Every year threads emerge asking the same questions, who does porting, who has the best,etc,etc. They all end up the same in a "mines better then his" contest. The best thing anyone who is thinking of modding a engine can do is research. There is still quite a few 2 stroke builders, some better then others,but most all can get the job done if you ask the right questions and be specific on what you want done. Ask LOTS of questions not only on this forum but others/sites and then take the general consensus and go from there. If you can actually talk to customers/consumers of the company you want to go with the better. The next step would be to call the builder and talk over with them what your looking for, the more questions you ask the better your gonna get the feeling if you want to give them your hard earned money.
Some places wont give ya the time of day without a credit card number. If thats the case your better off going to your next choice. The reason is, after the sale you want to be able to call and discuss any issues or support you may need to get what you want from the engine. The engine will almost always need a differnt set of specs after work has been done along with clutching to grasp the newly added power, basicly its all about customer service,and that truly begins after the sale!
Remember,its your money and it will spend the same no matter where you go!!
If you can do the porting yourself thats great, but what most people dont have in thier toolbox is the tools to accomplish the job. A 90 degree foredom tool needed to do the aux. exh. work and transfer work can cost $400 and then you need the drive system to power it, then carbide cutters,etc. Your looking at over $1200 worth of tools just to get started. Of course you also need the correct specs to set up the ports to. This is where the "cost" comes into getting engine work done. You also will need to remachine heads to get back the lost compression from porting the exh port.
(There is a company by the name of race logic who sells templates to help the do it yourselfer, they work well for a trail port. they have many differnt brand applications. I have personally used this company before when I first got into modding these triple srxs,on my 1998 srx700.)
"Porting" is simply changing the port timing of a engine to make it perform either more efficiently or to make it make more power in a general rpm area or to perform a certain task, via trail port, race engine, speed run,etc.
Most 2 stroke engines will get the exh port raised to some extent and some engines get it widened, the exh. port is where "most" of the power is made. The transfers and intake bottom side do account for power gain but not nearly as much as the exhaust side is in a 2 stroke. When ever you raise the exh port you "lower" the compression in a 2 stroke because the port is open longer and the piston must move up in the cylinder further before closing off the port to compress the air. This is why you have the heads remachined when porting a engine.
In a car engine you can change the camshaft to make your valves open further and longer, in a 2 stroke you move the ports,as the piston is the heart of the engine and controls the timing of the port openings, it moves the same amount of degrees up and down so by raising the portsor lowering them the piston is the device that opens and closes the port, just at a differnt amount of time.
Lamen speaking,by raising the ports your gonna raise the rpm, by lowering the lower the rpm in general.
More porting or bigger is not always better, if you go too far you can ruin the engines powerband for the desired rpm range, if you dont go far enough, well.. you dont gain that much from stock. You have to find the sweet spot for the intended purpose. This is where the builder has more expertise,they have ruined many test engines and had to redo lots of specs to get to a point where it does everything they want. If some builder tells you they have never burned down a engine or gone backwards on power before getting to the desired task/power level, find another builder thats honest.
Some engines respond better then others do to engine mods, they dont all need the same mods nor do they all respond the same. As in the example of the srx, it has room to gain power even with the stock pipes,stock carbs,stock timing/ign.system, but ,theres a limit on what you can do without adding pipes,big carbs, etc. The viper has even better stock port specs then does the srx so it gains "less hp" in the same typical "port" job because yamaha already beefed up the specs. On the other side of the note the sx or red headed engine gain the most because they were so undertuned from the factory with extremely conservative specs. So it matters what engine your trying to modify as to what your really gonna gain or accomplish. Its not always the port heigth or width alone, the radius and floor/roof contours must also be correct to take advantage of power gain, so sometimes it wont look like much has been done but its usually a case where the height or width was "ok" for the application but needed a bigger radius put into a corner of a port.
Porting a engine does not make it less reliable. If the compression ratio and jetting specs are suited for the fuel octane used it wont be any differnt then stock except make more power. Fuel mileage can suffer some with differnt engine/jetting set ups compared to stock though, but it shouldnt be drastic. Usually its the clutching change or pipes,etc. that account for the mileage drop from stock. With a snowmobile theres a give and take concept is about everything you do to mod them, you must give up 1 thing to gain somewhere else.
Just a general explanation, hopefully this will help explain to some,ask questions and get the work they wanted done for them. Modding sleds is fun but it can be expensive if you have to learn the hardway by going company to company before getting what you wanted. I have had numerous topends and then 2 complete engines done at a couple big names when I got into this modding/racing thing, they didnt perform . I spent relentless time tuning, its frustrating to say the least. Check around and see whats performing well out in the field , talk to the builder and then to consumers and base your decision off that.
Have a safe and fun sledding season.
Some places wont give ya the time of day without a credit card number. If thats the case your better off going to your next choice. The reason is, after the sale you want to be able to call and discuss any issues or support you may need to get what you want from the engine. The engine will almost always need a differnt set of specs after work has been done along with clutching to grasp the newly added power, basicly its all about customer service,and that truly begins after the sale!
Remember,its your money and it will spend the same no matter where you go!!
If you can do the porting yourself thats great, but what most people dont have in thier toolbox is the tools to accomplish the job. A 90 degree foredom tool needed to do the aux. exh. work and transfer work can cost $400 and then you need the drive system to power it, then carbide cutters,etc. Your looking at over $1200 worth of tools just to get started. Of course you also need the correct specs to set up the ports to. This is where the "cost" comes into getting engine work done. You also will need to remachine heads to get back the lost compression from porting the exh port.
