[boris.h]79 GS 550 / 673cc project

[Rensdw]

ok, speaking to myself lol but the aim is to keep something to help and share my issues...

- clutch issue: that was the basket big central nut: when I unscrewed it, the basket got free... Maybe I overthightened it.. The manual says between 40Nm and 60Nm, I'll try to screw it again, to 40Nm and see how it works....
- carbs jetting: I'll test # dynojet 160 main jets, drilling old jets... as the dynojet kit says. I think I am too lean.

Maybe you forgot the shim that sits behind the clutch basket?

[boris.h]

no I did not, I think I overthightened the clutch basket, with a couple above 60nm. The manual says between 40 and 60nm, and there is a shim that we have to bend on the nut to avoid any screwing out by itself.... I think the couple between 40 and 60nm is very important.

[boris.h]

overall, drille the main jets to 1.50mm, starting it tonight

[BoCoMoMann]

Hi everyone!
I'm boris, from France

Hi Boris, nicely done!

Just FYI and for what it's worth, I was once told that the heads will flow better without a knife edge in the intake - if that's the exhaust, probably OK.

The reason a knife edge flows less on the intake - think airfoil. The knife edge points which way?

There's my nickles worth of suggestions, thank you!

[tkent02]

Hi Boris, nicely done!

Just FYI and for what it's worth, I was once told that the heads will flow better without a knife edge in the intake - if that's the exhaust, probably OK.

The reason a knife edge flows less on the intake - think airfoil. The knife edge points which way?

There's my nickles worth of suggestions, thank you!

An airfoil works differently. Has to be able to flow a lot of air with little drag at different angles, like a propellor blade at different speeds or a wing at a low or high angle of attack. A rounded leading edge does this better. Knife edge probably isn't so bad if the angle is set correctly for the airflow. Probably not as good as a small radius rounded edge but certainly better than a rough casting with a squared off edge.

[boris.h]

ok, so first you have to know that this picture concerns a renault clio williams, and the picture you showed is about the exhaust port. Personnally I always reduce that edge, for intake and exhaust. This edge causes a lot of air / fuel turbulences and reduces air / fuel velocity. So, every edge I work on finaly looks like a knife edge. BUT you do not have to consider this only, for intake. The surface has not to be polished, because there is air and fuel at this place, and they have to be as is it possible, be mixed together before arriving in the combustion chamber (it's better). So the intake ports surface helps that. That's also why I use to polish the exhaust ports, the velocity has to be high and no mixing anymore.

BUT (again) it's important to consider the valve seat diameter and the valve diameter because you do not have to drill too much the intake and exhaust ports. If you do it too much, the velocity will decrease and so the performances will do also.
That's the same scheme for exhaust ports. Ever having to consider the ports as "cones" increasing or reducing velocity. And that "cones" have to be determinated before doing the port job.
In the clio williams case, I use to not drilling the intake ports because they are too large as standard. I reduce sharping and that edge, that's all. But I remplace the valves to increase air / fuel flow, and the same for exhaust valves and ports because the engineering of the clio's head is a good base to do that.

[Nessism]

Ok! So I did few start but nothing, no fuel at all on the spark plugs... I decided to go until 2.75 turns on the fuel screw... it started immediately, without any crappy noise... yes I won So happy everytime a rebuild engine start...
So, My question concerns how many turns have I to put to my bs 32 carbs??
The configuration is quite "not oem"
- gs 650 ported head on gs 550 base "the famous swap", plus the ported and milled head
- no restriction for the exhaust: bandit header, and danmoto conical end
- velocity stacks



For the instant, I put 3.25 turns, and the idle is about 1500 / 1800 rpm, so a little high. Regarding the fact it did not want to start at 2.75 turns, and it wanted to start immediately at 3.25 turns...I did not any plug shop but I think i am too lean... and i wanted to ask you how many turns I had to put?

thanks a lot

The pilot screw setting should be fine at 3.5 turns or so. 4 turns open is about the max before further opening does nothing. The pilot screw affects the idle mixture and just off idle, it doesn't have a profound effect on the mixture while you are riding the bike other than just off idle.

[boris.h]

ok nessim, thanks a lot. About the idle screw, do experienced BS32 guys have any idle when the idle screw is completely unscrewed? Choke off, of course

[boris.h]

ok, put 1.50mm diameter main jets (mikuni #132.5), it seems to be a lot better! I also managed to solve the clutch issue. Have to ride it
concerning the idle adjustment, idle is stable, about 1000 rpm, I am about 3.5 turns on each cylinder for the idle mixture screw, idle speed screw at 0.5 / 1 turn from all unscrewed.

[boris.h]

3D printed, NYLON / FIBERGLASS...

Going to put a bandit danmoto conical exhaust....

The bike started. I started it with 42.5 idle jets, and 130 main jets.... Too lean I think.... I put 142.5 main jets yesterday and still have to try it

[Chuck78]

Do you have any more photos of that 98/99 gsxr 600 exhaust mounted on the bike? Were all of the angles correct to put the collector parallel to the frame cradle/oil pan, & have the head pipes perfectly perpendicular to enter the head straight on?

[boris.h]

Hey! No no more picture of it. It would fit but it's a 4/2, I prefered to fit a 4/1. But I think this is the same because I went with a bandit header. This is a gsxr engine so the pattern and so the issues are the same.
2 things to do to make it fit:
-cut the #1 and the #4 tube to weld them with an angle.
-warm the tubes and bend them to the inside to reduce the angle between the beginningame and the end of the exhaust

If done everything fits. You can see on the pictures above that all feet very good.

[Chuck78]

Ahhhh.... I see. I was thinking that it was more of a direct bolt in the way you talked. I did see the welds on the downpipes and wondered why I did not see those on the GSXR 600 exhausts on eBay. There are a couple of Yoshimura pipes on eBay for $200 in a 4-2-1, which is much better for low-end response than a 4 into 1. That might be my eventual plan for my wife's gs550-673cc/740cc build.

[tkent02]

There are a couple of Yoshimura pipes on eBay for $200 in a 4-2-1, which is much better for low-end response than a 4 into 1. That might be my eventual plan for my wife's gs550-673cc/740cc build.

Got a link? I would love to have a Tri-Y for the 550/700. If no link were they for a GSXR 600?

[Chuck78]

Tom, several hours ago today on ebay there were 2 Yoshi 4 2 1 Tri Y pipes listed. I searched "98 gsxr 600" or "98 gsxr600" and saw the Chrome $200-ish header & pipe, painted or darkened coloration $176 (?) header without the mid pipe.
Listings seem to imply 96-99 or so interchange.

Also a $$$ 369 + $90 shipping NOS Marshall Deeptone gs550/650 4:1 - much more money than a new MAC ($350 shipped) but very nice. Probably not any difference in performance, but slight chance it has more cornering clearance if you run your tires to the edge and scrape your foot pegs