Why is changing the timing belts so critical? And just what ARE timing belts?
To understand this, you need to know how an engine breathes. Every four-stroke gasoline engine has pistons that move up and down inside of cylinders. At the top of the cylinders are valves. These valves open in order to allow fuel/air mixture into the cylinder, and to allow burned exhaust to exit the cylinder. As such, in our Goldwings, there are two valves per cylinder: Intake and Exhaust.
The four cycles of an engine are intake, compression, power, and exhaust. On the intake cycle, the intake valve is opened, and the piston moves downward, drawing fuel/air mixture into the cylinder. The intake valve then closes, and the piston moves upward, compressing the fuel/air mixture. When the piston reaches the top of its travel, the spark plug ignites the compressed fuel/air mixture. This causes it to burn, creating pressure which forces the piston downward. When the piston reaches the bottom of its travel, the exhaust valve opens. The piston then moves upward, forcing the burned fuel/air mixture out the exhaust valve. Just before the piston reaches the top of its travel, the exhaust valve closes. As the piston starts to move downward again, the intake valve opens once more, and the whole cycle repeats. When you are cruising along the highway with your engine at 2500 RPM, this happens 42 times a second, in every cylinder! Your valves are moving faster than the eye can see!
Our Goldwings (and most modern auto engines) have what are referred to as "interference engines." This means that if a valve is open, it occupies the space that the piston will be in when it reaches the top of its travel. That's why the exhaust valve closes just before the piston reaches the top of its travel, and why the intake valve opens just after the piston starts moving downward again. This allows the piston to compress the fuel/air mixture more, giving the engine a higher compression ratio, and allowing it to generate more horsepower from a given engine size.
If the valve were to stay open when the piston reached the top of its travel, the piston would hit the valve. This is why it's called an interference engine - the valve and piston interfere with each others movements. What happens if the piston hits a valve? Very bad things. At best, the valve is bent or broken, requiring the head to be removed to replace the damaged valves. At worst, the valve punches a hole in the top of the piston, spraying metal throughout the engine, breaking connecting rods, and essentially destroying the engine.
Not a pretty sight. So as you can see, it is of critical importance that the valves open and close at exactly the right time to prevent this disaster from happening. Our Goldwings are "overhead cam" engines, which means there is a camshaft directly overhead the valves. The camshaft turns at one-half the engine speed. On the camshaft are elliptical pieces of metal called "lobes" which push on the valves as the camshaft rotates, opening the valves at the correct time. Springs on the valves pull the valves closed when the cam shaft lobe moves away.
These camshafts are connected to the engine by...you guessed it, timing belts. These timing belts are not like the regular serpentine drive belts you see in your car. Automobile serpentine belts can stretch over time, and they have spring-loaded idler wheels that take up the slack as the belts age. If a timing belt were to stretch, it would throw the timing of the valves off, and the result would be catastrophic. Therefore, timing belts are designed not to stretch, not even the tiniest bit, EVER.
Therein lies the problem. Serpentine drive belts start to crack as they stretch and age. Timing belts, with their special fibers inside, don't stretch, so they don't crack - so a timing belt that is 20 years old with 80,000 miles on it can look virtually identical to one that was put on six months ago and has 500 miles on it. Honda's service schedule says to "inspect" the timing belt - but there is no practicable way of doing this, other than looking for broken teeth on the belt itself. A timing belt wears on the inside, where you can't see it. A timing belt that is about to break can look exactly like one that will run for another 50,000 miles.
So what to do? Simple - if you don't know how long the belt has been on your bike, or how many miles are on it, it's time to change it - now, before you start the engine again. Spending $80 and an afternoon replacing your timing belts is cheap insurance, and a great alternative to spending weeks and thousands of dollars on a new engine.
How long is a belt good for? It varies. Honda's official word is to "inspect" the belt every 24,000 miles, and replace it every 100,000 miles. It doesn't speak to belt age. A more realistic belt life schedule is 50,000 miles or every 10 years, whichever comes first. Personally, I replace mine at around half that: every 25,000-30,000 miles or every 5 years, whichever comes first.
More important: Belts that have been in an engine that has not been run for years will have taken a permanent "bend," with associated weak points and should be replaced BEFORE the engine is run. If you are buying a bike that has sat in a garage for a couple of years, replace the timing belts BEFORE starting the engine!
Replacing the belts
There are lots of horror stories of people attempting to replace timing belts, doing it wrong, and destroying their engines. However, if you have reasonable mechanical skills, a day to spend on the procedure, and pay attention to the steps involved, you can do it yourself with no problems. If you do not feel comfortable performing the procedure, please, take your bike to a mechanic.
