GT550 ports brass sticky up thingy????

[andyp666]

Ok I have what is probably a daft question I am ripping my GT550 down and spending a lot of time and effort researching porting etc. What I need to know is there are plastic tubes coming from the crank case to the back of the barrels then they enter and I think connect to the brass spigot tube that emerges from the opposite side of the inlet port "corrrect?".... I am guessing there is a tube in the casting process somewhere??? What does it do what is its function???? any help here thanks.

[csd4t]

The tubes and that sticky up thing are what stop your engine going bang, they inject the oil

[andyp666]

I dont mean the oil pump to engine block tubes the other ones from the crank case to the small spigot at the lower rear of the barrels

[Alan H]

Those will be the SRIS tubes. That's Suzuki Recycle Injection System. In eack crankcase base there is a small connection with a one way valve, the idea is that the oil that normally collects in every two stroke crankcase, can on Suzukis equipped with SRIS, be pumped into another cylinder and burnt instaed of waiting until a bit of clear road appears and creating the 'two stroke plume' of smoke when the throttle is opened up. It worked fairly well, and the plume was never so bad as on other two strokes. As the crankcase pressurises on each power stroke, the oil is pushed past the one way valve and into another inlet port which is in the later induction part of the cycle, and then burnt as part of the normal running.

[Suzukidave]

If you are talking about the brass tubes in the intakes they are part of the oil injection system http://www.oldjapanesebikes.com/mraxl_G ... 50-37.html" onclick="window.open(this.href);return false; but it could also be part of the recycle system http://www.oldjapanesebikes.com/mraxl_G ... 50-36.html" onclick="window.open(this.href);return false;

[Cliff]

The tubes from the bottom of the crankcase to the back of the barrels are the SRIS tubes. They go into the transfer ports. The brass tube in the intake port is the oil feed from the oil pump.

[andyp666]

Thanks guys that clears that little one up... the oil injection tubes are going to be a pain in the Harris when Im porting the inlet then.... I will just have to work around them as best I can.
I have the 2 transfer port barrels and I can see already there is a lot of material to come off there and the bottom of the liners tapering in etc. any tips on inlet outlet ports from any one???

[tz375]

Why do you think that there's a lot of metal to remove from the intake ports and why do you want to lower the intake floor? That doesn't add much power but does kill the bottom end unless you are careful.

[Alan H]

'Back in the day' all I did with my 550J was match and smooth what there is and take a shave off the head. Made a big difference without spoiling low end. A 550 will never be a racer, so enjoy what there is easily gettable.
Just cut the baffles in half, or just leave off the stuffing around them. Noisier, but free-er running. You'll have to check mixture by looking at the plugs though. You might even get away with lifting the needles one notch as I did.

[andyp666]

There wont be much coming out of the intake but a brass spigot is going to be a pain in the ass... most of the work I will be doing is on the transfer ports and a clean up and polish of the exhaust port.

[Vintageman]

I once changed a T305 to have those inlets tubes. The T305 feeds oil right into the cylinder wall below the inlet port

I thought the brass tube would mix better. I used a flat punch perfect dia size and tapped tube out from set of GT250 Cyls. If it flattens out the tube end a tad you can drill by hand turning carefully. Probally don't even need those things as it would still mix just like T305 or T500!

I thought if you shave the piston skirt 2mm that would be better/easier if you want to change intake timing. I think the GT550 is week on both exhaust and intake timing. Although I have never put the stroke, rod length port height etc. into software to check what it is now for degrees. Just sure it is tuned mellow and for broad and early torque. What’s nice about it, but also does run out of breath early. Intake timing change would make a diff and think that bike has some low end to spare. Wish I had a couple more gt550s t to try. Chambers are the best easy performance boost trick

[tz375]

I run the 750 without the tubes. That makes it the same as any number of sleds.

Word of advice on inlets - do not change them unless you have crunched the numbers. Dropping the floor a couple of mm will generally make a difference to how it feels. It will lose power below about 5500 and will gain a tiny touch above that, so it feels more "pipey" because it makes less power at low revs than it used to.

Longer inlet duration in general is a bad idea on a piston ported motor.

[Vintageman]

Tz375

I can tell you that the ~2.5 mm (have to look at my early post to see what it was exactly) lower intake port difference on the T500 Early vs Late makes a difference and I see no loss in bottom end. I am sure it has lost bottom but again nothing I can feel. What I feel is it has a more mid and top for sure. I use later intake system for now as well. I think that length although a little longer is tuned which helps lower mid due to resoance ramming affect, but top end still under 8000 rpm so short intake won't help much. I try someday

This was no risk for all factory stuff. Not interested in a racer

I am curiuos what the intake timing is on the GT550 ( anyone have the dimension, easy to calculate if you do),

Man that piston has a long skirt! I'll bet another beer (yeah I already owe you one) that intake timing has room to spare and still streatable. If true such an easy mod if one can't leave well enough alone

[andyp666]

Im going to have a good play with these ports sod it... I have 2 spare barrels so if all fails I only need to shell out for 1 more on ebay they aint that rare yet WTF.. lolz... I have been looking in the Kawa triple pages too some good stuff in there I think I will drop and raise 1mm sort the asthmatic trans ports out and plane the heads down for skwish and saw int 3. seems to be the sensible thing to do with them might as well have fun and experiment with it thats the only way to learn. And besides I got a windy die grinder hehehehehehe and Im off to play with it...

[tz375]

Andy, what sort of performance are you looking for and have you thought about what pipes and carbs you will be using? A couple of 550 race bikes have been built and one was reported as making over 75hp at the rear wheels with an SCR stage 1 port job on 5 port barrels http://autos.groups.yahoo.com/group/GT750/message/88589" onclick="window.open(this.href);return false;. Jeff K posted his 550 tuning secrets on the old Kawasaki Triples board 2 or 3 years ago.

Eric V on the Yahoo group has a mildly modified 550 called Pepe after a certain cartoon skunk that he's very happy about the performance of.

The thing about 2 stroke ports is that a very small amount of metal can make a huge difference to performance. Big ports and stock carbs and pipes makes for a miserable ride with no bottom end or midrange. Raising compression is always a good idea - within reason. A little more helps everywhere. A little too much creates holes in pistons.