Home brew YT175 Porting / Reed upgrade

[RubberSalt]

Picked up a yt175, the rod bearing went out and that was it. bought another engine, had a spare piston/cylinder at that point.

Didn't have much to loose, my trike ran pretty good, but i wanted more power. So i took my trust dremel to my spare cylinder, and bam, more power... after 20 hours of work.

After everything was said and done, I would honestly say, I doubled the power.

More Information in following Post!
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After:

[RubberSalt]

Tools list for porting - if you have better ideas, let me know!
Rotary tool(dremel)
Flex tool - This for dremel
Bits for rotary tool: HSS cutter, Green Grinding stone, Sanding bands, Diamond tip burr bits, Collets
Files - Variety of sizes
Sand paper - 220, 400, 800 grit
Depth Gauge
Calipers
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Most 2 stroke engines that are ported have 30-35 degrees of blowdown. This is the duration, in relation to the rotation of the crank, that the exhaust port is open before the transfer open. To much blow down and the exhaust gasses lose velocity and don't help pull the new charge in. If there is to little, the engine will not remove all the exhaust gasses. This results in less air/fuel entering the cylinder

This is my recommended port job for dune riding for the yt175. This provides power all around, most of it is near the top of the rpm range, 6000-7000rpm on stock pipe. A trail port is listed also, the process is similar with less work. It will provide more bottom end than my dune porting.
Stock port info:
Exhaust - 155 degrees
Transfers/Intake - 118 degrees
Blowdown - 18.5 degrees

Desired results - Dune riding
Exhaust - 192 degrees
Transfers/Intake - 124 degrees
Blowdown - 34 degrees

Trail Port - my trail port for the 175, dunno bout other machines. I ran this before i opened it up to the 192, this gave a ton of power, but nothing like my dune porting with triple exhaust.
Exhaust - 178 degrees - Raise 4.10mm and square the port out similar to the transfers. Polish to a mirrior. - no triple exhaust.
Transfers/Intake - 120 - Follow guide below, only raise .3mm
Blowdown - 29 degrees

This is all at your own risk, if you gouge to the cylinder, it probably will be fine, but I'd recommend a bore job first. 1mm can equal more than 4degrees on a 50mm stroke!

Step 1, Remove head and install degree wheel on flywheel. Locate bottom dead center(BDC)

Step 2, Exhaust
*1983 cylinder - raise exhaust 7.18mm
Use the degree wheel and find out when your exhaust is opening and closing. Mark it 84 degrees before and after BDC. Score cylinder above exhaust port where piston is located. This is where you will raise the port too.
Using the rotary tool, raise the exhaust port to the line made earlier. You'll want to square the port out, make sure there is rounded edges, similar to the transfers. Widen the exhaust port by 3mm on each side.
Match the exhaust up to the gasket at this point
Polish your exhaust to a Mirror finish with sand paper. This helps prevent carbon from building up.




Step 3, Transfers
*1983 cylinder - Raise transfers 1mm
Mark the degree wheel 62 degrees before and after BDC, score the cylinder above the transfers at 62 degrees. Raise the transfers to this line.
Looking at the base of the cylinder: You'll notice that the cylinder wall hangs below jug nect to the transfers. Cut/grind this wall out so that you can lay something across the transfers, 1 side of the jug to the other.If you can find pictures of the IT175 cylinder, youll notice what i'm talking about. Next, the casting next to the sleeve is rough, smooth it down until you cannot catch your finger nail on it.
This video and this video are very good examples of what needs to be done
Leave rough, do not polish.

Step 4, Intake
*1983 cylinder - Raise transfers 1mm
Mark the degree wheel 62 degrees before and after BDC, score the cylinder above the transfers at 62 degrees. Raise the transfers to this line.
Widen the intake port 4mm on each side.
Looking through the intake, you'll see a wall of metal on the top. Smooth it down until it's a ramp and not a wall.
Make the gap between the 2 holes skinnier. Match it up to the piston.
Raise each intake hole 2mm
Lower each intake hole 2mm
Leave rough, do not polish.