IMPORTANT: It is extremely important that the motorcycle be DEAD COLD when you perform this procedure. This means it has not been run for many hours. Sitting overnight without running is sufficient.
I show the removal and disconnection of several wires and coolant tubes in this procedure. While not absolutely necessary (it's physically possible to do this procedure while leaving them connected) it will make the job FAR easier and less stressful. I recommend that you do it this way.
You will need:
- Two timing belts
- Four quarts coolant
- Six spark plugs
- Red Loctite thread locker
You can use Honda OEM timing belts, of course. You can also use Gates T275, NAPA 250275, or Goodyear 40275 belts. Gates manufactures both the NAPA and the Honda OEM belts, and the NAPA belts are less than half the cost of the Honda OEM belts, so you can make your decision there. Timing belts are NOT the place to economize. If it's not a name-brand belt, is made in China, or comes from questionable vendors such as Saber Cycle, then you need to look elsewhere.
Can you re-use the old coolant? Sure, if you collect it into a clean pan. But coolant is cheap, and you might as well check off "change coolant" from your maintenance list at the same time as we do the belts. Same goes for the spark plugs - we'll be removing them, and plugs are cheap, so why not change them now?
Disassembly
1. The first step is to take off the lower cowls. If you have any accessories that need to be removed before you can remove the lower cowls, do so now. In my case, I have a set of wind wings that I need to remove.
2. I also have a set of air horns that need to be disconnected, loosened, and pivoted out of the way.
3. To remove the fairing front cover, press inward at the center of the top of the cover. This will expose the posts seated in the grommets at the top corners.
4. Gently pull the top corners away, one at a time, to unseat the posts from their grommets. Note the black tab that is holding the front of the lower cowl in place - it's important that the lower cowl is fitted back behind these tabs when it is replaced.
5. Once both posts are unseated, remove the front cover.
6. Remove the screws on either side of the under cover.
7. While holding the under cover in place, remove the center screw.
8. Pull the under cover away.
9. Gently pull the inner edge of the lower cowl screw cover away from the screw head.
10. Be very careful removing these covers - pulling them back too far will snap the tab off of the outer edge. See how the tab hooks into the cowl. Gently rotate the inner edge back, then pull it straight out.
11. Remove the lower cowl screw.
12. Gently remove the lower cowl deflector. It pulls out approximately one inch at the bottom, then is pulled straight down to disengage the top tab, then is pulled straight back to disengage the front tab.
13. This is the top tab that needs to be disengaged.
14. And this is the front tab.
15. The side marker light trim needs to be removed next. OEM Honda trim is black plastic and looks different than my aftermarket chrome trim. My trim has screw caps that must be removed to access the screw heads.
16. Remove the three screws holding the trim and the marker light in place.
17. Once the screws and marker light are free, the lower cowl will easily pull away. Disconnect the cornering lamp wire and remove the lower cowl. Repeat steps 9 through 17 for the other side of the motorcycle.
18. Remove the ignition switch cover by gently pulling up at the bottom as shown until the posts disengage from the rubber grommets. Then release the tabs at the top and remove the cover.
19. Remove the left top inner cover by pulling the tab free at the rightmost edge as shown.
20. Follow by pulling each tab free in sequence until you get to the front tab.
21. This tab locks in place - be careful not to break it. Next, remove the right top inner cover the same way as you removed the left side.
22. Open and remove the radiator cap. This allows air in as we drain the coolant.
23. Place a pan (at least 5 quart capacity) underneath the water pump at the front of the motorcycle, and remove the drain bolt as shown.
24. Allow the coolant to drain into the pan. This will take a little while.
25. While the coolant drains, start removing each of the spark plugs. We will need to rotate the engine by hand during the procedure, and the compression pressure in the cylinders will make this very difficult. Removing the spark plugs eliminates the compression in the cylinders. Gently pull each of the spark plug boots (NOT the wires) until they come free of the spark plugs.
26. It's essential that no dirt or foreign debris fall into the cylinder when the spark plug is removed. If you have an air compressor available, use it to blow the debris out of the spark plug well before removing the plug.
27. Using a spark plug socket (there should be one in your bike's tool kit) gently loosen the spark plug, then remove it from the engine. You might want to check out the "how to read spark plugs" section of How to remove, analyze, gap and replace your spark plugs to check on the health of your engine.
