BST36SS "Slingshot" Carb Question

[TxGSrider]

Funny you're using Factory's tuning method, and running rival jet kit parts.
What do the airfilters look like? Are they the dual oval style K&N?
Did U change the O-ring on the bottom of the plastic slide glide?
Mine were all smashed and cracked.
I'm running 32.5 pilots. Stock was 30 on 1990 GSXR-11 carbs.

Ive replaced all the O-rings, and emulsion tubes, and needles and main jets. It runs pretty dang nice with good a/f and idle, a slight richness at lower rpms at full throttle that I would never notice riding the bike but the LM-2 shows it and so I keep messing with it-lol. In fact, at all speeds and rpms its more responsive than it was with my OEM carbs w/pods and Dynojet kit... and although I cant prove it, I think Im getting better mileage too. The other day it finally cooled off here into the mid 60's and I did a full throttle test and from mid range (5000 or so+) it ran between 12.1 and 12.6... so im done messing with main jets. (Usually its in the 90s - 100s and humid when I get a chance to mess with it on my weekends- Texas heat...)

I use the Factory Pro method, because the carb doesn't know what who made the parts inside... its just a good solid method for checking jetting. :-)

Oh, and Im using oiled K&N "lunchbox" style pods. I believe its the 4-2-1 exhaust, and super mild cam timing of my stock 82 gs1100e that keeps the main jet size smaller than expected.

Note: I think if I had a regular 4-1 exhaust and individual style K&n Pods, or maybe the 1983 cams it would need allot bigger mains. But I don't have any way to test that theory.

[limeex2]

If vacuum caps blow off (I had a GSF1200F that had this issue), your can buy little tiny vinyl vacuum caps at an auto parts store that will stay on small vacuum fittings. Rubber caps lasted about a day or two before flowing off and those that lasted longer usually cracked and leaked soon anyway. I think I bought those little vacuum caps in the "HELP" section and they were red.

Fuel line and a ball bearing worked well

[posplayr]

On the GS I haven't used the tach function on the LM-2. For full throttle tuning Ive been using the Factory Pro method... so I use the long hill behind my house. I get rolling in 2nd gear at about 2 grand, click record, open throttle WOT and let the motor run up to 9500... then let off and stop recording. Its pretty easy to see from the readings where I start and where I let off by the jumps on the readings.
For part throttle I have the meter zip tied to my tank bag and watch it and the tach and note the readings, along with feeling any flat spots or surges. At off idle to about 3200-3500rpm and light throttle the mixture seems to be mostly controlled by float level. Beyond that at part throttle is mostly needle height.

On the quads the Tach lead is always finicky, sometimes it will work sometimes it wont and other times it'll quit reading after the RPMs get over 6000 or so.

You mentioned before having the RPM clamp, I don't recall ever getting it to work but Katman went around in circles within it and bit never worked although that has been a while and so I don't know what board revisions they might have been selling. To clarify I used the LMA-3 for both SPEED and RPM but only after getting around some of the inherent design flaws of the LMA-3 and I have never seen anybody able to use the LM-2 RPM features.



I was fortunate and had had a very long hill within driving distance. I did 1/4,1/2, 3/4 and Full in gears 3,4, and most of 5 (full throttle top gear).
All this is just recording without looking at the gauge; I do a full off pause between throttle settings. With SPEED and RPM it is easy to see the AFR reading and identify each.

[posplayr]

Funny you're using Factory's tuning method, and running rival jet kit parts.

The tuning method is based on the carburetor designs and not the specific type of jet.

The main jet feeds the needle/emulsion tube so adjusting the needle without having the main set is meaningless because it will change again once the main is set. IIRC the pilot might be independent but it is such a small contributor, it would be like using the fine adjust on a meter and then as a final set set the coarse adjust. Changing the coarse adjust totally invalidated the fine adjust.

Granted with a O2 Sensor (at various throttle settings) you can make pilot and needle adjustments together easier, you still do the main first.

Without the O2 sensor you are at such a disadvantage that it is pretty much a waste of time to do anything that the order of adjustment mention.