(There is a company by the name of race logic who sells templates to help the do it yourselfer, they work well for a trail port. they have many differnt brand applications. I have personally used this company before when I first got into modding these triple srxs,on my 1998 srx700.)
"Porting" is simply changing the port timing of a engine to make it perform either more efficiently or to make it make more power in a general rpm area or to perform a certain task, via trail port, race engine, speed run,etc.
Most 2 stroke engines will get the exh port raised to some extent and some engines get it widened, the exh. port is where "most" of the power is made. The transfers and intake bottom side do account for power gain but not nearly as much as the exhaust side is in a 2 stroke. When ever you raise the exh port you "lower" the compression in a 2 stroke because the port is open longer and the piston must move up in the cylinder further before closing off the port to compress the air. This is why you have the heads remachined when porting a engine.
In a car engine you can change the camshaft to make your valves open further and longer, in a 2 stroke you move the ports,as the piston is the heart of the engine and controls the timing of the port openings, it moves the same amount of degrees up and down so by raising the portsor lowering them the piston is the device that opens and closes the port, just at a differnt amount of time.
Lamen speaking,by raising the ports your gonna raise the rpm, by lowering the lower the rpm in general.
More porting or bigger is not always better, if you go too far you can ruin the engines powerband for the desired rpm range, if you dont go far enough, well.. you dont gain that much from stock. You have to find the sweet spot for the intended purpose. This is where the builder has more expertise,they have ruined many test engines and had to redo lots of specs to get to a point where it does everything they want. If some builder tells you they have never burned down a engine or gone backwards on power before getting to the desired task/power level, find another builder thats honest.
Some engines respond better then others do to engine mods, they dont all need the same mods nor do they all respond the same. As in the example of the srx, it has room to gain power even with the stock pipes,stock carbs,stock timing/ign.system, but ,theres a limit on what you can do without adding pipes,big carbs, etc. The viper has even better stock port specs then does the srx so it gains "less hp" in the same typical "port" job because yamaha already beefed up the specs. On the other side of the note the sx or red headed engine gain the most because they were so undertuned from the factory with extremely conservative specs. So it matters what engine your trying to modify as to what your really gonna gain or accomplish. Its not always the port heigth or width alone, the radius and floor/roof contours must also be correct to take advantage of power gain, so sometimes it wont look like much has been done but its usually a case where the height or width was "ok" for the application but needed a bigger radius put into a corner of a port.
Porting a engine does not make it less reliable. If the compression ratio and jetting specs are suited for the fuel octane used it wont be any differnt then stock except make more power. Fuel mileage can suffer some with differnt engine/jetting set ups compared to stock though, but it shouldnt be drastic. Usually its the clutching change or pipes,etc. that account for the mileage drop from stock. With a snowmobile theres a give and take concept is about everything you do to mod them, you must give up 1 thing to gain somewhere else.
Just a general explanation, hopefully this will help explain to some,ask questions and get the work they wanted done for them. Modding sleds is fun but it can be expensive if you have to learn the hardway by going company to company before getting what you wanted. I have had numerous topends and then 2 complete engines done at a couple big names when I got into this modding/racing thing, they didnt perform . I spent relentless time tuning, its frustrating to say the least. Check around and see whats performing well out in the field , talk to the builder and then to consumers and base your decision off that.
Have a safe and fun sledding season.
Great and accurate info as always! I believe your time put into this will not go unappreciated. Articals such as this is what makes this forum so good and helpful to members at all knowledge levels!
Bob
Bob
I thought the same as I read this!
Thank you Sir... Much more clean now. Very good.
FJViper
New member
Great read as always! Your expertise is always appreciated no matter what your commenting on. Wasn't planning on porting my viper but this article certainly gave me some good insight into what goes into porting a 2 stroke. 
mopar1rules
Active member
Mrviper, don't forget to account for the expensive TSR software that's usually used and now unavailable, on top of the expensive foredom motor w/foot petal, that's powers each pricey handpiece. I got lucky and got my 90deg cc specialties handpiece when it was on sale for $345. Its one handy unit.
Thanks for the info, a well needed thread!
the problem is not the one who do the porting is the one who will run the engine and tune it ..........bad tuning result in big damage ...
patsxr700
New member
Great info!!
Had my Viper "Trail Ported" by MrViper, and I was very happy with the transaction, the suggested setup, and the customer service/advice after the sale. The above read, in my opinion provides a lot of insight into what is involved, for a "novice" to make an informed decision as to whether to get you sled ported and who/what to look for. Keep up the good work Don! 
SWEDE
New member
Thats a good read there Don!
the way ive always looked at it. engines are like an air pump. the more you can flow thru it with the required amount of fuel, the better the result will be power wise. then of course the correct timing to fire your newly aquired mixture. "in high compression setups that is" "otherwise if your just gaining back lost compression from porting through head work there should be no worries "spark timing wise" what it comes down to for the head "after you port" is the proper squish band width depth and clearance to get all that exta power in fuel mixture, as close as possible to the spark plug without predetonating in the squish band area "beause" of either low grade fuels or not enough clearance in the squish band on the cylinder head. im an expert by no means but i do a lotta reading. ha ha good thread.
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the squish band is the outer indented machined surface on the inside of the cylinder head. it has very minimal indented angle compared to the actual dome, where the spark plug is in the middle. its sole purpose is to help speed up and compress the mixture to the actual dome and closest to spark for a bigger better more satisfying, bang.
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