Suzuki Central Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter #1
My dad has an 04 ltz and it was running lean. He has a Yoshimura slip on, and k&n filter. With the stock jetting it would backfire when letting off from full throttle. The spark plug looked really lean. I just installed a 6sigma jet kit. Moved the clip position down 1 slot, installed the recommended 146 main jet, and 27.5 pilot. Also set the fuel mixture screw to 3 turns out. After finishing the carb work it started right up. Sounded like it was running smoother than ever at idle. When he revved it up it sounded great and didn't backfire at all like it used to. We also had the airbox cover off, as recommended with the jet kit. My dad took it for a spin and he said it felt like it would bog ar high rpm in 1st gear. We installed the airbox cover and I took it for a test ride. I noticed the bog or power loss at high rpm in 1st gear. Adding the airbox cover didn't seem to matter, all though with the stock jetting it wouldn't stay running with the airbox cover off. Well it got late so we had to stop for the day, but my Dad did notice afterwards that the fuel valve was in the prime position. He said he's heard that you shouldn't drive it in the prime position and I'm hoping when he tests it out tomorrow it runs great.
 

·
Super Moderator
Joined
·
3,452 Posts
Are you hitting the rev limiter? Hard to test in first gear, without running out or rpm, unless your going straight up.. Prime wont affect the running, but will allow the carb to flood when parked, if you have a bad needle valve.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #3
It kind of feels similar to that but no. We went through 2nd and 3rd gear as well but it ran great after 1st gear. We rarely ever hit the rev limiters, that was never an issue before we worked on the carb.
 

·
Super Moderator
Joined
·
3,452 Posts
Is it fully warmed up doing this?
 

·
Super Moderator
Joined
·
4,679 Posts
No. You can run in prime, just can’t leave it in prime when not running.
 

·
Super Moderator
Joined
·
3,452 Posts
Only thing I can think of that would act in first gear and not higher gears, other than rev limiter, is maybe the float level is off a bit, allowing spillover under the harder acceleration in first gear.
 

·
Administrator
Joined
·
7,841 Posts
A slip on and K&N filter don't require any jetting changes if the air box lid is on. The popping on decell means it's lean at an idle. All you probably needed to do was open the fuel screw about 3 turns out.

The contents of that jet kit don't even sound close to right. The pilot is definitely too big, and with that big pilot, it definitely will be getting too much fuel at idle, at 3 turns out. Also that main jet is too small to run with the lid off. It might even be too small with the lid on. I've seen those kits and I don't think they're any good.


To run with the lid off, it should be closer to a stock pilot at 3 turns or 25 pilot at 2ish turns. The main depends on the needle, but should around a 150 (140 mikuni) with an aftermarket needle. With the stock needle it will be quite a bit bigger yet like a 165, but if your needle has multiple clip positions, it's not stock.

Also, as if things needed to be more complicated, it matters what brand of jet you are using. Mikuni jets and aftermarket numbers don't line up.

Here is a chart comparing them.
aefd709b-7cce-b81b.jpg




In my opinion, I would do one of 2 things.

1 Put the stock jetting back in, make sure the pilot is clean, and open the fuel screw to 3 turns out. This will require running with the lid on and the snorkel in place.

2 Get a dynojet kit. Run with the lid off and gain a little power over stock. The DJ kit comes with everything you need, although a 25 pilot is a nice addition.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #11
A slip on and K&N filter don't require any jetting changes if the air box lid is on. The popping on decell means it's lean at an idle. All you probably needed to do was open the fuel screw about 3 turns out.

The contents of that jet kit don't even sound close to right. The pilot is definitely too big, and with that big pilot, it definitely will be getting too much fuel at idle, at 3 turns out. Also that main jet is too small to run with the lid off. It might even be too small with the lid on. I've seen those kits and I don't think they're any good.


To run with the lid off, it should be closer to a stock pilot at 3 turns or 25 pilot at 2ish turns. The main depends on the needle, but should around a 150 (140 mikuni) with an aftermarket needle. With the stock needle it will be quite a bit bigger yet like a 165, but if your needle has multiple clip positions, it's not stock.

Also, as if things needed to be more complicated, it matters what brand of jet you are using. Mikuni jets and aftermarket numbers don't line up.

