fitting bst38ss to a bandit questions

[boilerdude]

On 5/11/2016 at 1:16 AM, Captain Chaos said:

As for jetting, it depends on the exhaust and air filter and camshafts and ignition timing and more stuff, main jets should be around 150, start from there. Mine has only bigger main jets, pilot screws turned out a bit more, everything else standard 750 settings.

standard 750 needles?

[boilerdude]

After cleaning the pilots I got it idling great at 3 1/2 turns out on the screws. But it blabbers and sputters when i try to give it throttle. Tried pulling the vent hoses. I think that made it worse but still having them back on it's not quite right either way. 

The diaphragms looked perfectly fine.

The only mains I had for the moment are DJ 155 out of my bandit carbs. They fit... I figured they should at least get down the road. Now I'm thinking I should go ahead and try the DJ springs and needles also. Or maybe just the springs. 

Or do I need to break down and actually buy a jet kit for a 1991 gsxr 750.

Or perhaps just some proper mikuni main jets and not DJ ones. 

Edited May 16, 2016 by boilerdude

[Captain Chaos]

Yes I use standard 750 needles. But the American needles and jets are different from the European ones.

The 155 jets you have are not from Dynojet, because they do not exist, DJ makes jets in 2-size increments. There is 154 and 156 but not 155.

As far as I know Factory Pro make a jet kit for 38mm carbs on an 1127 engine, might also work on a B12. Or maybe they already have a jet kit specifically for the B12. Worth asking them.

[boilerdude]

I still have the box and instructions with my dyno jet kit. It is the stage 1 or stage 3 combo kit. For stage 3 there are a choice of 155 and 150

anyway I think the dynojet needles and springs took care of it. Whichever main jets those are the american gsxr needles and soft springs did not agree with them. 

I'll have to wait till tomorrow to find out. It was about midnight when I swapped the needles and got it back together. I let it idle for a few seconds gave it a few small barks and I think It's getting there.

Edited May 16, 2016 by boilerdude

[boilerdude]

Yep that did it. I dont know if it was the springs or the needles that were needed but it's better now. Dj needles and springs and then I had to pull the float vent hoses. So pretty much all I had to do setup wise was completely swap over the stage 3 kit.  And then it was simply lean in the midrange until I raised the dynojet needle all the way up which pretty much means I could use a bigger main. Pretty sure 155 is whats in there.  

And I have the fuel screws like 4 1/2 or 5 turns out to get it crisp off the bottom. So Perhaps could use a size up on the pilots as well. They are 32.5 on mine. indeed those are the little guys. probably 35s would be perfect. Just that little bit more. Or maybe just try the bigger mains first... slight overlap and whatnot. 

But I do have the 89 cams supposedly. 

So... I had to fit the vacuum actuator thingy off of the gsxr petcock onto the bandit petcock. Which involved grinding down 2 tiny little 1 millimeter plastic posts so the gasket fit flush... you'll see what I mean if you do this.  The plastic sandwich piece. Has 2 little guide posts on it that the gsxr vacuum port does not have holes for. grind those down so the gasket fits nice and flush.

Then you'll need to grind down just a bit of metal off of the petcock indicator between the on and prime positions. So it clears the #2 diaphragm cap. 

T fitting for the fuel hoses and thats about it. And yes it is noticeably faster now and sounds meaner. I dont feel any huge deficiencies that I'm not confident about curing with a little more fine tuning. 

There we go. Hopefully this helps someone in the future. 

Edited May 16, 2016 by boilerdude

[wraith]

The UK pilot jets are 37.5 on a b12.

[boilerdude]

Yes same here in the us. These arent bandit carbs though. they are a set of 91 gsxr750 slingshot carbs we're talking about. bst38ss. not bst36ss. 

Setting up 1991 (and 1992 in the us) gsxr 750 slingshot carbs on a bandit. Thats what is going on here. They are a slight upgrade. Slightly bigger.

 

Edited May 17, 2016 by boilerdude

[Fula28]

Just read your posts and I can share by experience with abiet we had tuned dot-750 head and cams gasflowed etc. But all  the same b12-& bst38,s we ran 142 mains upto 145 in winter rich setting. standard needles and tubes, standard pilots too. Foam dual filters are best pulses from each carb pair seem smoother!  I would never use Dyno jet needles made of shite and , we used factory pro kit, don't bother with enabling power jet circuit. It was only for supersport applications in USA, with airbox.750m-L models.

[boilerdude]

Yea I figured just get the main jet right and I wont need the powerjet. Bike isn't a 14000 rpm screamer after all. More than 80% throttle on a road going b12 is not exactly very frequent or long in duration. 

Pretty sure mine feels too lean though. on 155s. I'n fact I'm certain. It kept running better and better as I lifted the needle up until it's all the way up now. whack the throttle in 3rd or 4th and it makes the woofy woof woof airy sound. Not the fat sparky rich sound.

First thing I'm gonna change now is just the filters. With the intake stacks. See what that does and go from there

Mine did not seem to like the stock needles and springs at all. Maybe I'll try them again in a day or 2 here. For now I'm tired of dicking with them. Had the tank and carbs on and off quite a few times over the weekend. The bike runs ok ish now. I'm taking a little break.

Edited May 18, 2016 by boilerdude

[boilerdude]

http://www.Eblag.com/itm/RAMAIR-PERFORMANCE-AIR-FILTERS-MS-017-YAMAHA-YZF750-FCR41-FITMENT-NEW-/271286409262?hash=item3f29ee182e:g:3w8AAOSw9mFWGC5c&vxp=mtr

[boilerdude]

So you used a factory pro kit... but you still used standard needles?

I have mikuni 145s in now. with the american standard needles. It does not work. I need to get me some of you guys' needles or some FP needles. Obviously the dj ones kinda work but are not really right for the application.