Note: this was originally written for the SOHC 400/450's so some information may not apply.
Congratulations, you are the proud owner of a Vintage Honda Twin. One that may or not may have been maintained properly. Of course, the previous owner told you that everything is absolutely perfect and the oil was just changed and he rides it every day and has never had a problem with it. Yeah, right :lol:
OK, so it started, you rode it around a little and it seems ok. Or maybe it didn't and you bought it anyway.
So let's cover the things that you should take a good hard look at to make it safe and sound.
First you need the Factory Service Manual (FSM) since it has the most accurate information. If you don't have one go to General Topics Technical Stuff where you’ll find the library post. https://www.vintagehondatwins.com/forums/index.php?threads/76
ENGINE:
Check the compression to see where you're really at. A decent quality screw in gauge is needed. It’s best to do this on a hot engine but cold is ok, just expect lower than spec numbers. With both sparkplugs removed crank the engine until the gauge stops rising, usually 10 revolutions is enough. The choke must be off and the throttle held wide open. You want both cylinders to be reading very close to each other.
Adjust the valves. Simple to do and rarely did the PO ever do it even though the Maintenance Schedule (MS) calls for every3,000 to 6,000 miles depending on model. Now is a good time to put in new properly gapped plugs.
Change the oil and filter even though the PO said he did. You have no idea what he used. Correct oil is a motorcycle JASO MA rated conventional oil, 10-40w in most cases. No blends or synthetics allowed since this is a used motor and a wet clutch. When you go to start it, leave the kill switch off while cranking it several revolutions or until you see the pressure light go out if equipped. Now you can actually start it.
Check the balancer chain adjustment if equipped. See the FSM that you've downloaded.
Check the cam chain adjustment. See the FSM that you've downloaded.
Check points gap and ignition timing per the FSM.
TRANSMISSION and DRIVE:
Check the clutch adjustment. See the FSM you've downloaded.
Check the chain adjustment. See the FSM you've downloaded.
Check the condition of the chain and sprockets carefully. The chain should have a max side to side play of @3/4" and each link should be able to move freely. The rear wheel should have no stiffness/drag in certain positions since that indicates the chain is binding. The sprockets should have a nice even valley between each tooth and the teeth should have a flat area at the tip, no pointy teeth allowed.
It is not uncommon that the clutch won't release on a bike that has been parked for any length of time. Don't panic. It just means the clutch friction plates are sticking to the steel plates and the oil is acting like a glue. Start the engine and let it get hot, shut it off. Put the bike in gear and rock it back and forth.
BRAKES:
Inspect the linings/pads for wear, cracking and delamination. Delamination is where the actual lining is separating from the backing plate. Recommendation is to replace the linings unless there’s documentation they were recently done.
Lube the contact points of the pads/linings.
Lube the caliper slides and pins. Remove, clean, inspect and lube brake cables.
Change the brake fluid. Should be done on a regular basis. See the FSM you've downloaded.
Adjust the brakes. See the FSM you've downloaded.
FRONT FORKS and STEERING:
Drain and refill the forks with the proper amount and type of oil. Yes, it normal for it to come out looking and smelling really bad. That's because no one ever did it. See the FSM you've downloaded.
Inspect the steering head bearings, lubricate and adjust. See the FSM you've downloaded.
Check the torque of the triple trees clamping bolts. See the FSM you've downloaded.
Check the handle bar play fore/aft, should be fairly snug. The rubber bushings are known to dry out and shrink causing the bars to move excessively.
REAR SUSPENSION:
Remove the rear shocks. Try compressing them against the ground. Won't move? They're frozen up and have to be replaced, they compress really easy? They're blown and need replacement. They move some but stiffly? May be they're OK.
Remove the rear swing arm to clean the swing arm bushings and pivot points. Replace the zert/lubrication fittings since the old ones have a habit of freezing/plugging up. See the FSM you've downloaded.
