Dynojet Kit any good?

[spray____]

Here's the story:

I've got an '06 GS500F which is running pretty lean. It pops like crazy under hard deceleration. I've heard these bikes are pretty lean from the factory to start with, one of the previous owners added a Yoshi exhaust, and I'm looking to add a K&N Lunchbox when it arrives in the mail next week. With all that together, it's gonna lean like crazy.

Looking at a matrix and a rejetting wiki I found, I figure I'm looking to get some new jets, and possibly some washers to use as spacers. The numbers I landed on are:

[TD="align: center"]Pilot: 20[/TD]
[TD="align: center"]Mid: 65[/TD]
[TD="align: center"]Main: 145[/TD]

Went into Studio Cycle the other day and asked if they could order jets. After a somewhat confusing conversation, I got talked into buying the Dynojet Kit. It's supposed to include everything I need to the point I just answer a few questions and it tells me what sized jets to use. Sounded good.

Got the kit today and it's not exactly what I was expecting. Turns out it only has a single pilot jet, 4 main jet sizes, and comes with new needles, springs, and all kinds of spacers. Read through the instructions a few times, and as far as "answering some questions", it suggests the 124 size for stock exhaust, the 128 size for "aftermarket exhaust with high flowing baffle". That's it. Surely that can't be enough information to get a good starting point. 3/4 of the included documentation is all troubleshooting, which makes me think this isn't going to work out well for me.

So my question is, what would you suggest I do? Should I go ahead with the kit, or just order the jets I was planning on? What's the deal with these Dynojet Kits? I tried finding reviews on the net, but not much comes up. Are they the way to go, or a common rookie mistake?

Also wouldn't mind some confirmation on the exhaust that's on the bike. My thought is it's a "slip on" that's been permanently attached to the stock headers through a weld, and it will give some small performance increase but increase the current lean condition. Is that right?

 

[tricky]

I have the K&N lunchbox with a Jardine full system exhaust and I am running 20 65 145 (though I'm still dialing it in, perhaps I need to go up a size) with the needles shimmed 1.1mm (2 washers). You might be on the rich side with those sizes, the Yoshimura system you have there is not a full system, just a "slip on" (for lack of a better term), as you thought. It doesn't affect the air fuel mixture.

Though, like I said, I'm still tweaking my jet sizings, so maybe you'll have it bang on with those.

I did the same thing as you, bought the Dynojet kit, then figured out I'd be better off ordering individual jets. I ordered mine from PJ motorsports, using the GSTwins wiki to find the correct sizing.

 

[ItalStal]

I have a jet hit and KnN on my 08 zzr. It was worth it Imo. I used the jets for after market exhaust and I have a yoshi slip on. Read the instructions and your service manual. Seems intimidating when you first start but just keep track of everything and don't strip any screws or loose any of the ridiculously small o-rings

Sent from my Z10 using Tapatalk 2

 

[kneedragger88]

Follow the instructions use the clip to fine tune it. Installed hundreds over the years abd they are usiually pretty close. Biggest prob with your bike is the cooling is very efficient and they run very cool. I have known owners actually having to use the choke coming off the highway on a cool fall day.

 

[skapan]

Not sure if it's still the case, but Dynojet used to have a toll free number that you could call for advice about jet sizes and so on based on your specific pipe and/or system. Don't forget that the Dynojet needles often have a different taper, so stock jet settings are out the window. Their kits worked well for me.

 

[spray____]

the Yoshimura system you have there is not a full system, just a "slip on" (for lack of a better term), as you thought. It doesn't affect the air fuel mixture.

Didn't realize that, but very good to know. I guess it just affects sound then? Seems like those things cost a lot of money for just sound.

I did the same thing as you, bought the Dynojet kit, then figured out I'd be better off ordering individual jets. I ordered mine from PJ motorsports, using the GSTwins wiki to find the correct sizing.

Thanks. I'm thinking there's got to be a place in TO to get them without paying for shipping and duties, but I haven't found it yet. Ordering from the states they end up being about $10 each delivered

 

[spray____]

Not sure if it's still the case, but Dynojet used to have a toll free number that you could call for advice about jet sizes and so on based on your specific pipe and/or system..

That sounds like a great idea. I think I might call them and see how confidence inspiring the expierience is.

Don't forget that the Dynojet needles often have a different taper, so stock jet settings are out the window. Their kits worked well for me.

So the 124/128 aren't necessarily as far off 145 as one might think?

 

[Iggy76]

That sounds like a great idea. I think I might call them and see how confidence inspiring the expierience is.


So the 124/128 aren't necessarily as far off 145 as one might think?

And dynojet's numbers have no relation to the stock numbers. A 145 in one manufacturer is not the same as a 145 from another.

 

[spray____]

And dynojet's numbers have no relation to the stock numbers. A 145 in one manufacturer is not the same as a 145 from another.

Didn't realize that, I thought it was a standard physical measurement of something. Thanks.

 

[tricky]

Didn't realize that, but very good to know. I guess it just affects sound then? Seems like those things cost a lot of money for just sound.

Yea, that is why I ended up going for the Jardine full system. ~$300 for the Yosh slip-on vs ~$400 for the full system. It made sense to me, plus now I have aluminum headers so there's no more nasty surface rusting. I don't know what Suzuki was thinking using that black paint on what I assume was mild steel.

Didn't realize that, I thought it was a standard physical measurement of something. Thanks.

The sizing holds for Mikuni jets, so if you buy them individually, then the sizing works. Dynojet must've gone off and done their own thing

 

[TwistedKestrel]

I am necroing this thread just for whoever finds it in the future (I just got a GS500 and have been researching carb jetting) ... the reason why the Dynojet kit supplies "small" jets in the GS500 kit is down to the fuel needle. If you compare the stock needle to the Dynojet one, you will see the Dynojet needle tapers more rapidly and is narrower at the end. Trust it!

 

[spray____]

I am necroing this thread just for whoever finds it in the future (I just got a GS500 and have been researching carb jetting) ... the reason why the Dynojet kit supplies "small" jets in the GS500 kit is down to the fuel needle. If you compare the stock needle to the Dynojet one, you will see the Dynojet needle tapers more rapidly and is narrower at the end. Trust it!

Since this is up again, I'll update everyone.

I called their toll free line and they confirmed that they don't make a stage 3 kit for newer GS500s, and even the biggest jets would leave my bike running lean. I could always buy more jets, but getting the jets I needed was the whole point of buying the kit.

Ended up taking the kit back. Had to pay a restocking fee, but whatever. I still had enough refund to buy just the jets I needed in the first place anyway. Got a starting point dialed in with help from gstwins.com forum members and their wiki. Bike is way better now, pulls strong and sounds better as well. Might not be perfect, but it's way closer than it was when I bought it.