is the latest video of how she sounds...

 

Not sure how easy/hard it is to get at your float bowls, but after switching on the fuel drop all float bowls from the carbs and look at the level of fuel in them. They should all be the same. If 2 and 3 are low, that is probably the problem. If the levels are the same and all spark plugs fire (lay them on top of the cylinder head and check them for a spark as you crank the engine) then obviously fuel isn't getting to No 2 and 3 cylinders. You'll have to remove all four carbs, strip them down and clean them out thoroughly as it sounds like you have a blockage somewhere. It doesn't take much to block the tiny holes in the jets etc and please don't go poking any wire through the holes. Try getting access to compressed air to do the job. Wish you all the best in solving it!

 

Thanks, yeah I am getting good spark.. so i think it has to do with fuel... i am able to access the float bowls and unscrewed the drain underneath 2 and 3 and fuel is there.. but i don't know how much is in each compared to 1 and 4...

think it could be a fuel screw issue? carb sync?

 

Hi. Unfortunately, there are so many things that could be stopping your bike from only running on two cylinders. Valve clearances could be tight on 2 & 3, which would not allow the valves to close properly causing a lack of compression, thereby no power from those two cylinders. You say you have a spark from all four spark plugs so that can't be the problem. Double check that the plug leads are in the correct firing order. I'm not sure of the correct order without looking in my handbook, but it should be something like 1,3,4,2 or 1,2,4,3. I'll take a look and let you know. Do the fuel test on all four carbs by draining the float bowls down one at a time and measure the amount from each bowl. They should be the same whatever the amount is. If 1 and 4 have more fuel in the bowls than 2 and 3 that could affect the running on those cylinders (2 & 3). They won't be getting enough fuel through to the jets. Run the bike for a few seconds then stop the engine. Take out all four plugs and check plugs 2 and 3 to see if they are wet with petrol. If they are and 1 & 4 are dry, then 2 & 3 are receiving fuel but not firing. If 2 & 3 are dry also, then no fuel it getting to them. Sometimes spark plugs fire out of the cylinder head but can lose their spark once screwed back in. This could be weak coils feeding those spark plugs. Substitute the coils feeding 1 & 4 for those feeding 2 & 3 and see if 1 & 4 stop firing. I think it is possible to swap them over, but you'll have to check. On older bikes of the sixties and seventies you could remove the air filters and look through the back of the carbs and watch for fuel coming from the main jets into the engine as it was running, but with today's bikes I'm not sure if this is possible and would mean a lot of work I guess. Hope I haven't given you too much to think about, but elimination is the only way I'm afraid. Keep us informed as to the results of your tests if you decide to do them?