Step 5, Piston
Do not go past reinforced walls on piston. Reinforced parts are visible from inside before the ports. Below is a safe limit on each piston
*OEM Piston only! Raise the each port 2mm and widen by 2mm. Do not remove or make bridge between ports smaller on piston.
*Wiseco piston only! Raise each port 2mm and widen 3mm
Line the piston up to the bottom of the sleeve. Match the cutaway in the sides of the piston to the cylinder. Removing material from cylinder to match piston and vise versa.

Step 6 - VERY IMPORTANT
Chamfer(taper/bevel) ALL Ports, including piston. Run a finger over each port, if you feel a sharp edge, it semi-sharp, you need to bevel that port more. This includes the sides of a port. Rings will catch a sharp port. If you plan on boreing the cylinder after the port job, then you need to chamfer them again after the bore. Do before and after. It makes life easier if they have been done before you bore.

Extra credit! Triple port exhaust and intakes - go from 8 port to a 12 port design - These are not easy and not recommended unless your confident at doing this.
Triple exhaust - Take a drill and poke a hole right above the transfers. Take a long skinny bit and drill a hole beside the cylinder directly to the 1 above the transfer. This is tricky and if you mess up.. youll need to get the cylinder welded or tossed in the trash. The tops of the triple exhaust needs to meet up with the top of the main intake. You can shape this square or circular, i kept mine round because i am lazy.
Boost ports for intake - Take a drill and go from the intake walls near the bottom corners to the transfers, the closer to the bottom of the transfers the better.Do not drill through the base of the cylinder, If you do this, you may need to port your crank case out. Then youll need to match the case to the cylinder.

http://www.youtube.com/watch?v=x0kRsYzg5g8
http://www.youtube.com/watch?v=fdb_8...=youtube_gdata

[bcredneck]

did you do any reserch or use a program first or did you just go at it at random if you did it at random and got more power you should go run out and buy a lottery ticket

[RubberSalt]

I did more than my shareof research. Then I spoke with HPD, flowtech, AAEN and a few other guys also. Flowtech gave me information that actualy came close to what i had. They gave me what is conidered a good trail port.. Then i added a little more to it , I'm currently adding a guide on how, mostly done with a dremel and a degreewheel.

Main portion of this goes to testing and experience.
I did research before doing any port jobs.
The first ported cylinder was really fast.. but like a light switch, all or nothing great for dune riding. This was based of pictures found on the net, I knew enough to be dangerous. power reeds, fatty pipe - blaster
The second had more bottom end, more mid range, and a CRAP ton of top end. The last 1 i did made the machine(blaster in this case) scarey fast. Based of the same pictures, but took my time measuring everything. pro series reeds, fatty pipe- blaster
No more guessing after this point, now we are using math, science, ect.
The third, is scary fast, hit the power band and wheel comes off the ground. - haven't checked the higher gears it's to cold. - carbon fiber reed petals(home made), 34mm carb, stock pipe - YT175
The fouth, worked patiently, spent a ton of time on it. The pictures of the polished exhaust are of this cylinder, You can lug it around in 3rd gear, hit the gas and hit the powerband in 40 feet or so, wheels come off the ground and stay off, once again.. too cold. fatty pipe, pro series reeds - blaster, this cylinder is not done yet, fitting cr125 reeds to it.

The fifth, fitting blaster reeds, going to spend more time on the intake and transfers, if it improves over current cylinder, i will update. if not.. well atleast blaster reeds fit:-p

[RubberSalt]

This involves shaving the intake walls and the walls of the reed cage down. Youll also need a spacer.

A yamaha Blaster reed cage is needed. They never changed between the years, so they all will work.

Using a file, remove material evenly as possible from the sides of the reed cage until your about .5mm from the edge of the petals at the tip.
Now remove material from the sides on the intake walls. I recommend using a file, but i cheated and used a highspeed cutting bit. Remove a little material from 1 side then go to the next. Keep doing this until the reeds fit! . Now i forget the measurements of everything, but its seems to be aboue 3mm or so removed from the intake walls. Keep checking until the reeds fit most of the way.

You'll also need to round the edges of atleast 1 side of the base of the reeds for it to fit the yt cylinder. This is shown in the pictures below

Once the reeds are all but 12mm in, you'll need to make a spacer. Make a gasket for the intake first, then trace that on to some thick aluminum or steel - what ever your using for a spacer, then cut the material to the shape of the gasket. Drill holes for the screws into the reeds and spacer. Make gaskets to go between cylinder and spacer, then spacer and reeds, then reeds and intake boot... and your done!

