Dynojet kit jetting questions

[Smokinapankake]

So I did a search but wasn't really satisfied with what I found, so....

I committed a probably cardinal sin by rendering my airbox unuseable when trying to replace the o rings behind the intake boots. Those phillips pan head screws Suzuki used are worthless!
1984 Katana 750
I now have individual filters and the stock exhaust. I've been through the carbs a few times (fiddling with jetting) and they are clean. No issues there, no air leaks. Fuel valve is functioning perfectly. Valves have not been adjusted but my compression readings are between 130 and 145 all the way across.
I have it running acceptably well, maybe a little rich, but tolerable. Idles okay, accelerates okay, but have low mileage.

My question is this: Jeff at Z-1 has advised me that the Dynojet kits are kind of a one size fits all deal and may not get your carburetion to its optimal. However, I want my throttle response to be sharper, mileage to be better (I currently get 35 ish MPG with pod filters and stock exhaust) and top end to be sharper as well. Currently I can feel it bog down a little at WOT. Will the dynojet kit address these problems? Drilling the slides makes me a bit nervous, but I have downloaded the instructions for the kit I presume I need (1980-1985 GS 700 all models) and it specifically states that for stage 1: "For mildly tuned machines using the stock airbox with stock or K&N filter". For stage 3: "For mildly tuned machines using individual filters or velocity stacks".
"Both stages may also be used with a good aftermarket exhaust".

Note that it doesn't say MUST be used with a good aftermarket exhaust.
At about 120 bucks for the kit I wonder if I will notice that big a difference between what I have now and what the kit will bring?

This may all seem a bit vague, I just want some of your more professional and knowledgeable opinions....

Thanks so much!

 

[Guest]

The money basically buys an adjustable jet needle. This will resolve any bogging on throttle roll when adjusted properly. You can use Mikuni jets with the Dynojet needle so getting the main perfect doesn't just have to come from Dynojet.
I do believe the kit also comes with the main air jet press in jets? This will change the main jet size by richening the main with a smaller air jet.

 

[doctorgonzo]

The money basically buys an adjustable jet needle. This will resolve any bogging on throttle roll when adjusted properly. You can use Mikuni jets with the Dynojet needle so getting the main perfect doesn't just have to come from Dynojet.
I do believe the kit also comes with the main air jet press in jets? This will change the main jet size by richening the main with a smaller air jet.

Mine came with the press in air jets for GS1000G. Stage 3 is for any kind of pods or velocity stacks with or without aftermarket exhaust. Mine came with a DJ 165 main jet and a DJ 170 main jet. 165 is pods only 170 is pods and exhaust. Drilling the slide is pretty common, lots of people do it with out without jetting change. It causes the slide to move more quickly I believe giving better throttle response. Mine runs good and accelerates well. I have been fighting an over rich condition though, just finished a complete teardown, o-ring change, patching of a couple diaphragms. I was going to drop main jet down, but going to have to order jets. I have the satge 1 and stage 3 kit, so I got DJ 117 and DJ 118 in the stage 1 and DJ 165 and DJ 170 in the Stage 3, with nothing in between. I'm currently getting (before this last round of work) about 25 MPG.

 

[Griffin]

It can be tough getting the aftermarket pods/stock exhaust combination jetted correctly. The backpressure created by the exhaust (that an aftermarket performance exhaust would not create) can be an issue, because the pods can flow so much more air than the stock airbox. I don't know which is more restrictive to flow, the stock airbox at atmospheric pressure, or the stock exhaust at discharge pressure. If it's the airbox, then you will probably need to go with the stage III kit. The stage I kit is perfect for the stock airbox and stock exhaust.

That being said, when I got my Dynojet kit for the 700, it was a stageI/III kit, and there were three sets of mains in it. One set for stock, one set for stock airbox/aftermarket exhaust, and a set for pods and aftermarket exhaust, so you will have some options.

Between the three sets of mains and the flexibility of using the easy to adjust needle clips, I'd say the odds are pretty good you'll be able to get it dialed in correctly. It would certainly save you a lot of time and effort over trial and error tuning, expecially due to your particular setup.

 

[Smokinapankake]

Thanks for the replies everyone, it's reassuring to know others have drilled their slides without having to replace them because now they're ruined.

As the bike is a Japanese Domestic Market version, i.e., never marketed in the states, the air screws are fully accessible (never plugged off) and the needles have multiple clip positions. Maybe I just run the stage 3 jets with factory exhaust (130 for pods and factory exhaust vs. 134 for the pods and aftemarket exhaust option, as per the instructions I downloaded), set the clips in the notch DJ instructs, drill the slides and see what happens.

At the best, I get crisper response, better mileage, and higher speed at WOT.

At the very worst, I'll end up buying the DJ kit to get their needles if my notches aren't in the same place the Dynojet needle notches are in, thereby causing my mixture to be off from what DJ says it should be....right?

 

[Smokinapankake]

By the way, my 82 1000 Kat is piped, podded and jetted by the previous owner and it delivers approx. 45 mpg, so 35 on my 750 seems low. My 83 GPz 750 gave me about 45-55 mpg with factory airbox and F-1 slip ons. Seems reasonable to think the 84 Kat 750 should be in the same neighborhood, right?

 

[Griffin]

One other thing, the DJ needles are slightly smaller in diameter and also have more taper than the stock needles.

At least on US models.

 

[Griffin]

By the way, my 82 1000 Kat is piped, podded and jetted by the previous owner and it delivers approx. 45 mpg, so 35 on my 750 seems low. My 83 GPz 750 gave me about 45-55 mpg with factory airbox and F-1 slip ons. Seems reasonable to think the 84 Kat 750 should be in the same neighborhood, right?

I've put almost 1,000 miles on my 700 with sthe Stage I kit, and mileage was reduced from about 45-46 mpg stock to 42.7 mpg so far. It's a good trade off though, considering the improved performance and decreased warmup time.

 

[Smokinapankake]

Thanks Griffin, I'll forge ahead and post updates. Hopefully tomorrow.

 

[Guest]

I'm running 30 mpg with my mods riding HARD. 35 under normal riding (whatever that is) and 40-45 highway. (closer to 40)

 

[Smokinapankake]

So I chickened out of drilling the slides. Rather, I did something Jeff (Z-1)recommended I try before spending any real dough. Since the bike was running okay, but rich due to a multitude of plug chops I performed, he suggested I raise the clip one notch, thereby lowering the needle, thereby leaning out the mixture.

I've yet to perform any more plug chops but intial impressions are favorable. The motor is much smoother, much more responsive, and idles more consistently. I didn't think the needles affected idle so correct me if I'm wrong. At any rate, I'm pleased with the progress made. Will look at the plugs to see how they look off idle. That may or may not give some indication as to how the mixture is throughout the throttle range.

Sure glad I got rid of that damm airbox because the carbs come in and out in about 3 minutes now.....