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  • Newbie Question.

    Hello all, First off I am not a machinist, but am in need of ones help. My father is a machinist, but doesn't offer his expertize to my "dumb" hobbies.

    I big into racing two-stroke engine motorcycles and am currently doing work on my engine for the up coming season. I have done a search to try and find the answer to my question but I have no idea what I was reading was correct or not as I am not familiar with most terms used in this forum.

    On to my question... I want to put a boost port in the inside of a cylinder bore. Boost port is basically a slot in the cylinder bore which MUST stop with in the cylinder bore, NOT all the way thru it. Please see pics below for clarification.





    Question #1: Can these be done with a Drill Press?

    Question #2: If so what is the name or what kind of bit do I need to use to accomplish this task.

    I imagine it would have to be something that not only cuts on the sides, but must be able to "plunge" down into the bore.

    All help and suggestions are much appreciated. Thank you for your time.

    -Nick

  • #2
    First off, tell your Dad that another Dad says he is LUCKY to have a son who NEEDS his help and expertise. It sounds like you would accept it ???

    That slot can be done on a milling machine by plunging with a ball end mill.

    It could be done on a drill press if you had a solid rod which fit into the bore (or could be shimmed on one side). You could then drill thru the rod and the cylinder bore since the drill is now supported all around its diameter. Use a similar material for best results.

    You can also make fake keyways this way but not for high power use. Den

    [This message has been edited by nheng (edited 02-07-2005).]

    Comment


    • #3
      It might be done on a drill press if it's solid enough and the bearings are good. I'm not sure if you want a flat bottom or rounded; I assume rounded would give better flow, in which case you'll want a ball end mill, as nheng says. Check out www.mscdirect.com for end mills. A good one is expensive, but it may be worth the money because it will give you maximum chance of a clean cut. You might get by with doing it just in the side of the cylinder, with no filler plug, but the suggestion to fill the bore with an aluminum plug so the end mill is supported on all sides is a good one.

      If you do this, you will need to clamp the cylinder SOLIDLY to the drill press table so it WILL NOT MOVE. For goddsake do NOT try to hold it in your hand. My apologies if you already realize this....
      ----------
      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie

      Comment


      • #4
        I thank you all for your quick replies.

        nheng: I certainly would appreciate my fathers advice but unfortunately, he is neither interested in or has the time for things that I am into. I had asked him on numerous occasions just to tell me what the name of the bit, but no reply. Though I greatly appreciate you helping me and giving me the info I need.

        SGW: HAHAHA yes I know to secure the cylider in a vice before drilling. Thanks for looking out for me though.

        I am not sure if I will be able to get my hands on a 44mm Dia. Plug, so I may try it without on one of my old heads, just to see how good it does with out it. I was also looking on that site that you posted SGW and I noticed a cutting length spec. for each bit. Does this matter? Because the longest I seen was 12mm and it is going to have to go at least 30mm - 40mm into the bore.

        Again Thank you both!

        Comment


        • #5
          (I can't see your pictures here at work)

          But: I should mention that many cylinders have special linings. nik-a-sil plating, hard chroming, etc.... that may make it very hard to machine, or if you do cut through it it may start flaking off badly where cut.

          I'll bet that your cylinder will need rebored "one over" afterwards so plan on that. In fact, weather your cylinder is re-borable or not will indicate weather you will be able to do this or not. if it can be re-bored it isn't plated.

          I don't know where you heard about this boost port but it sounds hokey to me. very likely the product of a bunch of hype and no science. many such "hot tricks" are just that.

          good luck,

          Dan

          Comment


          • #6
            Bikoholic,

            I'm with Den on this one. To go that deep, I think you will be better off plugging the bore with an aluminum billet, and using a drill. There are longer end mills on the market, but I would be wary of tool deflection with that depth. How close do the tolerances need to be? I'm assuming it isn't real critical. I would guess that these ports are simply designed to increase the displacement of the engine without going to a larger bore. Good luck with the project, and if you need more help, just ask. There's a good bunch of really smart people here that love to help.
            Arbo & Thor (The Junkyard Dog)

            Comment


            • #7
              As long as the cutting diameter is larger than the shank diameter, you can go deeper than the flute length. For instance, you may be able to get a 1/2" diameter end mill with a 3/8" shank, or whatever. Then you can cut deeper than the flute length...assuming there is shank length below the chuck! I haven't looked to be sure, but I think you ought to be able to find some "extra long length" end mills listed in that catalog that may do the trick.

              What diameter are you talking about here? Since apparently your cylinder is 44mm, or about 1.73", you may want about a 3/8" dia. cutter for the ports?


              If you can find (or make) a close-fitting plug for the bore, you could probably do this with a drill, assuming the plug material is similar to the cylinder's so the cutting characteristics are about the same. An end mill will tend to wander less though.

              ----------
              Try to make a living, not a killing. -- Utah Phillips
              Don't believe everything you know. -- Bumper sticker
              Everybody is ignorant, only on different subjects. -- Will Rogers
              There are lots of people who mistake their imagination for their memory. - Josh Billings
              Law of Logical Argument - Anything is possible if you don't know what you are talking about.
              Don't own anything you have to feed or paint. - Hood River Blackie

              Comment


              • #8
                SGW 3/8" Dia is 9.525mm So yes You are correct I was planning on doing a 10mm wide boost port. The pictures I have posted show 2 of the parallel to each other, though I am only going to attempt one.

