2001+ carb question

[Getafix]

Hello guys,

I'm preparing the bike for a 5k+ km trip across europe so I've started with valve clearance and carbs. I've opened the carbs for complete clean up and rebuild and noticed a part which I'm not sure if it's supposed to be there. At the images below you can see one of the jets removed and another jet beneath that I'm not sure if it's there to meet some regulations or that's how supposed to be. The bike's having trouble to pull after 5-6k in 4th 5th and 6th gear. So my assumption was a problem with the carbs or compression. Did compression test and the readings are okay, 150psi per cylinder. Other things I did to the bike is changing fuel lines, brake pads, installing volt meter, phone holder and things like that.
The jets used in the bike are 17.5 pilots 60 mids and 135 mains. Shim needle is clipped at 3th place from top and beneath that there was big plastic washer you can see at the pics. This was the same setup and the problem was there even before i rebuild the carbs. Could someone confirm the little jet in the hole supposed to be there and if the plastic washer under the C clip is not overkill? Another things I could mention is that the diaphragms are free of holes, all the o-rings are swapped with new ones, rubber intake boots are okay and their O-rings are new. You cannot view this attachment.You cannot view this attachment. 

[herennow]

Plastic washer is standard.

Struggling at WOT around 6k is usually due to too rich. I think the main jet should be 115 for UK 2001. 135 will make it fall on its face.

What air filter do you have? If it's a aftermarket replace it with the Suzuki one, 2001 to 2003 had a little snorkel in the airfilter. Without that you also run too rich. Search the forum, theres loads of info.

[Getafix]

I think the bike is made in Spain. The factory main jet is 135, air filter is stock hi-flow I think. I've tried to remove it just to see if things go for the better (in case the bike run too rich)  but only the sound changed. Bike really struggle to pull after 6k in 4+ gear. Not sure if this is normal or there is anything else I can check for. Also I noticed that after riding for longer, when I blip the throttle RPMs does not drop as quick as before. Perhaps I should tighten the air/fuel mix under each carb. Now they are at 3 turns out. Could this setting mess up the mixture at higher rpms as well?

[The Buddha]

Yes I believe 01-09 bikes were made in spain. Post 2010 or 11 its made in Colombia. I believe it still is made in Colombia. TBH they should make it in India. There is likely even a huge market for them. Afterall Yamaha R3 and similar sized bikes are flying around over there.
Cool.
Buddha.

[herennow]

Ive got a 2003, and these carb settings.When I had 130's in mine and a hi-Flo it fell flat on its face when accelerating hard. When I went down to 127.5 and Suzuki air filter I can now accelerate as hard as I want.   Notem, the mid is not actually a mid, its the starter jet.CHanging it can mess with start idle and choke etc.

Drop main and get a proper filter and you will thank me.

Pilot = 17.5
Mid = 60
Main = 127.5
Needle = 5DH42
Note Needle jet is  09494-00881   (P5M - id no 771)

[The Buddha]

No we swap the 60 for a 62.5 when available. Some have even put in a 65. What you cant do is put the 130 mains in there by mistake. Because it will fit and look right, but ruin the bike.
Cool.
Buddha.

[Roofaloof]

The bike's having trouble to pull after 5-6k in 4th 5th and 6th gear. 

Check the o-rings between the carb boots and engine head. These can develop air leaks over time. If they're smashed flat, just replace them.

[herennow]

No we swap the 60 for a 62.5 when available.

Hi buddha, I can't find the post now but some years ago with a couple of other members we analyzed the flow around that "mid" jet by studying it, and sprayng cleaner in different holes and seeing where it came out, etc.

The end conclusion was that that jet only does anything when the choke is open. I did miss around with a bigger and smaller jet there, and the only effect I could feel was abnormal choke behavior.

[The Buddha]

You could be right. I've sort of forgotten what went where in those carbs.
Cool.
Buddha.

[Getafix]

Thank you for your replies,

Already changed the O-rings. Bike seems to pull harder when cold.

Does anybody know if other make/models motorcycles use the same type of carb parts as this bike ?
I could find that DRZ400 and BMW F650GS share few same parts.
Where I'm from is hard to get the right parts so this will help me ask around for different models as GS500 is pretty rare here.
I would like to change the main to 127.5, pilot mixture screw with longer one which can be adjusted by hand and replace the diaphragms with the needles if it happen to find spares.

Cruising at 4500-5000RPM with 80 km/h (according to google maps speed and distance) the consumption is 3.7L per 100km but if I hold the throttle open at 6000-6500RPM the consumption can double or even more to 9L per 100km. My guess is that the mains should be decreased in size. When I replace the mains I will reply as how it goes.

[Getafix]

Searching the forum and online docs noticed that this is the restricted GS500FU K4 model.
My assumption is that the hole at the center of this piston valves are there to reduce the vacuum and the movement of the needle.

Could someone confirm if plugging this holes does any good for the bike? Would it affect the RPMs and top speed ? Anyone before made this mods?

I've checked everything, thinking there's some fault with the bike but it turns out its restricted model. Strange but on the registration document it's stated as 33kw engine.

Could not find hard proof that plugging the holes would do any better.
Really hope that someone knows how to squeeze few more HP without throwing tons of money on the restricted model.

[SimonF]

I had the same issues and found my bike was restricted. I plugged the holes with epoxy putty and all is good. pulls all the way up the revs.

[Getafix]

Good to hear someone else had the same issue. Did you plug the both sides of the pistons?

[SimonF]

Yes both sides. Then I used some fine grit sand paper (1500) on the epoxy to make sure everything is smooth and flush so it doesn't catch on the carb body when in operation.

[herennow]

Guys, leave those holes alone, I think th bikes restricted by a plate between the carb and the head...

https://www.ebay.com/itm/225093513263?hash=item34689e702f:g:V5MAAOSwEK9UE13I&amdata=enc%3AAQAIAAAA8M8t17Xa%2BqFQhPYiFG2UOn5NM6toy4J%2BPoyg3cYSoPFeo0V0LfcBL37fJzPYGOH%2BRs%2FhvUKgpOtx%2Fqu4uqaEiWYjy%2BobLixCV%2B1O0dUY9xqNFqi9LlUPh0UW%2BtJxteqhkQhkWohnRKTCOppU6GXmMqKaln03%2BifSWykbaBpQZ0cQdU8ISzFZUgGIQFMjJxCaEWffpzWtFVpJUZK0ZH0KwlYrc5MFJzvn9PRQ%2F7h%2FiXshUNW4rgd2DDCRoBxCt3S4HPfLd4xWHxIB%2BHDzw1ch%2Fz%2FpsTe5vBB9%2FgBND60QqKbM69pEC7pp%2FS3BrDnXcp%2BSMw%3D%3D%7Ctkp%3ABk9SR8LTv4yAYg

[Getafix]

There are not any plates between the carbs and the cylinder head.

[herennow]

Then I dont think it was restricted, all those holes do is change the RATE of response to the vacuum signal. not the final power delivery.

I might be wrong but buddha can confirm.

[SimonF]

 Getafix and my bike are U suffix and were restricted by Suzuki factory. They did this buy drilling two holes 180 degrees from each other (front and back) towards the top of the slide. those are the ones to plug. I plugged mine years and years ago and the bike pulls all the way to red line. herennow is right, as not to plug the small holes at the bottom of the slide where the needle comes out.

[Getafix]

Did you change the jets?

[Getafix]

Does not work with stock jets. It stops the revs at about 5k, it's like you pulled the brake or something. Maybe with different main jet it would be better. I've return to stock piston valves