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Educate me on performance engine mods

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  • Educate me on performance engine mods

    As the title of the thread says, educate me on building a performance engine. What are the parts that would go into building a strong motor - not unlike what Hord used to do... I realize parts are becoming harder to source but humor me.

    What pistons? What coatings (if any)? Valve springs? Best cams (probably Megacycle). On and on - what does it take to build a great Hawk engine?

  • #2
    For an uber-build follow Matt Bashfield’s recent build.

    for a “basic” built motor the one thing I will add is that you’ll want to upgrade at least 2 of the 4 clutch springs to heavier ones when you add power.
    Flock of Hawks | '13 Tacoma | '69 Falcon (currently getting reassembled!)
    I've spent most of my money on women, beer, cars and motorcycles. The rest of it I just wasted.


    • #3
      Originally Posted by JackalHack
      As the title of the thread says, educate me on building a performance engine. What are the parts that would go into building a strong motor - not unlike what Hord used to do... I realize parts are becoming harder to source but humor me.

      What pistons? What coatings (if any)? Valve springs? Best cams (probably Megacycle). On and on - what does it take to build a great Hawk engine?
      Man we need Hord to check in on this thread. But like all experts, he’s going to give out a “that depends” answer:

      What do you want, a street motor or race motor? Do you want max power, reliability or somewhere in between?

      As an engineer, I study the topic. I both build my own engines and hire them out to experts (when I can). I went with Hord because I agreed with his philosophy which I would say is “maximized reasonableness”:
      • Adjust the limiting factors of the engine to increase performance (increase bore, increase intake valve size, bigger cams)
      • Do not move away from the core architecture of the engine to make it something it’s not (no short/long stroke, no custom cylinders, etc)
      • Focus on power quality, not big numbers.
      From today, the biggest struggle will be fitting bigger intake valves. A machinist who is expert on this topic needs found. If you go the big valve route, things get complicated, because you can make enough power that reliability comes in. If you stick with stock valves, the formula is simpler.

      I do want to give a shout-out to a Blashfield who has made some badass stuff, but that said, it’s barely a hawk anymore given the number of parts left on his bike that actually came from Honda!


      • #4
        My Hawk is not competitive on the track - partly rider problems but partly power problems... While I am mostly a back marker on the track, there are Hawks that are out front also. Mine is still bone stock engine and carb. Rules allow 2mm overbore and some decent tuning. I am being munched up hills like between 10 and 11 at Gingerman Raceway or 8 and 9 at Roebling Road. Clearly that is a power issue. If Hord was still in the biz, I would be selling a kidney to fund an engine from him...

        My skills need some honing too but I think that being able to understand what goes into a great race engine is knowledge worth acquiring.


        • #5
          The Hawk is not a power house and it's going to be a hard battle in straights and going up hills, most especially stock, but then again that also depends on what you are competing against. It's secret sauce is in handling and cornering so you probably just need to invest time in studying and emulating what the out front guys are doing to ride better and get out front and stay there. The secret to a race engine is all about volumetric efficiency. It's just an air pump and the fewer restrictions you have the more efficient it will be in creating power. If the out front guys are running bigger lumps, with cams and head porting then that is part of the path to success. On JD Hords's engines the key ingredient was porting, cams, and tuning. He no longer offers the head porting or cams unfortunatlely so you'll either need to find a guy with a flow bench and the knowledge or become the guy, that or find a Hawk with a Hord motor and be ready to pay that premium. I'm not sure if you can get the cams direct from Megacycle but if they are still in business you can give them a call. I'm leaning towards probably not since I see folks asking on the facebook group and getting no tractionm but that might just be because they are asking for an easy answer and not digging deeper, or more than likely just not reporting back with what they found. You can call 415 472-3195 and find out if they are still doing cams and go from there.
          88 Blue Hawk GT - Under construction but rideable (guest approved)
          89 BlackHawk 2.0 - On the lift and being assembled
          90 Hawk GT (color as to yet be determined) - Still on the shelf in crates


          • #6
            That makes sense.

            In deference to what rpcraft said, you do have to play to the Hawks strengths:
            • Light weight, so you gotta carry corner speed.
            • Smooth power so you can get on the gas early, early, early.
            • Late brake your competition (see point 1)
            All if this is a great tool to help make you a great rider - that is why a Hawk is a great starter track bike. But that said, if you are still running a stock motor, with an exhaust, pods and a jet kit, you are probably at around 55hp or less. To be fair, that just isn’t enough to keep pace with a good rider on an SV650.

            The generallly accepted “bang for the buck” hawk would be:
            • +2 mm pistons (696cc) from Wiseco or JE (if they still have them). These pistons will usually bump up your compression to 11:1 or so (big improvement over 9:1 or whatever pathetic cruiser number the Hawk came with)
            • X153 Megacycle cams
            • slotted cam sprockets
            • mild port job that cleans up the casting junk in the runners
            • Some form of ignition adjuster (but only if you are going to get some dyno time)

            That can take you from about 55hp up to maybe 70, and you have stayed out of expensive bottom end stuff.

            As for reliability, well if you are wringing out your Hawk to catch the other guys, eventually you are going to break something. You could start building out your bottom end etc, to keep that 70hp motor together longer, or for about the same money, you could just build 2x the top end only motor and accept some attrition.

            I will say that JD used to lighten the wiseco’s he sold, to get them closer to stock piston weight for balance. They are still heavier than stock, but lighter than the ones sold directly by Wiseco. Not sure if we can get him to explain that mod.

            JDs stage 1 heads have some kind of mysterious sand-blast looking smooth rough finish that I never figured out, other guys just have a port tool finish that looks like what you’d expect. There may be some old documentation on this mod.

            Now you may have seen some Hawk engines making power in the 80-90hp range, maybe more! This is stupid money. Unless you have a special attachment to the Hawk in particular, they make faster bikes.

            In my case that was just it, I wanted a Hawk that was the most it could be. I think Blashfield may have me beat there, but I like to think I would have a package that is competitive with his, if I ever got mine done. Unfortunately, I am now distracted by building the best Vintage 250 2-stroke short track bike ever, so the Hawk keeps waiting. None of this makes sense except I have a bizarre desire to work each bike out to its max potential, instead of just giving in and buying a better bike. My disease is a little inexplicable, and most definitely not advisable


            • #7
              700 kit, cams, are the starter pack. Anything after that the law of diminishing returns starts to come into play drastically.

              The last 5 horse power will cost a lot more than the first 15..

              That said, I've ridden a 90ho hawk and it's a fucing hoot.. Its also a 5 digit endeavor getting there.

              I raced a stock motor hawk and that was enough to get though and out of novice racing in into AM, win the majority of my amateur races and get into expert class whilst racing a hawk against SV's, ninja 650, motards and the like..

              You can do a lot with 50 HP and some motivation.
              Don't spend money and buy, spend time and learn.