Raider Sport Ports - Let The Power Out

The Thread Spread

- Raider Sport Ports -

Let The Power Out

The Question - I found your Website while searching for information about cylinder porting. I also saw where you had ported a 700 Raider to make it run 60 MPH. I must say, That's pretty impressive. I am in the process of doing some porting on an 1100 Raider. Up to this point I have only cleaned up the intake ports and matched the crankcase with the cylinders. I am a little scared to alter the exhaust or intake timings for fear of bad results. I was wondering if you had any experience with the 1100 engine. Also I am curious about the additional intake ports that you added to the 700 engine. I have a formula for the exhaust timing that seems to give accurate results however the one that I am using for the intake timing, does not give the right result. If you know of any formulas, or port timings for the 1100 I would very much appreciate them.

Craig

The Response - I try to post as much information about the modifications I've made to the 2 stroke motors I've worked on to help other people with their own projects. When I started porting and modifying 2 stroke motors there was very little information available, fortunately this has changed somewhat over the years. Two strokes are not as much of a mystery as they once were and can be fun and very rewarding to work on.

Bill's Wave Raider has had almost every part of the motor replaced with Riva components. The cylinder in not a Yamaha part (the stock one cracked), it was replaced with the Riva #RY 10015 Pro Series Race cylinder. This cylinder (see http://www.rivayamaha.com/ctcylin.html ) comes bare, and the sleeves are not installed. They cylinder has to be ported though the

sleeves (liners) have aggressive timing cut into them. They just need a good clean up and match. The extra transfer ports tunnels are cast into the aluminum block and match holes cut into the Riva sleeves. This makes for a cylinder that has almost a full circle of transfer port area. So much area that the piston ring end gaps must pass across the extra ports - right in the middle of them. There is not enough cylinder wall to support the ring end anywhere so this set up was mandatory.

The timing of the 1100 is very similar to the 700. The 1100 is just 3, 81 mm x 68 mm cylinders instead of 2. The two motors share the same bore and stroke though the compression of the 1100 is somewhat lower which seems to be normal for triple cylinder watercraft. In stock form these 81 mm cylinders are greatly under ported. That is to say that the transfer port time/area is way too small and the direction of their charge is aimed too far back in the cylinder for high power. Additionally it is aimed too high and can be corrected by cutting the roofs of the ports flatter. The exhaust port timing can be improved upon as well. The exhaust needs to be widened and raised for more power.

As always, widen the ports before raising them to gain additional time/area, though these motors will need both kinds of modifications. If you're using the stock exhaust you may want to mill the head to gain back the compression you will lose when you raise the exhaust port roof. I would think that you'll be shooting for about 150 lb. compression in each cylinder (static) when you're done.

Since these motors are case reed design, I don't understand your question about intake timing. The intake area of the case is good. A good clean up and rounding of corners will help a bit. Case porting always helps and never hurts but the gain is marginal.

Like it says on my Watercraft web page the exhaust port timing of the Riva cylinder is 194 degrees open (opens at 83 degrees ATDC). The stock Yamaha cylinders open their exhaust port at about 86 degrees ATDC for a duration of 188 degrees. The Riva cylinder has its exhaust port cut to a width of 70 % of the bore and is a large oval hole, much different from the small square hole of the 1100 or 700. The open duration of the transfer ports of the Riva cylinder is 132 degrees - they open at 114 degrees ATDC, that's up from the 120 degrees duration of the stock Yamaha pieces which open at 120 degrees ATDC. As you can see there is a huge difference in the transfer port timing and area.

Remember, the 1100 has enough cylinder material to be bored out to 84 mm and still leave room for two over bores (to 84.5 mm) later. This adds 80 cc to the displacement. Don't forget to have the crank trued and welded and add a billet drive line coupler to handle the extra power. I understand Extrude honing the stock exhaust is a good improvement as well.

Spend some time checking out some of the 2 stroke articles that I've created links to on my 2 stroke page http://www.macdizzy.com/2stroke.htm there's some real good information in some of those pieces. Here's my recommendations for interesting reading which might help you with your motor.

