KZ650 Mods ?

The KZ650 seems to be the bike of choice to do anyv and all mods to . Lucky me bought one with out even knowing , C model with rear disc , I see posts on here about all the different things that can be done , swing arm , forks , engines ,, Is there a post in the past that put it all in one thread ,, Maybe this could be that thread if not .. Thanks , Shoe

Hey Shoe48. I have a 650Custom and it is a fantastic middleweight and they have been popular since their introduction in 1976. They were designed to outrun any 750 in this era and they did until the GS750 Suzuki arrinved. 650's are popular because they are bulletproof and inexpensive compared to their bigger brothers the 900/1000. The Kz650 is a sweet handling little bike and you can build them to pack quite a wallop but you will be hard pressed to build one strong enough to spank a fully-built big bore 900/1000. There is no replacement for displacement when it comes to cranking out the power.

I don't believe that there is one thread that covers all potential upgrades for any bike. You might just want to post the question "What would you do to build the ultimate Kz650." I am sure members will chime in on this invitation. Also check the archives under 650, 750 or 810.

You will hear the obvious...750 cylinders bored for an 810 Wiseco kit. Bigger carbs, 750 head mildly ported, electronic ignition, lighter wheels, aluminum swingarm, header pipe...etc. I'll leave the rest to others to kick in.

Cheers-Colin Firth

The chasis could use some help too.

If you have a lot of miles on your 650, the rear shocks "are barely adequate" to begin with and could use an upgrade. The front fork springs will sag over time, and would benifit with a set of heavy-duty dual rate/progressive fork springs to give improved ground clearance and stiffer suspension under hard riding conditions. A front end or back end swap to a more modern bike will do this as well.

A fork brace will improve front end flex/twist.
Good performance tires will make a big difference.
The braking system can be improved as well. If the discs are not drilled, wet weather stopping will suffer.
A performance clutch could help as well. Although I find mine hurts my hand on long rides.

Post edited by: rstnick, at: 2006/02/12 21:04

reborn650 wrote:

They were designed to outrun any 750 in this era and they did until the GS750 Suzuki arrinved.

Ive often wondered and asked how did the 650s compare to the 750 4cyl. The 750 4 didnt come out until 80 correct?

I think the ability to run with 750's was mostly factory hype. Not sure of Norton twin performance specs or Honda 750-4. When did Suzuki make their first 4 stroke inline 4. Giving up 100cc is a bit. I never had a problem running with Honda CB750's but then again those guys where kinda wimpy (like most Honda pilots "You meet the nicest people on a Honda"). If I flogged it to redline I could walk away from the Hondas. Doubt they ever went over 9000 rpm. Then again they had SOHC not doubles.

I always thought the swingarm was the weak point. 70's era bikes not known to be handling machines. Swingarm mods, front springs (Progressives), dual disc front, dragbars, 4-1 pipe and pods and away we go.

I'm still not a fan of 16" backwheels, which I think the C model customs came with.

Post edited by: RomSpaceKnight, at: 2006/02/13 18:42