tuning carbs after jetting

TANNER · July 01, 2007, 08:21:33 PM

1994 GS500E, K&N filter, V&H supersport DynoJet stage 3.
I just had the dynojet kit installed on this bike, I balanced the carbs and took it out for a cruiz. The bike idles fine until you hit the throtltle, it then seems to hang around 3500 rpm and slowly come back down. I can bring it back down to idle if i slip the clutch a bit- put a load on it- the next problem i ran into was once i hit 5000 it starts to sputter and fall on its face., If i let off and lean into it again it will run fine up to redline. The place i had install the dynojet kit did not install the washers on the needles. Could this be the cause? Any help is greatly appreciated! i searched this earlier and found a relative post, but could not find it again.. Thanks

Clay Tanner

coll0412 · July 01, 2007, 08:54:45 PM

Which k&n filter do you have, the drop-in replacement for stock or the clamp on filter(lunch box)?

The hanging idle is a sign that you are too lean at idle. Hopefully the shop that installed you DJ kit popped out the covers to the mixture adjustment. If they did you will need to adjust that, do a search on it or look in the rejetting how-to to see where it is. This adjustment the metering at idle which is where your problem is? A good starting point is 2.5 turns out, but each bike varies so it may need to be a bit richer.

Did the person who work on your bike give you back the rest of the jets? I have Dynojet and lost my jets and was wondering if I could buy your unused DJ122 jets off of you?

As far as the stumble at 5K, I think that you could try adjusting the needle, the washer should be installed so that the spring doesn't somehow manage to go through the e-clip, not a huge deal. You may want to try raising/lowering the needle a spot to see if that helps.

TANNER · July 02, 2007, 05:37:28 AM

The K&N is a drop in filter pod, NOT the lunch box. Will the lunchbox make a big difference over the drop in filter? The remaining jets,Yeah i still have them, Yeah we can work out a deal once i get this damn thing running right, Just wanna make sure i wont need them to get running.

Thanks

Clay Tanner

scratch · July 02, 2007, 08:11:11 AM

Yes, the lunchbox will make it run even leaner.

coll0412 · July 02, 2007, 08:41:39 AM

There is a restriction ring deal on the drop in K&N filter, it will need to be removed to get rid of the 5K-6K lag you experience. I had the same setup on my bike and that fixed it.

TANNER · July 02, 2007, 11:34:42 AM

I understand it would make it run leaner, But would the improvements in airflow be worth upgrading from the drop in to the lunch box? Also the 5-6k is not just a lag it stops accel and sputters and complains. then once i let off a little and can it it runs fine.

coll0412 · July 02, 2007, 11:53:14 AM

There is considerable improvement from the stock airbox to the clamp on lunchbox, or so I have heard from many people on the forum.

The drop-out in power, or lag, sounds exactly like mine, at about 5K I could open the throttle all the way up and the bike would sputter and lose power, and I would actually slow down a bit. Once I got past 5K-6K it was fine all the way up to redline. I removed the restrictor on the K&N filter and it went away, which means that the bike is too rich at this RPM, so you could leave the restrictor and drop the needle one spot, but I would rather have the power gain from having a free flowing intake.

TANNER · July 02, 2007, 08:19:57 PM

are you talking about that rubber o-ring on the top of the air filter?

coll0412 · July 03, 2007, 09:08:31 AM

Its not really an oring since it doesn't seal anything and doesn't have a round cross-secition...aww never mind..I made a quick model of what it looks like, see below

TANNER · July 03, 2007, 09:27:26 AM

NICE

ben2go · July 03, 2007, 09:59:58 AM

looks like a volosity stack or however ya spell it

coll0412 · July 03, 2007, 10:23:13 AM

Its very similar to a velocity stack but they use it to restrict the air going into the K&N. The reason they do that so that if you replace your stock filter with a k&N drop in replacement you should not have to re-jet(they make up for the reduced restriction of the k&N element by putting a restricter in it)

TANNER · July 03, 2007, 06:19:58 PM

Ok.. removed the rubber (grommet) off the air filter installed the washers between the e-clip and the donut on the needle (shop did not install them dunno why) and i still have the 5k through 7k bog (sputter and spit).. Wondering if this is running too rich to process all the fuel at 5-7K.. the e-clip is in the correct spot on the needle according to stage 3 dynojet kit(2nd notch from the top) ..

