Tuning an '81 GS1000 - Jet Needle Woes

[trippivot]

tough luck on the cable - where are you tuning this at? elevation and temperature are factors in this. you got it running - you are making changes - it is linear - that is progress towards success.

ok kit 3103 has 2 settings. stg1 and stg 3 what main jet are you using? I did not see it in the thread so I am guessing you did not choose the 170DJ main . * the air correctors are very important part of this kit . as is getting the stack of washers correct inside the slide holding the needle.

45 / 47.5 I have seen both work- from description in the thread yours seems to want more gas - 2.5 is good mixture setting when throttle is fully closed, but the pilot jet also feeds the bypass circuit- and that is the bridge from pilot to needle just as the throttle plate is opened. (open the throttle they are the 3 little holes) OK SO drilling the slides makes them lift slower to increase/maintain the intake velocity at smaller throttle input and drilling them is the replacement of the plentum effect of the airbox. installing stg.3 jet kit makes having the pilot to needle relation more important than needle to main - most relevant for street riding


you get the bottom into middle tuned in first - and accept the fact weather is going to mess with your tune on occasion- keep it a little lean on top you'll be able to forecast what the weather is doing.

[Phaedrus]

Really interesting... When you went back to mikuni jets, did you also remove all of the Dynojet air adjusters/restrictors?

What stands out most about your post is that I've found that the bike is SO much happier with the stock needles, 4 notches down from the top. Such a smoother ride all around EXCEPT for the bogging down/hesitation at 4k rpms... Carbs really don't appreciate the Dynojet needle...

I attempted to alleviate the hesitation with the stock needle and found that raising to notch 5 affected idle, and idle to 1/8 response. Too rich.

I'll have to check out the 5D59 needle. Though I was hoping to not have to spend too much more tuning this beast... :/ I did find some 5D58 needles on ebay for relatively cheap http://www.ebay.com/itm/Suzuki-GS110...36286b&vxp=mtr Worth a $40 shot?

I've gone through the same issues you are mentionning with my BS 34 carbs.
My bike is a GS 1000 ET that was sold in France with the CV carbs.
The engine is stock, the exhaust is a Kerker 4 into 1 with std baffle and my pods come from Dynoman.
I had the stage 3 Dynojet kit installed with the restrictors and the slides drilled.
I will not mention all the issues I had as it would be a strict repeat of what you encountered.
Like you I discovered that the Dynojet needle doesn't work at least on a european spec carb.
In the end the setting that worked for me is:
137.5 Mikuni main jet
5D59 needle of the 4th groove ( from the top)
I don't remember if I have a 40 or 47 idle jet

The 5D59 needle came from GS 1100 ( 16 valve) carbs but there is almost no difference to the 5D57's that come std on the the GS 1000 spec'd carbs.

In practice, the transition from idle to 1/8 throttle is very good, lots of power from there on to 1/2 throttle and then it will pull to redline very easily.
The only small issue is that sometimes it will not take full throttle when you are trying to get the max out of the beast.
Reducing the size of the main jet to fix this brings back all the issues you have seen below 1/2 throttle.
I've settled at that as the bike is a real pleasure to ride.
A professional mechanic tried my bike and was amazed at how smooth the throttle response was.
I wish you the same!

I'm AT sea level -- coastal town in CA. Using the Stage 3, 170 main jet. Fairly certain my washer stacking is on point, though I'm sure exactly what you're referring to. The Stage 3 directions tell you to start 3 notches down with dynojet needle. Bike runs like **** (as described earlier in this thread) @ 3 notches. Only seems to want to run with the dynojet needle 6 notches down, + a washer or two. Even then, it's a rough ride--not nearly as smooth as the stock BS34SS tapered needle. The bike responds without hesitation throughout the throttle band with Dynojet needles (haven't tested full yet), but it's not has happy as it could be.

Are you saying that adjusting the mixture screw may help with performance otherwise attributed to the needle jet and jet needle? Should I try some different mixture screw settings to see if it affects 4k rpm (~1/4-1/2 throttle)?

tough luck on the cable - where are you tuning this at? elevation and temperature are factors in this. you got it running - you are making changes - it is linear - that is progress towards success.

ok kit 3103 has 2 settings. stg1 and stg 3 what main jet are you using? I did not see it in the thread so I am guessing you did not choose the 170DJ main . * the air correctors are very important part of this kit . as is getting the stack of washers correct inside the slide holding the needle.

45 / 47.5 I have seen both work- from description in the thread yours seems to want more gas - 2.5 is good mixture setting when throttle is fully closed, but the pilot jet also feeds the bypass circuit- and that is the bridge from pilot to needle just as the throttle plate is opened. (open the throttle they are the 3 little holes) OK SO drilling the slides makes them lift slower to increase/maintain the intake velocity at smaller throttle input and drilling them is the replacement of the plentum effect of the airbox. installing stg.3 jet kit makes having the pilot to needle relation more important than needle to main - most relevant for street riding

I dismantled the carbs down to the needle jet, soaked them, sprayed them, went to town. All hardware was replaced. I really don't think the needle jets are clogged up, carbs look emaculate, but it is possible. I'm gonna take a peek at them just for my own peace of mind. Don't wan't to chase my tail if I don't have to be...

Thanks for everyone's input! I feel like I'm getting close... 45 pilot works well. 170 main works well, with dynojet air correction/restriction. Just need to get this needle jet/jet needle honed in...

What else did you not take off the carbs when you "rebuilt" them?

Did you actually dip them and let them soak for about 24 hours each, or did you simply unload a can of spray on each one?

