Help/suggestions needed

[Guest]

Hello guys, i'm Sergio from italy and i already introduced myself in the appropriate section

i need help

i own a suzuki gsx1100ex (1981 m.y.)

i bought for my bike a 4 into 1 marving free exhaust (racing)
dQAPcL9.jpg

now, given the fact i love the torque of the bike on the low range of rpm
i'd like to know from the experts of the forum the jetting situation...

i want to go "open exhaust + stock air box + stock filter"
original jets are the followings:

main fuel jet 107.5
main air jet 140 (different from yours due to different emission rules)
pilot jet #45
needle with clip in 3rd notch and upper rubber spacer replaced by a washer to run richer

when i was running pods i modified the jets going 115 - 160 - #47.5 respectively , but i lost torque on low rpms as predictable.

i prefer running with stock air intake and thus my question is:
should i put on all the ORIGINAL (STOCK) JETS?
will the bike run perfect with all stock plus the open exhaust?

right now, i have all the mods i previously told (and the stock airbox and filter), the bike runs rich and from half throttle to full, it's just freaking awesome
but i experience a problem in the low range. when i open the throttle progressively the bike is great, when i fully open it, the bike is great. but when i'm driving on constant rpms (say, 4000 rpm) and then i open, the bike stalls for a sec before starting to go super...
is it the pilot? the raised needle?

with the stock intake (airbox and filter) + open pipe, what's the best setup in terms of jets and needle?
do i go back to standard + pipe?
thanks in advance

[sergio]

by the way
this is my bike(with no pods anymore) and i have mikuni bs34ss carbs

NFbDadn.jpg

[AMK]

Can't help you, but I can say welcome and your bike looks awesome. Really nice.

[sergio]

Can't help you, but I can say welcome and your bike looks awesome. Really nice.

thank you very much, Alan

[JTGS850GL]

I would have left the pilot jets stock. Maybe up the mains and raise the needle just a tad but there was no need to increase the pilot jet size from stock.

[sergio]

I would have left the pilot jets stock. Maybe up the mains and raise the needle just a tad but there was no need to increase the pilot jet size from stock.

tnx Julius
when you say "pilot jetS" you mean both fuel AND air, i guess

[JTGS850GL]

Yes, never mess with the air jets. No need to.

[sergio]

no one other than Julius that has suggestions?

[Steve]

Most of the restriction imposed on a stock engine comes from the airbox. The stock exhaust actually flows quite well, with minimal restriction. Therefore, with the stock airbox re-installed and an "open" exhaust (we'll get to the definition of "open" in a minute), I would start just a little bit richer than the stock settings. Might try a main of 115, the stock pilot jets and stock needle setting or maybe one clip richer.

Now, what do you mean by "open" exhaust? it appears that you have at least a megaphone beyond the collector, is there any kind of baffle installed at all? Some "performance" pipes will have a perforated tube between two disks that will restrict the flow a bit. The diameter of the perforated tube will determine whether it is more toward the "street" side or the "competition" side of performance. The perforations in the tube are to allow the sound to disperse a bit, you can then wrap acoustic material around the baffle to control the echo in the outer chamber.

It should be obvious that different diameter tubes will allow different amounts of air to flow through, but they will still be limited by what the stock airbox will allow to go IN to the engine, so will likely just add more noise, rather than actual power. If you quest is more noise, many of us will stop right here with help. If you quest is more power, you will need to go back to pods. If you just want a nice running bike, you may in for some fun times with jetting, but I would start with the 115 mains (assuming a smaller "street" baffle) and go up from there. If you have no baffle in the megaphone (shame on you ) you might need something in the 120-125 range. Only experimentation will tell for sure.

.

[sergio]

Most of the restriction imposed on a stock engine comes from the airbox. The stock exhaust actually flows quite well, with minimal restriction. Therefore, with the stock airbox re-installed and an "open" exhaust (we'll get to the definition of "open" in a minute), I would start just a little bit richer than the stock settings. Might try a main of 115, the stock pilot jets and stock needle setting or maybe one clip richer.