From GroupK - http://www.groupk.com/intro.html

http://www.groupk.com/yamtriples.html

http://www.groupk.com/tripleupdates.html

http://www.groupk.com/rearseizures.html

From HPT Sport - http://www.hpt-sport.com/

http://www.hpt-sport.com/cylmap.htm

http://www.hpt-sport.com/flowrivr.htm

You may need to map your cylinder for proper modification and get some formulas to help you sort it all out.

Rick

Hey Rick! Thanks alot for the information you sent concerning the porting information for the 1100 Motor. It was very helpful for calculating the information below. I have a degree in Electrical Engineer, therefor the math part is not so confusing unless you have to derive the formulas from scratch. I wrote some Basic programs using the formulas that you provided. It helps alot not to have to punch 50 keystrokes on a scientific calculator. As I might have mentioned before, about a year ago I had gone in and cleaned up the exhaust ports and the transfer ports and matched the cases with the cylinder. At that time I also raised and widened the exhaust port just ever so slightly. I have also raised the compression to 150. psi. Due to the unavailability of an after market exhaust system, I am using the stock setup which has been Extrude Honed. I have also taper bored the stock carbs and removed all the casting flaws, and polished them to a mirror finish. With this set up the engine was turning about 7040 rpms with the stock impeller, on smooth water. I have since installed a Solas J impeller, which pulled the rpms down to about 6750 on smooth water. I don't know exactly what the top speed is, though I can say that is faster than a Seadoo GSX limited, by about 2 mph. (You Gotta Love That). This setup is probably very similar to Group K sleeper 1100. So as not to die from boredom this winter, I decided to Tear the motor down and replace the Pistons, Rings, Seals and so on. Since I am going to be this deep into the motor, I thought I might as well try to tweak a little more out of this machine. I would like to keep the engine running on 93 octane fuel. That is where I'm currently at with this project.

EXHAUST PORT INFORMATION Port distance from top of cylinder 36 mm

Port width 50 mm

Port Height 35 mm

Port opens at 85.5 deg. after TDC

Exhaust port duration =(360-85.5) - 85.5 = 189 deg.

TRANSFER PORT INFORMATION Port distance from top of cylinder (all transfers) 54.4 mm

Transfer port duration= (360-120) - 120 = 120 deg.

According to the information you gave me on the stock 701 motor, this seems to be a very similar setup. Would you consider it a wise move to port the cylinder to the same transfer and exhaust duration, as the Riva cylinder #RY 10015. I must also keep in mind that I am using the stock exhaust system. Due you think that there is any room for improvement or am I wasting my time.

Craig

I always enjoy 2 stroke tuning. It sounds like you've done quite a bit to your motor actually. The 1100 motor is a great motor to modify since it has the added displacement for lot a low RPM power as well. This lets you get away with a little more port timing without worrying so much. The Raider hull is a fast hull, perhaps the fastest flat water hull ever made. If you could get the boat to pull the J prop at 7040, you'd really be flying. I think it is possible with a few more modifications. Klemm offers a re-pitch modification to the J prop which is said to get back the lost RPM (it seems they changed the J prop a while ago and it caused some RPM loss problems) and increase the boat speed as well ($48 and 2-3 days in the shop). Another modification you might want to consider is getting the pump blueprinted. It helps hook up a lot - especially in choppy or rough water.

I had the opportunity to put a degree wheel on a Klemm 92 Octane (Sleeper kit) 701 cc Wave Raider last year. Klemm likes to keep

things simple (read - reliable) He goes out of his way to make the most of stock parts when ever he can. I appreciate that. The 701 cc Sleeper exhaust opened at 85 degrees ATDC (not much change from stock - about 1 degree) and widened to match the aluminum

cylinder, and the transfers were raised a bit to opening at 118 degrees ATDC (about 2 degree change). These porting mods along with an increase in compression (to 170 lb.) and a Coffmans Rocket pipe made the boat quite a bit faster. It seems to me though that the pipe and head modification may have added almost all the new found power, since the porting was basically a blueprint. Though the top speed was only improved by about 5 mph, the time it took to get there was much improved.

