Tuning advice needed following dyno test

[John Kat]

I'm still playing with the jetting on my GS 1000 ET engine fitted with BS 32 CV carbs
The bike is fitted with pods and a 4 into 1 exhaust.
The current setting is :
Main jet : 147.5 ( Mikuni)
Needle : position# 4
Idle jet: 40
All mods done according to Dynojet stage 3.
We took two readings: one at WOT in red, the second at 1/2 WOT in green.
The corresponding AFRs are in the same color but in fine print.
The leaner curve corresponds to 1/2 WOT.
I have an idea at what to do but I'd appreciate some advice

 

[salty_monk]

Looks to me like you need to go with a smaller main jet & move the needle up...

Interestingly I believe this is the same result PosPlayr came to on his 1100 (although his is a big bore etc).

 

[gearhead13]

Which DJ kit did you use on those 32mm carbs?
Why are you running smaller than stock carbs?

 

[posplayr]

Looks to me like you need to go with a smaller main jet & move the needle up...

Interestingly I believe this is the same result PosPlayr came to on his 1100 (although his is a big bore etc).

Dan, you beat me to it. I think my results are more to do with the 4:2:1 but you are correct in your recollections

I'm with Age, on the crabs being too small, I don't see a whole lot of room to drop the main as at WOT red line it is already getting lean (13.2-13.4), yet at low mid RPM it is very FAT (RPM<6K AFR <12!!!).

So how to drop the WOT reline AFR but raise the mid range? Bigger Pilot Jets? 1/2 Throttle is way lean

My final results

http://www.thegsresources.com/_forum/attachment.php?attachmentid=19024&d=1363822154

 

[John Kat]

Which DJ kit did you use on those 32mm carbs?
Why are you running smaller than stock carbs?

Sorry for the confusion, the bike is equipped with the OEM BS 34 SS carbs

 

[John Kat]

Looks to me like you need to go with a smaller main jet & move the needle up...

Interestingly I believe this is the same result PosPlayr came to on his 1100 (although his is a big bore etc).

Strange enough but my reasoning leads to the exact opposite with all due respect.
Here's what I read on the chart:
To me at WOT the mixture leans out above 7000 rpm where I suppose we are in main jet territory?
Putting a larger MJ would also be in line with the DJ kit recommendation that provides both a 165 and a 170 MJ to be used in conjunction with pods.
The reason I did not use them in the first place is due to the fact that I thought my 4 into 1 is far more restrictive than US made exhaust systems.
Looking at the WOT diagram below 6000 rpm the situation is the opposite with a very rich mixture.
Isn't this the territory of the needle height?
Dropping it by one notch should probably help?
What really puzzle me is the 1/2 Wot readings?
Maybe it is normal for the mixture to go real lean when you are not asking for power?
My proposed first step would be to change the main jets only and take a new dyno before touching the needle heights.

 

[posplayr]

I think the first thing is to decide what it is you are trying to correct. My guess is that you should only look at the AFR at the maximum RPM whether WOT or 1/2 WOT.

AFR is NOT supposed to be a function of RPM but rather throttle position. Yours is obviously varying wildly.

I did not do my AFR tuning on a dyno but rather a relatively constant steep hill and I generally paid attention to the AFR as I approached redline regardless of throttle position.

Under that theory your steps would be correct to richen the main(to get WOT below AFR=13), but you would also want to richen the needle to get the 1/2 WOT below AFR=14:1.

http://www.thegsresources.com/_forum/showthread.php?t=164565&highlight=AFR+Info

Quote:

As A guide, this is what I saw near my optimum tune point.
1 notch rise in needle ( e.g. 4 to 3 from bot) at 1/2 throttle will lower AFR 1 full point (e.g. 14.0 to 13.0).
A drop in Main by 2 sizes (e.g. 140 to 135) at 1/2 throttle will raise AFR 1 full point.(e.g. 13.5 to 14.5)
A drop in Main by 2 sizes (e.g. 140 to 135) at WOT ------- will raise AFR 1/2 a point.(e.g. 11.0 to 11.5)
SUMMARY: @ 1/2 Throttle: 1 needle notch = 2 jet sizes

Based on my results,
I would recommend that would want to drop the main by 2 step sizes to drop 1/2 AFR point at WOT.