[TxGSrider]

The tuning method is based on the carburetor designs and not the specific type of jet.

The main jet feeds the needle/emulsion tube so adjusting the needle without having the main set is meaningless because it will change again once the main is set. IIRC the pilot might be independent but it is such a small contributor, it would be like using the fine adjust on a meter and then as a final set set the coarse adjust. Changing the coarse adjust totally invalidated the fine adjust.

Granted with a O2 Sensor (at various throttle settings) you can make pilot and needle adjustments together easier, you still do the main first.

Without the O2 sensor you are at such a disadvantage that it is pretty much a waste of time to do anything that the order of adjustment mention.

The RPM clamp was never very consistant on my atv either, but its got an FCR41 (bored to 43mm) and I needed to know throttle position allot more than RPM (unlike the cv carbs most of us have on our bikes that RPM has allot more importance).

As for doing this project without a wideband... I would've gave up along time ago with it... and now I'm just nit-picking the jetting... its actually really smooth and more fun to ride than ever.

I also don't think I could've done the full throttle tests without the data logging feature.. theres just too much going on at full throttle on a public road to try and read the little constantly changing numbers on the screen. lol - but I marked the throttle grip at 1/3, 1/2, and 2/3 throttle position and rode around looking at the meter and the tach and noting the readings and getting a feel for any misses or rough spots. In the 90-100's it liked the needle in the 2clip from top, but after it cooled off in the 60's it surged slightly and showed a little lean, it was better in the 3rd position, so I left it there since the weather is finally cooling off for fall riding here.

It also seems to like the float about 1mm lower (15.6mm), but Im still fine tuning that... .6mm was a little rich and 1.5mm was too lean off idle with light throttle to about 3500rpm.


Now I'll probably mess it all up when I add a big bore kit, 1150 head, cams... and I'll have to start allover again with tuning. lol

[posplayr]

Now I'll probably mess it all up when I add a big bore kit, 1150 head, cams... and I'll have to start allover again with tuning.

Well that is what I had.

I also don't think I could've done the full throttle tests without the data logging feature.. theres just too much going on at full throttle on a public road to try and read the little constantly changing numbers on the screen.

Even with the data logger, you can't get the carbs to settle well enough on flat ground; acceleration is too fast. I went around in circles with a moderate hill going out of town, till I found something steep. After those setting the front wheel got real light.

[TxGSrider]

Well that is what I had.




Even with the data logger, you can't get the carbs to settle well enough on flat ground; acceleration is too fast. I went around in circles with a moderate hill going out of town, till I found something steep. After those setting the front wheel got real light.

Ive got a nice hill near my house that Ive been doing the full throttle/2nd gear tests. Like I said, I'd have never gotten close without the meter.

And the "Butt dyno" can be deceiving... when the low end was real rich it made the bike feel faster as the engine built rpms (even when the main jets were a little too large) - more "peaky" like an over cammed motor or a two stroke, now that the a/f is more flat, the engine pulls more evenly from all RPMs and throttle positions but actually feels slower as the "peakiness" isn't noticeable. I think the BST36SS carbs are a fantastic upgrade... once they are tuned for your bike.

[posplayr]

Ive got a nice hill near my house that Ive been doing the full throttle/2nd gear tests. Like I said, I'd have never gotten close without the meter.

And the "Butt dyno" can be deceiving... when the low end was real rich it made the bike feel faster as the engine built rpms (even when the main jets were a little too large) - more "peaky" like an over cammed motor or a two stroke, now that the a/f is more flat, the engine pulls more evenly from all RPMs and throttle positions but actually feels slower as the "peakiness" isn't noticeable. I think the BST36SS carbs are a fantastic upgrade... once they are tuned for your bike.

I did most of my best data in 4th gear

I can email you an example if you like. I have a bunch of logs but found one annotated as 4th gear 1/4, 1/2, 3/4.

[TxGSrider]

I did most of my best data in 4th gear

I can email you an example if you like. I have a bunch of logs but found one annotated as 4th gear 1/4, 1/2, 3/4.

