Stock Header Pipes With Slip-On Mufflers

Somewhere during my ownership of my two 750’s, I came to discover that the stock header pipes with the cross-over pipe noticeably helps the performance of these bikes.

On one 750, I had a complete stock exhaust system, with rotted out ends.  This bike pulled like a freight train; waaaaaaay better than the other 750 that was otherwise identical except for a non-crossover system with Jardine Classics (that breathe very well).

So when I replaced the rotted stock system, I made sure to retain the stock headers and crossover, but replace only the rotted mufflers.  Unfortunately, I didn’t take pictures or notes of that work on that bike.  However, I finally got sick of the power difference between the two bikes, and decided to add the crossover to the other bike as well…  And *this* time, I got pics…  So here we go…

First, the parts.  Besides a complete stock exhaust system to be cut up, you need a few things:

Replacement mufflers…  I chose some MAC tapers, that I got from Dennis Kirk “Scratch and Dent” for chump change:1-macExhaust12-macExhaust2

Optionally, fiber wrap (because in my case, the pipes are cosmetically challenged):3-wrapPackageAnd the stainless steel straps to hold the wrap in place:4-wrapStrapsAnd the high-temp paint to 1.) paint the pipes after sanding and before wrapping and, 2.) paint the wrap after it dries (from wetting during application):5-highTempPaintAnd of course, muffler clamps (again, from Dennis Kirk)…  you don’t want your mufflers to fall off do you? Or leak…:6-mufflerClampsFirst, you have to cut the stock mufflers off the stock headers.  Inside the pipes, underneath the chrome and the outer pipe of the double-wall pipe, there is a gap between where the inner-wall of the header pipe and the baffle in the muffler almost meet up.  This is where you cut.7-whereToCut2Looking inside the now-cut-off muffler, you can see how close I cut next to the baffle pipe, just catching the edge of it:8-cutBaffleCloseHere’s the whole carcass:9-cutBaffleFullBut now here’s where you approach the main catch of this whole thing.  At this point, you have to clean up the left-over bits of the muffler that are still welded to the header pipe.  But, once you grind all that off, you have to keep going; because the clean pipe is actually about 1 9/16 inches.  This means that your 1 1/2 inch slip-on does not yet fit.  So, grind, grind, grind, and let me tell you; this pipe is no soft metal…  Here’s what it looks like ground down to about 1 1/2 inch:10-cutGroundHeaderEndCloseThen, if you haven’t already at this point, it’s time to optionally apply the fiber wrap.  You need to sand the pipes, paint them with the high-temp paint, let that dry, apply the wrap (wetting it along the way), let the wrap dry overnight and/or in the sun, and then paint the wrapped pipes again, this time to seal it from the elements.  Here’s a look at the wrapped, but as-yet un-painted headers:11-wrappedHeadersFull…and a close-up of the top strap in action.  Note that I started at about the place where the pipes clear the head; you don’t want to start to close to the beginning, or you can’t get the header clamp in place.  Also note that at the start of the wrap, you wrap it *under*, so the loose end is not exposed: 12-headerTopEndClose…and here’s the other end, where you really need to fold the end of the wrap under before strapping it down… I did a sloppy job, but it won’t be visible… :13-headerBottomEndCloseOkay then!  So in summary, here’s the requisite “before” pic, with the rusty, non-crossed-over headers, and Jardine Classics:14-bikeBeforeAnd here’s the “after”, with the picture taken right before the first ride:15-bikeAfter1And Did I mention they smoke like CRAZY when you do this?  Oh yeah… make sure that when you take your first ride, you stay in motion, or you will be bathed in the rising noxious smoke of the baking paint and fiber… Anyway, here’s the “after” taken right after the first 15 minute ride, with the freshly wrapped pipes still smoking… :16-bikeAfterSmoking2And a little closer view of the pipes:17-bikeAfterClose3And another pose:18-bikeAfterFront4And finally, once from the rear:19-bikeAfterRear5

12 Comments

  1. Doug Johnson

    So, the slip on mufflers fit over the outside of the header pipes, and you used those pipe clamps to secure the muffler to the header pipes. Okay.

    Most likely, you used an angle grinder to remove 1/16″ from the header pipe, then the slip on mufflers are 1 9/16″ diameter?

    Looks easy enough.

  2. Biquetoast

    @Doug

    Easy enough, it’s true.
    My main goal in that post was showing the cutting point and technique for preserving the crucial cross-over pipe.
    The rest sorta takes it from there..