I wouldn't modify your cylinders to the RIVA specs because it is way too much for the triple - especially without the benefit of a pipe AND you'll probably want to run it pump gas. He (Bill) runs the Raider on 92 pump gas with 180 - 185 psi cranking compression. The motor revs to 7400 and would go much higher if not for the MSD ignition which is set to shut off at that RPM. Watercraft have much different parameters to work around because of their unique situation, they can pop out of the water and rev to the moon (and perhaps twist the crank) if not limited, and they run almost all the time at full speed. He set his peak RPM at about 3300 FPM up from about 2900 FPM. Personal watercraft that are recreational rides should keep their piston speed under 3500 FPM, and really a couple hundred under that is quite a bit safer. Gordon Jenning wrote the book on piston speed 25 years ago and with all our new technology the 4000 FPM speed for high output racing engines is still very valid.

On your motor you should feel comfortable cutting the exhaust to open at 84 to 84.5 degrees ATDC and increase the transfer port timing to open at 115 degrees ATDC. The stock design of the Yamaha cylinders prohibit the shape of exhaust port the Riva cylinders have - they're just too square; which is good for low to midrange power, but hurts it on top. The Rive ports are beautiful - for a single exhaust port design. They are calculated at 70% of bore (for width), an old rule of thumb, and oval, so the power delivery is a bit smoother than if the port had a flat top - which would have it hit the power quite a bit harder. The Yamaha cylinders can't be (safely) brought out to 70% of bore because there simply is not enough room to open them up and still have enough material left to hang an exhaust pipe from. If your exhaust port is 50 mm wide, that's about 62% of bore. You might get it opened up to 51.84 mm for 64% of bore. The Riva web page doesn't have s good picture of the porting in their high performance cylinders but R&D racing sells what must be an exact copy of them because the picture of their cylinders at http://www.rd-performance.com/yamcylin.htm looks exactly like the Riva pieces. When you look at them you'll immediately see the difference. Also notice the picture of their modified and sleeved stock Yamaha cylinder, they cut an extra transfer ports in the liner of it too.

Keep in mind also that - like I mentioned last time - that the direction of the charge into the cylinders is made to favor lower speed power. They are aimed WAY too high. Cut the transfer port roofs as flat as possible to gain a bunch of midrange AND top end power. Also make them enter the cylinder at less of an angle.

If you have a PC or are running a Mac with Virtual PC or Softwindows, you can download and run some free Two-stroke modeling software which includes a bunch of Win95 spreadsheets and some pretty good DOS stuff. It worth the download. Check out these sites:

http://www.info.com.ph/~hanukkah/download.htm

http://pages.hotbot.com/port/tune_2_stroke/index.html

Also Bimotion offers what is probably the best $75 2 stroke software package. Their URL is http://www.knuten.liu.se/~bilal270/ - but I know nothing else about it except it seems to include quite a bit for the money.

Rick

Hey thanks a lot for such a quick response. Your information has been extremely helpful . I forgot to mentioned in my last email that I had Group K repitch the Solas J impeller. Before I had it repitched it would only turn 6550 rpms (way to low). I also installed a second cooling line from the pump to the exhaust manifold. This setup makes the 1100 motor run very cool even at high rpm. This is a little different than what group K does with there extra fittings on the head. I have also flattened the transfer roofs as you mentioned. I guess you could say that I was lucky on that one because I definitely didn't know What I was doing a year ago. As you mentioned, flattening the roofs will give it strong midrange, boy did it ever. My friend has one of the Blue GP 1200's which I consider to be as strong as any out of the hole. I can usually pull him by about 15 boat lengths in about 6 seconds. I will only engage in this type of activity in smooth water. As you probably know, the Raider hull is subject to project you about 50 feet though the air at any time. (very painful at 60 plus)

I have heard the rule of thumb concerning the exhaust port width being 70% of the bore diameter. I have book on 2 cycle performance tuning written by A. Graham Bell. He also suggest a maximum port width of 70%. I have sat on the couch for many hours with the cylinders sitting on the coffee table in front of me, thinking how in the world am I going to widen this square port to 70% and give it a nice oval shape without going overboard on exhaust timing or snagging a ring on the way up. I agree with you totally, when you mentioned that the stock port is way to square to be brought out to 70%. I believe I will follow your advise on going with 64% as the port with. As for the transfer and exhaust duration you suggested, I feel comfortable with 115 deg. ATDC transfer and 84.5 deg.exhaust. I am also planning on installing some 44 mm carbs this season. Like you said, if I could get this motor to turn 7040 with the J prop it would probably be very fast. I am shooting for around 65 or 66 MPH with the 44 mm carbs.

