Quote from: The Buddha on January 24, 2021, 11:27:07 AM

Quote from: moe_tunes on January 22, 2021, 05:22:02 PM

Quote from: The Buddha on January 22, 2021, 09:50:56 AM
... a well documented case of slides coming up too fast ...

I'd like to read about that. Can you point me to any info on this?

Cheers

Dynojet offers plastic plugs to constrict and/or to close off those holes. I actually dynoed my bike with 1 hole closed off, it still showed signs of the slide coming up too fast. I trained myself to open the throttle slower.
When you whack the throttle open and the bike falls on its face when it was running along fine, and if in that same rpm/speed/gear it reacts fine when you open the throttle slowly, that's a sign the slide is coming up too fast.
Cool.
Buddha.

So it's not documented somewhere that you can point me to? I would have liked to read about that.
I know there are plugs for the slide holes that are used on four cylinder race bikes where low and mid range fuelling is less important.
I'm trying to have the 2009 GS500 I have now fuelling like the GS450 I used to have. That bike wasn't leaned down to meet Euro emissions and would rev from 1500 to 9000. The 500 is basically the same engine so should be capable of a similar rev range once the carbs are sorted. Changing jets and mixture screws is just a part of the solution...
With the first stage of the mod I have 1000 extra usable revs, a crisper pickup and more smiles per mile.

Quote from: moe_tunes on January 26, 2021, 12:52:44 AM

Where do you think the vacuum that raises the slide comes from?
I don't think you quite understand how CV carbs work. Have a look at Benoulli's Principle. It might help you get that bit sorted.

Cheers.

wow. Welcome to my ignore list. You can screw your stuff up and I won't  get distracted by it. We all go home happy.

That does seem a bit sensitive, I was just trying to help...

For a simple $0 mod I have an extra 1000 usable revs and crisper throttle response. Not really screwing any stuff up at all.

Cheers

Quote from: moe_tunes on January 26, 2021, 01:12:09 AM

I'm trying to have the 2009 GS500 I have now fuelling like the GS450 I used to have. That bike wasn't leaned down to meet Euro emissions and would rev from 1500 to 9000. The 500 is basically the same engine so should be capable of a similar rev range once the carbs are sorted. Changing jets and mixture screws is just a part of the solution...
With the first stage of the mod I have 1000 extra usable revs, a crisper pickup and more smiles per mile.

A 100% stock 2009 GS500 will rev from 1200 rpm to 10500 no problem. There may have been an issue with the carb that you are trying to bandaid.

I believe you are getting a different throttle response as a result of the mod..............not necessarily a better one

Quote from: Bluesmudge on January 26, 2021, 11:56:11 AM

Quote from: moe_tunes on January 26, 2021, 01:12:09 AM

I'm trying to have the 2009 GS500 I have now fuelling like the GS450 I used to have. That bike wasn't leaned down to meet Euro emissions and would rev from 1500 to 9000. The 500 is basically the same engine so should be capable of a similar rev range once the carbs are sorted. Changing jets and mixture screws is just a part of the solution...
With the first stage of the mod I have 1000 extra usable revs, a crisper pickup and more smiles per mile.

A 100% stock 2009 GS500 will rev from 1200 rpm to 10500 no problem. There may have been an issue with the carb that you are trying to bandaid.

Yes I also found the comment about extra rpm  surprising, especially considering that originally the statement was made that WOT is rarely used

It's like nobody bothered to read the first post...

If you read through this forum you will find that over the years there has been a consistant opinion that the GS500 isn't very usable under 4000rpm which to my dissapointment I found was true with my stock GS. Nothing like I expected it to be. Even from 4000rpm it feels pretty anemic, not anything like these engines are capable of which is obviously due to Suzuki leaning out the fuelling to meet 2009 Euro emission limits.

When I started this thread I knew I was interacting with the internet of 2021 and was fully aware there would be people who hadn't tried the mod who would poo-poo the idea just because they had nothing else to do, didn't like the idea of someone doing something to their bike, didn't like that someone else could have something positive to contribute to the community or some other petty reason. That's our modern internet...