                You are all correct in assuming that it doesn't have to be dead accurate, I would say a 1mm tolerance is allowed. The most important things I have to worry about is to not go too deep into the cylinder wall that it breaks through. The 10mm width is not a factor to worry about as that distance isn't close to coming to the Ring openings. The Biggest Factor in doing this is how deep I go down into the bore as this affects port opening and closing Duration (usually measured in degrees of the stroke)

                dsergison, you are right the inside of the cylinder is nik-a-sil. As I have done a lot of chamfering and small porting on these I have never had a problem with the finish flaking. The important thing is that after all porting is done to go over and make sure all port edges have a nice .5mm chamfer. This not only keeps the finish from flaking, but more importantly the piston rings from catching on an edge. And I can see by the cheesy name "BOOST PORT" how one would think it is a bunch of hype. As Arbo said, it sort of is a way of increasing displacement without really doing it, and they are a Big Part of two-stroke engine performance and Tuning. They're purpose is to simply bring in more Air/Fuel Mixture into the cylinder.

                Most porting on these are done with a dremel and Tungsten Carbide Bit, but as you can imagine it is kind of hard to get a dremel way down in the barrel and still do a clean job.

                Comment


                • #9
                  Since there doesn't seem to be anything magic about 10mm, you might look at the 3/8" dia. ball end mills, which will give you a much wider selection. For instance, this http://www1.mscdirect.com/CGI/NNSRIT...PMPXNO=2137687 one might do it.
                  ----------
                  Try to make a living, not a killing. -- Utah Phillips
                  Don't believe everything you know. -- Bumper sticker
                  Everybody is ignorant, only on different subjects. -- Will Rogers
                  There are lots of people who mistake their imagination for their memory. - Josh Billings
                  Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                  Don't own anything you have to feed or paint. - Hood River Blackie

                  Comment


                  • #10
                    Don't clamp your cylinder in a vise, clamp it down to the table. You'll want to hold it quite solidly, but you don't want to put a big squeeze on the bore.

                    Finger ports/boost ports etc have been done for years with die grinders and even riffler files. It is interesting to see the tracks when the burr in the die grinder catches and makes a couple of circuits of the bore!

                    You could also do it with several passes from a very small flycutter which you could make by brazing a tool bit on the end of a steel bar. Or buy a premade boring bar of the right OD and use that.

                    If I did one I'd probably just use the endmill, but I'd want a very sturdy drill press in excellent shape if I wasn't going to use a milling machine.

                    This looks like a case-reed machine that you are adding extra transfer area to. What is it, a 250MX bike?

                    cheers,
                    Michael

                    Comment


                    • #11
                      <font face="Verdana, Arial" size="2">Originally posted by Michael Moore:

                      This looks like a case-reed machine that you are adding extra transfer area to. What is it, a 250MX bike?

                      cheers,
                      Michael
                      </font>
                      The drill press I will be using is brand new, got it for christmas and have only used it once so far. And you are right it is a case-reed engine. Nothing real fancy to them, believe it or not they are only 50cc Motorcycles no bigger then a weed wacker or chainsaw engine really. But we've got them going up to 65mph.

                      Comment


                      • #12
                        wow. I see the pics now. just a drill press? dang. if you could fill the cylinder with an aluminum slug and drill it that would be great. But you don't have a lathe.

                        I think you drill press will not be up to the task of milling the slot at that reachout. it will not handle the sideload.
                        (But I'd try it anyway

                        you may try and grind or burr the slots with the drill press. They make long stout carbide burrs for port work. I think I have one 5" long.

                        just maybe if you take many small bites you can do it with the press at max rpm.

                        of course any failures and it will be ugly.

                        Comment


                        • #13
                          It would likely be Really Good if you could practice this on a junk cylinder before you do it for keeps.
                          ----------
                          Try to make a living, not a killing. -- Utah Phillips
                          Don't believe everything you know. -- Bumper sticker
                          Everybody is ignorant, only on different subjects. -- Will Rogers
                          There are lots of people who mistake their imagination for their memory. - Josh Billings
                          Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                          Don't own anything you have to feed or paint. - Hood River Blackie

                          Comment


                          • #14
                            I'd like to add a little to all the good advice above. Never run an endmill in a drill chuck. Also forget about those wimpy 2 strokes. Use a H-D Shovelhead, a 5" stroker ought to do it. It might be a little heavier than you want, but the nitrious will make up for it. You will be the envy of all the mini-motos. Seriously though, be careful and double check every set-up before you turn your machine on. Things go bad mighty fast in the machine trade. Good luck, Smitty
                            Smitty.... Ride Hard, Die Fast

                            Comment


                            • #15
                              Nick, a buddy of mine took a Derbi 50 to Bonneville this summer. Unfortunately he failed to run all of his plans past me and therefore he wasn't as prepared as he should have been.

                              If you have a Derbi there are race-kit cranks, pipes, cylinders etc available.

                              It's a cute little engine, though the chassis is way more than is needed for an LSR bike. I thought about picking up an engine to build a bike around as I like small motorcycles, but I already need to get rid of about 10-15 bikes just to get down to 10 or so, so I've not acted on that impulse.

                              Riffler files may be slow to remove metal, but then again they have the advantage of removing metal slowly, if you get my meaning. You'd probably be better off roughing the finger ports with your die grinder and then filing them to final shape instead of messing with the drill press.

                              cheers,
                              Michael

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