Craig

I'd forget 70% of bore for the stock cylinders too. It's just not practical. Though I have seen a couple tricks used to get the most of what there is to work with. Consider this... If the exhaust port opens at 84 ATDC - widen the port only from 90 to 104 ATDC or there about (2 to 3 mm additional width on each side). Taper the new tracks into the port. This makes for a port shape that's still square, but has a cut out on each side that allows additional area during the most important part of the stroke. So the port is square, then bulges out for about 15 degrees or so, then goes back to square. Carefully bevel the edges and you've got a motor that effectively has quite a bit more exhaust port.

The problem with single exhaust ports is the ring snag thing. That's their main draw back. I like bridged ports which allow exhaust ports to be widened much further than that. My TRX motor has a port width of almost 90 % of bore. As you may know some other motors have more exhaust ports which allow for exhaust port width of 100% of bore and create even more area by making the ports large and long. They are positioned above the normal transfer ports - but they are exhaust auxiliary ports.

With the modifications you have outlined I see no reason why your 1100 won't turn in the speed you're shooting for. Keep me informed on its progress and let me know if there's anything else we need to cover.

Rick

I have almost finished with my 1100 Raider motor, and will begin putting it back together soon. I have done a tremendous amount of work on the cases and the cylinders. I finally decided on a port design that I hope will give me that little extra that I'm looking for. From it's original design I raised the port about a 1/2 mm and widen it to 65%. It is about 2 or 3 mm wider on each side near the top. Also the widest point is about 6 deg. lower than the top of the port. This is what was recommend for this type of port design in order to prevent the ring from snagging. I attached a bitmap file of this design to the email.

After laying out and grinding the new port, I finished the inside of the exhaust to a mirror finish "very time consuming". I then raised the transfers to open at 119. deg and then flattened the top of the as they were before. I did not change the angle at which they shoot into the cylinder, as this was done the last time I worked on the porting. Let me know what you think of this port design.

Craig

I think that port design looks fine. It is wide where it needs to be. Be sure to taper the port all the way into the exhaust pipe if you can - otherwise you may not get its full effect. Ideally it would taper outwards from the port window a couple of degrees - though I know this may be difficult to achieve with the material that is available.

Rick

Back to The Thread Spread index of articles.