WHEELS:
Spoke/Wire wheels need to have each spoke checked for being intact and tight. Missing spokes are a big no-no. Loose spokes are a no-no. Test each spoke for tight and then tap it with a wrench. You should hear a ring note. Each spoke should have the same sound. If you get one that doesn't have it, it's an indication something is wrong with it. Possibly cracked.
Inspect for rim damage like dents in the edge.
COMSTAR wheels need to have the rivets checked for tightness. Loose rivets mean rim failure and no they cannot be replaced.
Inspect for rim damage like dents in the edge.
Check the wheel bearings for smoothness of rotation. There isn't such a thing as "it seems ok" or "just a little roughness". That's like being a little bit pregnant. Recommendation is replace them.
TIRES:
Inspect them carefully. Your life depends on them! Here's a link with good info about them
http://www.roadrunner.travel/magazine/r ... 6/page/32/
Check the manufacturing date on the sidewall and if the last 2 digits are -5 or higher from the current year they should be replaced. IE: tire reads 4212 in the year 2020. 42 is the week produced, 12 means 2012. So 2020 – 2012 = 8 years old.
If the tires show any cracks in the tread or sidewalls regardless of age they HAVE to be replaced.
The tires “generally” can be increased in size by 1 number, 100/90 to 110/90, but there's no real point to doing that unless you need more load rating of the tire. It may be unsafe to use larger tires due to rim width and age of the rim.
Tube type tires should have a new tube every replacement even though they look ok.
Always check the tire pressures before riding!
ELECTRICAL:
Check the battery. If it's the normal lead acid type and more than 2 years old it's done even though it seems ok right now. If it's an AGM type then get it load tested. When in doubt replace it.
Check the fuses and connections. Typically the fuse connections are corroded and need to be cleaned to get a good connection and not overheat. The standard auto fuse is not the correct length and will cause problems.
Check that the lights all work including the brake light from both the lever and foot pedal. Consider replacing all of the light bulbs.
Check the alternator for resistances if the information is in the FSM.
CABLES:
Take the cables off the bike. I know, the throttle cables are PITA. Disassemble them where possible, clean and lubricate with a light oil or motor oil in a pinch. The ones that don't come apart flush them with a solvent, let them dry for a couple of days and lube them with a good quality cable lube. WD40 is not a lubricant!
FUEL/INTAKE:
Take off the fuel tank cap and petcock sediment bowl and look for rust and contamination.. use a flashlight.. at the very least install an inline filter in the fuel line if the tank is rusty or the sediment bowl is full of "stuff". If the tank is rust free there is no need for an extra fuel filter assuming that the petcock filters are intact and clean.
Take out the air filter and inspect it, if it's dirty the bike will run poorly.. they're very sensitive to air filter condition
Take the plugs out of the 'drain tubes' that come off the airbox, if equipped. a bunch of oil, water, and disgusting stuff will probably come out of them.
Attach some short pieces of tube to the float bowl drains if they are missing, and open them. If the fuel that comes out is not completely spotless and clean, just pull the carbs right off and start taking them apart, it's worth it. If there's any particulate in the float bowls, that means there's probably stuff clogging your jets. Even if the carbs are clean, think about balancing them soon.. on an old bike, they're probably way out
Now that you've become intimately familiar with your new bike and everything is in order, go ride and have fun knowing that everything is good and will get you home.
Notes:
1) You've seen multiple references to using the FSM, Factory Service Manual. This is the only reliable information about your model. Every aftermarket service manual has errors, some small and some not so small.
2) Ball bearings have been standardized for a 100 years. Look at your old bearing for a number like 6302, that's the standard number. You can also use one of the Honda online parts fiche sites and frequently they have the standard bearing number listed in the description. Take the numbers to your local bearing supply house and buy them. You will save 50% at least over Honda pricing. Caution: do not buy the cheap Chineseium bearings, there's a reason they are cheap called inferior material.
3) When the FSM's were written and these vintage Honda's were produced things like fork oil and air cleaner oil were not created. Even engine oil was in a primitive state. You will see ATF for forks, 80-90w gear oil for air cleaners, etc. as recommended fluid. Use the modern fluids for the best results in reconditioning your bike.
