Take a look at my cylinder/porting...does this look right?
- Thread starter skithis
- Start date
I can see that. I thought you just had a cylinder ported.
waxhead
wannabe backflipper
- Location
- gold coast
You will make a lot more torque
Its not just about timing its about airflow in a cylinder
Also the flow from the cases into the cylinder is a critical area
How much is it going to make difference well how much hp does a sport port make now
Its not something you can actually put a figure on but the guy who got me to fix his cylinder was very happy with the extra gain and I didnt do the cases
Its not just about timing its about airflow in a cylinder
Also the flow from the cases into the cylinder is a critical area
How much is it going to make difference well how much hp does a sport port make now
Its not something you can actually put a figure on but the guy who got me to fix his cylinder was very happy with the extra gain and I didnt do the cases
- Location
- Ontario, Canada
Polish jet pilot
4aces4aces4aces4aces4aces
- Location
- Warsaw, Poland
Sorry to once again bring this up, but I feel this has not been well explained: Should we match the the cylinder casting to the OEM sleeve windows? Some say that by doings this you loose bottom end.
As I understand this would allow more mixture to flow through cylinder, why would it take away from the bottom end? Please keep in mind that I would match these in conjunction with the sport port template (new FS version)
As I understand this would allow more mixture to flow through cylinder, why would it take away from the bottom end? Please keep in mind that I would match these in conjunction with the sport port template (new FS version)
- Location
- Mechanicsburg, PA
If you match the top of the casting window to the sleeve window, you'll be changing the timing from what it currently is. With that said, is the height of the sleeve correct or is the height of the casting correct (as Yamaha intended in stock format)?
waxhead
wannabe backflipper
- Location
- gold coast
It determined by the sleeve
the mismatch in the casting just means the port flows really badly until it clears the alloy then its progress,s to just flowing crap
the mismatch in the casting just means the port flows really badly until it clears the alloy then its progress,s to just flowing crap
Polish jet pilot
4aces4aces4aces4aces4aces
- Location
- Warsaw, Poland
I was reading a book on 2 strokes yesterday before bed time and there were great pics showing flow inside the cylinder. Since Yami cylinder is a 5 port design it flows generally well. If you look closely there are certain angles to the casting and sleeve that direct the flow (it has to be in harmony with flow from all ports). Thus my conclusion (correct me if I am wrong here), port matching the cylinder to sleeve is OK, as long as we do not increase the heights of ports and we do not change their angles which direct flow. Making them smooth is key.
Am I right or just silly?
Andrew
Am I right or just silly?
Andrew
waxhead
wannabe backflipper
- Location
- gold coast
waxracing $300-350 as well
Midlake Crisis
Site Supporter
- Location
- Bakersfield, CA
What is the answer?
I have searched and read and can't get a definitive answer to this question.
I just purchased a 61x cylinder in great shape but with the same mismatch.
I have a friend who is a very competent machinist who has successfully ported race motors and is willing to clean it up and do a simple port match for me.
BOTTOM LINE:
Should the cylinder ports be matched to the sleeves or not?
Boost AND transfer ports?
Port height AND width?
I have searched and read and can't get a definitive answer to this question.
I just purchased a 61x cylinder in great shape but with the same mismatch.
I have a friend who is a very competent machinist who has successfully ported race motors and is willing to clean it up and do a simple port match for me.
BOTTOM LINE:
Should the cylinder ports be matched to the sleeves or not?
Boost AND transfer ports?
Port height AND width?
jetski9010
Team RTYD
- Location
- Lancaster PA
correct me if I am wrong but as soon as the piston uncovers the transfer port window it will be pulling the charge in even if the port is a few mm lower. Because the casting is back a few mm from the sleeve there will be a opening as soon as the transfer window in the sleeve is uncovered right? I would think it would just make it flow like crap and even cause unwanted turbulence. Also if you are saying the stock port timing is set off the sleeve then if the port was mismatched lower and it had the angle is was designed for then it would be pointing in the wrong spot. An 18 degree angle (or whatever the angle is stock on a 701) that is 4 mm lower then is was designed for would either have to be rised to the correct location or need the angle adjusted. I am just trying to think logically here but I could be way off.
