Air-cooled bikes like my ’76 KZ900 have lots of nooks and crannies – the finned cylinder head/upper engine block especially. Plus, the bike is almost 40 years old – and like people who are getting up there, it tends to leak some.
Well, seep is more like it.
Gaskets get brittle, gaskets shrink. Even if you replace them all (which I did, on this bike, about five years ago when I rebuilt the engine) they still seep a little and the more you ride, the more obvious the seepage becomes. Left uncleaned, it accumulates, cooks off – and after a certain point, it’s practically impossible to get rid of it all without putting the parts in the parts washer… which entails taking the bike apart.
I prefer to keep ahead of it and do thorough cleanings once every 2-3 years. By “thorough” I mean more than a casual hose-off and wipe-down.
Which entails removing some parts. Not a major disassembly. Just so you can get at the engine. So, off comes the tank and side covers, the pods (cone air filters, used in place of the stock air box) and then – the big one – the exhaust headers and can (what bikers call the muffler).
On an air-cooled bike, this is easy enough. Remove the eight 10 mm nuts and lock washers (on an in-line four cylinder bike) that hold the header to the cylinder head, plus whatever’s holding the can to the frame. Save the hardware (plastic baggies are good for this) and stuff clean rags or crumpled up paper towels in the now-open exhaust ports, to keep crap – and water – from getting in there while you clean. With the header off, you’ll be able to get at the engine’s cooling fins much more easily – and at the header tubes, too. They probably need de-bugging and polishing (if chrome, as mine are). It is much more pleasant to clean/polish headers with the headers off the bike.
I like to use Honda Brite “total cycle cleaner/degreaser.” Not a product pitch – just a recommendation. The stuff is not caustic and will not damage chrome or plated/polished/powder-coated surfaces. It won’t harm rubber or plastic, either. With the bike cold, soak it down with the cleaner/degreaser. Let it sit for a couple of minutes, per the instructions on the bottle. With a masonry finishing sponge – pick these up at Lowes or Home Depot, etc., they are extra thick and extra soft and just the ticket for cleaning a bike – and a bucket of sudsy water (use a good quality car wash) – thoroughly scrub down the bike, then hose it off. Keep everything wet while you work. Don’t let the cleaner – or the sudsy water – dry on the bike. And wash it down thoroughly once you’re done with the sponging.
Don’t do this in bright sun, by the way. Direct sunlight will evaporate the water – and dry out the cleaner/degreaser. An overcast day – or dusk/early morning – is the ticket.
Once washed down, roll the bike inside the garage (if you have a garage) to dry it off. Use soft towels for this. I use big bath towels to get the big water, then small hand towels to get into the nooks and crannies and mop up the small pools.
From here on, it’s just a piece-by-piece process of cleaning (and if need be, polishing) each case, cover, nut and bolt – the shininess standard being entirely subjective and to be determined according to your own degree of anal retentiveness.
Before you reinstall the pipes, you will hopefully have gone to the bike store (or gone online) and ordered/got a new set of copper crush gaskets. The old ones are crushed – and if you reuse them, there’s a good chance the pipes won’t seal right and you’ll have an annoying/obnoxious exhaust leak – ftt! ftt! ffft! fftt! – which is easily avoided by using new gaskets every time you remove/re-install the exhaust.
This is also a good time to get out your torque wrench and check the tightness of the cylinder head bolts. Check/tighten each one – being sure to use the correct measure and also the correct tightening order (this is very important; don’t be a Clover and just tighten them in whatever order you think seems right). Often, some of the bolts will be slightly loose, especially if the engine was rebuilt fairly recently – as mine was. I found four bolts that needed slight tightening.
Also check the cam cover bolts – and the cam cover gasket (and those “half moons” especially). The bolts are often loose – or were over-tightened – and the gasket may have deteriorated beyond the point of no return. If it looks questionable (if you had a lot of seepage) replace the bugger – and spare yourself further seepage.
At least, for awhile.
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