A drop in Main by 2 sizes (e.g. 140 to 135) at WOT ------- will raise AFR 1/2 a point.(e.g. 11.0 to 11.5)

Raise the needle by one notch
and that coupled with one notch should drop you two points total in AFR at 1/2 throttle.

SUMMARY: @ 1/2 Throttle: 1 needle notch = 2 jet sizes

[/QUOTE]

 

[salty_monk]

WOT means you are running on the Main Jet only, has nothing to do with the RPM's, more to do with throttle position.

Did you put in the air jet correctors with the DJ kit?
Be aware that your air jets & the main jet cylinder (Can't remember the name off hand but the big long one that the main jet screws into the bottom of) could be different to US spec. I had a set of Canadian carbs on my GS1000G that had differences in those places.

On 1/2 Throttle you will be out of the pilots & running on the needle. At that point the Main jet size is not really important.

 

[John Kat]

Did you put in the air jet correctors with the DJ kit?
Be aware that your air jets & the main jet cylinder (Can't remember the name off hand but the big long one that the main jet screws into the bottom of) could be different to US spec. I had a set of Canadian carbs on my GS1000G that had differences in those places.

You are right.
I was suspecting there could be a difference here?
I should maybe pull the main air correctors out?
What's really strange is that the bike was running fine with the pods and an OEM 1100 Katana exhaust with the following settings:
MJ : 157.5
Needle#4
Pilot jet : 40
After fitting the 4 into 1 I started having problems when accelerating.
I then lowered the needle from 4 to 3 then to 2 and it went better and better.
That's when I decided to lower the MJ to 147.5 with the needle still in #2.
Again an improvement with some hesitation around 6000 rpm and then full power.
By raising the needle to #3 everything was OK except a slight hesitation coming out of idle.
I dropped the MJ to 142.5 and found out that the best position for the needle was in #4.
The only remaing issue was the slight hesitation when coming off idle as when driving in traffic.
I tried a 47.5 idle jet but it was not conclusive.
In summary the best "on the road" settings are:
MJ 147.7 / needle#3
and
MJ 142.5 / needle#4
The dyno test was done with
MJ 147.5 / needle#4

PS: the needle position is quoted from the top as per DJ manual
PS2: I tried to pull the DJ main air correctors out without success

 

[John Kat]

Based on my results,
I would recommend that would want to drop the main by 2 step sizes to drop 1/2 AFR point at WOT.

Raise the needle by one notch
and that coupled with one notch should drop you two points total in AFR at 1/2 throttle.
[/B]

[/QUOTE]
I suppose you mean raise the main jet to drop the AFR?
Please see my comments to Salty Monk where I've retraced the history of my tuning.

 

[John Kat]

In the end I decided to replace the Dynojet needles by the OEM needles to make sure the needles match the "needle jet" following Salty Monk's comment.
The only issue is that the "original" needles on my BS 34 SS ( marked 5D50) are apparently not the OEM needles? They should have been according to my source the 5D57s for the GS 1000ET?
On top of that the 5D50s are not ajustable as they only have a single groove
Not to worry, I still had some needles from the BS 34 SS carbs that came with my Katana 1100.
These are marked 5D59.
The first picture below show the DJ MJ on the top compared to the Mikuni 5D50
The second picture shows the DJ MJ on the left compared to the 5D59 ( the jet on the right hand side is irrelevant)

I'm waiting for the rain to stop to test this combination...

 

[salty_monk]

The taper on the DJ need should be a lot steeper (more pointy) to allow more fuel out at a faster rate. I think you will need that with Pods but if it's just a pipe then the stock one (with washers or if you can use the grooved one great) will be fine.

I ran my 1000G with a slightly bigger main jet & the needle raised a bit. It had a V&H 4:1, no other mods at that point.

 

[John Kat]

The taper on the DJ need should be a lot steeper (more pointy) to allow more fuel out at a faster rate. I think you will need that with Pods but if it's just a pipe then the stock one (with washers or if you can use the grooved one great) will be fine.

