Dyno Jet kit on my GS1000

[terry]

Hey GS'ers I just finished installing a DynoJet stage 3 kit in my spare set of 34mm CV carbs, (the conversion was actually nice and "tantrum free"!) then fitted them to the bike, it started ok, but I thought it was running a tad rich so I leaned the fuel mixture screw from the recommended setting of 2 turns out, to about 1 and 1/4.

I took it for a ride, but it ran like crap, wouldn't pull at all and backfires even at idle, so I guess it's actually running too lean. Anyway, I was wondering if any of you guys have any experience with the conversion (I imagine it's pretty common) and what advice can you give me to get this sucker up and running sweet?

I'd really rather learn from your experience rather than my normal method of stuffing something up before I work out what I did wrong, so I'm happy to hear your advice, and I WELCOME your opinions, ha ha! Thanks in advance! :twisted:

 

[Dink]

Terry you are correct that backfiring generally means it is to lean , however the only way to diagnose properly is to read your plugs.
Dink

 

[KEITH KRAUSE]

I have a '79 1000 with a Stage 3 Dynojet kit,but I have the older VM26 carbs so I don't know what help I can give.What mod's have you done?Pod filters and a pipe?Are the 34mm carbs the stock carbs?Did you just re-jet the carbs according to the "base settings" Dynojet suggests?The base settings are only a starting point and results are seldom what you like.On my carbs,the pilot and air screws have an effect up to around 65 mph in top gear.They have an overlap effect with the needle. The needle actually begins to have effect just above idle.The needle has the most effect up until around 3/4 throttle,then the main takes over.There is also an overlap or transition period between the needle and main.The hardest part of jetting is to get the 3 jetting circuits to blend smoothly or overlap into each other.I have seen lots of jetting charts and sometimes my bikes motor did not fully agree.After much trial/error,it runs great,but it took patience.

 

[terry]

What mod's have you done?Pod filters and a pipe?Are the 34mm carbs the stock carbs?Did you just re-jet the carbs according to the "base settings" Dynojet suggests?

Thanks Keith, the settings as per the dyno jet fitting instructions are as follows: Main jet up from 125 to DM175 (out of dyno jet kit) new DN0405 needles, clip in position #4 from top of needle, air correctors (restricters) fitted, fuel mixture screws 2 turns out, and slide lifter holes drilled out to DD#32.

Dyno Jet recommend fitting K&N Pod filters, but I don't like them, so I've fitted a free flow foam filter in my airbox with the lid off. (it flows so much better than the stocker that the bike wouldn't pull at all under load with the stock carbs fitted, so I'm assuming that the air flow would be similar to running pods)

As for the rest of the engine, it's got a Yoshimura 1085 high comp big bore kit, Yoshimura stage 2 cams, Dyna 3 ignition and 3 ohm coils and a Megacycle 4 into 1 race pipe. I'm running the standard B8EA NGK plugs, but I'll replace them shortly with the new "Iridium" plugs.

Dink, I'm tempted to buy a set of those "color tune" plug thingies to get the mixture just right, but funds don't permit right now, but I guess they would be just the thing for getting the mixture spot on. I haven't balanced the carbs yet either, I thought I'd try and get the mixture just right before I went the next step.

If I can't get it right this weekend I'm going to take the Cv's off and refit the 33mm slide carbs that were one it, or a set of flat slides that a mate loaned me to try out, but I've heard good things about the dyno jet kits, so I'd like to get it right.

 

[Anonymous]

I believe that the setup you ae running for air intake would not be similar to pods . In fact it should run richer than pods i believe.

 

[terry]

I believe that the setup you ae running for air intake would not be similar to pods . In fact it should run richer than pods i believe.

Hey Scotty, why do you say that? As I mentioned before, the foam uni-filter flows so much air compared to the stocker that it wouldn't accelerate at all under load with the stock carb set up, it flows so much air it's almost like not running a filter at all, so how could pods flow more air than that?

My previous experience with pods (on my old Honda CB750) was that there was a requirement to alter the mixture to richen it slightly, but I don't think they flowed as well as the uni-filter.

 

[Anonymous]

I have a heavily modified air intake setup. No air filter box at all and yet retained the air box. I have a pro stock exhaust on the machine and it is over bored. All which should produce leanness. the only thing i had to do was change the mains. Normal driving plug color remaINED QUITE NORMAL. iF I HAD REMOVED THE AIR BOX AND GONE TO PODS, LOTS OF TRIAL AND ERROR WORK WOULD HAVE BEEN NECESSARY.

((CAPS AS A RESULT OF SCREWED UP LEFT HAND)))
Im just saying that your better air filter setup is not the same as pods. I'm working on a larger system with an enormous air cleaner and an air box with a 4 inch intake hole and it still shouldnt be as free flowing as pods. Close maybe or at least i hope. The plugs dont lie.

 

[KEITH KRAUSE]

Terry.I used to run the stock air box with a K&N with the lid off the box.It was much less restrictive than stock,but the pods are even less restrictive.Just the shorter distance the air must go to enter the carb throats makes the pods draw more air.I'm still not sure,did they suggest "base settings" and is that where you're at?Since your jet kit was designed with pods in mind,your base settings will actually be richer.On your first test ride you said it ran rich,so you tried to compensate by turning in your mixture screw to lean it out.This made it run like crap you said.You added backfiring even at idle to your complaints.Were you just cruising around town(using the pilot and needle circuits)or were you riding hard(using the needle and main circuits)? It's obvious to me the bike needs that richer mixture screw setting,so I would put it back where it was.Does your kit tell you to leave the pilot jet stock(as it does mine)?If so,then to lean it out a bit you will have to lower the needle a 1/2 notch,using a spacer.This will lean it out a bit and you said at first it was running a bit rich.This seems fair compensation for you not wanting to run pods as they assumed.At least on my bike,the needle has quite an 'overlap' effect on the pilot circuit.This overlap starts right above idle.You should also balance the carbs.If they're not, it just makes jetting even more confusing.PS: I am not familiar with your carbs(what are air correctors and drilling out slide lifter holes?)Hope I've helped some.

