GT550 Cafe project

[imquattro]

After reading Dave's suggestion, I grabbed one of the many infant medicine droppers we have laying around due the benefit of having two kiddo's under 3yrs old during the winter.
(Hope the wifey doesn't mind! )

I removed the pump, then decided to try to use the hand oiler I had already filled with 2 cycle oil.
I simply pressed the tip to the port and it filled the circuit up without even trying.
I filled each circuit, then added a few extra pumps just because.
Here's what I used:


Here's a link to a video of how I did it:
https://picasaweb.google.com/lh/photo/Y ... directlink

[Suzukidave]

excellent

[drøn]

Here's what I used:
(picture will appear here too with I get home to post it)

Here's a link to a video of how I did it:
(video link will also come alive when I get home)

Such suspense...

[tz375]

Good. That's how most of us here do it, with one or other of those two devices or something similar.

It's a nice easy simple way to fill the lines. I tend to use a different color of oil to the tank to make it easier to see that the pump has replaced the fill oil with tank oil once it runs.

[imquattro]

The cylinder's are now torqued down.



I then laid my straight edge across them and found .002" difference between the Center cylinder and the Left & Right cylinders. Not very much, but some regardless.
I entertain the thought of cutting the head into three pieces... metal band saw next door.....

But when measuring the head, I then find the Center dome extends .002" beyond the Left & Right cylinders.
Seems like a perfect fit? by design? :shrug:

[imquattro]

Prior to calling these 100% accurate, let me toss in this disclaimer:
It may not be: It's a paper wheel, a homemade pointer, but hopefully close to within a degree or two.
IF someone would PLEASE check these out, I'd really like to get these right.
I found NOTHING web in all the searching I've done & while someone here thought they had some somewhere, they have yet to show up.
So here goes:

I printed a degree wheel, adhered it to some card stock, mounted it to the crankshaft (in place of the alternator)
attached a dial indicator and found absolute TDC and zero'd the wheel.


I then rotated the crankshaft until the exhaust port opened @97°. I then zeroed the wheel and rotated the crankshaft counting the number of degrees the exhaust port was open until it closed (open for 163°)
I then followed this procedure for the intake port, and transfer port, jotting things down:

Didn't have colored pencils, but if you look real close you can see the semi-circular sweeps inside the hash marks indicating the port openings.

Bottom line:
GT550 Port Timings::drum roll::
One crankshaft revolution = 360° (duh)
Exhaust Port Timing: Opens @ 97° ->to-> 260° (open for 163°)
Intake Port Timing: Opens @ 285° ->to-> 72°AfterTDC (open for 147°)
Transfer Port Timing: Opens @ 120° ->to-> 240° (open for 120°)

If there are any corrections needed, please let me know.
I'm hoping the help out the next guy...

[Coyote]

I guess all those figures are nice to know, but somewhat pointless. Ignition timing is what you need be concerned with. For all GT550 triples, that figure is 3.37mm BTDC. In English that's .132/.133 BTDC. It will run fine within .005 either way.
Looking great! What did you ever decide to do with the spokes?

[imquattro]

I guess all those figures are nice to know, but somewhat pointless.

They're important if you are planning on building/researching expansion pipes.

[tz375]

Al the ports should open and close symmetrically around TDC +/- 0.05 degrees allowance for the piston pin offset.

The best way to get TDC is to use a positive stop. Bring the piston up until it hits the stop (gently) forward and backard and then split the difference. There is so much dwell/latency at TDC that it's hard to determine the exact crank position that matches the piston position within a few degrees.

We always measure ports in terms of MM from TDC and let the software convert it to degrees and it's still hard to get those numbers 100% accurate.

Edited for clarity:
The last set of numbers we have from another GT550 owners are:
75/ 6 model
Ex - 40.8mm ATDC
Tran - 50.9
Inlet top 75.2, bottom 94.0mm


I'd be interested to see your numbers in mm from true TDC (not from the top of the block), though the deck height number is also important.

For pipes, you could do worse than to copy a set of Jemcos. They don't look anything like the numbers that come out of any software I've tried, but they do seem to work quite well on the street.

[imquattro]

I'm lost on your #'s and how they've been attained.
If I grasp what you're saying, from TDC the exhaust port opens @ 35.7mm of piston travel ATDC?

The software I've played with is Two Stroke Wizard. There are others out there, it's just what I have. You input a number of parameters (cylinder layout, type of vehicle, # of cylinder, 2 or 3 angle transition, straight or 45° angle off exh. port, expected HP @ what RPM, etc... One of the inputs are the number of ° (degrees) the exhaust port, transfer port, and intake, are open. It also asks how long the primary, secondary, and boost ports are open. The GT550's have none but a matched set of transfers.

TDC is easy to find with a dial indicator & your thumb. Place your thumb w/ pressure on the head of the piston as it rises, rock the crank back and forth and watch the guage. At absolute TDC the gauge's needle stops moving(all play in bearings are removed by thumbs pressure) , zero the gauge, zero the wheel.

