Carb problems

cantdecide

I have a mate with a '97 Bandit 1200 and it's running very badly. The carbs have been rebuilt with "gixxer internals" by a previous owner and it's also restricted but it was running grand up until recently.

Carbs are a bit of a black art IME and he went as far as getting spare carbs which turned out to be w*nked. He is switching the sliders and diaphragms back to standard to see if that improves matters but since he was thinking about shifting the bike anyway.

The question is what is the worst case scenario? Full specialist rebuild? Any idea what this might cost or who could do it? Any other low-risk options that don't involve endless testing and removal and refitting?

bitburger

in what way is it running badly? if theyve been finddled with recently they might be out of balance which will result in poorer running

steveone

yep before stripping them down etc I'd have got them balanced first off.
what caused it to start running badly? did someone fiddle with them or what?
anything you do is going to involve stripping and refitting them..does the fuel tank have to come off to give access?

cantdecide

Nothing actually happened to them. It just started running more and more rough over a couple of weeks. Before, if you really jabbed the throttle hard, it would stutter before accelerating but now anything more than a brisk twist of the throttle and the engine coughs and splutters and won't accelerate.

His mechanic told him that larger jets will cure the problem too but it will cost him more fuel. I feel if it was running fine and now it isn't, it can only be something gone wrong that requires repair. This problem is dragging on despite attempts to rectify (I don't know what specifically) and my mate is so sick of it, he's thinking he'd rather sell the bike as is rather than spend any meaningful amount of money on it (which is mad, IMO) so I just want to find out what the worst case scenario is before I stick my oar in.

I did have a similar problem with my Bandit 600 years ago and it turned out to be a split carb boot.

bitburger

bigger jets, on a restricted carb, not a good idea i dont think.

JimmyCrackCorn

Start by balancing them. It makes a huge difference if they are slightly out of balance.

Then strip and clean them. Put them back in as they were set-up and see if its just crap or un-settled carbs. Check all the vac lines etc while your at it.

After that re-tuning the carbs is a bit more difficult but the settings the carbs were running on should still be ok. The bikes breathing wont have suddenly changed unless you were changing bits or have a vac leak.