I'm not finished with mine, but here are some pictures of the work and the sizes of stock(1983 big version) vs blaster.

[bcredneck]

have you ever seen the yamaha port book they made one in the 80s for all 2 stroke yamies over 125cc some one should scan it and put it on this site the only reason i aksed if you did any research is ive seen people just go at it and end up with a powerband about as wide as the tip of a needle

[RubberSalt]

Yup, on my 5 cylinder, each much better than the last. Most people are just scared to port, they don't fully understand what is going on... yet i do Thats why all of mine work. If you want to go faster and have everything at the top end, you can raise the transfers to 130 and the exhaust to around 205. The bike ends up more like my first 1, a light switch, but everything is at the top end. If you want that, then you might as well get a drag pipe. Not as fun as the other porting.
The setup i use is based more off of the trail port givin by flowtek. Most of the power is at the top, but alot is retained in the bottom and mid range. I'm sure if i had a pipe to go with mine, i would be a differnt story, ore power everwhere:-p. It currently works wounders in the sand

[Bretmd94]

Now I understand enough about 2 strokes to know that there are insane things involved when it comes to pulling the fuel/air into the cylinder, and porting requires research like what you have done above.

But what about 4 stroke? Like say, a 200x? Is it safe for me to go at the intake and exhaust ports with a dremel and clean them up a bit?

[bcredneck]

i got the book but it starts at 250cc im going to post it on a differnt thread tons of info cant belive i found one

[bcredneck]

and on 4 strokes you sand the intake port with 600 grit and polish the exaust port

[Ironbnder]

Now I understand enough about 2 strokes to know that there are insane things involved when it comes to pulling the fuel/air into the cylinder, and porting requires research like what you have done above.

But what about 4 stroke? Like say, a 200x? Is it safe for me to go at the intake and exhaust ports with a dremel and clean them up a bit?

Any casted metal that controls air flow could be cleaned up a bit to improve flow. BUT, the big trike manufactures have done way more research than any of us could have imagined and it is how they think it should be. There are many upgrades to be done to your X before you take a dremel tool to your head. Rubbersalt must be very talented and brave to accomplish what he did.

[RubberSalt]

There isn't to much to be gained in a 4 stroke. Remove extra castings, match the material up to the exhaust gasket, polish exhaust. match intake port to intake manifold... thats about it that i would do, i haven't done to much research on 4 stroke porting. I'd look else where for improvments on a 4 stroke first. cam, head milling, valves, ect.

BUT, if you like the top of your powerband more than anything, you can get a fatter exhaust and widen your intake. They allow more air/fuel at high RPM, but the air/fuel losses velocity at lower rpm and can hurt power.

[Bretmd94]

Any casted metal that controls air flow could be cleaned up a bit to improve flow. BUT, the big trike manufactures have done way more research than any of us could have imagined and it is how they think it should be. There are many upgrades to be done to your X before you take a dremel tool to your head. Rubbersalt must be very talented and brave to accomplish what he did.

Yes, but they also design the heads to be produced in large quantities and as cheap as they can with out compromising the product. They probably did it all on paper too, I don't think CAD was very far along in 83. I also doubt that they designed the intake and exhaust for top end power in the dunes.

And yes, I am preparing for a full build on my 200x motor. There is already a cam sitting on my workbench, an exhaust hopefully in the works soon, a xr or aftermarket 10.5:1 piston coming soon, and I am planning on probably using an xr 27mm carb and intake boot.

It would be nice to match the intake to the boot if there is any difference, but I really was just wondering if the 4 strokes were less touchy so I could go farther than just cleaning up the stock cast surface. But I understand that some dummy with a dremel shouldn't attack his head.

[bcredneck]

4 stroke porting is damb near idiot proff if you do some reading

[RubberSalt]

I started out being brave, then i just got more talented :-p

Porting isn't as scary as it sounds, but if you have a yamaha blaster or a yt175 and want it to go fast, send it to me with some cash and I'll make it go fast:-p

When it came to the reeds, i was honestly ready to patch the walls up if i had too lol - all the measurements came out to the point it would work.. but i had doubt. In the end, they fit! and with plenty of room honestly. I could go without a spacer, but spacers help increase the velocity on the intake and give a little more torque.