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Main Area => General GS500 Discussion => Topic started by: TANNER on July 01, 2007, 08:21:33 PM

Title: tuning carbs after jetting
Post by: TANNER on 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  :bowdown:

Clay Tanner
Title: Re: tuning carbs after jetting
Post by: coll0412 on 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.
Title: Re: tuning carbs after jetting
Post by: TANNER on 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
Title: Re: tuning carbs after jetting
Post by: scratch on July 02, 2007, 08:11:11 AM
Yes, the lunchbox will make it run even leaner.
Title: Re: tuning carbs after jetting
Post by: coll0412 on 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.
Title: Re: tuning carbs after jetting
Post by: TANNER on 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.
Title: Re: tuning carbs after jetting
Post by: coll0412 on 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.
Title: Re: tuning carbs after jetting
Post by: TANNER on July 02, 2007, 08:19:57 PM
are you talking about that rubber o-ring on the top of the air filter?
Title: Re: tuning carbs after jetting
Post by: coll0412 on 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

(http://i90.photobucket.com/albums/k240/coll0412/untitled.jpg)
Title: Re: tuning carbs after jetting
Post by: TANNER on July 03, 2007, 09:27:26 AM
NICE
Title: Re: tuning carbs after jetting
Post by: ben2go on July 03, 2007, 09:59:58 AM
looks like a volosity stack or however ya spell it
Title: Re: tuning carbs after jetting
Post by: coll0412 on 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)
Title: Re: tuning carbs after jetting
Post by: TANNER on July 03, 2007, 06:19:58 PM
 :dunno_white: 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) ..  :mad: 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 ..  :dunno_white:
Title: Re: tuning carbs after jetting
Post by: 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..
Title: Re: tuning carbs after jetting
Post by: Egaeus on 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.
Title: Re: tuning carbs after jetting
Post by: TANNER on 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..
Title: Re: tuning carbs after jetting
Post by: Egaeus on 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.
Title: Re: tuning carbs after jetting
Post by: TANNER on July 04, 2007, 07:08:18 AM
how bout the fuel line is that in the correct configureation?
Title: Re: tuning carbs after jetting
Post by: Egaeus on July 04, 2007, 08:27:32 AM
Doesn't fit the symptoms. 
Title: Re: tuning carbs after jetting
Post by: coll0412 on 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.

Title: Re: tuning carbs after jetting
Post by: Gisser on July 05, 2007, 06:45:01 PM
Quote from: TANNER on 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

Hang onto those DJ122 jets.  You need them.  Because the problem is that the carbs are jetted for Stage-3 while the K&N drop-in filter is strictly Stage-1.  If problems persist with the DJ122's consider that there may be additional Stage-3 work needing to be reversed. 

Doesn't anyone read instructions anymore?  :icon_rolleyes:
Title: Re: tuning carbs after jetting
Post by: TANNER on July 08, 2007, 08:32:38 PM
the only thing that i see different in the directions is the use of the LUNCHBOX filter, k&n RU-2970 would this make that much difference?
Title: Re: tuning carbs after jetting
Post by: Gisser on July 08, 2007, 11:49:24 PM
Re: Lunchbox

Big difference in jetting; small difference in HP. 

:cheers:
Title: Re: tuning carbs after jetting
Post by: TANNER on July 10, 2007, 06:23:30 PM
Bingo! Jets were too big, took care of my 5-7k bog THANKS!!!! :thumb:
Title: Re: tuning carbs after jetting
Post by: TANNER on July 10, 2007, 06:33:03 PM
Now then here are a few more questions. Besides the fact of the stage 3 reversal, I have the throttle hanging at a high rpm(3500-4K) after acceleration. I read before that this could be a lean problem solved with the idle mixture screws, it smells kind of gassy when idling.. but im not for sure. Another thing it cackles and pops like an old straight pipe pickup when i let off it at high rpm 5K and up. Another thing how  :mad: HOT  :mad: should these things run, mine gets to the point where it tough to hold your hand on the case for any length of time after a quick 8-10 min ride through town  :nono: i dont think this should be the case. All the help has been awsome! i thank you guys a lot!
Title: Re: tuning carbs after jetting
Post by: genEricStL on July 10, 2007, 06:42:16 PM
8-10 minutes of riding for me heats my engine up enough that it burns the back of my hand when adjust the idle screw ( i should'nt have messed with it at all lol ... it just ended up getting set back to where it started)
Title: Re: tuning carbs after jetting
Post by: TANNER on July 10, 2007, 07:18:51 PM
OK> went for a little test ride, and it seems to stay pretty cool out on the highway 55 mph, prolly just me beating on it in town making it hot, eh? as for the idle problem it got a lot worse as it warmed up all the way.. .................................

idle 1300, hit the throttle a little and it jumps to 3500 rpm and stays there. slip the clutch a little with hand on brake and it pulls it back down to idle.. hmmmm. ?  :dunno_white:  It even jumps when shifting, pull clutch to shift and hit 3500....
Title: Re: tuning carbs after jetting
Post by: Gisser on July 10, 2007, 08:36:18 PM
If your mechanic had done a good job with the jet kit installation he would have uncovered the mixture screws.  These lie at the bottom front of each carb and are factory preset on the lean side for emission requirements.  They need to be turned clockwise until they lightly seat then turned out 2-1/2 to 3 full rotations to steady the idle and quiet the pipe to the extent that it can be quieted.  If you do not have access to the mixture screws ask the mechanic why not?  Because the carbs will have to be pulled to perform the procedure.  :2guns:
Title: Re: tuning carbs after jetting
Post by: TANNER on July 11, 2007, 04:35:50 AM
I can see the mixture screws (with a mirror) and i will try resetting them, just wanted to make sure that was where my problem was. Now i just need to find a really really ... really short straight screw driver..
Title: Re: tuning carbs after jetting
Post by: bosozoku on July 11, 2007, 05:16:39 AM
Quote from: TANNER on July 11, 2007, 04:35:50 AM
I can see the mixture screws (with a mirror) and i will try resetting them, just wanted to make sure that was where my problem was. Now i just need to find a really really ... really short straight screw driver..