I have said it before, I'll say it again, ... "Every shortcut you take is just another opportunity to do it over."

[John Kat]

[QUOTE=Phaedrus;2131937]Really interesting... When you went back to mikuni jets, did you also remove all of the Dynojet air adjusters/restrictors?

What stands out most about your post is that I've found that the bike is SO much happier with the stock needles, 4 notches down from the top. Such a smoother ride all around EXCEPT for the bogging down/hesitation at 4k rpms... Carbs really don't appreciate the Dynojet needle...

I attempted to alleviate the hesitation with the stock needle and found that raising to notch 5 affected idle, and idle to 1/8 response. Too rich.

I'll have to check out the 5D59 needle. Though I was hoping to not have to spend too much more tuning this beast... :/ I did find some 5D58 needles on ebay for relatively cheap http://www.ebay.com/itm/Suzuki-GS110...36286b&vxp=mtr Worth a $40 shot? QUOTE)

I've kept the air restrictors and the holes in the slides are as per Dynojet recommendation.
I personally would first try using the 137.5 Mikuni main jets before touching the needles.

[Phaedrus]

I've kept the air restrictors and the holes in the slides are as per Dynojet recommendation.
I personally would first try using the 137.5 Mikuni main jets before touching the needles.

Right on. I'll give 137.5's a shot with the stock needles and see how she does. Thanks.

[Joe Guilbeau]

Steve, you are correct...G, T, E... they all swim around in my head. For some reason I had a typo on a Pilot Air Screw and referred to it as a Jet. Good catch!

Alas, that makes the Main Jet with pods somewhat higher as well. My mistake..., 'cause I am not a complete idiot...some parts are missing.

[Phaedrus]

Update

Alright, so the 137.5 mains finally came in and I was able to tune a bit more. Much closer, but still no dice.

- With the needle @ notch 4, as suggested, 1/8 -/1/4 was solid, but 1/2 -3/4 was too lean, and full throttle seemed strong enough to pull through redline.
- I was able to remove all hesitation 1/4 - ~3/4 throttle by richening the stock needle all the way to max + a washer. Now, the hesitation is gone, but the bike doesn't want to pull ~<3/4 through full. It seems that the last bit of the taper on the needle is just a tad too rich. My conclusion is that the 137.5 main is very close and with the proper length/tapered needle, this bike could ride smooth as butter.

My last swing at this will be to remove the stock needles and compare their length/taper to the dynojet needles. The dynojet needle's taper is far less severe (leaner) and the needle itself is much shorter. I'll try to see if I can line up the current notch on the stock with a sweet spot on the dynojet needles. If that doesn't work, I'll have to measure the stock needles and try to find some shorter, slightly leaner needles.

This has been glacially slow progress, but it's getting closer with every little adjustment. Thanks John Kat for the recommendation of trying 137.5 Mikunis and a different needle. Definitely on the right track

[Edit: A Few Hours Later...]

Dynojet needles are way too lean at WOT for a 137.5 Mikuni. A few people have expressed their surprise that the Dynojet kits provide such "large" main jets. It turns out that this is because of the needles that they supply with the kit. They're so lean at WOT (about the same as the root diameter of a stock needle), that they need a gigantic main jet in order to balance the mixture. It's a main-to-jet needle taper ratio. Stock needles require much richer tapers in conjunction with the smaller Mikuni main jets.

Now I just need to find the right jet needle....

[John Kat]

Alright, so the 137.5 mains finally came in and I was able to tune a bit more. Much closer, but still no dice.

- With the needle @ notch 4, as suggested, 1/8 -/1/4 was solid, but 1/2 -3/4 was too lean, and full throttle seemed strong enough to pull through redline.
- I was able to remove all hesitation 1/4 - ~3/4 throttle by richening the stock needle all the way to max + a washer. Now, the hesitation is gone, but the bike doesn't want to pull ~<3/4 through full. It seems that the last bit of the taper on the needle is just a tad too rich. My conclusion is that the 137.5 main is very close and with the proper length/tapered needle, this bike could ride smooth as butter.

My last swing at this will be to remove the stock needles and compare their length/taper to the dynojet needles. The dynojet needle's taper is far less severe (leaner) and the needle itself is much shorter. I'll try to see if I can line up the current notch on the stock with a sweet spot on the dynojet needles. If that doesn't work, I'll have to measure the stock needles and try to find some shorter, slightly leaner needles.

This has been glacially slow progress, but it's getting closer with every little adjustment. Thanks John Kat for the recommendation of trying 137.5 Mikunis and a different needle. Definitely on the right track

[Edit: A Few Hours Later...]

Dynojet needles are way too lean at WOT for a 137.5 Mikuni. A few people have expressed their surprise that the Dynojet kits provide such "large" main jets. It turns out that this is because of the needles that they supply with the kit. They're so lean at WOT (about the same as the root diameter of a stock needle), that they need a gigantic main jet in order to balance the mixture. It's a main-to-jet needle taper ratio. Stock needles require much richer tapers in conjunction with the smaller Mikuni main jets.

Now I just need to find the right jet needle....

I'm glad to hear this was usefull.
You must be right about Dynojet's marketing trick suggesting that you can fit much larger main jets...
To illustrate your report, here's a picture I took some time ago that compares the Dynojet needle, the OEM needle and to the right the OEM needle from a non CV Mikuni carb.
I've come to the conclusion that we will never get the CV carbs to work perfectly with pods for the simple reason that the air flow is disturbed at high intake velocity.
Before changing your settings further, go for a ride without the pods.
I bet this will fix the hesitation above 3/4 throttle...