I ran my 1000G with a slightly bigger main jet & the needle raised a bit. It had a V&H 4:1, no other mods at that point.

The issue is that I'm running with pods...
I was really disappointed by the dyno run be cause I was looking for a simple answer: too rich or too lean?
The WOT result was slightly lean at high rpm and way too rich in the midrange???
The fact that the AFR is measured by a probe stuck in the exhaust must introduce some errors for sure but now where's the truth?
My plan is to progressively go back to OEM settings and see if it improves or not?

 

[posplayr]

The issue is that I'm running with pods...
I was really disappointed by the dyno run be cause I was looking for a simple answer: too rich or too lean?
The WOT result was slightly lean at high rpm and way too rich in the midrange???
The fact that the AFR is measured by a probe stuck in the exhaust must introduce some errors for sure but now where's the truth?
My plan is to progressively go back to OEM settings and see if it improves or not?

Why not put on the standard DJ kit with pods and 4:1 pipe you should be close enough to dyno tune.

 

[John Kat]

Why not put on the standard DJ kit with pods and 4:1 pipe you should be close enough to dyno tune.

That's where I started but with very poor results
My current thinking is that the Dynojet kit is not suited for european spec bikes...
I've reinstalled an OEM needle and I will try to adjust it tomorrow!

 

[John Kat]

Finally some good progress
I did a first ride with the 5D59 needles in position #3 ( from the top), 147.5 MJ and 40 IJ.
Very good power above 1/2 WOT but lots of hesitation between 1/4 to 1/2 WOT.
That's easy! The DJ instructions tell you to raise the needle by one and maybe two slots.
No hesitation! I went for two slots meaning I'm now at the last slot (#5).
New try on my favorite twisty road
The bike pulls very strongly above 1/2 WOT AND there is now only the slightest hesitation ( but not always!) at around 1/3 WOT.
Idle is perfect and it pulls very nicely off idle.
A problem that I've been wanting to fix since the beginning...
I'm almost certain the bike is more powerfull as I went 10 km/h faster than my previous max.
What's the logic in all this?
The DJ needle doesn't seem to work correctly with my BS 34 SS carbs.
A dyno test will now probably show a more constant AFR throughout the rev range at WOT.
Another potential culprit could be the pods?
I bought mine from Dynoman but most "experts" tell me that only the K&N pods are tunable???
Last but not least my 4 into 1 is made by Laser and I have the feeling it's very much tuned for the mid-range.

 

[GregT]

I'd suspect that the idle jets are still a tad lean for that pipe/pod setup and you're compensating by raising the needles.
IMO with the right idle jets the needle should come back to the middle notch.
In my experience the 8V motors like what seems an overly big idle jet no matter what carbs are fitted.

The idle jets have a lot of overlap into the early/mid stages of the needle's range.

 

[John Kat]

I'd suspect that the idle jets are still a tad lean for that pipe/pod setup and you're compensating by raising the needles.
IMO with the right idle jets the needle should come back to the middle notch.
In my experience the 8V motors like what seems an overly big idle jet no matter what carbs are fitted.

The idle jets have a lot of overlap into the early/mid stages of the needle's range.

I had suspected that early on by replacing the 40s by 47.5s.
At first, I thought I had the off idle issue solved but sometimes it worked and sometimes it didn't
I will try again with the new needle set-up.
Thanks

 

[posplayr]

I'd suspect that the idle jets are still a tad lean for that pipe/pod setup and you're compensating by raising the needles.
IMO with the right idle jets the needle should come back to the middle notch.
In my experience the 8V motors like what seems an overly big idle jet no matter what carbs are fitted.

The idle jets have a lot of overlap into the early/mid stages of the needle's range.

I'm seeing that the 8V bikes are a different animal to the 16V but when I was tuning my 1166 with 4:2:1 and ported head, I was searching through the combinations and ended up moving the needle from the 2th position all the way to the top position (leanest) and the bike just would not run. So going to the extreme on the needle produced very poor results. if memory serves, I backed the needle position back and reduced the pilot jet and got a much better result..