Getting your vintage motorcycle running smooth - Driving

You’ve finally found that gem of an ’80s motorcycle that you always wanted. It could be one of the granddaddies of all superbikes, a GSX-R750, a pristine example of the original luxo-tourer, Honda’s Gold Wing, or that early BMW GS you’ve always dreamed about. You could have found it in a barn (always a classic story for later), in the back of a buddy’s garage or even at an estate sale. You could have gotten a deal —free even! — or you could have paid a fair penny.

Whatever the case, like any internal combustion vehicle, it’s going to need at least a little tender love and care before it’s right for the road. Besides, you’re probably looking for a Coronavirus project, but haven’t we always social distanced in our garages, anyway?

So, here’s a list, in quasi-descending order, of the three things you absolutely need to address in order to get riding on your newfound treasure:

Hit the brakes!

Assuming we’re not talking about a complete basket case that’s been left outside for 11 winters in a row, it is very possible that the major mechanicals — i.e. the engine and transmission — will be in fine working order. But, no matter how well the old beast was stored, if it’s been in hibernation for more than a couple of years, it’s probably going to need a major brake overhaul.

Brake fluid is nasty stuff. In a best-case scenario, the fact that it attracts water will cause some corrosion in pistons and calipers. In the worst possible case — and I’ve seen this in practically every motorcycle that has sat for more than five years — its turns into a crystalline nightmare that takes some serious elbow grease to remove.

In either case, that means you’re removing all the calipers, and stripping them down to their constituent parts. At the very least, you’re replacing all the seals, two seals per bore. So in two front four-piston calipers, that’s 16 seals. Price accordingly. The caliper pistons themselves may be re-used but only if they are unmarked and all the build-up can be removed. If not you’ll need those replaced too.

Be gentle when cleaning the caliper bore and the piston. It is a fine mating surface and braking performance/safety can be affected. It is, however, a job easily accomplished in the garage. And although special piston-removal tools are recommended by most service manuals, I have never felt the need for anything other than vice-grips. Yes, they can leave a few marks on the top of the piston, but that’s the part that sticks out of the bore so the seemingly ham-handed handling will not affect their performance. And, if they’re really stuck and you have access to an air compressor, 100 psi through the brake-line mounting hole should be enough to force out the pistons. Just make sure you’re pointing the pistons away from you.

The Bikemaster brake bleed tool is a very useful piece of equipment. Handout

Finally, when bleeding the brakes after they’ve been rebuilt, if you still have access to that air compressor, then a vacuum-operated bleeding tool will be your new best friend. I got mine for 60 bucks from Fortnine.ca. Five minutes of suction in your lower calipers’ bleed holes will eliminate all the air bubbles in the lower lines. Then squeeze your brake lever as tightly as possible and tie-wrap it to the handlebars. Leave it overnight. The next morning you’ll have a perfectly-bled and rebuilt braking system. This one is a must for any bike that has sat for a long time. Not only is it a safety issue, but I’ve never seen any brake system unaffected by long time storage.

The perils of petrol

Chances are, if someone just left their motorcycle in a shed or barn, they probably didn’t take the time to drain the fuel from the carburetors. This is not a good thing. Bad gas can’t quite rival bad brake fluid for nastiness but it does have a lot more intricate and vital places — jets and air bypass passages — to wreak its havoc.

Bikes that have sat for a long time need to have their inner workings cleaned out well before being road ready. Costa Mouzouris

How important is it to get the carbs thoroughly clean? Well, in 90 per cent of the cases I’ve seen of a motorcycle running poorly after a restoration, the carbs have been at fault, even if, as is seemingly always the excuse, they were given “a good going over.” The mistake all those DIYers make is to try to do all this internal cleaning mechanically, i.e. with spray fluids and brushes/wires. To get truly baked-on gas gunk out of all the microscopic channels that make up the body of a carburetor, it absolutely must be cleaned in an ultrasonic bath — nothing is able to resist the combination of caustic cleaning fluid and microscopic pressure waves.

You have two choices in this process. Invariably, every classic motorcycle forum will be able to direct you to a local entrepreneur — i.e. a retired forum member with nothing else to do — who’s bought an ultrasonic machine. Normally for small bucks — $100 or so — they’ll dump your carb bank in their bath and shake most of the stuff loose. Note that you will have to still disassemble each carb to ensure all the detritus has been removed.

If you’re bucks up and the bike in question is a true classic, there are professionals that will do all that plus detail the inside and outside of each carb and then bench synchronize the whole set. If, for instance, you have an old Honda, The man is Mike Nixon at the motorcycleproject.com. And, if you do choose to ignore my advice and you do find yourself chasing a mysteriously bogging motorcycle and you’ve checked everything from valve clearance to ignition coil secondary resistance, remember that I told you so.

There is nothing sweeter than cleaned-up carbs. Costa Mouzouris

Get clearance before you start

I have assumed, as I mentioned, that your new pride and joy isn’t a total write-off. If so, there’s a good chance the engine is in good mechanical nick. It’s amazing how long some motors can remain dormant without damage as long as they haven’t been stuck outside in the rain.

That said, you should make a few inspections before awakening it from its extended coma. Primary amongst these is a valve clearance check. There’s a number of reasons for this, the most important one being that the reason the motorcycle might have been abandoned in the first place might have been that “she just started running badly.” Almost invariably, this is a result of tightening valves that allow compression to bleed off because the valves are being held open.

The first symptom is hard starting followed by a rough idle even though high-rpm behaviour won’t be dramatically affected. Another reason to check this before the first revival is because tight valves are one of those mistakes that can cause permanent damage. Running a bike with tight valves — especially the exhausts because they run so hot — for any extended period of time can cause valve seat recession and/or valve damage. Both are expensive fixes.

I won’t go through the procedure since every motorcycle is different, but most will be in the realm of ability of backyard mechanics, save perhaps the ultra high-performance shim-under-bucket affairs, which require removal of the cams (and, more importantly, timing them when reinstalling) to get the clearance within spec. I would advise that you set said clearance to the widest of recommended specifications and not their tightest, even though that will make the engine sound quieter. Again, this is especially true of the exhaust valves.

Finally, I have deliberately not gone into the more rudimentary rules of motorcycle resurrection such as replace even low mileage tires if they are old and the need to replace the battery (low performing but operational batteries can cause damage to starting system), not to mention making sure that all your cables and switchgear are in order. If you’re planning to do serious work on a motorcycle, you probably already know that.

There are also some basic tests that can rule out typical problems down the road. For instance, even though experts recommend more detailed testing of a bike’s charging system, simply hooking up a voltmeter across the battery posts while the engine is running will immediately alert you if there any charging system issues: if the meter doesn’t budge as the engine revs up, you have a problem.

Note also that I have not gone in to model specific issues — wonky cam chain tensioners on Eighties’ Hondas, suspect charging system on early Suzuki fours, etc. — that can be better addressed by a specific Google search.

And lastly, service manuals for many old motorcycles can be found online, either in pdf form or in the service section of specific model online chat forums. If, however, your new-to-you bike was running before it was so callously tossed aside, the three fixes listed here will solve perhaps 80 per cent of your headaches and just might get you the fine-running classic you always dreamed of.

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June 11, 2020 at 08:00PM
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Getting your vintage motorcycle running smooth - Driving
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