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flat spot in power on 83gs550es

  • Thread starter Thread starter reem98
  • Start date Start date
R

reem98

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Hi I am working on a 83gs550es trying to get it tuned right. I have a 4into1 exhaust a K&N air filter and a K&N Stage 1 jet kit. It runs good on the low end and top end but in the middle as I go under full throttle from like 4k up it hesitates and studders up around 6-7k then does fine after that.
would this be my neadle position or my main jets.
Thanks
 
What kind of exhaust? I think its partly the pipes fault. They tend to compromise the power somewhere in the rev range. You could always try a washer under the needle .5mm or raising the mains 2.5 sizes depending on the plug color.
 
Is there a place I can find or does anyone know what size mains come with an old K&N Jet kit for an 83 Gs550es.
Thanks
 
Yup, they are DJ 114 and 116 jets. Which are different than mikuni numbers. However... the problem you're running into a needle issue. :-) Time to raise them a little. You may also wanna opening up the pilot screws a little.
 
Mine actually read 98 for the mains. Do you have a jet kit in your GS550es??
 
98? Sounds right for a stage 1 jet kit. the 114 and 116's are for stage 3. It reallys sounds like you need to raise your needles a little.
 
hey thanks for the help
I was also wondering if you remember did you delete that nylon spacer above the needle when you put in the jet kit in the gs550e and do you have any idea what that 98 dyno jet size is in Muniki jets.
Thanks
 
I was wondering what this might mean if I hold the throttle steady at like 6k and then punch it it stumbles. but if I go up from like idle under load it is fine.
why might is stumble when I punch it if its already revd up.
thanks
 
I would guess the 98 DJ are 95 mikuni. Aren't stock 92.5?

Have you raised the needle with a washer yet. You should be able to do this w/o removing the carbs. Just take the tank off.

It sounds like your getting on the mains from down low and sort of bypassing the needle, when introducing a lot of throttle, but when your at a cruising state you're probably on the needle.

Not scientific, just a guess
 
Don't guess. The numbers DO NOT directly relate. In fact the numbers get further from each other in a exponential manner. DJ numbers are diameter. Mikuni numbers are flow. say a dj 50 and a dj100 jet... the dj 100 jet will flow four times as much fuel as the 50. A mikuni 50 will flow 50cc's a minute. A mikuni 100 jet will flow 100cc's.
 
Guess what. I'm allowed to guess if I like. My guessing got you to respond, but you failed to tell him what jet size he has in Mikuni world.
 
Carter Turk said:
Guess what. I'm allowed to guess if I like. My guessing got you to respond, but you failed to tell him what jet size he has in Mikuni world.
Click to expand...
:-? Not sure what you're saying.....to me? I'm just guessing too. I think it's an accurate guess though. A 98 DJ should be equal to either a 90 or 92.5 Mikuni.
 
When I jetted my 1100e with individual filters and 4-1 exhaust I had a flat spot at 4-5 k. I raised the needle. I then had a sputter at 4-5k so I raised the needle again. It runs smooth now throughout.
 
Keith,

I was refering to the nerobro post.

Curious though, wouldn't DJ stage one main jet be at least 2.5 bigger than stock, assuming stock is 92.5? I wonder if the jet came from a GS 450 stage one kit.
 
I'm not familiar with that stage 1 kit. Yes, the main would have to be larger but I don't know how much.
 
The part that bugs me on that is that the stock jets are 97.5 and 102.5 mikuni's. With the inboard cylinders being richer. So it sounds like the stage 1 kit actually LEANS the bike out? That makes complete nonsence to me. I know my 550ES is running quite lean. And that's the factory setup.

Dynojet's stage 3 kit actually gives you 4 jets that are the same across the board.

The problem I have with guessing is that this is a place where you could severely hurt your bike, and or, set yourself up on a wild goose chase. "I" was on a wild goose chase for a long time. That's why I have 10 sets of jets.

http://roadstarclinic.com/content/view/61/96/ There's a chart. And you'll see that the numbers part ways. If you graphed it, you'd see the mikuni's are a straight line. The dynojets are going to be on a curve. Hmm... maybe I could graph that and extrapolate the data. *grumbles something about doing real work for the forum*
 
*made the chart*

I guess this is to small of a cut to show just how big of a difference different bores make.. according to the graph. a DJ 98 would be a 93 mikuni. so 92.5 is as close as you can get. Good job keith.

Is a stage 1 kit REALLY 98 dynojets? That sounds so wrong now.

92.5 is the stock jet size for a 80-82 gs550. Not the dual carb setup of the 83+ models. Those come with the "odd" jets.
 
I thank you guys for really goin into depth on this one
Now one thing I must say is that this Jet kit I have is an old K&N kit but it does say DynoJet in the instruction manual. It was never opened and the part number matches for a stage 1 83-86GS550ES
I am wondering the same thing about the jet size being smaller.
The one thing I can say is that the stock neddles have a very small taper to them so I'm guessin to bring more gas in you need to go to like a 110 muniki which I did and had very little gain on the top end. after I put in the new needles (which have a very sharpe taper) and used the DJ98 mains. I got alot more out on the top end. SO I'm guessin the sharpe taper of the new needles allows for the smaller main jet to be used.
The one thing someone mentioned was the inside cyls using larger mains, do you think this is a prob since they are all the same size??
Thanks alot again guys for all your help.
 
Ok heres what I have found I took out the DJ 98's (dynojets) on the mains, cause around 7k it would sputter bad
I put in 102.5 outers and 107.5 inner mains. not it had power up to redline but sputtered alittle around 6-7k so I dropped the needle from 5 to position 3. Well it got really bad had no pickup (way to rich) I went to positon 6 it lost the sputter but didn't have good power up around 10k. So I went between 5 and 6 on the needles it has alittle sputter around 6-7 and decent power up to redline.
Can someone please explain how I can get rid of the mid sputter and still have good top end.
Thanks
 
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