1975 Kawasaki S1 Rebuild: Installment 2

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July 31, 2011 –

The S1 is now at its most pitiful state – just a bare, shivering in the breeze frame with nothing holding it up but a pair of soon-to-chucked (because much-rusted) wheels. Shorn of its jaunty triple outlet exhaust, the bike’s skeleton looks emaciated and generic now; it could be the remains of almost any bike.

Little evidence of its former coolness remains.

I pulled the engine a few days ago and it’s now sitting on a stand, with the case fasteners soaking in PB-40 penetrant. If you’ve never worked on an old Japanese motorcycle, here’s a tip: The factory fasteners are typically made of frustratingly soft metal and that, combined with decades of heat-cycling and gunk/rust accumulation, can make them very tricky to extract. Instead of using a Phillips head screwdriver, I recommend using a Phillips bit and a ratchet. This will give you more torque and also let you press in as you turn, which helps keep the threads intact long enough to remove the fastener – or at least to get it loose. You can also use a hammer to tap the driver into the “+” of the fastener if it’s already a little chewed up and you’re having trouble getting the tool to bite.

As a last resort, you may be able to do what I did to get the last of the three bolts that hold the stator/points plate onto the left-hand side engine case. The “+” on that bolt was severely worn; no chance of getting either a screwdriver or bit to grab. So I got a hacksaw blade and used it to very carefully cut a long “-” across the width of the fastener’s head. Don’t cut too deep or you’ll weaken the remaining shoulders on either side and they’ll probably just snap off – leaving you with an embedded stud to drill and tap. Cut just enough so that you can get some bite with a flat-blade screwdriver or bit. If that doesn’t work, there’s a final option. Cut a notch into a top corner of the mutilated fastener head, enough so that you can use a flat-blade screwdriver and hammer to tap the fastener loose.

Once everything’s apart and when the time comes to out it back together, you might consider using a set of aftermarket replacement stainless steel – and hex head – fasteners. These will make future teardowns (and normal maintenance) a lot easier on you. These kits are available from a number of suppliers, including Z1 Enterprises and Johnny’s Vintage Motorcycle Co. I have done business with both and been very pleased with the quality of their products and service. Another place I found that looks really promising is the Vintage Connection. I haven’t dealt with them – yet – but they appear to be specialists in Kaw triples and – from the pictures on their web site – have a large inventory of repro/NOS and used parts.

I’m going to need their help with this project, too.

The gas tank is a mess. I doubt it’s repairable – or at least economically repairable. The lower portion is severely rusted, in some places to the point of perforation. So – for now, at least, the tank has become a garage object d’ art.

The gauges are iffy. The speedo can probably be re-used and at least, restored. But during take-down I discovered the tach is damaged in the back. The fitting that the tach cable screws onto is broken off. I doubt this is fixable, so I will be looking for a new gauge cluster in addition to the gas tank.

The seat pan, though, was by far the most far gone. Unfortunately, from what I have gathered from the “triple fraternity,” seat pans are among the toughest items to find in any kind of decent condition. Those who have ’em won’t part with ’em and those who are willing to part with ’em are parting with ’em for a very good reason (they’re junk).

Well, that’s part of the fun, right?

One area where I did luck out is the exhaust system. Not only is it all there – including the hard-to-find original clamps that connect each header pipe to the muffler – but the pipes, collars and mufflers are all in very good to excellent condition. Even the mufflers are not rotted through – which turns out to be a virtue of the two-stroke engine. The exhaust stream of these oil burners is heavy with – well, oil – and it coats the insides of the exhaust, keeping them from rusting out from the insides. So, even almost 40 years later, these parts are still structurally sound. They just need cleaning – and in the case of the mufflers, rechroming.

This is going to (hopefully) save me a pile of money, because while repro triple exhaust systems are available, they’re expensive enough to give you heart flutters – about $1,900 and that’s before shipping. I paid $400 less than that for my entire (and running) 1983 Honda GL650!

Another item that cleaned up nicely is the plastic side-saddle tank for the two-stroke oil. After wiping off the bulk of the built-up grunge, I was able to hand wash the container in the sink and it came out looking like a new part, ready to install. The plastic oil lines are brittle from age, though – but these are very inexpensive and easy to replace.

Here are the bike’s three – apparently factory original – coils. One hangs upside down by the steering head; the other two mount side by side on the upper frame tube. I haven’t tested them to see whether they’re still viable – because that won’t matter for a long time yet! But I did carefully mark what wires went where (photos and drawings) and made sure to keep (and properly tag) every nut, bolt and washer for do it right (don’t guess) down-the-line re-assembly.

I still have a few things to take off before the frame is ready to degrease, blast and paint – but I’m almost there.

This, then, is the Lowest Point. The bike is now literally just a pile of parts. You can’t even push it around anymore. But it’s also The Beginning. From this point forward, the S1 will be on the road to recovery, one step at a time.

(For Installment 1, see here.)


  1. “Boogered up phillips bolt” I’ve successfully used a big pair of dikes (wire cutters) to grab the bolt head with them and turn it. If that doesn’t work I do the same as you – but I use a dremmel tool to cut the slot. And finally, just cut off the entire screw head. After you get the cover off there will be a good bit of bolt left you can grab with vice grips. Never had any kind of luck with ez outs. Almost always wind up drilling out the entire bolt and re-threading in the worst case.

  2. JIS fasteners…. I hate them. They break very easily. On the screws, JIS Philips (+) head screws aren’t the same as US ones. That’s why they strip so easily with a US driver and then become impossible to turn with it. A JIS driver is needed for best results. With the correct driver on a T-handle the probability of successfully removing such screws undamaged skyrockets from unlikely up to reasonable. Even if it has been damaged by US style driver such that a US driver has no chance of working there is a decent shot the correct JIS one will remove it.

    For those who don’t know: JIS = Japanese Industrial Standard.

    • Yep!

      I also find the metal is often very soft and easily damaged. That’s why I always replace all the factory fasteners with stainless hex-key bolts. I’ve had no problems with those, ever.

  3. Eric:

    You don’t want to reuse those coils. Trust me.

    They weren’t very powerful in the first place, and were a major source of plug-fouling, hard-starting, etc., on the bikes of the era. You’d be far better off finding some lookalikes with modern innards.

    In any case, best of luck!

    • Probably right!

      I’d like to upgrade the bike to non-points ignition, but I’m betting no one makes a kit. As you know, these triples are effectively three single cylinders fused together on a common crank. Each has its own set of points… in my other antique bike (’76 Kz900) it was an easy drop-in upgrade to replace the points with a transistorized aftermarket replacement.

      • Take a look at a Dyna ignition booster. You can use the points, but they don’t wear out because they’re just used for switching the transistorized ignition. Dyna coils work very well, too, but they don’t look stock.


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