Now, what do you mean by "open" exhaust? it appears that you have at least a megaphone beyond the collector, is there any kind of baffle installed at all? Some "performance" pipes will have a perforated tube between two disks that will restrict the flow a bit. The diameter of the perforated tube will determine whether it is more toward the "street" side or the "competition" side of performance. The perforations in the tube are to allow the sound to disperse a bit, you can then wrap acoustic material around the baffle to control the echo in the outer chamber.

It should be obvious that different diameter tubes will allow different amounts of air to flow through, but they will still be limited by what the stock airbox will allow to go IN to the engine, so will likely just add more noise, rather than actual power. If you quest is more noise, many of us will stop right here with help. If you quest is more power, you will need to go back to pods. If you just want a nice running bike, you may in for some fun times with jetting, but I would start with the 115 mains (assuming a smaller "street" baffle) and go up from there. If you have no baffle in the megaphone (shame on you ) you might need something in the 120-125 range. Only experimentation will tell for sure.

.

Thank you very much Steve
First thing first
The exhaust has a racing baffle, which is perforated and surrounded by acoustic material. It's not totally open
That said, my main concern is to make the bike running properly and not experiencing any torque loss in lower rpm
Right now the bike runs good on higher rpm but somehow poorly on low
So that translates into some poor job on my part with the Pilot and air jets. With pods the Jets were good and the bike would run great in higher range, but at the expense of torque on low engine range, which is my favorite part
So i think I'll do as you suggest.
115 main, which I already have inside the carbs, and I'll downsize air and fuel pilots, going back to stock. I think I'll leave the needle a little bit higher cos Europe bike had already a bigger air jet (140) thus running already leaner

[Steve]

I think you will also find, according to multiple sources, that a 4-into-1 pipe in general will lose a bit of torque in the lower RPM range. If designed properly, it will enhance scavenging and flow in the upper range, but there is a noticeable dip in torque near the middle.

Your "racing" baffle will be pretty much the same as a "street" baffle, just a larger diameter tube, which would allow more airflow. Doing some "plug chops" will help you determine how it's running and what you need to change.

.

[sergio]

I think you will also find, according to multiple sources, that a 4-into-1 pipe in general will lose a bit of torque in the lower RPM range. If designed properly, it will enhance scavenging and flow in the upper range, but there is a noticeable dip in torque near the middle.

Your "racing" baffle will be pretty much the same as a "street" baffle, just a larger diameter tube, which would allow more airflow. Doing some "plug chops" will help you determine how it's running and what you need to change.

.

Actually the spark plugs are pretty good. A light brown
And you lose not much on low rpm, at least with the marving exhaust.
The thing is that the engine stalls for a sec if you run at a constant rpm and you go full throttle all of a sudden. Then, when the gasoline flows normal, and the engine "opens up" it goes just awesome

[sergio]

ok, today i tried to go "half stock"

meaning stock pilot jet 45 and stock air jet 140

main fuel jet 115 (+3)

needle lowered by 1,5 mm

the bike was revving great but as soon as i went for a ride, it was clear that something wasn't right

the bike was "flying" exactly like a bat outta hell ... what a ****ty setup!

coming up next: everything stock except the main jet
and if it doesnt work, everything stock with needle totally raised
and if it doesnt work, everything stock including the main jet
and if it doesnt work, back to square one (pilot 47,5 - air 160 - main 115) which is, to this point, the setup with less problems

[Carter Turk]

Maybe take the lid off airbox and invest is a stage 1 dyno jet kit. Needles are more tapered than stock allowing more precise fueling.
I think most 4-1 pipes have a hiccup at one point in the rev range, usually the middle as Steve mentioned.
Or do the wide open throttle at higher rpm's to avoid the bog.