Misaligned sleeves/ports

[superjetincairns]

I've just pulled my engine down for a rebuild and have noticed how poorly the ports in the sleeves align with the ports in the cylinders. Bores still measure 81mm so id assume they're original. Is this normal? Blind Freddie could port these cylinders and do a better job im sure. Id assume there are gains to be made just by matching up these ports without touching the timing or size of the ports? Anyone done this themselves with any success?

 

[Quinc]

The 701's are known to have the worse sleeve to port alignment of any pwc engine made. Port matching the sleeves is a great idea.

 

[JetManiac]

The 701's are known to have the worse sleeve to port alignment of any pwc engine made. Port matching the sleeves is a great idea.

...If you know what you are doing or take the time to reseach and learn, otherwise you can easily make it worse, much worse.

 

[Quinc]

http://www.x-h2o.com/index.php?threads/home-porting.1540/

 

[Freakrider]

It's normal ! Designed this way ! The cylinder casting determines the port timing, start cutting on transfer casting and you can alter the proper blow down timing and ruin the crisp throttle response. XS Chucky does not alter the transfer casting on the 701 motors for this reason.

 

[superjetincairns]

I've rebuilt many two stroke racebike engines and ive never seen anything like this before. surely they arent designed to hav 4-5 mm lips and ledges where the sleeve meets the ports in the cylinder. what would be the point in obstructing flow like that. freakrider, by "transfer casting" do you mean the cast iron sleeve or the cast alloy cylinder? I was planning on just smoothing the transition between the two pieces, not changing any major dimensions of the transfer ports or actual port timing,

 

[kevbo]

For some reason they used 120 degree sleeves on a 110 degree cylinder casting. Be careful raising the roof because it is close to the water jacket. A 62T cyl casting and sleeve are matched at 120 degrees. I am going to try lowering the sleeves on a 61X and raising the cylinder for 7000 rpm porting. I will have to custom cut a head once it is finished. I expect more power than a low port 61X and better response than a 62T.

 

[Freakrider]

I've rebuilt many two stroke racebike engines and ive never seen anything like this before. surely they arent designed to hav 4-5 mm lips and ledges where the sleeve meets the ports in the cylinder. what would be the point in obstructing flow like that. freakrider, by "transfer casting" do you mean the cast iron sleeve or the cast alloy cylinder? I was planning on just smoothing the transition between the two pieces, not changing any major dimensions of the transfer ports or actual port timing,

Cast cylinder.

 

[JetSlut]

Cast cylinder.

I've opened up a '94 701 to find similar misalignment of sleeve ports to cylinder casting. Freakrider you said the cylinder casting determines port timing but that doesn't make sense to me as the port is opened/closed as the rings/pistons pass the edge of the sleeve port, not the cylinder casting. The rings/pistons are held several millimeters away from the cylinder casting by the sleeve so the air/fuel mixture enters through the sleeve port after navigating some stepped transitions where the cylinder casting meets the sleeve. You may be right that these are supposed to be like this but is seems like opening up the cylinder casting to match the sleeve port would not alter the "timing" only the flow. Anyone? The exhaust ports are aligned but the transfer ports vary and is most misaligned on the smallest ports opposite the exhaust ports.

 

[eastcoastjumper]

Exhaust ports are clearly ported and cleaned up. But the side ports look terrible with the aluminum casting to sleeve overlap. Hard to see in my pics but that is what @superjetincairns is talking about?

 

[Kawastyler]

.

 

[JetSlut]

I think so eastcoastjumper; looks just like mine. kevbo may have gotten it right too when saying that the cylinder casting port timing/locations are different than the sleeves on some of these units, perhaps only on the intake transfers as the exhaust is aligned very well on my '94 61X and on your unit. I wonder if aligning the cylinder casting alloy to the existing sleeve ports (being careful not to reduce the material between transfer channels and coolant channels too much) would improve performance??? This is the only reason to it matters to me. I wish someone who was on the Superjet design team would chime in on these threads to let us all know WTF is up with this and if there is anything to gain by removing the cylinder alloy to match the sleeve ports on the intakes.

 

[Bar jumper]

Out of interest what are the numbers stamped on top of the each exhaust port . My old motor had 00 00 and the sleeves matched up perfect and it went quite a bit better than mates with exactly same mods

 

[JetSlut]

Yes interesting... mine has a 6 6 or 9 9 on the top of one exhaust port (depends which way you read it) and no numbers on the other. I also have "Y-1" stamped on the unit below the exhaust ports. The other side has "61X" and "3 X 1" or "3 1 X" on it as shown.

Anyone have some different numbers so we know which way to read these?

 

[BruceSki]

All the stock class racers search for 00 00 cylinders because they are believed to be the best sleeve alignment ones out there. Although that is just a rumor as to what those numbers mean.

 

[Bar jumper]

That's what I had heard but was abit skeptical till I pulled the head off last year . I guess there inspected then stamped after having being assembled to help with initial carb settings on the assembly line.

 

[JetSlut]

eastcoastjumper what numbers do you have above your exhaust ports and elsewhere? I have similar sleeve-to-cylinder misalignment on the intake transfer ports and my numbers are 6 6 or 9 9. Here's a pic of the three middle intake ports on mine, and the most drastically misaligned. The 2 intake transfer ports not shown are misaligned up/down like the ones shown but they are fine on the sides. Anybody hazard an educated guess as to the performance results of matching the cylinder casting to the sleeve ports on these? Better, worse, same? Opening them up seems sensible but I don't wanna F this thing up or do a pile of work that has little or no benefit.

 

[Bar jumper]

I'll post a pic of my 00 00 ports , I did match the ports I had on an older 61x I had , kept the same angles in the transfers just matched them to the sleeve but that skis unriden been under the bench for about 4 years

 

[TheBuzzard]

the transfer ports are the harder ones to do and most knuckleheads with a dremel just hog out the main exhaust port, with mixed results. anybody that knows their ass from a hole in the ground, does the transfers and its required if you want max power. anybody that tells you the transfers dont need to be done, doesnt know sh*#!!
00 is the best factory port alignment that is possible and the higher the number , the worse the alignment/flow. back in the day, limited class racers sought after 00 stamped cylinders since those created the most power out of an unported cylinder.

 

[JetSlut]

barjumper you may be onto something... these numbers are "stamped" rather than "cast" into the cylinder alloy so are likely applied during assembly. Maybe they are an indicator of which sleeve went into the casting while the cast-in numbers indicate which alloy cylinder cast was used. This suggests there are different cylinder-sleeve combinations and some align better than others. Also suggests that riders may have some preference depending on their style (race, freestyle, freeride). I am curious about this and still want opinions on whether opening up the casting to match the sleeve will rocket my ship.

For comparison my "6 6" (or "9 9") 61X sleeve intake ports are 55 through 70mm from the top deck and the exhasut ports are 40 through 70mm from the top deck.