CV Flatsides pilot jet size and fuel screw turns

[liloaty]

OK guys, I need help getting a baseline for these carbs. For those of you that have put 36mm flatsides (GSXR1100 carbs) on a GS1100 or 1150, please do me a favor and let me know a few things:

1. What intake/fuel/engine mods are currently on your bike
2. What size pilot jet you're using
3. How many turns your fuel screw is out

This would be a great help, thanks in advance.

 

[rapidray]

Start with the stock pilot jets & the mixture screws 2.5 turns out. After you get it started & warmed up, set the mixture screws to what the motor tells you it wants. If you have to turn them too far in or out to get it to idle, change the jets up or down 1 size accordingly. Ray.

 

[liloaty]

Start with the stock pilot jets & the mixture screws 2.5 turns out. After you get it started & warmed up, set the mixture screws to what the motor tells you it wants. If you have to turn them too far in or out to get it to idle, change the jets up or down 1 size accordingly. Ray.

Any idea what the stock pilot jet was in these?

 

[Tomas03]

I am in the process of putting these on my machine and pulled the pilot jet out today. It is a 37.5 from an Australian 88 model but check this link for yours
http://www.gixxer.com/forums/showthread.php?t=159718.

I am having issues with my converstion (gsxr750 carbs onto gsx1100), I cannot get the thing to idle below 1500 rpm. It generally is running fine, except that it idles fast and thus is running rich. I have checked if anything is getting stuck open (ie choke or throttle) but can't find anything. I have now dropped down a pilot jet size and it hasn't made a difference.:-k

 

[rapidray]

If it is idling fast & won't come down, my money is on it being LEAN! Ray.

 

[liloaty]

If it is idling fast & won't come down, my money is on it being LEAN! Ray.

If he's running lean at idle with a 37.5 pilot I can say without a doubt that he's got a good size vacuum leak somewhere. 35s were way too rich so far in my trials.

 

[Tomas03]

Would the fact I'm missing a little rubber o ring that sits on the top of the carb body be causing this? I am missing one. I've tried to temporarily replace it with a piece of gasket.

Today I started again. Made sure my fuel line to the carbs were good, put the original pilot jets back in and set the mixture screws to 2 1/2 out. Started fine, the commenced to idle at 1500rpm It was running real rich at that time (put hand behind muffler and it got blackened). I turned in to 2 and it still revved at 1500.

 

[liloaty]

Would the fact I'm missing a little rubber o ring that sits on the top of the carb body be causing this? I am missing one. I've tried to temporarily replace it with a piece of gasket.

Today I started again. Made sure my fuel line to the carbs were good, put the original pilot jets back in and set the mixture screws to 2 1/2 out. Started fine, the commenced to idle at 1500rpm It was running real rich at that time (put hand behind muffler and it got blackened). I turned in to 2 and it still revved at 1500.

It shouldn't cause that drastic of an idle problem, especially if you made an attempt at replacing it. Those parts are cheap, go pick up 4 new ones and cross a possible problem off the list.

What size are the original pilots?

 

[rapidray]

Yes, that could be a vacuum leak. Ray.

 

[Tomas03]

GSXR carbie set up

GSXR carbie set up

I've finally got this thing sorted. It just took me a bit to slap myself out of my stupor.
Firstly, as outlined earlier, I was using BST36 Mikuni's off a 750, not an 1100. This means I had different needle jet and needles to the 1100. So I bit the bullet and went and paid the premium at my local Suzuki dealer to rectify this. I installed them and immediately the fast idle dissappeared. So now I think I will change the pilot jet to match the 1100 as well, just to be sure to be sure.
But the bike is running good (absolutely flying) so to answer the original post here is what I have ended up with:
GSX1100 with 1145 piston kit
4-1 exhaust
K&N pods
No other work done
Carbs: Main Jet 140
Jet Needle 5E56 (using 3rd clip position)
Needle Jet 0-9
Pilot jet 37.5
Mixture screws out 2.
I am still fine tuning and will probably move to a 40 pilot jet, but I was told by another person, and my experience supports this, if you have GSXR1100 BST36 carbies, and you put them on a GSX1100, then you will have to run pods and then the only thing you will need to change from stock is the main jet, then fiddle with the mixture a bit.
It is important to remember that I am in Australia, and the settings for these carbs were different around the world (especially in California????) but the ones I have chosen are considered the 'general' settings and they work. :clap:

 

[posplayr]

thanks just what I needed

 

[trippivot]

too bad the needle has...a..... nothing to do with idle..

I bet good money you just got them more correctly assembled like getting a slide to fully seat down where it belongs eh?

 

[posplayr]

too bad the needle has...a..... nothing to do with idle..

I bet good money you just got them more correctly assembled like getting a slide to fully seat down where it belongs eh?

So the needles don't matter at all? I'm looking to sort out what needs to be done to convert a GSXR 750 set of carbs to a GS 1100.

From that post it looks lke a GSXR 1100 carbs just needs the mains set. Other than fine tuning, the GSXR 1100 carb should be a good starting point for the GS1100. Right?

I have two sets of these and the can't tell if they are 750 or 1100. One set is jetted with 144 DynoJets and has the Main Air Jets drilled (looks like 1.5mm?)

The other set has 137.5 Mikuni's with a very small MAJ.

What is the easiest way to tell what I have?

 

[Tomas03]

too bad the needle has...a..... nothing to do with idle..

