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Neway valve seat cutters

Discussion in 'Mechanical & Technical' started by Ryanthegreat1, Oct 9, 2008.

  1. Does anyone have any experience with the Neway valve seat cutters? Maybe some of you eat through the valves in 20 hours 4 stroke MX guys have experience?

    If someone could give me some insight as to how adjustable they are for valve size and how cleanly they cut that would be excellent.
  2. i have a few sets and that is all i use. if you have no experience using them or any seat grinders, i suggest buying shitload of old scrap heads to practice on. cutting valve seats is an art that is learned over years. a novice user will probably wind up fucking up a few sets of seats using them.

    you need to buy cutters for whatever size seats you have. they will adjust up to 10mm +5/-5 either direction but if you choose the wrong size cutter for the job and it hits around the chamber before it hits the entire seat, you will have serious problems.

    if you are doing mx smaller than 20mm there is a mx style multi valve kit. i would probably opt to use a 46degree for your sealing angle cutter instead of a 45 degree is it is a slight interference fit. titanium valves found in modern mx stuff is hard on seats. the slight interference angle will peen over and seal much better over time.

    a hint on making valves last longer on the mx stuff is to adjust them about .001" looser than factory spec. so many of them run tight after a while that the true destroyer of the seats is scorching from the valve not seating all the way when the clearnaces get tighter from the titanium valve peening the seat in even more.

    now the cut on those things is perfect. even better than stones. carbide steel cutters will not lose the angle like stones do and do not require dressing. stones clog and when they do, they casue uneven cuts and small metal particles burnishing onto the seat. at a microscopic level, they are high spots that cause leakage. the neways leave such a good cut you really dont need to lap them in but i always use fine compound to give them minor lapping just to see where they are seating on the valve. if they are centered on the valve, you will see it. it also allows you to see the width of your primary cut on the valve.

  3. Thank you for the awesome information.

    So you say they are adjustable in size +/-5mm. Hmmm...

    So then If I am looking at a cutter that is 19mm to 39mm with the carbide bits at the smallest setting the max diameter of the cutter would be 29mm? This would be very helpful in my particular application with some tight port shrouding in areas.
  4. well you could move the cutters even further out but then you wont have a lot of it seated on the cone and it could cause an uneven cut or hit the combustion chamber if there is a lot of shrouding in the seat area. once the cuters are more than 1/4 off the cone, you need to go to the next larger size.

    just keep in mind that those things remove stupid amounts of metal with one cut. dont put a lot of pressure on them and go 1 turn at a time and measure the seat width each cut until you get the hang of how much each cut takes off. it is all to easy to pocket one too deep or too wide. also clean them after each cut. just brush off the cutters before taking another cut and you will get a much nicer seat.

    also, do not use the adjustable pilots. get pilots for every size and also get one in .001 over in case you have a slightly loose guide. it is very important that the pilots fit snug and botttom square with the guide or the cut wont be concentric.
  5. Bubba: So far you have been way more helpful than anyone else combined with three days of internet research. Seems like no one wants to share the secrets of the valve job.

    So I have a final question before I pull the trigger on these bad boys.

    They list a body size for each cutter. I assume this is the size of the aluminum body that holds the carbide bits. For example one cutter I am looking at has a body of 31.6mm. Can the carbide bits then be adjusted in far enough so that they do not extend past the 31.6mm body?
  6. no, the body will be a bit larger once the blades are in place. so your minimum cut will be the body size plus the height of the blade which would be around .5mm protruding from the body.

    just remember that it is a cone and whatever the body diameter is will be the max size measurement. so the cut can be as little as the small end of the cone diameter or as large. if you stick a 31mm body in a 20mm seat, the tip of the cone is what is doing the cutting. if you stick it in a 25mm seat, the middle of the cone is doing the cutting.

    you want to find a cutter that closely matches the exact size of your seat.

    FYI i am a retailer for those things as well. there is a multivalve mx kit that will do 90% of all japanse multi valve mx engines. you will need all 3 angles and that kit covers all your bases. the cutter for the primary cut is 46 degress and then there are several others for the inside and outside angle.
  7. You sell these tools?!


    Do you stock them?

    I believe what I am after is a 6.58mm solid guide and cutters to support valves of 37mm and 32mm. I was thinking I would go with 30*, 45* and 60* as per the service manual. Plus I hear the 46* is an interference fit that is hard on coated valves.

    The part numbers I had in mind are:
    And one of the tools to turn the cutters either the Ez thing or the t handle.
  8. no they are by special order only and they are in kit form only. the kits are the way to go as they have taken out all the gueswork for what cutters you need to do mx bikes.

    the 45 is fine, i prefer the 46 even with titanium valves. the valves are way harder than the seats to begin with so it is not really hard on them. the biggest problem most mx heads suffer from is the seats peening, then the valve clearances run tight and valves get a bit crispy.

    if you ask me the titanium valves are crap. the only reason to run them is for higher rpm ceiling. stainless valves last much longer but becasue they are heavy they need a stiffer spring to control them and of course that robs hp.

    at any rate, if you need single cutters, goodsons is a good palce to buy them from. i can only get you whole kits from my distributor and they are pretty pricey at around $1000. but you will be able to do almost all mutli valve heads including a lot of sport bike stuff.
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