Midlake Crisis
Site Supporter
- Location
- Bakersfield, CA
Yabbut
I have even seen someone post their opinion that the sleeve mismatch was intended by Yamaha.
I just don't want to ruin the bottom end on this cylinder.
I understand. Your reasoning "makes sense" but no one that really knows from training and experience seems willing to post a definitive answer.
I have even seen someone post their opinion that the sleeve mismatch was intended by Yamaha.
I just don't want to ruin the bottom end on this cylinder.
Polish jet pilot
4aces4aces4aces4aces4aces
- Location
- Warsaw, Poland
My builder said to clean them up. Do not change angles. Not that difficult really.. Lets test...
jetski9010
Team RTYD
- Location
- Lancaster PA
If you really want to be sure get a degree wheel and a TDC locator like these ones
http://www.watcon.com/Catalog_Pages/Degree_Wheel.htm
http://www.watcon.com/Catalog_Pages/Top_Dead_Center_Tool.htm
Then find out what the stock port timing is and check it agaisnt your engine. If you bring them all to spec or you find out you need to lower or rise your port timing a bit or your want to lower it for better bottom end you could get one of these base gaskets http://www.watcon.com/Gaskets.htm in the thickness you want and at that time you can also open up your cases a little and blueprint them as well.
http://www.watcon.com/Catalog_Pages/Degree_Wheel.htm
http://www.watcon.com/Catalog_Pages/Top_Dead_Center_Tool.htm
Then find out what the stock port timing is and check it agaisnt your engine. If you bring them all to spec or you find out you need to lower or rise your port timing a bit or your want to lower it for better bottom end you could get one of these base gaskets http://www.watcon.com/Gaskets.htm in the thickness you want and at that time you can also open up your cases a little and blueprint them as well.
jetski9010
Team RTYD
- Location
- Lancaster PA
Here is a website that talks about port mismatch. Its not talking about a superjet motor but still good info. http://www.macdizzy.com/atc.htm
I do not know definitive answers to these questions. I gave up on home-porting and went to paying a pro to do the work.
That said, I have ported some cylinders where I matched height and width, and some with only the width matched.
The difference was never dramatic, and I always had different accessory components, anyhow (ignition, carbs, etc).
I will say that one of the best performing cylinders I have done was a 760 62T, which doesn't have nearly the mismatch a 61X does. (Or the one I had was drastically better than most, I don't know).
You're not getting a definite answer because the correct answer is "it depends".
If you want the answers to these questions then take a known running engine, pull the cylinder off, port it how you think, put it back together, tune it in and see what happens. If you have done well then do the same thing and go futher. Now you'll have to ask yourself is the porting good or is the tunning off. If your not a good tunner then how do you know how good the porting was. Don't forget you'll have to match your more powerfull engine to the correct impeller/nozzle combo (a whole nother animal) Is it really better or just feels better. This is what racers do, and they use side by side drags to see the results. It may feel stronger (the hit) but it may be weaker because you've messed up the porting) untill it comes on the pipe. Two strokes are amazing, you can screw up the porting and they will still run. It costs a lot of money (blown engines) to get good, this is why builders charge. Life experiences don't come cheap.
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Midlake Crisis
Site Supporter
- Location
- Bakersfield, CA
I think Matt_E's answer sums up my own conclusion pretty good:
Effective porting is above the pay grade of 99% of us.
If there isn't even consensus on whether to match a mismatched casting to the sleeve it seems to me all these porting threads may be a big waste of time, except the part where they say to consult a professional . . .
Effective porting is above the pay grade of 99% of us.
If there isn't even consensus on whether to match a mismatched casting to the sleeve it seems to me all these porting threads may be a big waste of time, except the part where they say to consult a professional . . .