Again, I'm aware that my wheel is lacking in definitive accuracy, so maybe I'll hunt for a degree wheel with 10ths instead of single degrees.
The piston does extend approx 5mm from head, so those #'s appear somewhat correct, depending how they were measured. The piston is domed, so I'd go with the # lacking 5mm as the edge of the piston is flush with the head of the cylinder & the edges (& rings) are what open & close the ports (with the exception of the intake, which is controlled by the skirt).

[tz375]

Thanks. The posting came out a little mushed up. I've edited it to make it clearer.

Let me try that again TDC explanation again.

A degree wheel can be up to +/- about 10 degrees out at TDC. It's easy to find TDC with a dial gauge but not so easy to get the degree wheel zeroed because of the latency around TDC. the play in the bearings should be negligible BTW. The only way to get a wheel zeroed is to use a positive stop. It can be as simple as your piston flat piece of metal held down over the top of the block or it can be something bolted down. Or you could use a piston stop which screws into a plug hole. Bring the piston up until it stops dead and read teh degree wheel. Reverese direction and get the reading in reverse and then adjust the pointer/wheel to get it spot on.

The point being that if we use a degree wheel to determine port opening timing, the wheel must first be zeroed at TDC, your appears to be out by a couple of degrees. For example the exhaust opening you quote as 97 degrees ATDC and closing at 100 degrees BTDC. They should be the same. The timing disk/pointer is out by 1 - 2 degrees. Or it may just be the usual error in measuring. It's really hard to determine exact port opening and closing points with chamfered edges.

Once you have the degree wheel zeroed at TDC, then you can determine port timings using the wheel or the dial gauge. We use a 3 inch range dial gauge plus a degree wheel as back up, but it's the dial gauge reading we use and we convert them to degrees. Even with a 10" dial gauge, it's too hard to be accurate.

Hope that made more sense.

For your numbers, I split the differences. That would give you:

Exhaust: (100-97)/2= 98.5 ATDC
Transfers: 120 ATDC
Intake: (75+72)/2 = 73.5 BBDC

Those work out to 39.4mm down for the exhaust port and 49.3mm down for the transfers compared to 40.8mm and 50.9mm for the dimensions as measured by an OP that I quoted earlier. I can't tell you what the "accepted" specs are because we have not measured one in the shop.

With exhaust software, they are supposed to generate dimensions for parameters entered but they do nothing to determine the optimal dimensions for a street motor. It takes a simulation program to work out the potential performance all across the rev range. In other words, that software will help to generate dimensions for the given set of parameters that may or may not work on the street.

I suggested copying Jemco because we know that they work. Whatever you come up with will probably work as well as OEM at the top end and should weigh a truck load less. Just don't forget the mufflers.

[imquattro]

It's really hard to determine exact port opening and closing points with chamfered edges.

You're right about that!, quite difficult to determine, but I believe I'm pretty close, thanks for the carification on your former explanations, I understand now.

I suggested copying Jemco because we know that they work. Whatever you come up with will probably work as well as OEM at the top end and should weigh a truck load less. Just don't forget the mufflers.

I have yet to see any in person, I've seen this post http://www.caferacer.net/forum/topic.asp?TOPIC_ID=16266 but the pictures are dead and items missing.
Is there another source out there w/ the Jemco measurements? I have the means to cut, shape, weld and fabricate the pipes.

[Suzukidave]

Here's a 550 with Jemco's

[tz375]

The JR pipes in that CR.net thread are very similar to Jemcos on Coyote's RedZone that I think he posted earlier and the JR dimensions are still in that thread.

Wasn't there a thread on this site for that bike that Dave posted?

[imquattro]

So, I started working on the gauges.
1972 on the Left, and 1974 on the Right.

The PO's of the bikes were hard on the gauges, particularly the '74's.
He said he couldn't see the speedo & tach so he rammed a screwdriver through the plastic and knocked it out.
Damaging the gauge face.

The '72's plastic cover's are so clouded they're unusable.


You can see there's a difference in the wiring on the back of the gauges.

The '74 has the gear selection LED in the center, which I'd like to incorporate into the '72's gauge pod -in place of the "S" symbol.

The '74 came apart rather easily.


I did the same to the '72. I then pulled both gauges out of their housings. (not pictured.)
I removed the needles, and pulled the gauge faces.
I sent them down the hall to the High-Tech lab and had them scanned.

I have them in two formats.
My idea is to change them to white face, black #'s and hash marks, and RED for the red line.
Then print them out w/ a laser printer, cut them, and stick them to the factory faces. I'm concerned with them fading, but with all the riding I do, I doubt they'll see the sun very much...

I also started lacing the wheels.
That's interesting....
I had some students start the job and after a couple tries, one student laced the front wheel:


and I took over and finished the rear wheel.


They're just laced and loose. They still need tightened and trued. The real time challenge.