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  1. #1
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    Beginning my journey into porting

    Hey everyone! I am starting my journey into learning porting and I am wondering what are some mods you guys recommend for a beginner to start with? I will be porting a 470.Name:  IMG_0753.jpg
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    I'm not a 460 guy, but I do know you should match the piston skirts to the transfers.

    In general:
    Lower the intake, raise the exhaust. Widening the exhaust is also an option.

    Really, most guys do not like to release this kind of info in detail. A lot of people have learned from endless trial and error and tend to hold out on what they know works. Really, you can't blame them.
    Hell Fab

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    Yeah I get it. At the same time I don't. I am always happy to help anyone out with anything I know that may help. Ohters I know aren't. Same thing in the machining industry. A lot of old timers hate giving anyone advice. Some tool makers go as far as to cover up what they're working on with shop rags. They're gonna take that knowledge and their tool box to the grave with them i guess. I personally find that attitude lame. I have been reading the jennings tuning book over the past couple days and it's given me some ideas If you don't mind me asking what do you mean by matching the skirts to the transfers?
    Last edited by Drunkenpedrider; 08-13-2017 at 01:46 PM.

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    When you match the piston skirt to the transfer ports, that means that you are making the window on the bottom of the skirt (half moon rectangle cutout on either side of the piston) the same width as the transfer ports on the cylinder (the 2 channels on either side, 2 exhuast and 2 intake which I believe are called auxiliary ports) . From the factory the piston skirt is narrower than the transfer ports on the cylinder, measure the transfers or put the piston in the cylinder and mark the piston with a sharpie (less accurate way), and take the material away to make them identical to each other. I also raise mine just a tad but for your first port job I would just stick to matching it to the transfers.
    Gsr40/46 full mod, Gsr40/60

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  6. #5
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    dremel 4000 is one to start with. That thing will make things more difficult to port with.
    Quote Originally Posted by Ogre View Post
    I knew I was forgetting something, LUUBE!!!

  7. #6
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    Actually it's great. It gives me great control of my speed, plenty of torque at low speeds, and it isn't so bulky in hand as a hand piece plus the heat isn't in my hand. I been practicing with it.

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    Quote Originally Posted by Pushinit View Post
    dremel 4000 is one to start with. That thing will make things more difficult to port with.
    ++++++++++++++++++++++++++++1 !!!!!! A good variable speed Dremel tool is a must. I personally have the 3000 and love it. However if you are more comfortable with your equipment that will be fine. I actually ported an ADA 460 headkit and matched the piston for someone today using the dremel. Turned out great!!! Does over 50mph. Maybe when we pull it off later on to check it I can post a few pics of it to show you.
    Gsr40/46 full mod, Gsr40/60

  9. #8
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    It's a dremel 9100

  10. #9
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    You're gonna want a slimmer head on that Dremel. That thing looks bulky which will make it difficult to get it into the cylinder.

    Also, read books. There are quite a few books out there on porting. Many links have been posted on BB. I even wrote a basic reed porting article a few years ago. In today's scene, there is no shortage of information on porting, unlike how it was 10 years ago.
    Some people will say that the information in some of the books is useless just because the books are old, but those people never actually read them in the first place. Plus 2 stroke engine design (specifically the weed wacker engines that Go-Peds use) has not really changed much in the last 10-20 years...

    Also many people who guard their "porting secrets" usually don't actually have anything interesting to show. The guys who know their shit will usually share more. The people who know less usually are more guarded. That's been my experience.

    But seriously, read a book. It will be more valuable than any half assed information you can scrape from an internet forum.

    edi: I see you've been reading Jennings' book. That's a great start. Look at Bell's as well. With those two alone, you should be able to figure out how to build a decent engine in your first go.
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    Thanks BC! And yes, I will order a slimmer hand piece. I already factored that in because this one is indeed pretty bulky.

    Your guide was the first thing i read and that's what basically got me wanting to try it on my own 🙌

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  13. #11
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    Also another thing, there is a program that you can get from porting software . com. There was I guy I spoke with who used that software to calculate what port timings he'd need to hit certain benchmarks that he was going for with his 460. It seemed like the software did a good job in terms of helping him figure out his port maps because, from his description, the engine ripped pretty hard. I must add the caveat that I never saw this engine in person though and haven't tried the software myself, but it might be something interesting to investigate.

    Oh and one thing that is lacking in some of the 2 stroke books is a chapter on modern fuels. By moving to E85 or something like that you can unlock quite a bit more power from these engines, so that's something I'd recommend looking into when you're experimenting. E85 is easier on your gaskets and stuff vs methanol so I'd start there. You should still purge after use with gas, but Cale (Calius Optimus) has come up with a really cool solution to make purging easier (he runs a second baby tank to a T-valve that allows him to switch between his alcohol tank and his gas tank).

    Finally, sometimes DDM sells used cylinders. At one point there were selling CY29 top ends for 20 dollars a pop. I bought a bunch of those and used them as a platform to test out porting specs. It was a great way to learn, so I'd recommend keeping an eye out on DDM's stock since every once in awhile they'll have a deal like that.

    It's always great seeing someone new get into porting . Honestly I feel like anyone with a steady hand can get pretty good results if they're willing to do some research and reading on the topic beforehand.
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  15. #12
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    I feel like i should start just trying to make my tranfers a bit more dynamic like more sweeping arcs and such first. Maybe Raise exhaust? I am running tscr47 with a wj71 and it runs great once in the pipe but the mid is very average. And opening the trottle at a stand still is very tricky when trying not to bog the hell out of it. I thought porting it out will help. I am running VP c14 and Q16 as far as fuel. Haven't thought about alchy. I was gonna try a 17:1 dome with the Q16

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  17. #13
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    Quote Originally Posted by Depths of Hell View Post
    I'm not a 460 guy, but I do know you should match the piston skirts to the transfers.

    In general:
    Lower the intake, raise the exhaust. Widening the exhaust is also an option.

    Really, most guys do not like to release this kind of info in detail. A lot of people have learned from endless trial and error and tend to hold out on what they know works. Really, you can't blame them.
    I tried raising the exhaust on a 460 once. Even a 0.02" change was a huge mistake. The 460 is way over-square (1.27:1 IIRC), and over square 2 strokes are very sensitive to exhaust timing. A bit of widening should be fine. If you really want to change the timing, do all of your other port work, ride it, then go back in there and change the timing. That way it should be obvious if you went too far.

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  19. #14
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    Cale is right.

    On 460s it seems like the transfers are the limiting factor so you have a good idea there. If you can increase your transfer time area with some eyebrows that will definitely help the engine breathe better. I never usually mess with the exhaust timing on 460s although I will widen the port quite a bit. You can actually cut out a bit of the bottom of the port to make it more oval; this won't lower the exhaust port since you're only reshaping the port, but it gives you more area since th port is shaped like an upside down triangle in the stock configuration.

    If you wanna start with a piston ported 460 then cutting eyebrows on the transfers and trimming a bit of the intake side piston skirt to increase intake port timing is a decent place to start. Just be careful with the intake work since the longer the intake port open duration, the further up in RPMs you shift your peak power which can result in a laggy bottom end. This could still yield an engine that has you passing all the other fools at top speed on big rides though, haha


    edit: Ideally, if you're patient and you have the time, I'd recommend just changing one thing at a time, then running the engine and seeing how you like it. You can always cut more material away, but once it's gone, you can't put it back.
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