Let The Power Out
The Question - I found your Website while searching for information about cylinder porting. I also saw where you had ported a 700 Raider to make it run 60 MPH. I must say, That's pretty impressive. I am in the process of doing some porting on an 1100 Raider. Up to this point I have only cleaned up the intake ports and matched the crankcase with the cylinders. I am a little scared to alter the exhaust or intake timings for fear of bad results. I was wondering if you had any experience with the 1100 engine. Also I am curious about the additional intake ports that you added to the 700 engine. I have a formula for the exhaust timing that seems to give accurate results however the one that I am using for the intake timing, does not give the right result. If you know of any formulas, or port timings for the 1100 I would very much appreciate them. Craig
The Response - I try to post as much information about the modifications I've made to the 2 stroke motors I've worked on to help other people with their own projects. When I started porting and modifying 2 stroke motors there was very little information available, fortunately this has changed somewhat over the years. Two strokes are not as much of a mystery as they once were and can be fun and very rewarding to work on. Bill's Wave Raider has had almost every part of the motor replaced with Riva components. The cylinder in not a Yamaha part (the stock one cracked), it was replaced with the Riva #RY 10015 Pro Series Race cylinder. This cylinder (see http://www.rivayamaha.com/ctcylin.html ) comes bare, and the sleeves are not installed. They cylinder has to be ported though the sleeves (liners) have aggressive timing cut into them. They just need a good clean up and match. The extra transfer ports tunnels are cast into the aluminum block and match holes cut into the Riva sleeves. This makes for a cylinder that has almost a full circle of transfer port area. So much area that the piston ring end gaps must pass across the extra ports - right in the middle of them. There is not enough cylinder wall to support the ring end anywhere so this set up was mandatory. The timing of the 1100 is very similar to the 700. The 1100 is just 3, 81 mm x 68 mm cylinders instead of 2. The two motors share the same bore and stroke though the compression of the 1100 is somewhat lower which seems to be normal for triple cylinder watercraft. In stock form these 81 mm cylinders are greatly under ported. That is to say that the transfer port time/area is way too small and the direction of their charge is aimed too far back in the cylinder for high power. Additionally it is aimed too high and can be corrected by cutting the roofs of the ports flatter. The exhaust port timing can be improved upon as well. The exhaust needs to be widened and raised for more power. As always, widen the ports before raising them to gain additional time/area, though these motors will need both kinds of modifications. If you're using the stock exhaust you may want to mill the head to gain back the compression you will lose when you raise the exhaust port roof. I would think that you'll be shooting for about 150 lb. compression in each cylinder (static) when you're done. Since these motors are case reed design, I don't understand your question about intake timing. The intake area of the case is good. A good clean up and rounding of corners will help a bit. Case porting always helps and never hurts but the gain is marginal. Like it says on my Watercraft web page the exhaust port timing of the Riva cylinder is 194 degrees open (opens at 83 degrees ATDC). The stock Yamaha cylinders open their exhaust port at about 86 degrees ATDC for a duration of 188 degrees. The Riva cylinder has its exhaust port cut to a width of 70 % of the bore and is a large oval hole, much different from the small square hole of the 1100 or 700. The open duration of the transfer ports of the Riva cylinder is 132 degrees - they open at 114 degrees ATDC, that's up from the 120 degrees duration of the stock Yamaha pieces which open at 120 degrees ATDC. As you can see there is a huge difference in the transfer port timing and area. Remember, the 1100 has enough cylinder material to be bored out to 84 mm and still leave room for two over bores (to 84.5 mm) later. This adds 80 cc to the displacement. Don't forget to have the crank trued and welded and add a billet drive line coupler to handle the extra power. I understand Extrude honing the stock exhaust is a good improvement as well. Spend some time checking out some of the 2 stroke articles that I've created links to on my 2 stroke page http://www.macdizzy.com/2stroke.htm there's some real good information in some of those pieces. Here's my recommendations for interesting reading which might help you with your motor. From GroupK - http://www.groupk.com/intro.html http://www.groupk.com/yamtriples.html http://www.groupk.com/tripleupdates.html http://www.groupk.com/rearseizures.html From HPT Sport - http://www.hpt-sport.com/ http://www.hpt-sport.com/cylmap.htm http://www.hpt-sport.com/flowrivr.htm You may need to map your cylinder for proper modification and get some formulas to help you sort it all out. Rick Hey Rick! Thanks alot for the information you sent concerning the porting information for the 1100 Motor. It was very helpful for calculating the information below. I have a degree in Electrical Engineer, therefor the math part is not so confusing unless you have to derive the formulas from scratch. I wrote some Basic programs using the formulas that you provided. It helps alot not to have to punch 50 keystrokes on a scientific calculator. As I might have mentioned before, about a year ago I had gone in and cleaned up the exhaust ports and the transfer ports and matched the cases with the cylinder. At that time I also raised and widened