PARTS/MODIFICATIONS/PERFORMANCE:

ENGINE MODIFICATIONS:

After market performance parts were made contrary to popular belief. Most stores will tell you they never existed because the 650 wasn't popularly raced. Unfortunately, the companies that made these parts are now out of business.* They included Action Fours, who made pistons, cams, and springs, and I believe Weisco used to make a overbore kit too. Good luck trying to find this stuff, because it's rare. Keep a steady eye on Ebay, because that's where it shows up now and then.

If you're crazy like me, then you may want to look into actual improvised modifications. Ideas I'm investigate include:

  • Mill the head, notch pistons for valve clearance for more comp.
  • Look into CB750 pistons, the CB750F piston is a good starting place for high comp.
  • Have a custom regrind cam made.
  • Motor Swaps: Very overrated idea in my opinion, 750 won't fit without extensive modifications. The '83 and on 650 dohc would be interesting though. Of course, you could always just buy a different bike and be done with it, but if you're like me you're always involved in projects that seem to have no end and no point to them.
    • *There is a rumor that Megacycle makes a regrind for the 650. Nobody could confirm this with me, and there webpage is not operational yet. (www.megacyclecams.com) If you can confirm this please tell me, otherwise I will try to contact megacycle and find out. Another 650 owner has informed me that Colt Cams in Canada can do a regrind, hopefully I'll have more information/specs once I get to that stage of my project.
  • The 650 was made using the factory tooling used for the 550. This means that the cylinder bore was increased, but they weren't spaced out any farther. I don't know how drastic this really is, but I happen to know that only .25 and .50 oversize pistons were ever provided by Honda for the 650. I know the 750 and up had optional .75 and 1.00, don't know about the 550 and smaller. May be a problem with the cylinder walls being too thin or just too close together, leading to overheating among other things. Some people say that because the 650 is basically a 550 stroked that it is unreliable, but I have seen no evidence showing this.
  • Below is Action Fours overbore kit. Ups the compression from 9:1 to 10.5:1, and increases displacement from 627cc to 675cc. Unfortunately, no longer made and hard to come by. But check out the dome and the huge valve notches compared to stock! I just bought this set on Ebay, and it will be going into my project motor. I am looking into having them blueprinted and another set fabricated for a different motor.

CLUTCH:

  • Barnett Clutches provides an aftermarket clutch set, but it's a little more expensive than the rest. I bought a cheapo set from my dealer for around $32.00, because while some people will try to sell you on brand name 'racing' parts, you have to sit back and realize what you're dealing with here. There isn't some obnoxious amount of torque passing through our clutch like there is with some of the modern sport bikes, so the low end clutches will suffice. One note, the Vesrah springs pictured below are not the correct ones for the bike. They are listed and sold for '79-'82 CB650 but are in fact too long.

SUSPENSION/STEERING:

  • Available from Progressive Suspension. I purchased the 12 Series Vintage dual shocks, and combined them with 75/120 rate springs. Also available are front fork springs. The 12 Series are the big shocks in the picture, the 14 Series is the small one in the left corner. Both sets are available with black or chrome springs.

    • 12 Series:
      • 13" Shocks w/o springs: 12-1204B
      • Heavy Duty Spring for 12 series: 03-1367B/C
      • Standard Spring for 12 Series: 03-1394B/C
    • 14 Series:
      • 14 Series w/o springs: 14-1285B
      • 14 Series Heavy Duty Spring: 02-1353B/C
      • Standard Spring for 14 Series: 02-1352B/C
    • Fork Springs:
      • Fork Springs (Standard, '79-'82): 11-1103
      • Fork Springs (Custom, '80-'81): 11-1108

CARBURATOR/AIR FILTER STUFF:

  • K&N: It would appear that K&N has discontinued their jet kits. I'm not sure, but they don't list them on their web page anymore. Also, below all models used KN-401 Oil Filter. (K&N Website)
    • 1980-81 CB650C
      • HA-7580 Stock Air Filter
      • RC-2362 Clamp on Filter
    • 1979-80 CB650
      • HA-0750 Stock Air Filter
    • 1981-82 CB650 (SC)
      • RC-2362 Clamp on Filter
      • HA-7580 Stock Air Filter

    • Here is the K&N RC-2362 filters currently on my bike:

  • Dynojet:
    • Dynojet makes kits only for the 1980-82 CV carbs. (Dynojet Website)
    • Part #1131, Stage 1 & 3 available, around $122.00.
    • Below they show a dyno, but I wouldn't really trust the numbers. Check out some other dynos for the 650 here.

EXHAUST PIPES:


  • For a look at what is out there, go to Accessory Warehouse (here), find the 650cc section and select what you have. You'll find that Jardine and Mac have a number of different setups, including 4 into 1 Black/Chrome or combo, 4 into 2 megaphones and turnouts, and generic slip ons. Here's a picture of my current set, picked up used from a used parts dealer:

SEAT:


  • If you're still using electrical or duct tape, might be a good idea to spend some cash and get the seat recovered. I had mine done by Sargent Cycle out of Florida. Mailed it out - took some time, but being in Wisconsin I had all winter to wait, so no rush. Much more comfortable, and looks sweet with the CarbonFX cover material. Would highly recommend them.