I purchased this bike June 3 and have only got to put 100 miles on it... really need to get this thing on its feet, running out of summer, any help is appreciated ..

TANNER · July 03, 2007, 07:16:19 PM

also since this thing runs like a crazy ape once i get on the high side of 7K (wide open throttle) think i may need to add a washer and richen it up, or.. drop the needle to lean it out? dunno whats going on..

Egaeus · July 03, 2007, 08:02:54 PM

Quote from: TANNER on July 03, 2007, 07:16:19 PM
also since this thing runs like a crazy ape once i get on the high side of 7K (wide open throttle) think i may need to add a washer and richen it up, or.. drop the needle to lean it out? dunno whats going on..

This right here screams (screams!) partially blocked pilot jets, probably caused by rust in your float bowls coming from the tank.

Look in your tank, and you will see rust.

Keeping the carb upright. Take the carb out. Get a coffee filter, and drain the carb bowls through it. Set it aside to dry.

While still keeping the carb upright, take the float bowls off. Look in them. There will probably be small pieces of rust in the remaining drops of fuel. That's your problem.

Clean out the carbs well.

For a temporary fix, install a cellulose fuel filter designed for carbureted engines (not fuel injection) between the petcock and the carburetor. That should pick up the particles that pass through the screen filter in the tank.

For a more permanent fix, you will need to acid wash and coat your tank.

TANNER · July 03, 2007, 08:50:01 PM

I will check into this, seems like the problem is too consistent know what i mean, something mechanical. But the guy who tore the carbs apart said there was some gunk and garbage in the bottom of the little mikis. So im willing to give anything a shot.. i also stuck a fuel filter on tonight cause i ws kinda thinking bout that,.. another thing.. the clymer manual and the diagram i found on this site show two different ways of routing fuel lines.. one question, thee longer nipple on the tank and the nipple with the 90 degree bend down on the petcock are connected and are the reserve portion of this correct? Thanks for the input coll0412 & Egaeus..

Egaeus · July 03, 2007, 09:05:54 PM

It will be consistent with the rust, believe me. I fought with it for months.

http://gstwins.com/gsboard/index.php?topic=33403.0

The symptoms would subside when I opened it up because I turned the carb over to take the float bowls off, washing the rust up into the carb. It would slowly start to settle again, causing it to come back. That's why I thought fixing the choke had fixed the problem.

I thought for a while it was one side or the other, but it wasn't. The attempt at balancing with clogged pilots was causing that. Well, that, and a faulty balancer, but fixing the balancer didn't fix the problem.

Depending on how the sediment was distributed in the bowl, running on just the left or right carb gave different results every time. That's why I couldn't pin it down. It was a confusing problem until I started thinking about why taking the carbs apart would fix it for a few miles.

Check it out. Seriously. The only cost is time, and one coffee filter. Oh, I forgot to mention that once the filter is dry, check for rust. It's hard to see when the filter's wet.

TANNER · July 04, 2007, 07:08:18 AM

how bout the fuel line is that in the correct configureation?

Egaeus · July 04, 2007, 08:27:32 AM

Doesn't fit the symptoms.

coll0412 · July 05, 2007, 08:02:21 AM

The problem with Dynojet is the taper of needle. It causes it to be really rich in the 6K-7K range. One thing you could try doing is be at about 6K and put full choke on, if this helps the problem then you are lean, if it makes no difference its probably too rich(this may or may not work just something I was thinking).

Whats tricky with the DJ kit is that at part throttle the bike is actually lean, you can pull the plugs and they will be white, but if you do a WOT run at 6k-7K then shut the bike off, t he plugs will be nice and tan(assuming its running right yours may vary). If would recommend this if you have somewhere you can do it and safely kill the motor and pull over as it give a pretty good indication of rich or lean.

Other option is to assume its lean and drop the clip one spot up the needle causing it to be a bit more lean, other than that I am not sure. If none of these things work then you may have another problem.

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tuning carbs after jetting