the exhaust port just ever so slightly. I have also raised the compression to 150. psi. Due to the unavailability of an after market exhaust system, I am using the stock setup which has been Extrude Honed. I have also taper bored the stock carbs and removed all the casting flaws, and polished them to a mirror finish. With this set up the engine was turning about 7040 rpms with the stock impeller, on smooth water. I have since installed a Solas J impeller, which pulled the rpms down to about 6750 on smooth water. I don't know exactly what the top speed is, though I can say that is faster than a Seadoo GSX limited, by about 2 mph. (You Gotta Love That). This setup is probably very similar to Group K sleeper 1100. So as not to die from boredom this winter, I decided to Tear the motor down and replace the Pistons, Rings, Seals and so on. Since I am going to be this deep into the motor, I thought I might as well try to tweak a little more out of this machine. I would like to keep the engine running on 93 octane fuel. That is where I'm currently at with this project. EXHAUST PORT INFORMATION Port distance from top of cylinder 36 mm Port width 50 mm Port Height 35 mm Port opens at 85.5 deg. after TDC Exhaust port duration =(360-85.5) - 85.5 = 189 deg. TRANSFER PORT INFORMATION Port distance from top of cylinder (all transfers) 54.4 mm Transfer port duration= (360-120) - 120 = 120 deg. According to the information you gave me on the stock 701 motor, this seems to be a very similar setup. Would you consider it a wise move to port the cylinder to the same transfer and exhaust duration, as the Riva cylinder #RY 10015. I must also keep in mind that I am using the stock exhaust system. Due you think that there is any room for improvement or am I wasting my time. Craig I always enjoy 2 stroke tuning. It sounds like you've done quite a bit to your motor actually. The 1100 motor is a great motor to modify since it has the added displacement for lot a low RPM power as well. This lets you get away with a little more port timing without worrying so much. The Raider hull is a fast hull, perhaps the fastest flat water hull ever made. If you could get the boat to pull the J prop at 7040, you'd really be flying. I think it is possible with a few more modifications. Klemm offers a re-pitch modification to the J prop which is said to get back the lost RPM (it seems they changed the J prop a while ago and it caused some RPM loss problems) and increase the boat speed as well ($48 and 2-3 days in the shop). Another modification you might want to consider is getting the pump blueprinted. It helps hook up a lot - especially in choppy or rough water. I had the opportunity to put a degree wheel on a Klemm 92 Octane (Sleeper kit) 701 cc Wave Raider last year. Klemm likes to keep things simple (read - reliable) He goes out of his way to make the most of stock parts when ever he can. I appreciate that. The 701 cc Sleeper exhaust opened at 85 degrees ATDC (not much change from stock - about 1 degree) and widened to match the aluminum cylinder, and the transfers were raised a bit to opening at 118 degrees ATDC (about 2 degree change). These porting mods along with an increase in compression (to 170 lb.) and a Coffmans Rocket pipe made the boat quite a bit faster. It seems to me though that the pipe and head modification may have added almost all the new found power, since the porting was basically a blueprint. Though the top speed was only improved by about 5 mph, the time it took to get there was much improved. I wouldn't modify your cylinders to the RIVA specs because it is way too much for the triple - especially without the benefit of a pipe AND you'll probably want to run it pump gas. He (Bill) runs the Raider on 92 pump gas with 180 - 185 psi cranking compression. The motor revs to 7400 and would go much higher if not for the MSD ignition which is set to shut off at that RPM. Watercraft have much different parameters to work around because of their unique situation, they can pop out of the water and rev to the moon (and perhaps twist the crank) if not limited, and they run almost all the time at full speed. He set his peak RPM at about 3300 FPM up from about 2900 FPM. Personal watercraft that are recreational rides should keep their piston speed under 3500 FPM, and really a couple hundred under that is quite a bit safer. Gordon Jenning wrote the book on piston speed 25 years ago and with all our new technology the 4000 FPM speed for high output racing engines is still very valid. On your motor you should feel comfortable cutting the exhaust to open at 84 to 84.5 degrees ATDC and increase the transfer port timing to open at 115 degrees ATDC. The stock design of the Yamaha cylinders prohibit the shape of exhaust port the Riva cylinders have - they're just too square; which is good for low to midrange power, but hurts it on top. The Rive ports are beautiful - for a single exhaust port design. They are calculated at 70% of bore (for width), an old rule of thumb, and oval, so the power delivery is a bit smoother than if the port had a flat top - which would have it hit the power quite a bit harder. The Yamaha cylinders can't be (safely) brought out to 70% of bore because there simply is not enough room to open them up and still have enough material left to hang an exhaust pipe from. If your exhaust port is 50 mm wide, that's about 62% of bore. You might get it opened up to 51.84 mm for 64% of bore. The Riva web page doesn't have s good picture of the porting in their high performance cylinders but R&D racing sells what must be an exact copy of them because the picture of their cylinders at http://www.rd-performance.com/yamcylin.htm looks exactly like the Riva pieces. When you look at them you'll immediately see the difference. Also notice the picture of their modified and sleeved stock Yamaha