Over the next few months I will, step by step, experiment with what's known to work with other bikes to see what works with the GS because no one has done much to sort out the weak spot of the GS, the low to midrange fuelling.

Cheers

The stock GS exhaust and airbox keep air flow down to a point that the 2 hole slide isn't your limiting condition. In fact the exhaust is the first limiting condition, specifically the can.
Take that out and you instantly run into the next limit. The airbox.
If you were running say 3K and whacked the throttle open and have the bike seem to gasp and want to stall, that means your slide is rising too fast. Open slowly and it reacts better, open fast and it seems to just gasp like you opened the window on a car going 100 and stuck your head out the window.
Now with a K&N and pipe and closing off 1 hole I had my bike dynoed and there was a flutter they said was a slide still rising too fast. I didn't bother partially closing off the other hole. I just trained to open a little slower.
The 89-00 GS does not need more holes.
That DR carb video doesn't apply to the 01+ GS, the slides, springs etc etc are different. Yea suzuki fixed a problem no one was having and ignored all the problems people were having. Exactly what we needed was 3 jets with smaller holes.

Cool.
Buddha.

After 2 tanks of fuel, no change in fuel consumption and only benefits from the first stage of the mod it was time to try the second stage.

As mentioned previously the slide springs in my 2009 carbs have a free length of 100mm. For the first step I cut them down to 95mm. Throttle response down low has improved again and going from a closed throttle to a slightly opened one mid corner is much less snatchy. Very happy with the improvement. I'll put a couple of tanks of fuel through it and then see if taking another 5mm off the slide spring free length is an improvement or a bit too much.

Cheers.

Have you told Suzuki and Mikuni about this revelation yet?

I think you should 

Today was my first chance since the second stage of the mod to do some country road scratchin' and it's great not to have to be constantly changing gears to have some acceleration on the GS.
During the last week I performed a couple of tests on my daily commute to various parts of suburbia where i am limited to 60 km/h to check out how the fueling is now with the mods. My normal mode of riding is to filter to the front at a red light and take off briskly to get away from the half asleep, myopic, facebook reading tin top drivers and change up at around 5000 rpm's from first to fourth, change into fifth and cruise 'till the next set of lights. On Tuesday I didn't go higher than fourth and Wednesday no higher than third. Each day the the fueling was fine, the bike rode great and was very responsive but there was an obvious difference compared to my previous 17 months with the bike. Towards the end of the commute I felt heat from the engine on my lower legs  which I hadn't had before and after parking the bike I could smell the extra heat coming off the engine, moreso when fourth was my top gear for the day rather than third. Sure signs of the bike running lean in the midrange and probably why the DR guys from the vid grind a taper on the needle for the DR's carb. When I drilled the slides in the first stage of the mod I noticed the needles were closer to having parallel sides than a taper which I attribute to Suzuki constantly leaning out the fuelling for a carb'd bike to meet increasingly restrictive Euro emissions. So instead of the next stage of the mod being removing another 5mm off the slide spring free length it makes more sense to add some taper to the needles. Following the $0 mod ethos of this thread I'll use a grinding wheel to add the taper to the needle. As a starting point I'll reduce the tip by 0.5mm and taper it up 20mm 'cause it's easier to take more off later than add some back... I'll put another tank of fuel through the bike and retest what happens with fourth and third being the highest gear I use to confirm things.

I'm sure sledge won't be happy to read about someone using a bench grinder to add a taper to the carb's needles and I'm OK with that, hope it gives him something to fill his day. From what I've read on this site and others the GS500 provides a low cost of entry to the motorcylcing world and plenty of low cost opportunities to experiment and learn and personalise a bike.

Cheers

You use a bench grinder to change the needle taper While you're at it brush your teeth with bench grinder too.

Needle taper can be changed by putting the needle in a hand drill and spinning it with wet emery paper between your fingers.
You're using an atom bomb to squish that little ant at your foot. BTW the stock needle is in short short supply, so you grind it up and we'll all connectively say ... WTF, you ground up what

And stock needle is nearly ideal as well, ofcourse you can grind up any part you like. Its your bike.

