Hi all,

First time post, short time reader. 
I'm from Melbourne, Australia and recently purchased a 2008 GS500F that was bog stock standard.
So far I'd been reading up on GStwins and slowly buying up parts and did the mods for rejetting which included:

- K&N Lunch Box (this isn't oiled from factory is it? I need to buy a K&N filter oil kit? Does normal foam filter oil spray work for this?)
- Megacycle Slip On carbon exhaust
- Mikuni jets 20/62.5/142.5 in consideration that it is a slip on exhaust
(from standard jetting of 17.5/60/130) - god it was terrible taking off those bolts off the bowls, half destroyed half of them, mainly because I didn't have the right tools

Anyway, after the rejet, she seems to be running well. Only gripe is, when I try to start her without choke, in which she fires up, when I'm using throttle to hold the revs, I notice that the engine does a click or knocking sound and the revs drop about 1000rpm. In some situations if the revs are low and it does this knocking, it will just die.
I don't have this problem that bad when I use choke to start her up.
Is this a problem? That can be easily fixed?
I read somewhere it could be lean misfire?
I only get this problem when cold, she rides fine when warm.
Also note, weather here at this time of year is quite cold in Melbourne. Could this be affecting it to be lean?

Also prior to getting the lunchbox and rejet, the slipon was making heaps of crackle and pop misfire under engine braking.
I noticed now after the rejetting, this is less evident but I do still get the occasional misfire pop sometimes. Is this normal, or should i run some slightly bigger jets?

Thanks for reading  ,

Lawrence

Hi and welcome.  The mysterious black magic of carb tuning.  Good luck.

Oil your K&N filter.  Foam filter oil may be too thick.  Try some 80 90 gear oil if you are desperate.

Why are you starting cold with no choke?  Choke increases the fuel:air RATIO for a cold start.  Throttle alone puts more gas and air, with the same ratio, which is lean for cold cylinders.  Use the choke.

Did you reset the air mix screw?  Shim the jet needle?

That's all I got.

Take a look at the wiki for more detailed instructions.

Cheers

Hi BeerGarage,

That is one thing I did not do.

I left the air mix screws and the needles as what they were.

I read somewhere someone with a similar setup left these components and ran fine.

Can someone advise where the air mix screws are?

I assume its under the carb bowls? but which plug is it? I see a brass looking flat head screw, but then i read in the wiki it is covered by a brass plug which you have to drill out.

Anyone have a definitive pic?

Also what is that big adjustable screw inbetween the carbs underneath? is that for adjusting something?

Starting without choke, I was thinking it wouldn't need it as the jets are running richer. Running the choke might be too rich and flood the carbs?

But I guess for now it seems safe to keep starting with the choke.

The choke (enrichment circuit) adds a little fuel to compensate for the fuel that condenses on the bore of the carb while it is cold.

On the aussie bike that screw is your idle mix screw. You don't need to drill out anything to get at them.

Quote from: chopobo
Starting without choke, I was thinking it wouldn't need it as the jets are running richer. Running the choke might be too rich and flood the carbs?

With the lunch box filter and jetting (you have the same ones I currently have) you will no longer be rich (or at least not overly. Haven't had it professionally examined for it's current air fuel ratio). Increased jets increases fuel, Lunchbox filter increases your air so they balance out to some degree.

# 27, Air mix adjust screw.  (This is outside the float bowl, so you do not need to take off screws # 38.)  Sounds like in Oz you may not have to remove the small metal cap, #42A,  covering the adjust screw. 

Read this first for better pics:
http://gstwins.com/gsboard/index.php?topic=12928.0

Also, tuning a carb over the internet is impossible. 
Have you seen this Mikuni carb article?  Awesome writeup by some Yamaha guys.

http://weislake.com/sig/mucker/carb%20tech3.pdf

This book gives a great overall picture:

http://www.google.com/products?q=book%3A+motorcycles+fundamentals+service+repair&hl=en&btnG=Search

Good luck.

QuoteK&N Lunch Box (this isn't oiled from factory is it? I need to buy a K&N filter oil kit? Does normal foam filter oil spray work for this?)

