Carb balancing, poor running

Hi,

When I balance my carbs, do i keep the air filter on or off. I think the Haynes book said to take it off.

I balanced them with the air filter off and the bike seems to run poorly at around 4-5k revs, almost like its misfiring. I can't think what else would make the bike run badly as theres no way of fiddling with timing.

I've also got fairly bad vibes through the pegs and bars...after about 1.5 hours my fingers are a bit numb. What could be causing this? The bike is due for valve clearance check.

Any help would be appreciated.
Thanks, Jim

[yorkie_chris]

You've not put something back right.

Originally Posted by yorkie_chris

You've not put something back right.

+ 1, check to see the airbox is seated properly.

[embee]

Balancing in theory can be done with or without the airbox, at idle the effect of the airbox on intake pressures will be negligible.

Idle mixture adjustment is best done with the airbox on if at all possible. On the curvey SV650 it is very difficult to get to the mixture screws without using a special right angle drive tool, though it can be done.

I have found a thin thermal glove will let me have my hand in there just long enough to tweak the carbs with the engine hot. Front one I use a long thin electrical type screwdriver, rear one I use a small screwdriver bit in a 1/4" drive socket and hex adapter, you have to develop the tools for yourself, what will fit and what you can get your hand in with.

The rear one is a lot easier to get to from abovee with the airbox off, and I've found it makes very slight difference to the final adjustment, so is probably the easiest way. You may find the screws siezed, in which case remove the carbs to sort it out on the bench.

Carbs often benefit from having the floatbowls removed and cleaned, water/rust powder inevitably collects in there.

Also check the choke plungers for closing off properly, corrosion often is seen where the cable meets the plunger and it van easily stop them fully seating, which causes all sorts of poor running. I has this on my bike after only a few months from new.

Sounds a bit to me klike you could have some dodgy ignition item, maybe a coil, maybe just connections, maybe plug cap or HT lead.

I'd recommend iridium plugs as they will tolerate more mixture variation than "conventional" plugs, though it sounds a bit more fundamental in your case.

[embee]

...and something else to check is that the carb diaphragms aren't split.

[yorkie_chris]

Unlikely to be caused by balancing though.

[Sid Squid]

Originally Posted by Jimbo_Bimbo

The bike is due for valve clearance check.

It's pointless trying to balance an engine unless everything else is right first, valves, plugs etc. As all of those things affect balance you may be trying to get equal vacuum readings from cylinders that aren't drawing equally, your twiddling may actually be unbalancing the motor.

Thanks guys. Looks like its a good time to take the bike off the road and get it all sorted ready for spring (I'm not a fast worker!).

[dizzyblonde]

Originally Posted by embee

...and something else to check is that the carb diaphragms aren't split.

ahh, another one is inlet rubber underneath the carbs. I had a crack in one of mine, the rear one, I stuffed some electric tape over it, and it did the job. It made for very odd behaviour with carbs and running.