cylinder, they cut an extra transfer ports in the liner of it too. Keep in mind also that - like I mentioned last time - that the direction of the charge into the cylinders is made to favor lower speed power. They are aimed WAY too high. Cut the transfer port roofs as flat as possible to gain a bunch of midrange AND top end power. Also make them enter the cylinder at less of an angle. If you have a PC or are running a Mac with Virtual PC or Softwindows, you can download and run some free Two-stroke modeling software which includes a bunch of Win95 spreadsheets and some pretty good DOS stuff. It worth the download. Check out these sites: http://www.info.com.ph/~hanukkah/download.htm http://pages.hotbot.com/port/tune_2_stroke/index.html Also Bimotion offers what is probably the best $75 2 stroke software package. Their URL is http://www.knuten.liu.se/~bilal270/ - but I know nothing else about it except it seems to include quite a bit for the money. Rick Hey thanks a lot for such a quick response. Your information has been extremely helpful . I forgot to mentioned in my last email that I had Group K repitch the Solas J impeller. Before I had it repitched it would only turn 6550 rpms (way to low). I also installed a second cooling line from the pump to the exhaust manifold. This setup makes the 1100 motor run very cool even at high rpm. This is a little different than what group K does with there extra fittings on the head. I have also flattened the transfer roofs as you mentioned. I guess you could say that I was lucky on that one because I definitely didn't know What I was doing a year ago. As you mentioned, flattening the roofs will give it strong midrange, boy did it ever. My friend has one of the Blue GP 1200's which I consider to be as strong as any out of the hole. I can usually pull him by about 15 boat lengths in about 6 seconds. I will only engage in this type of activity in smooth water. As you probably know, the Raider hull is subject to project you about 50 feet though the air at any time. (very painful at 60 plus) I have heard the rule of thumb concerning the exhaust port width being 70% of the bore diameter. I have book on 2 cycle performance tuning written by A. Graham Bell. He also suggest a maximum port width of 70%. I have sat on the couch for many hours with the cylinders sitting on the coffee table in front of me, thinking how in the world am I going to widen this square port to 70% and give it a nice oval shape without going overboard on exhaust timing or snagging a ring on the way up. I agree with you totally, when you mentioned that the stock port is way to square to be brought out to 70%. I believe I will follow your advise on going with 64% as the port with. As for the transfer and exhaust duration you suggested, I feel comfortable with 115 deg. ATDC transfer and 84.5 deg.exhaust. I am also planning on installing some 44 mm carbs this season. Like you said, if I could get this motor to turn 7040 with the J prop it would probably be very fast. I am shooting for around 65 or 66 MPH with the 44 mm carbs. Craig I'd forget 70% of bore for the stock cylinders too. It's just not practical. Though I have seen a couple tricks used to get the most of what there is to work with. Consider this... If the exhaust port opens at 84 ATDC - widen the port only from 90 to 104 ATDC or there about (2 to 3 mm additional width on each side). Taper the new tracks into the port. This makes for a port shape that's still square, but has a cut out on each side that allows additional area during the most important part of the stroke. So the port is square, then bulges out for about 15 degrees or so, then goes back to square. Carefully bevel the edges and you've got a motor that effectively has quite a bit more exhaust port. The problem with single exhaust ports is the ring snag thing. That's their main draw back. I like bridged ports which allow exhaust ports to be widened much further than that. My TRX motor has a port width of almost 90 % of bore. As you may know some other motors have more exhaust ports which allow for exhaust port width of 100% of bore and create even more area by making the ports large and long. They are positioned above the normal transfer ports - but they are exhaust auxiliary ports. With the modifications you have outlined I see no reason why your 1100 won't turn in the speed you're shooting for. Keep me informed on its progress and let me know if there's anything else we need to cover. Rick I have almost finished with my 1100 Raider motor, and will begin putting it back together soon. I have done a tremendous amount of work on the cases and the cylinders. I finally decided on a port design that I hope will give me that little extra that I'm looking for. From it's original design I raised the port about a 1/2 mm and widen it to 65%. It is about 2 or 3 mm wider on each side near the top. Also the widest point is about 6 deg. lower than the top of the port. This is what was recommend for this type of port design in order to prevent the ring from snagging. I attached a bitmap file of this design to the email. After laying out and grinding the new port, I finished the inside of the exhaust to a mirror finish "very time consuming". I then raised the transfers to open at 119. deg and then flattened the top of the as they were before. I did not change the angle at which they shoot into the cylinder, as this was done the last time I worked on the porting. Let me know what you think of this port design. Craig I think that port design looks fine. It is wide where it needs to be. Be sure to taper the port all the way into the exhaust pipe if you can - otherwise you may not get its full effect. Ideally it would taper outwards from the port window a couple of degrees - though I know this may be difficult to achieve with the material that is available. Rick