Carbs make spitting sound??? What the heck!

[jason9775]

okay, here is the story. My neighbor, who can't keep his hands of motorcycles, :-),   installed a "custom jet kit" on my bike.  In addition to
installing the jets, he cut a round hole in the airbox, (the part that covers the filter and is removable to change filter).  I guess this is a "custom tune"! Anyway, the bike is ballz out fast now but the carbs make an awful spitting noise, especially when I just start it up.  It subsides a little bit after warming up, but it still there. Yeah, I know, I am a waterhead   , but it is really annoying! Anywho, what is causing this and if I install stock jets and cover the hole, will this illiminate the problem?  I don't really talk to this person much anymore for more reasons than one, so that is why I am here!!

Thanks,

Chuck

[PaulVS]

Sounds like one of the rubber caps over the sync tubes came off.

[kedeg_97B12]

Sounds like one of the rubber caps over the sync tubes came off.

or check the manifold boot clamps. You want tight but not too tight.

[B12Teuton]

That jet kit scares me just thinking about it.

It may be backfireing through the carbs into the airbox.  This a just a guess as I'm sure the bike does not run 100% healthy despite feeling faster.  Not dissing your neighbor, but Bandits are pretty particular to jetting.  More so than a lot of other bikes.  Without specifics on what he did to customize the carbs, we can't help much.

If it is backfiring into the airbox, the risk of a fire is big!!
Many bikes have burned to the ground in minutes from this sort of thing.

[jason9775]

B12Teuton, I believe he installed thinner main jets. That's about all I know, besides hacking the airbox cover!

Thanks!

[rider123]

Holy!! That's one jihad jetting job!(JJJ)    It your own personal jetting 9/11. I would take it to a real mechanic ASAP. Why would he jet it leaner without an airbox or airbox mod??!! Dude I wouldn't do this again! Leave it to a professional please. Theoretically if your very lean you can burn holes in pistons! Don't ride it till it's checked at a dealer or LICENSED mechanic. What are your A/F mixture screws set at?

In theory you could be just sensitive to the extra sound of a hacked airbox but why take a chance? Is there anyway to tape the sound and turn it into an mp3 or wav file we could listen to it. I could host it for a while for you. The "Spittin" that goes away as you warm up could be misinterpreted as misfiring on a lean mixture which could be caused by loose boots or sync caps. Hmmm... Good luck.

P.S. if you can give us some sort of specs on what your "friend" put in there at least we'd know where you stand. Any idea what the pilot jet and main jet size he put in there is? Also A/F screw turns would help also.Is it a first generation('96-2000) or a second generation?(2001+) Do you have an aftermarket pipe? Which brand? Try and get the specs please.

[B12Teuton]

It's worse than I though!

[rider123]

Maybe not, if Jason can just give us what he has in specs and some of the guru's like RED01 and the other might be able to help you out. Anything can be fixed. It could be as simple as he left the A/F mixture screws at the stock setting which is horribly lean. Could be as simple as turning em out a half a turn. Keep us posted.

Also with this airbox mod is sound alot like a holeshot. Did you have to pay for this "custom" jetting or was it free from weird parts he had laying around? If this Jetting "job" was just ppoking a hole in the airbox then 100% you will be lean. If you would like to fix it yourself for sure and be %100 on the jetting go over to holeshot and order their stage I jetting kit with advancer. Is your pipe stock or aftermarket? Does the "spitting" go away or get better with the choke on?

I can't with 100% certainty say what your A/F should be turned out but for example on my bike which was horribly lean from factory are at 3.5 turns out to fix the stumbling, from what I've seen on this site most people with stage 1 jet kits(sounds like yours) have theirs turned out around 4- 4.5 turns. Of course this is with the stock pilot jets. If the pilot jets have been changed, then it's a whole new ballgame. If the mixture screws were set at stock which according to the Haynes Manual is 3.0 turns out which is already lean, then not changing them with an airbox mod would make it even more lean! Also many people report wild mixture screw setting from the factory, so who know what you have in there.

