jetting problems

[yfzrider729]

I have a 1996 katana 600. I put a vance and hines full exhaust on it and sent it to a shop with a dyno. They charged me for a rebuild and jetting. I got it back and it runs good when I am at 6500+ rpm and full throttle. There is a stutter around 4500-6500, especially if I cruise there and then try to take off. If i turn the choke on the stutter goes away.

I have cleaned the carbs twice using carbs 101 and found the emulsion tubes to be very dirty the first time. I cleaned those and replaced the orings when I cleaned everything. As dirty as they were and the condition of the oring leads me to believe the shop didn't even clean it, so I am beginning to wonder if they even really changed the jetting. I do know that they changed the float valves.

I know I am getting good spark and my carbs are clean now. So I am leaning towards the jetting as being my problem. My main jet is a 107.5, pilots are 32.5, and a/f screw is at 1.75. Because it is more of a midrange problem I am thinking maybe the needle needs to be shimmed up a little higher? And also what is the stock jet sizes? Thanks

O yea and the plugs are all a chocolate brown at a full throttle shutoff.

[yfzrider729]

Any ideas?

[DClark]

If they put in a jet kit, you should have adjustable needles. Move the clip down so that the needle is raised.

[yfzrider729]

They didn't install a jet kit they just installed individual jets and shimmed the needle up.

[yfzrider729]

??

[hardlydangerous]

the needles wont work well with the new set up, you will have to richen it a bit more by rasing the needle, also drop the floats level .5-1mm to faten up the 1/4 throttle. mixture screws out about 2.75 turns.

Im going to tell you though, in order to take advantage of the new full exhaust, you really should get a jet kit with better designed needles and mains to help correct the 1/4-12 throttle jetting.

Most jet kits use LONGER jets because it does the same as lowering the float height/rasing the fuel level) to help correct the 1/4 throttle jetting.

[yfzrider729]

Thanks for the advice Ill try that first. I am trying to avoid a jet kit right now because I already have over $400 in the first horrible jet job without any good results. I called factory pro today and they were very helpful, he suggested raising the needle first, and if that doesn't work go up on the pilot. I got shims from the hardware store today so ill see what that does this weekend. I wish I would have bought a jet kit to begin with but I want to exhaust all other options before spending more money.

[DClark]

First off, you got hosed. You do not have a jet kit on your bike, you have different size jets and shimmed needles. A jet kit consists of jets, adjustable needles and sometimes a few other things.The magic of the kit is in the needle as it is adjustable and has a special contour.
Since the shop changed out your jets, did you get your old ones? If not, get them. Look at the jets they put in, record their size. Buy a FP jet kit and install it. It might needle a couple of your old jets, maybe not, but a shop, if it's reputable, should give you back your old stuff.
Forget the $ aspect, just buy the kit and enjoy the bike. No amount of shimming can equal a good aftermarket needle as like I said, they have that special contour. And, unless you want to get hammered in the butt twice, stay away from Dynojet kits.

[edrawba]

First off, you got hosed. You do not have a jet kit on your bike, you have different size jets and shimmed needles. A jet kit consists of jets, adjustable needles and sometimes a few other things.The magic of the kit is in the needle as it is adjustable and has a special contour.
Since the shop changed out your jets, did you get your old ones? If not, get them. Look at the jets they put in, record their size. Buy a FP jet kit and install it. It might needle a couple of your old jets, maybe not, but a shop, if it's reputable, should give you back your old stuff.
Forget the $ aspect, just buy the kit and enjoy the bike. No amount of shimming can equal a good aftermarket needle as like I said, they have that special contour. And, unless you want to get hammered in the butt twice, stay away from Dynojet kits.

+1

What shop was that?

[yfzrider729]

Yea I realized that I got ripped off. And the shop was Lafayette, IN, not giving any names. I thought about small claims court but its not worth the trouble. After the conversation we had when he refused to fix his mistake or give me any of my money back, I don't think I could walk into his shop without some trouble. So I can't get the old jets back. I think my main is good because it runs awesome if I run the dogcrap out of it. And the plugs look good. I also have heard that different brand main jets have different sizing so it will take I while to figure out what size I need in the fp main. So right now I am at least going to try to get it good enough to last through the winter. I'm saving for next semester right now and cutting it kinda close so I need a fix until spring when I have more $$ and can afford a jet kit.

[yfzrider729]

Ok I messed around with it all weekend and can't get it to work without a jet kit. I bit the bullet today and ordered a factory pro jet kit and should have it by the thanksgiving holiday so I can get it put on this weekend.

[yfzrider729]

Put the jet kit in and runs perfect except the idle hangs up after I give it gas. The fuel screws are at 2.5 turns but I'm going to mess with it tonight to see if I can fix it

[yfzrider729]

Ok my settings are now, 115 main, 2nd clip from top, 2.75 turns out. It runs perfect once its warmed up other than the idle. I synced it with my homemade tool and it didn't really help. On the idle I think I'm too rich because it lets out a black puff after it idles. Also if I give it gas it hangs out at like 5000 rpm and slowly drops to 500 and dies after about 30 seconds. I think the 5000 rpm may just be were I have the idle set trying to fix it. The idle screw doen't really seem to change the idle much. I read the factory pro intrusctions and I know a hanging idle means to lean, but I think this is a dropping idle from the high idle setting. The problem is that I have that stutter when I try to go to 2.5 turns, and at 3 turns its a different stutter caused from richness. The stutter I am reffering to is at a 5000+rpm steady state cruise and <1/8 throttle. I am almost content without having a good idle, except that it loads up plugs when sitting and idling. Other than that it runs perfect.

[loudnlow7484]

If you have to be 3 turns out on your a/f screws, maybe you'd be better off jumping up a size on the pilot.

I know you said they are clean, but I also might clean out the pilot/idle circuit again.

[DClark]

I'd look for an intake leak.