Just use the bit from an electric screwdriver.  The mixture screws are quite easy to turn, so you don't need a big handle.  Also, put two marks of different colors on the body of the bit (use nail polish or something), so you can easily see how far you're turning the screw.

-b.
Title: Re: tuning carbs after jetting
Post by: coll0412 on July 11, 2007, 09:30:10 AM
Ahh dude, I totally missed the fact that you have stage 3 kit in there :doh:

What size jet did you end up using, the DJ122 or the DJ118
Title: Re: tuning carbs after jetting
Post by: TANNER on July 11, 2007, 10:23:47 AM
n/p.. i used the 122
Title: Re: tuning carbs after jetting
Post by: coll0412 on July 11, 2007, 03:37:52 PM
Do you still have your stock needles? I don't think I am going to find anyone with extra DJ jets anymore so I might have to run stock Miki jets
Title: Re: tuning carbs after jetting
Post by: bosozoku on July 11, 2007, 03:49:37 PM
Quote from: coll0412 on July 11, 2007, 03:37:52 PM
Do you still have your stock needles? I don't think I am going to find anyone with extra DJ jets anymore so I might have to run stock Miki jets

Not a tragedy -- I've heard that the stock jets are actually more precisely machined than the Dynojet parts.  You'll just need to open up the slide orifices if you have the Dynojet restrictors installed.

-b.
Title: Re: tuning carbs after jetting
Post by: TANNER on July 11, 2007, 04:25:27 PM
I will look what parts they threw in the box.. Ok.. another question. Is there a possibility my high idle is being caused by  fuel getting past the main jet needle? I cant get rid of this 3500 fast idle problem?
Title: Re: tuning carbs after jetting
Post by: bosozoku on July 11, 2007, 04:29:59 PM
Quote from: TANNER on July 11, 2007, 04:25:27 PM
I will look what parts they threw in the box.. Ok.. another question. Is there a possibility my high idle is being caused by  fuel getting past the main jet needle? I cant get rid of this 3500 fast idle problem?

Stupid question -- is your throttle cable (NOT the idle screw) adjusted correctly?  With the throttle released, you should have a bit of slack at the carb.  Not a lot, but enough to feel it.  Also, are your carbs synched?

-b.
Title: Re: tuning carbs after jetting
Post by: TANNER on July 11, 2007, 04:35:46 PM
yeah the carbs are synched, used the fishtank sync setup i founf here. worked really well once i got all the leaks out of those cheap connections.  I did ajust the throttle cable to where i thought was adequate before i put the tank on and havent checked since to see if i jarred anything :dunno_white:, i will give it another check. Can you use the stock needles with the dynojet jets?  Thank you for all the help, any advice is a great help..  getting close to back on the road. :cheers:
Title: Re: tuning carbs after jetting
Post by: bosozoku on July 11, 2007, 04:41:45 PM
Quote from: TANNER on July 11, 2007, 04:35:46 PM
Can you use the stock needles with the dynojet jets?

Probably, but you'd have to play with jet size, since Dynojet numbers aren't the same as Mikuni jet numbers.  Why bother, though -- Mikuni jets are stupidly cheap even at dealers.

-b.
Title: Re: tuning carbs after jetting
Post by: TANNER on July 11, 2007, 05:45:55 PM
plenty-o-slack in the throttle cable going to look for a possible vacume leak.?. :dunno_white:
Title: Re: tuning carbs after jetting
Post by: TANNER on July 11, 2007, 06:14:52 PM
Would it be possible that the needle is set a little to high and letting fuel slip by that jet? sprayed some carb cleaner around the carbs while running and didnt get the idle to jump at all.. going to do a bit more searching for vacume leak.. so far im empty handed  :mad:
Title: Re: tuning carbs after jetting
Post by: coll0412 on July 11, 2007, 08:13:21 PM
Also make sure the vacuum caps that you removed to hook the synch tool got put back on, and are not leaking or cracked
Title: Re: tuning carbs after jetting
Post by: bosozoku on July 11, 2007, 10:23:02 PM
Quote from: coll0412 on July 11, 2007, 08:13:21 PM
Also make sure the vacuum caps that you removed to hook the synch tool got put back on, and are not leaking or cracked

AND that the little o-ring under the black cap on top of the carbs under the nipple where you hook up the sync tool is still there!

-b.
Title: Re: tuning carbs after jetting
Post by: TANNER on July 12, 2007, 03:00:28 PM
the exhaust also might be a clue.. has the normal thup thup thup thup with a intermitent hollow thud..
Title: Re: tuning carbs after jetting
Post by: coll0412 on July 12, 2007, 03:29:30 PM
What are you mixture screws at, just turn them in clockwise until they GENTLY bottom. I turned mine 2-1/2 turns out and it runs great, you might want to see where yours are at.

Or let it idle for a bit and pull the plugs to see what color they are, just don't let it idle too long or throw a fan infront of  the bike and let it idle a bit longer...just shooting out some ideas