Congratulations, you are the proud owner of a Vintage Honda Twin. One that may or not may have been maintained properly. Of course, the previous owner told you that everything is absolutely perfect and the oil was just changed and he rides it every day and has never had a problem with it. Yeah, right :lol:
OK, so it started, you rode it around a little and it seems ok. Or maybe it didn't and you bought it anyway.
So let's cover the things that you should take a good hard look at to make it safe and sound.
First you need the Factory Service Manual (FSM) since it has the most accurate information. If you don't have one go to General Topics Technical Stuff where you’ll find the library post. https://www.vintagehondatwins.com/forums/index.php?threads/76
ENGINE:
Check the compression to see where you're really at. A decent quality screw in gauge is needed. It’s best to do this on a hot engine but cold is ok, just expect lower than spec numbers. With both sparkplugs removed crank the engine until the gauge stops rising, usually 10 revolutions is enough. The choke must be off and the throttle held wide open. You want both cylinders to be reading very close to each other.
Adjust the valves. Simple to do and rarely did the PO ever do it even though the Maintenance Schedule (MS) calls for every3,000 to 6,000 miles depending on model. Now is a good time to put in new properly gapped plugs.
Change the oil and filter even though the PO said he did. You have no idea what he used. Correct oil is a motorcycle JASO MA rated conventional oil, 10-40w in most cases. No blends or synthetics allowed since this is a used motor and a wet clutch. When you go to start it, leave the kill switch off while cranking it several revolutions or until you see the pressure light go out if equipped. Now you can actually start it.
Check the balancer chain adjustment if equipped. See the FSM that you've downloaded.
Check the cam chain adjustment. See the FSM that you've downloaded.
Check points gap and ignition timing per the FSM.
TRANSMISSION and DRIVE:
Check the clutch adjustment. See the FSM you've downloaded.
Check the chain adjustment. See the FSM you've downloaded.
Check the condition of the chain and sprockets carefully. The chain should have a max side to side play of @3/4" and each link should be able to move freely. The rear wheel should have no stiffness/drag in certain positions since that indicates the chain is binding. The sprockets should have a nice even valley between each tooth and the teeth should have a flat area at the tip, no pointy teeth allowed.
It is not uncommon that the clutch won't release on a bike that has been parked for any length of time. Don't panic. It just means the clutch friction plates are sticking to the steel plates and the oil is acting like a glue. Start the engine and let it get hot, shut it off. Put the bike in gear and rock it back and forth.
BRAKES:
Inspect the linings/pads for wear, cracking and delamination. Delamination is where the actual lining is separating from the backing plate. Recommendation is to replace the linings unless there’s documentation they were recently done.
Lube the contact points of the pads/linings.
Lube the caliper slides and pins. Remove, clean, inspect and lube brake cables.
Change the brake fluid. Should be done on a regular basis. See the FSM you've downloaded.
Adjust the brakes. See the FSM you've downloaded.
FRONT FORKS and STEERING:
Drain and refill the forks with the proper amount and type of oil. Yes, it normal for it to come out looking and smelling really bad. That's because no one ever did it. See the FSM you've downloaded.
Inspect the steering head bearings, lubricate and adjust. See the FSM you've downloaded.
Check the torque of the triple trees clamping bolts. See the FSM you've downloaded.
Check the handle bar play fore/aft, should be fairly snug. The rubber bushings are known to dry out and shrink causing the bars to move excessively.
REAR SUSPENSION:
Remove the rear shocks. Try compressing them against the ground. Won't move? They're frozen up and have to be replaced, they compress really easy? They're blown and need replacement. They move some but stiffly? May be they're OK.
Remove the rear swing arm to clean the swing arm bushings and pivot points. Replace the zert/lubrication fittings since the old ones have a habit of freezing/plugging up. See the FSM you've downloaded.
WHEELS:
Spoke/Wire wheels need to have each spoke checked for being intact and tight. Missing spokes are a big no-no. Loose spokes are a no-no. Test each spoke for tight and then tap it with a wrench. You should hear a ring note. Each spoke should have the same sound. If you get one that doesn't have it, it's an indication something is wrong with it. Possibly cracked.