Here is a chart comparing them.
View attachment 49605



In my opinion, I would do one of 2 things.

1 Put the stock jetting back in, make sure the pilot is clean, and open the fuel screw to 3 turns out. This will require running with the lid on and the snorkel in place.

2 Get a dynojet kit. Run with the lid off and gain a little power over stock. The DJ kit comes with everything you need, although a 25 pilot is a nice addition.
Thanks for the input here. I ended up ordering a dynojet kit basically just for the needle. I am running the stock needle with 2 very small shims underneath the e clip as per the jet kit instructions. I set this up exactly to the way the jet kit instructed. I also ordered a 155 mikuni main, and 25 mikuni pilot. I would like to run with the air box lid off if I can get it jetted correctly as that should equate to more power.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #12
Little update, haven't touched anything yet as I'm waiting on more parts to come. I stopped at my dad's house yesterday and took it for another spin, remember it was getting late last time I was there. First I tried it with the airbox cover on. It bogs I'd guess a little over half way through the rpm range if you gun it in first gear. Acts almost like a rev limiter, it takes off great, then at a certain rpm falls on its face. Hit second and third and it will rev much higher in the rpms. Did a few launches with the air box cover on and all were the same. Next I removed the air box cover and tried again. It seemed a tiny bit better, seemed like it would rev maybe another 1000 rpm before it falls flat. Second and third gear pull hard all the way though the rpm range.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #13
Over here at my Dads again messing with this carb. I have gone from a 146 Dynojet main (recommended per jet kit instructions) up to 165. It seems to have the most power with the 165 main jet which should be similar to a mikuni 155 main. Needle in the 3rd clip position. No matter what main, pilot, or fuel screw setting I use it runs very similar. Still doesn't seem to want to redline 1st gear. Hell I'm starting to think we are actually just hitting the rev limiter. Never did that with the stock (lean) jetting. I'm thinking maybe with more fuel and air it's just getting to the rev limiter faster than stock and maybe that's why we never noticed this when it had the stock jetting. I'm thinking about going back to stock on everything and see if I am in fact hitting the rev limiter or if something is causing a bog before we get to the limiter.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #14
Alright, we ended up with the stock pilot, the 165 dynojet main, dynojet needle in 3rd clip position, and 2.5 turns out on the mixture screw. Seems to have the most power or hardest feeling pull at this setup. I am thinking that with the better jetting it just revs faster and we were hitting the rev limiter.
 

·
Administrator
Joined
·
7,841 Posts
That main sounds a little aggressive, but if it runs good, go by that. If you have them, I'd try a size or two smaller and see how it acts. The rest of your settings sound pretty normal.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #16
That main sounds a little aggressive, but if it runs good, go by that. If you have them, I'd try a size or two smaller and see how it acts. The rest of your settings sound pretty normal.
According to the conversion chart the 165 dynojet is similar to the 155 mikuni. From my research most people with a similar setup are running a 155 mikuni main, so I think I'm actually right there. I did try slightly smaller main jets and it ran good with most, until I got down below the 146. Just seems to pull hardest with the 165. For those getting a backfire when letting off from full throttle, opening up the fuel screw should help with that.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #17
I replaced the chain on the ltz yesterday, took it for a spin afterwards and had the airbox lid on. It started bogging worse than ever when reaching about half throttle. Removed the airbox lid and it ran great again. I'm thinking maybe the 165 dynojet main might be a little rich, but runs great without the airbox lid. When I had the 146 main in it, the machine ran great with or without the lid. I'll let my dad decide if he wants to go down a little on the main. It feels the fastest how its setup now with the airbox lid removed.
 

·
Administrator
Joined
·
7,841 Posts
I replaced the chain on the ltz yesterday, took it for a spin afterwards and had the airbox lid on. It started bogging worse than ever when reaching about half throttle. Removed the airbox lid and it ran great again. I'm thinking maybe the 165 dynojet main might be a little rich, but runs great without the airbox lid. When I had the 146 main in it, the machine ran great with or without the lid. I'll let my dad decide if he wants to go down a little on the main. It feels the fastest how its setup now with the airbox lid removed.
The lid completely changes the jetting requirements. You have to run with it or without it. There is no jetting that's right both ways.
 
1 - 18 of 18 Posts
Top