[jason9775]

First of all, I did not have to pay for this... thank god!! . Thinking back, I believe he installed 130 Main jets and cut about a 2-2 1/2 diameter hole in airbox.. holeshot method.  He also took out the stock air filter and replaced with a uni filter. Another thing is that I have an extra Un-modified air box and when I put that on,  the bike would not go past 7-8K RPMS even with the throttle all the way open. It was sputtering something terrible.  The bike would not pull at all.  I think I should just get a "real jet kit" and have a professional install!!! WHADAAA think?  

[BurghBandito]

Hi all... I'm pretty new here too.  

Hey Chuck, I have a '97 B-12, which was modified by the previous owner.  It has a Factory Pro CRB-S74-3.0 jet kit, Two Brothers S/S exhaust/can and BMC air filter pods.  My B-12 was doing the same thing.  It would run like a... bandit at hi r.p.m.'s, had excellent throttle response from idle to red line.  It idled fine but spit thru the carbs (sounded like a puppy sneeze).  It also spit at hi r.p.m.'s with small throttle openings.  

I kinda suspected that it was running a bit lean down below, but what really shook me up was when I had it running head first into a dimmly lit garage (with the door open, of course) while checking the charging system.  When I revved it to about 5000 r.p.m., I noticed the headers turning red coming out of the heads.  I immediately checked for air leaks and found none.  I richened the A/F screws from 2-1/2 to 3 turns.  That helped quite a bit.  I then taped up 2/3 of each air cleaner and the problem was gone.  

So, to make a short story even longer, I installed one size larger pilots jets and set the A/F screws at 3.5 turns.  The bike runs as strong or stronger than before... and the spitting is now gone.  

Check out the Factory Pro web-site for lotsa tuning info... can't remember the address, but check on google...  Good Luck.

Tom

[rider123]

First of all, I did not have to pay for this... thank god!! . Thinking back, I believe he installed 130 Main jets and cut about a 2-2 1/2 diameter hole in airbox.. holeshot method.  He also took out the stock air filter and replaced with a uni filter. Another thing is that I have an extra Un-modified air box and when I put that on,  the bike would not go past 7-8K RPMS even with the throttle all the way open. It was sputtering something terrible.  The bike would not pull at all.  I think I should just get a "real jet kit" and have a professional install!!! WHADAAA think?  

You may not need a "real" jet kit, lets try the cheap fixes first. I may not be an expert but I believe your running a little lean on the bottom end. Try this first:

Go and get a Suzuki OEM filter. Dale from holeshot says himself that they are way better at trapping dust than any of the aftermarket stuff. This is going to help a little already as it doesn't breath as well as an aftermarket so the mixture will richen up slightly.

What are your mixture screws set at? To find out, mark where you have them set now with a marker, then count the number of turns in CLOCKWISE until they are LIGHTLY seated. Don't force them tight. Count the numbers of turns out untill you're at 3.5. I would highly suggest what the other posters are saying here. THe pilots on the Bandit are artifically lean. I have a stock Bandit with no aftermarket pipe and I'm at 3.5 out from lightly seated! I would set the screws out at 3.5 and give it a shot from there. If you want to have some shits and giggles try just setting the mixture screws out 3.5 turns with the aftermarket filter and see what happens, it's free.

This "spitting" sounds like a lean misfire(I had same thing I think without the EPA plugs drilled and fixed). Try opening the choke(enricher circuit) ever so slightly, does this stop the "spitting". If it runs pretty good once on the mains, you're almost there. Before spending hundreds of dollars, get the filter, set the screws out 3.5 turns and see what happens. If the "spitting" gets better give it another 1/4-1/2 a turn and see what happens. If it improves you're getting there!!


What year is your bike? It depends if you are a 1G ('96-2000) or a 2G(2001+) where you need to be on jet sizes and the like.

[jason9775]

finally got some time to write!!!  Well, I gave the carbs a clean and tweeked the A/F screws a tad and the spitting decreased quite a bit, but it was still there. So, then I said the hell with it and got  a Dynojet Stage 3 w/ K&N pods.. not only has the spitting dissapeared, but the bike runs the best it ever has! Torque seems to have dropped a tad, but the overall smoothness freak'in rocks! no spitting, instant throttle response, quicker warm-up and better idling. Geez, who would of thought that doing things the right way would work!!  

[Red01]

I'm impressed... I think that's the first Dynojet Bandit kit I've ever heard of that went in trouble-free!