Bandit Carb Rebuild
 

Have just purchased a cheap Bandit for an eastern european trip this summer. Although it ran sweetly for a few months the butterfly on my carb on cylinder three siezed and I had to strip and rebuild all four carbs to free it up. Although I completed the job as a usual carb rebuild I now find the bike won't start. I think its due to lack of fuel (checking the plugs..). I know I obviously disturbed all of the settings when I stripped everything but I was expecting it to run pretty roughly so that I could tune it from there.

I have checked the bowls and they are full of fuel. I made sure the butterflies were balanced perfectly before refitting the carbs, and I know the float valves are working. The only other thing I disturbed were the tickover jets. I returned them to factory start settings but wasnt sure where to set the butterflies. They are currently open to about 1mm with the throttle shut. Does this sound ok?

Alternatively (and although highly unlikely!) does anyone have any other suggestions???

Many thanks for any help, I know its possibly one of the more unusual bikes were likely to see on the forum!!!!

Dave

Couple of points:

You can't balance the butterflies prior to fitting the carbs to the bike. This is what vacuum gauges are for & should be done once the valve clearances have been checked & adjusted (easy on a Bandit - screw & locknut)

There are no tickover jets? I assume that you're referring to the brass screws on the front underside of the carb body - if so, these are your pilot mixture screws & affect throttle response. Unless you have different pipe etc, set as per manual.

Does the bike try to fire at all? I could understand one or two cylinders not firing but not all four?

Try charging the battery to be on the safe side. Also check that the plugs are clean, gapped & have a fat blue spark that can jump 5mm to earth.

No joy? Remove float bowls, carb tops, slides etc & blow through with an airline & try again. Ensure that the air box snorkel/inlet is not blocked.

If not firing at all, as a last resort - fit carbs without the air box, squirt/spoon/tip a little fuel down the bellmouth of each carb & try firing up. If it fires up, then it's a carb problem. If not, then there's a good chance it's electrical - coils, plugs. leads, ignition pickups, battery etc.

BTW, I'm assuming that you've tried fresh fuel? With the carbs apart, ckeck that the choke mechanism is actually operating as it should?

Steve

I followed your suggestions and was getting desperate until the last point you made.

I dropped fuel into the mouth of each carb and turned it over. It fired instantly. I am now more confused than ever!

Clearly the bike is getting no fuel. The float bowls are full, I can repeatedly drain them. The jets are all blown through, I have never touched the float levels. The pilot jets are all set as stated in the manual.

I can't believe that all four carbs are blocked/rich/lean/whatever. There is clearly fuel getting to the bowls of all four carbs.

I am stumped. Any ideas?

Many Thanks

Dave

Did you just the carbs through with an airline or did you remove each jet etc & clean it individually?

Check the carb tops for punctured diaphragms?

With no air filter on the carbs, open the throttle & confirm that all four needles are lifting with the slides.

If the bike refuses to fire up on a closed throttle, it sounds like the pilot circuit is blocked? If you look at the front of each bellmouth, there may be a small brass jet loacted towards the bottom of the bellmouth entrance, this is possibly related to the pilot circuit? I'll try to provide a betteranswer later when I will have a GSXR manual in front of me - carbs are the same make & very similar.

Steve

Finally!!!!

Many thanks for all of your input. I checked all of the circuits, but I just couldnt believe that all four could be blocked.

Eventually I stripped the carbs again and checked all the specs. For some reason all of the floats were 3mm out of setting...!?

I had altered non of them....

I reset them and opened up the pilot half a turn to richen the mixture a bit. When I reassembled everything it started first time...

Bloody odd. Just for future reference any ideas why ALL the float heights were out of tolerance? Assuming they must have been that way prior to initial disassembly how come it ran ok before but not when I put it all back?

The only thing I can think of is that because the bike was running ever leaner the last owner compensated by increasing the fuel input through the pilot jet. But if so, how come there was no problems with the throtle response?

Like I said, I am confused,

Many thanks for your time,


Dave Lomax

[This message has been edited by davidlomax (edited 14 March 2004).]

No problem, glad to help.

Steve