Oh yea you want a hacked up needle - look into dynojet, atleast that way you have a way back, those guys also drill and tap and this and that the slides too.

Cool.
Buddha.

exactly what Buddha said. Plus, the stock needle I probably aluminum, which will go bad real fast if you try to modify it. I have some stainless steel needles that are probably dynojet, already screwed up for you and much more forgiving when you try to modify them.

The thing Buddha didn't mention is that the tremendous value of the collective wisdom from three decades of GS500 owners experience is tossed out the window once you try re-engineering the carbs. That's probably the most valuable aspect of that bike.

Every day i ride the bike I become more and more happy that I took on the challenge of being the first to try this mod on the GS carbs. After a year+ riding the bike I have developed some habits, a way to ride the bike, which now that the bike is much more responsive on the throttle has me constantly backing off the throttle to slow the bike down and get back to the speed limit on our speed camera infested roads here. A sure sign to me that positive progress is being made.

This week I have repeated the two tests from last week during my commute and while each time the engine was a bit hotter than normal it was never to the extant of last week. Last week was full of pretty good weather and this week has been heavily overcast and raining so that has played a part. The engine still showed signs of being lean in the midrange and that will only become worse with the colder weather of winter approaching so on the weekend I'll take a long runup and a bench grinder to the needles to add some taper to them
Happy times

For a visual representation of how unscary and undangerous this is have a look at the vid I linked to early in the thread. All that's needed is a bit of patience and a medium level of coordination.

Cheers

 

So I am confused now, what is preffered, a fast rising slide or a slow rising slide? I am contemplating just switching to a set of Keihin flat slides. 2 stroke carb tuning gave me less of a headache. 

slide rising correctly in proportion to the air volume and corresponding needle profile is preferable. That's what you get stock. But when you screw up one thing, the whole system is out of balance and then you'll be chasing every other thing trying to get it to work wack-a-mole style.

OP solved a problem that didn't exist, created new problems, and now is trying to solve them, calls this "improvement". Maybe more charitable to say the OP misdiagnosed a problem and applied the wrong solution and now is in the spin cycle. Happens all the time with carburetors. I have done this myself many times.

It's hard enough with modern gas to keep stock carbs working correctly, and the easiest way to get them working right is stock.

Quote from: Henrico123 on February 21, 2021, 05:35:50 AM
So I am confused now, what is preffered, a fast rising slide or a slow rising slide? I am contemplating just switching to a set of Keihin flat slides. 2 stroke carb tuning gave me less of a headache. 

Your '91 was built before Suzuki had to start tuning the carbs for emissions instead of ride quality so this mod won't be necessary for you.

It's not about fast moving slides just a faster moving slide in my 2009's carbs. Smaller holes in the bottom of the slides for less vaccuum to lift the slides, a stiffer spring to slow the slide lift and a needle with bugger all taper means less fuel entering the engine, 2009 emissions levels met and crap throtle response...
If the early 90's carbs were 34mm instead of 33mm I'd just throw a set of them on.

Cheers

Quote from: mr72 on February 21, 2021, 06:13:03 AM
slide rising correctly in proportion to the air volume and corresponding needle profile is preferable. That's what you get stock. But when you screw up one thing, the whole system is out of balance and then you'll be chasing every other thing trying to get it to work wack-a-mole style.

OP solved a problem that didn't exist, created new problems, and now is trying to solve them, calls this "improvement". Maybe more charitable to say the OP misdiagnosed a problem and applied the wrong solution and now is in the spin cycle. Happens all the time with carburetors. I have done this myself many times.

It's hard enough with modern gas to keep stock carbs working correctly, and the easiest way to get them working right is stock.

It's like you haven't read anything I said...

Cheers

Well, I do have you on 'ignore'.

But what you have said is just wrong. So there's that. That's why I put you on 'ignore' in the first place. This thread is actually kind of funny because to me it looks like a weird conversation of nothingness between three or four people I have on 'ignore'.