    -‘Toast

  3. Blake

    Did u have to any kind of retunning to the carbs after u replaced the mufflers?

  4. Biquetoast

    @Blake
    Yep, I rejetted a bit… Definitely needed it.
    -‘Toast

  5. Blake

    I still have the stock mufflers, but they are rusting out pretty badly. I have dunstall replica slip on mufflers with removable silencers but if I have to ret net I don’t want to put them on cuz I can’t rejet my self. Does it depend on the mufflers as to if my bike will need rejetted or not. Thank u for your help

  6. Biquetoast

    @Blake
    It is my opinion that the 750 was on the verge of needing to use larger jets even in stock form. You shouldn’t fear re-jetting, really. There are some great tips on the Kawasaki Twin Owners Forum, including a few great pages on rejetting advice and vendors of replacement jets. If you put easier-breathing mufflers on and don’t put larger jets, you are basically starving the bike for fuel in a way… It’s a simple, affordable, do-it-yourself change that you won’t regret.
    -‘Toast

  7. Roland

    How many feet of wrap did it take to do both stock header pipes?

    -Roland

  8. Biquetoast

    @Roland –
    I can’t believe I didn’t put that in the article!
    I’ll do you one better, and give you all the info… I keep all my old packaging… But don’t call me a “hoarder”! 😉
    It was a 2″ x 50′ package, part # 11022, “Exhaust Wrap-Black”.
    I bought it from an eBay seller that turned out to be very good and reliable way back then (haven’t bought since, but would again), Shamrock Performance Auto, Inc. http://www.shamrockperformance.com
    I basically unrolled it, cut it in equal halves, and dragged each piece through a bin of water as I applied it (for pliability). It makes a horrible mess, and your jeans get soaked and stained, but it’s all good.
    I hope that helps!
    -‘Toast

  9. Ethan

    Can someone tell me the overall length of a removed exhaust stud on the kz750B/G motors. I believe Part# 92004-058

    Ethan

  10. Brent

    Revisited this post today as I finally sourced a factory exhaust for my ’76 B1 Twin. The 20 dollar price reflects its condition. Happily one muffler has already been cut away, right where you show it which is great cause I can use it for reference when I cut other rusted hulk off. The condition of the header pipes is 7/10 losing points only for scratches and minor dings. The crossover pipe is also good. Black, but solid. And now for the bad news.
    Someone cut the header pipes off BEFORE the crossover. Unevenly to boot. But my buddy the welder said if I install it on my bike, clamps and all, we can use extra 2″ t-bar clampsand three or four short pieces of square key stock and clamp the pipes at the cuts. Some tack welds and careful removal of the pipes from the bike and we can finish by welding in the 1″ piece of outer pipe which we’ll split and bend into place as we go. “Sounds like a plan.”, I told him. I said, “You sure are good at fixing and welding stuff. Must be cause you ride a Harley!” In lieu of costly slip on mufflers (unless I find good used ones for cheeep, I plan on using 1 1/2″ plainbexhaust tubing from the upseeep of the headers to just aft of the rear axle and follow the original line of the mufflers, mbe an inch or two higher depending on clamp hardware at hand.
    BTW, those t-bar clamps you buy at the cycle shop can be had at your local industrial supply house for half or less cost.
    Thanks for posting the amount of pipe wrap needed. Guess I’ll need two packs in order to do my pipes right to the end, plus the crossover. I also found the stainless steel zip ties at a discount farm, auto and industrial place for $7.00 per 20 pack. Ma middle name sin’t Cameron fer nuthin!
    I plan to weld 12 or 16″ insert baffles into the ends of the 1 1/2″ pipes and cap them off after wrapping, with chrome round rolled exhaust tips, ala JC Whitney VW custom parts section.
    Thanks for helping to keep the Lonesome Twin alive.
    Brent in Nampa.

  11. Josh

    How do those mac taper slip one sound? I’m getting ready to put some on mine.

  12. Biquetoast (Post author)

    @Josh –
    Lemme put it this way… Since I put those MAC tapers on, that bike is the loudest of my bikes. Louder than the Triumph with the British Customs Predators, for what that’s worth. During idle, it’s not bad at all. But get on it, and it’s noticeable. So on my commute, I start the bike in the garage, calmly ride out of my neighborhood, and then open it up a bit… 😉 Also, they sound like they look, if that makes sense… Less deep, but still full. A bit more of a mid-range pulse sound instead of a lower sound with larger resonance chambers.
    -‘Toast

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