All K&N filters come pre oiled and ready to install, when the time comes to oil it only use K&N oil and cleaner its the best.

Hi reason I asked was there was a stamp on the filter saying something along the lines of please oil filter.
Thought it was sealed in plastic bag.

So that plastic screw thing under the carbs is the air/fuel mixture screw.

Pave_Spectre: May I ask if you adjusted this screw at all? how many turns if you did?

Also on a side note:

Do you guys have problems with slipping gears?
I'm intermittantly getting problems shifting from 5th to 6th gear. Sometimes it will miss, go in, drop out and hit false neutral rev its fun bags and crunch back into 5th gear. This is without me doing anything just after shifting. Can be quite annoying sometimes. I'm hoping my next oil change will solve this.
Or it could be I am shifting too fast for the top gear? Or it needs a chain adjustment? Though the chain slack seems fine.

Also what do you guys think about this?
Heated grip inserts:
http://cgi.ebay.com.au/Motorcycle-Heated-Grip-Pads-Heaters-MX-Enduro-Road-Bike-/400128658783?cmd=ViewItem&pt=AU_Motorcycle_Parts_Accessories&hash=item5d2986cd5f

Could this work? Or just cheap copy stuff that would work in theory.

Thanks for the replies guys,

Lawrence

I used to very occasionally have the same problem changing from 5th to 6th. It may be pure coincidence, but since I started using good quality full synth oil it hasn't been a problem at all.

Whereabouts in Melbourne are you from? I used to live down there until I moved to Sydney 3 years ago.

QuotePave_Spectre: May I ask if you adjusted this screw at all? how many turns if you did?

Off the top of my head I have them about two and half turns open. I screwed them all the way in, then counted turns out. Started at 3 turns, and could smell a hint of fuel in the exhaust, so went a half turn in and that seemed to fix it. Could still be a little rich, but I haven't the time at the moment to fiddle around perfecting it.
Plus from what  little I have read, air temp, humidity etc can affect tuning, so YMMV.

Quote from: chopobo on June 14, 2010, 10:08:32 PM

Also on a side note:

Do you guys have problems with slipping gears?
I'm intermittantly getting problems shifting from 5th to 6th gear. Sometimes it will miss, go in, drop out and hit false neutral rev its fun bags and crunch back into 5th gear. This is without me doing anything just after shifting. Can be quite annoying sometimes. I'm hoping my next oil change will solve this.
Or it could be I am shifting too fast for the top gear? Or it needs a chain adjustment? Though the chain slack seems fine.

Ah, the old False Neutral.

Few things...

Thing # 1: Change into 6th slower - that is, without trying to make it a gear change that takes half micro second to achieve.
Thing # 2: Keep pressure UP on the gear change lever Until you have released the clutch lever.
Thing # 3: Check your oil level
Thing # 4: Try a different oil. I had Motul 1000 for the 1st couple of services - and a good deal of false neutrals. When I switched to Motul 5100 my False Neutrals all but went away. Occasionally (rarely) get one but only when *I* don't change gears properly.
Thing # 5: You will become attuned to the bike so that, any such false neutrals in the future will Not rev the guts out of the bike. You will be off the throttle almost as soon as it starts to rev freely.

Michael

Thanks for the info guys.
Will be looking to change he oil this weekend. Ordered and received a 20L can of Delo 400.
Hopefully that solves the false neutral mystery.

Hi Eduardo,
I live in Keysy down S.E side.
Loving the note change the k&n filter gives the bike when you give it a bit of throttle.

Quote from: chopobo on June 14, 2010, 10:08:32 PM

So that plastic screw thing under the carbs is the air/fuel mixture screw.

if it's plastic and in between the 2 carbs, that's just the idle adjustment. it does not change the air:fuel ratio, only the amount of throttle applied at idle. you use that to get your idle to about 1200rpm. in the picture im assuming part number 31 is the plastic knob you were thinking of.

each carb should have it's own idle air mix screws.

If the the filter is red, it's oiled; if it's white, it's not. I bought the K&N kit; I have one on my car as well. Lasts a long time, many uses.