For my part throttle it was a mix of various gears usually 3,4 or 5th on different roads around the house level, up hill, down hill... but the best reading for the part throttles were slight uphill. Level ground gives leaner readings and downhill produces even leaner readings.

I tried swapping slides for some that had bigger holes just for kicks, but it only worked in lower gears and worked progressively worse in higher gears (staggering/cutting out at lower rpms under load). I didn't take any readings but I wish I would've. I may play with the slide holes again sometime... maybe try blocking one off to see how it works. I enjoy experimenting with stuff like this.

[posplayr]

For my part throttle it was a mix of various gears usually 3,4 or 5th on different roads around the house level, up hill, down hill... but the best reading for the part throttles were slight uphill. Level ground gives leaner readings and downhill produces even leaner readings.

I tried swapping slides for some that had bigger holes just for kicks, but it only worked in lower gears and worked progressively worse in higher gears (staggering/cutting out at lower rpms under load). I didn't take any readings but I wish I would've. I may play with the slide holes again sometime... maybe try blocking one off to see how it works. I enjoy experimenting with stuff like this.

IIRC to ride down the freeway on flat ground in 5th gear at 70+MPH I'm at about 1/8 throttle; If I accelerate to where I need to shift gears, the AFR takes 2-3 seconds to settle during shifts(slide dynamics I suspect). I couldn't get close to dialing in the main without a steep long grade(6%), as you know that is where you start.

[Carter Turk]

I was joking about the methods of this jet kit and that one.
With regard to the pilot jet, I was merely mentioning what I was running.
His readings of richness at low rpms/throttle openings, seems to suggest a smaller unmodifed motor wouldn't like such large pilots (40).
Says the neanderthal talking to the engineers whose test methods I'll never grasp.

The tuning method is based on the carburetor designs and not the specific type of jet.

The main jet feeds the needle/emulsion tube so adjusting the needle without having the main set is meaningless because it will change again once the main is set. IIRC the pilot might be independent but it is such a small contributor, it would be like using the fine adjust on a meter and then as a final set set the coarse adjust. Changing the coarse adjust totally invalidated the fine adjust.

Granted with a O2 Sensor (at various throttle settings) you can make pilot and needle adjustments together easier, you still do the main first.

Without the O2 sensor you are at such a disadvantage that it is pretty much a waste of time to do anything that the order of adjustment mention.

[posplayr]

I was joking about the methods of this jet kit and that one.
With regard to the pilot jet, I was merely mentioning what I was running.
His readings of richness at low rpms/throttle openings, seems to suggest a smaller unmodifed motor wouldn't like such large pilots (40).
Says the neanderthal talking to the engineers whose test methods I'll never grasp.

sorry, I did not pick up on the irony although I was a bit surprised by the comment .
Hope I was not being too pedantic.

[TxGSrider]

I actually think I may be chasing down the "perfect" needle position forever as long as I keep using the DJ Gsxr1100 needles. I believe the taper is probably too steep so when I get it set right at 1/2 throttle its a little too lean at 1/4 throttle and a little too rich at 3/4 throttle. It may also be the cause of some of my rich mid-rpm reading at full throttle. Theres a pretty big difference in a fuel curve for a 140+hp GSXR from a 110hp GS1100. I do have a set of DJ needles for a GSX1100G (bst36ss, similar hp to my gs) that I have yet to try, just by looking at them, there doesn't seem to be hardly any difference in shapes, but I suppose that dealing with .001" differences may be a little hard to see. I was just trying to get it in the ballpark before making anymore changes (like the needles). One change at a time is usually the best method.
Also, I broke down and bought another LM-2 so I can continue testing again after I get back from a little vacation this weekend.

[posplayr]

I was using the DJ needles from the gs1100-1150 kit and came to a similar conclusion. I think it ran a little rich but without a dyno I had no way to convert afr to hp so it became a "close enough" situation. I had actually considered trying to sand down the needles a bit to make adjustments but in the end that was going to take too much effort.

sorry this was on the bs36 carbs .