Z1 frame is cracked

Shit… My kawasaki z1 frame is cracked. Anyone know anything about fixing frames?

That’s the z1…

The frame is cracked to the point where it’s sort of scary. Both my main downtubes are cracked. The left one is cracked all the way through. All the way around. Can’t believe I never noticed it. Adam randomly saw it!

This winter I’ve been doing some little engine stuff to the z1 making it faster and fixing a few things. While tinkering with it, that’s when the frame was noticed.

So I’m taking the entire thing apart down to the frame and Adam is going to help me repair the frame. Not only are we going to repair it, we’re going to strengthen it by doing some of the old school race frame mods in below pic.

Below pic shows the left downtube cracked through the gusset and completely cracked through the round tube.

Below pic shows the right down tube cracked completely through the gusset and about to start cracking the round tube. Hard to tell but it’s cracked.

Ok, enough about the frame for now.

Below pic shows a pair of vintage Kenny Harmon L1 cams I picked up. The Webcam 110 are the new version of these. Same specs. I’ve been told for a fast “streetable” bike you want cams around .400″ because above .410″ you have to go to shim-under bucket. And more duration = high rpm power, but the head / carbs have to be able to flow the power up top. So everything has to match.

For reference:

  • oem cams – .325″ lift intake – .300″ lift exhaust – 235˚ duration at .50″
  • webcam 118 – .365″ lift both – 246˚ duration at .50″.
  • KH L1 / webcam 110 – .400″ lift both – 256˚ duration at .50″

I had the cylinder head ported by the well known KZ engine guy – Larry Cavanaugh. He ported it to match my set up. Head should be able to take better advantage of the wiseco 1015 / L1 cams / CR29 smoothbore carbs.

Below pics show the porting Larry did.

Not only did Larry port the head but he also fixed my broken cooling fin, and fixed a broken bolt stuck in one of the cam cap holes. He also clearanced the tapped bores so the high lift cams fit. All seen in below pic.

Below pic shows some more goodies like ape clutch kit, ape cam gears, better master cylinder. Lots of little stuff.

Also lacing up 2 new rims.

So, if anyone knows anything about fixing frames, or if you’ve had experience with anything similar, feel free to chime in… thnx.

15 responses to “Z1 frame is cracked”

  1. Chris francione says:

    Damn your not messin around, those frame mods should stiffen up your zed to noticeable handling improvements, put raised clip ons in that pile of goodies!

  2. adam says:


  3. Ed says:

    Quit trying to bring me down… I’m having a skinny day.

  4. Mike K. says:

    lay off the carbs bro.. get your shit together.

  5. Jim says:

    LOL @Adam !

    I’d like to think that Ed was just ruling too hard and the stock frame couldn’t take it.

  6. Adam says:

    I’m gonna add a few inches to those down tubes…. get that front end raked out proper. Chopper shit.

  7. D car says:

    You’re going to want to have that thing in a jig when you repair it, make sure that puppy is nice and straight and that it doesn’t get tweaked during the repairs

  8. Ben the Man says:

    After you pour some more money into that bike you wanna race the Duc?

  9. Ed says:


    Your duc s2r800 should have about 80 horsepower. It’s lighter. That’s the only advantage I see. Pretty sure duc’s don’t have small gears like a sport bike does. Plus you’re fatter than me, ha.

    Pretty sure my z1 is gonna have a bit over 100hp. Maybe 110 depending how lean I run it and how I set my cams.

    I think it’ll be a good race… Which I’ll win.

    I’m more interested to race Jim’s mid 1990s yamaha fzr600.

  10. Jim says:

    @Ben @Ed its on!

  11. Adam says:

    I don’t think it’s the fastest but I think my KZ750 will be pretty damn quick when it’s done. Might be a contender.

    Just got my 810cc piston kit for it today.

  12. Frank says:

    There is an early Z1 frame w/ front end and assorted parts, up at Joe’s U-pull it (aka EZ Pull & Save Auto Parts)
    2401 Summer Valley Rd. New Ringold, Pa.17960
    570 386 2171
    It was still there last time I was up. Two weeks ago.

  13. ken says:

    Should run mid 11s with no slick or bar and some practice. Those frame mods should take away the “death wobble” at speeds over a buck and a quarter in addition to making it strong!

  14. […] my other post here regarding how my 74 Z1 frame was […]

  15. Ron says:

    Nice lookin z1 , what name is the rear wheel and size ? Also , what name of rear tire and size do you have on it ? I’m wanting to get a little more grip

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