 

[Dink]

Terry DO NOT use colourtune plugs at all, they are a waste of time and money, They do not fire as well as a normal plug and therefore lie.
Your single pod setup is my preferred set up for intake mods to a GS as they seem IMNSHO to prefer the plenum be retained.
Dink

 

[terry]

Thanks guys, I'm impressed with all your collective knowledge (geez I like this site) and hopefully there is enough info from you all to make my task a little easier.

I'm still not going to run pods unless I really have to, I know that you can anchor your carbs so they don't bounce around too much and fracture the intake boots, but I like the clean look of the airbox too much to let it go, so I'll play with the mixture to negate the requirement.

My cousin used to run a suzuki dealership and I think he's still got an exhaust gas analyser, so I might see if I can borrow that once I reckon I've got the settings close.

I'll let you know how it all works out.

 

[cbxchris]

Got lots of experience with stage 3 kits but not on your particular bike. On a cbx to run stage 3 it is absolutely necessary to run individual K&N`s to run the stage 3. Nothing flows that much but velocity stacks. I have messed around with a 1150 some and used the stage 1 on it with a K&N replacement filter...jetting worked out fairly close. As for overall most of the time the stage 3 usually is on the rich side on most bikes. Personally if I go to the trouble of engine mods the cv`s are the first thing I get rid of but I understand why you would like to run them....much smoother.

 

[Joe Nardy]

Terry,

For what it's worth, I just put a stage III kit in my '83 GS1100E this spring. I have K&N pods and a Supertrapp stainless 4-1 system. I also put a stage I kit in my "88 Honda Hurricane 1000 which has stock airbox with K&N replacement filter and Supertrapp stainless slip-ons. On both bikes I ended up going much richer on the needle. On the GS I went to the highest groove and I believe the Honda ended up on the next to richest groove.

 

[terry]

Thanks Joe, the carbs are coming off again this weekend so I can fit an oil cooler, so I'll have a play with the needles, as I'm not getting much sense out of the mixture screws! :twisted:

 

[Joe Nardy]

Terry, from what I learned during my jet kit adventures is that the mixture screws only had an effect on idle and just off idle. They did not seem to have any effect on partial to full throttle. The dynojet troubleshooting guide led me to the mixture screws because my GS1100E idled very poorly when cold. I had to run the choke for at least 5 minutes before it would idle. The troubleshooting guide said to turn the screws counter clockwise for this problem. The GS now starts and idles better than ever when cold. Another thought would be to run without the air filter or cover 1/2 of the filter with duct tape. If it runs better without the filter you are running too rich. If it runs better with 1/2 the filter covered you are running too lean. (These tips are also from the Dynojet troubleshooting guide)

Good Luck!!! If you get it right your bike will run stronger than ever!

 

[Anonymous]

Have a look at this

http://www.markvanderkwaak.com/dbbp/tech-tips/mm.html

This little apparatus could be of great help and save alot of time, even if it doesn't get the jetting spot on at least you are in the ball park.
I plan to use it when I put GSXR(dynojetted stage 3) carbs, pod filters and a free flowing pipe on my GS1150. The screw holes in the pipes can be sealed with a bolt and a copper washer.

 

[saaz]

I haven't played with CV carbs, but I do know that there will be a difference in the way they work with or without the standard airbox. If the jet kit tries to make up for putting on pods, you will probably have to change some parts of jet kit to get it to work with the airbox.

I have a colourtune plug, very handy for setting up the idle circuit as you can see the effect of changes in idle jets and air screw changes. You can quickly see when a change in idle jet is needed rather than playing with the air screw. A gas analyser would be much better!!

 

[terry]

Thanks mate, I'm waiting on my cousin to get his exhaust gas analyser "re-chipped" for ULP, then he'll loan it to me so I can get it right. I won't ride it until I get it right, but that's OK, the weather here in Melbourne is almost as bad as Canberra right now, ha ha! :twisted:

 

[terry]

Hey Thanks JD, Tandy Electronics (Radio Shack in Australia) sell a neat fuel/air sensor kit with both LED and digital readouts for about $35 US, so I'll pick one up on Saturday and get a tech friend to assemble it. Mark suggested the oxygen sensor out of a late model Suzuki car, so I'll pick one of them up from a wrecking yard too.

I'll drill a hole and weld a nut on my pipe for the sensor just past the 4 into 1 collector under the engine (which is different from where Mark said to mount it, but his harleys generally only run one carb so the mixture would be the same in either pipe) and permanently mount the guage where I can read it when adjusting the mixture, so probably under the seat or one of the sidecovers.

Thanks again for the tip mate, have a good weekend! :twisted:

 

[Anonymous]

I would be late in saying this, but for others reading this you should know that it would be better to have a fitting on each pipe not after they have collected. You want a reading for each carb not an average of all four.

 

[Jeff Tate]

One thing I've learned from my jetting experience is that you use all the components that the manufacturer recommends or you'll just be wasting time and flying blind. The biggest reason Jet Kits cost so much is due to the R&D that goes into getting them right. If you wanted to keep the airbox, why didn't you just get the stage 1 kit?