I bet good money you just got them more correctly assembled like getting a slide to fully seat down where it belongs eh?

Yes I seriously am that stupid. :clap: I should have just checked that

Pos - had written a lengthy reply because I found that comment a bit insulting. But instead I'll say this. Do you think a set of 750 carbs are going to work on an 1100? My bike obviously had a big problem that was only showing as an idling problem. The emulsion tube/needle jet and needle for 750 carbs are massively different to the 1100 ones. They wont work so check out the link I gave (it still works) and look to see what you got then put the 1100 bits in it if needed.

 

[posplayr]

Yes I seriously am that stupid. :clap: I should have just checked that

Pos - had written a lengthy reply because I found that comment a bit insulting. But instead I'll say this. Do you think a set of 750 carbs are going to work on an 1100? My bike obviously had a big problem that was only showing as an idling problem. The emulsion tube/needle jet and needle for 750 carbs are massively different to the 1100 ones. They wont work so check out the link I gave (it still works) and look to see what you got then put the 1100 bits in it if needed.

Thanks, I put together a spreadsheet of all the different combos depending upon year for the BST36SS carbs. There is quite a bit of variation in in the carb setup even on the same model and year depending upon country.

I primarily did the 750/1100 GSXR Sling carbs. The most pronounced pattern I see here is:

Main jets for stage 3 1100 are about 145 (Mikuni) 155 (Djet)

Main Air jet is 1.5 mm v.s. 0.5 for 1100 and 750 respectively but on the 1990-92 750 they increased both teh main jet and the MAJ to #127.5 and 0.9/1.2 mm where typically it would have been #112.5 and 0.5mm. So if the MAJ is smaller, then you would need a correspondingly smaller MJ. I see this seems to match your numbers were you probably had a MAJ=0.5 and ended up with a small 140 DJ main (130 Mikuni).

As far as needles are concerned about being different, I have compared the
DJ 3122.008 kit for 88-89 and Cal 90-92 GSXR 750 kit with the
DJ 3136.003 kit for 89-92 GSXR 1100 and they are identical except for larger mains in the 1100 (160/155 v.s 144/140) and there is no emulsion tubes in the 3122.008 kit.

Both 3122 and 3136 use the exact same needles (DNO356) and there is hardly any taper to them.

I added a summary of some of the results from different people on the side

P.S these results are approximate because there are many different combinations and some differences between teh Gixxer.com thread and the Gixxer OEM manuals.

 

[stain]

I am using the Mikuni BDST model from a 89 GSXR1100. Are these what you are using or did they put different carbs on some? I am trying to follow some of these threads concerning tuning these 36's on the GS 1000 but there are so many models its hard to get a direction. Right now I am at 147.5 mikuni mains, 37.5 pilot, 2 turns out on the fuel screw, needle up all the way and 1 slide hole plugged. It still seems to be a little lean with a little stumble in the midrange but it screams on top. Plugs still too white. Also my idle is inconsistant. I am really condidering RS 36 or 34's.

 

[posplayr]

I am using the Mikuni BDST model from a 89 GSXR1100. Are these what you are using or did they put different carbs on some? I am trying to follow some of these threads concerning tuning these 36's on the GS 1000 but there are so many models its hard to get a direction. Right now I am at 147.5 mikuni mains, 37.5 pilot, 2 turns out on the fuel screw, needle up all the way and 1 slide hole plugged. It still seems to be a little lean with a little stumble in the midrange but it screams on top. Plugs still too white. Also my idle is inconsistant. I am really condidering RS 36 or 34's.

The 36mm slingshot GSXR carbs are all BST36SS which is what I have listed.

BDST is a down draft and did not come on the GSXR 2nd Generation Slingshots (GSXR 1100's used BST36SS).

http://www.motorcyclecarbs.com/Mikuni_BDST_Carburetor_C686.cfm

Right now I am at 147.5 mikuni mains, 37.5 pilot, 2 turns out on the fuel screw, needle up all the way and 1 slide hole plugged.

That sounds like what would be my exact starting point(I'm just sorting out the combinations at the moment; I have three sets one bing on my GSXR 1052 1st Gen).

Hum, what jet needles and needle jets are you using?
Dynojet or Factory pro?

What size is your MAJ?

 

[posplayr]

If you really have BDST down draft carbs your float level is probably screwed up with the angle difference.

That would probbaly cause the inconsistency of idle and lean condition at low RPM.

 

[stain]

--My MAJ is 1.5. I am using factory pro needles and emulsion tubes which are mikuni parts.
I think I may be confused as to which carbs I have. I bought them as 89 GSXR1100 carbs but they look like BDST carbs. When getting parts I always use the 89 GSXR fiche and the internals look the same. I did notice after reading these posts that the float bowl sealing surface is not level when the carb is, That is the tops are flat but the float bowl sealing surface is tilted ? ? ?

 

[posplayr]

--My MAJ is 1.5. I am using factory pro needles and emulsion tubes which are mikuni parts.
I think I may be confused as to which carbs I have. I bought them as 89 GSXR1100 carbs but they look like BDST carbs. When getting parts I always use the 89 GSXR fiche and the internals look the same. I did notice after reading these posts that the float bowl sealing surface is not level when the carb is, That is the tops are flat but the float bowl sealing surface is tilted ? ? ?

I'm guessing BDST and BST share parts but the main carb body is different, floats need to be level. Everything else sounds right on.

So your jets are probably the O-8's if you bought them from the parts Finche for the 89 GSXR 1100