Inspect for rim damage like dents in the edge.
COMSTAR wheels need to have the rivets checked for tightness. Loose rivets mean rim failure and no they cannot be replaced.
Inspect for rim damage like dents in the edge.
Check the wheel bearings for smoothness of rotation. There isn't such a thing as "it seems ok" or "just a little roughness". That's like being a little bit pregnant. Recommendation is replace them.
TIRES:
Inspect them carefully. Your life depends on them! Here's a link with good info about them
http://www.roadrunner.travel/magazine/r ... 6/page/32/
Check the manufacturing date on the sidewall and if the last 2 digits are -5 or higher from the current year they should be replaced. IE: tire reads 4212 in the year 2020. 42 is the week produced, 12 means 2012. So 2020 – 2012 = 8 years old.
If the tires show any cracks in the tread or sidewalls regardless of age they HAVE to be replaced.
The tires “generally” can be increased in size by 1 number, 100/90 to 110/90, but there's no real point to doing that unless you need more load rating of the tire. It may be unsafe to use larger tires due to rim width and age of the rim.
Tube type tires should have a new tube every replacement even though they look ok.
Always check the tire pressures before riding!
ELECTRICAL:
Check the battery. If it's the normal lead acid type and more than 2 years old it's done even though it seems ok right now. If it's an AGM type then get it load tested. When in doubt replace it.
Check the fuses and connections. Typically the fuse connections are corroded and need to be cleaned to get a good connection and not overheat. The standard auto fuse is not the correct length and will cause problems.
Check that the lights all work including the brake light from both the lever and foot pedal. Consider replacing all of the light bulbs.
Check the alternator for resistances if the information is in the FSM.
CABLES:
Take the cables off the bike. I know, the throttle cables are PITA. Disassemble them where possible, clean and lubricate with a light oil or motor oil in a pinch. The ones that don't come apart flush them with a solvent, let them dry for a couple of days and lube them with a good quality cable lube. WD40 is not a lubricant!
FUEL/INTAKE:
Take off the fuel tank cap and petcock sediment bowl and look for rust and contamination.. use a flashlight.. at the very least install an inline filter in the fuel line if the tank is rusty or the sediment bowl is full of "stuff". If the tank is rust free there is no need for an extra fuel filter assuming that the petcock filters are intact and clean.
Take out the air filter and inspect it, if it's dirty the bike will run poorly.. they're very sensitive to air filter condition
Take the plugs out of the 'drain tubes' that come off the airbox, if equipped. a bunch of oil, water, and disgusting stuff will probably come out of them.
Attach some short pieces of tube to the float bowl drains if they are missing, and open them. If the fuel that comes out is not completely spotless and clean, just pull the carbs right off and start taking them apart, it's worth it. If there's any particulate in the float bowls, that means there's probably stuff clogging your jets. Even if the carbs are clean, think about balancing them soon.. on an old bike, they're probably way out
Now that you've become intimately familiar with your new bike and everything is in order, go ride and have fun knowing that everything is good and will get you home.
Notes:
1) You've seen multiple references to using the FSM, Factory Service Manual. This is the only reliable information about your model. Every aftermarket service manual has errors, some small and some not so small.
2) Ball bearings have been standardized for a 100 years. Look at your old bearing for a number like 6302, that's the standard number. You can also use one of the Honda online parts fiche sites and frequently they have the standard bearing number listed in the description. Take the numbers to your local bearing supply house and buy them. You will save 50% at least over Honda pricing. Caution: do not buy the cheap Chineseium bearings, there's a reason they are cheap called inferior material.
3) When the FSM's were written and these vintage Honda's were produced things like fork oil and air cleaner oil were not created. Even engine oil was in a primitive state. You will see ATF for forks, 80-90w gear oil for air cleaners, etc. as recommended fluid. Use the modern fluids for the best results in reconditioning your bike.
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