Carb Sync (Again)

[Dead Eye]

So another Carb Sync thread in as many days Haven't seen this issue before though so figured a new thread would be best rather than hijack the other

My bike does not run well below 3k rpm and in traffic (less than 5mph) its basically like a bucking broncho unless you feather the clutch. Now this pointed to a carb sync problem in my mind and I knew I had trouble doing it last time but it wasn't that far out. In any case, I striped the tank off and got my Carbtune hooked up. It showed pretty much how I had left it last time (only like 3 months ago) where cylinder two was slightly lower than cylinder 1, 3 and 4 which were fairly close to each other. The problem I have though is that the needles do seem to jump around a significant amount compared to videos I've seen before. This time I managed to get a screwdriver down to balance 1 + 2 and now they are fairly close to each other and 3 + 4 are still close but 1 + 2 were slightly lower now than 3 + 4.

Now the strange thing (to me at least) was when I attempted to balance 1 + 2 with 3 + 4. When I adjust the middle screw, 1 + 2 hardly move anywhere though they do a bit. 3 + 4 however move quite a bit and when they raise, the engine RPM increases quite significantly. Balancing them with 1 + 2 means that the engine gets close to stalling and I've adjusted the idle a fair bit to compensate but the mmHg is around 200-210 instead of the advised 230-250 range

Some background; carbs were stripped and cleaned only three months ago and were balanced at the time (still had this jerking problem though). Engine has had new oil + filter, air filter is a K&N but not sure when it was put in - judging by the K&N website, it shouldn't need cleaning yet (based on how dirty it is), also tried moving the vacuum pipes around to make sure the gauges weren't faulty (they aren't). The engine does have 86k on it and it hasn't run "well" since I bought it - lack of care from previous owners basically.

TL;DR (Too long, didn't read)
Balancing 1+2 against 3+4 causes 1+2 to stay relatively where they are (between 200-210mmHg) and 3+4 to move wildly - as the mmHg for 3+4 increase, the RPM of the engine increases quite a bit (from say 1.1k to nearly 2k)

[red98]

mmmmmmmmmmmmmmmmmmmmm....no replies on this one deadeye  :\ ....how about the seals on your inlet rubbers,engine side,you looked at them yet ?....also when you cleaned the carbs did you do the outside aswell,in particular the stops and linkages  .....i find a soaking of wd40 and then a blast from the air gun works quite well,gets in all the nooks and crannies  .....is that a new word  :o 

[Dead Eye]

Yeah, its quite a specific issue - I assume the way that things were behaving isn't normal

There may be other factors involved to be honest but figured I'd start with the carbs. I cleaned all the nooks and crannies I could find and gave the outside a good scrubbing - I checked that everything moved freely when I re-assembled them. I have and old OEM air filter so I'm going to try and pop that in and I've also just filled up with some Shell V-Power plus added some 99% Alcohol to the fuel to maybe get rid of any water - its a long shot but it might be worth it

[Kentish]

Turn the idle up and adjust them that way. I always adjust my mixture screws aswell. You can do this by ear. I wouldn't' worry to much about the manuals advise,Just try and get them all level at tickover

[red98]

" water in fuel " gets mentioned a lot on here something i have never come across,be interesting to see the outcome of the alcohol mix........just stay away from EXUPNUT  :rolleyes ...cant see the air filter being the problem but you got to change it to rule it out