You'll notice that on the left side of the engine, only two spark plugs are visible:
To access the rearmost plug, first remove the left side cover:
And then the left engine cover:
At which point you will then have access to the left rearmost spark plug boot:
28. Stuff a shop cloth or towel into the spark plug well to ensure nothing accidentally falls into the cylinder.
29. Once the coolant has finished draining, replace and tighten the drain bolt. Leave the pan in place, there will be more coolant to catch shortly.
30. Locate the coolant tubes on the bottom of each radiator. Loosen the band clamp on each of the tubes.
31. Once the band clamp is sufficiently loosened, slide it down out of the way.
32. Gently work each of the coolant tubes free of the radiators as shown.
33. Locate the oil pressure switch, on the right side of the oil filter as shown.
34. Gently peel the rubber boot away from the oil pressure switch to expose the electrical terminal.
35. Unscrew and disconnect the terminal. Screw the screw back into the terminal until we reassemble everything to avoid losing it.
36. Feed the oil pressure switch wire up and out of the way.
37. Tucking the boot up in the radiator grill is a good way of keeping it out of the way.
38. Use pliers to squeeze the hose clamps on the two hoses located on the front of the water pump.
39. When the clamps are squeezed and loose, slide them down the hose. The second hose clamp is being loosened in this picture.
40. GENTLY wiggle the hoses free of the pipes on the water pump - you don't want to split the ends of the hoses, or break the pipes. Coolant will drain from both the pipes and the hoses once they are freed.
41. Once finished draining, move the hoses out of the way.
42. On the bottom of the left side of the bike (SE and some Aspencades), you'll find the foot warmer heater hose.
43. Gently pull the heater hose free.
44. Pull the heater hose free of the frame and move it out of the way.
Timing Belt Replacement
45. We're finally ready to start work on the timing belts! Using a 10mm socket and extension, start removing the bolts holding the timing belt covers in place. There are two covers - the left one covers almost the entire front, and the right one which covers only the right pulley.
46. Gently pull the right side cover away. Note the cover gasket has been pulled away. This gasket seals the cover to the engine, keeping moisture and dirt away from the timing belts.
47. Gently push the cover gasket back into its channel if it was pulled free.
48. Remove the crank bolt cover. It needs to be removed in order to gain clearance to slide the left cover out.
49. Slide the left cover out to the left. Make sure you aren't snagging any wires or hoses as you do so.
50. Examining my left cover, I realized that a previous owner had installed the gasket incorrectly, allowing it to fold over during installation. This caused the gasket to become brittle and hard, and break into pieces when the cover was removed. I was forced to order OEM replacement gaskets from Honda. When I removed the gaskets from both covers, I discovered that both of them had become hard and brittle in several places, causing very poor sealing. I'm glad I replaced these gaskets as a result - you might want to consider doing the same.
51. There are three different sizes of bolts holding the covers in place. I measured the shaft of each of them (in mm).
52. When I need to keep track of different bolt sizes, I like to place the item I took apart on the ground, and insert the different sized bolts into their holes. In case you lose track of which size both goes where, you can refer to this image.
53. To rotate the engine crankshaft, fit a socket over the bolt in the middle of the crankshaft pulley.
54. Look for the "1.2 T/F" mark on the pulley as shown.
55. Rotate the engine counterclockwise (as viewed from the front of the engine) until the horizontal line between the "T" and the "F" on the "1.2 T/F" mark lines up exactly with the line in the center of the arrow on the engine block.
56. Look at the camshaft pulleys on both sides. You should see the word "UP", right side up, and the horizontal line underneath the "UP" should line up with the notch on the edge of the case. If the word "UP" is upside down, rotate the engine one full rotation, repeating step 55 and 56. Remember, the camshaft pulleys rotate once for every two rotations of the crankshaft pulley.
57. It is of CRITICAL importance that the crankshaft and BOTH camshaft pulleys have their lines matching up before proceeding further.
What if the crank is lined up, one camshaft pulley is lined up, but the other one is not? This means one of two things:
- A belt has skipped a tooth
- A previous owner/mechanic installed a belt incorrectly
A belt can be off by one tooth without causing engine damage, but one tooth only. However, the engine will run roughly and will get terrible gas mileage as a result.
58. Identify the right belt's tensioner. This pulley presses on the belt, making sure the belt has exactly the correct amount of tension.
59. Loosen (but do not remove) the two bolts holding the tensioner in place. Half a turn once the bolt breaks free is enough. You will notice that one bolt is the slider bolt, and the other is the pivot bolt. Here, the slider bolt is being loosened.
60. In this picture the pivot bolt is being loosened. As soon as both bolts are loosened, you will likely see the tensioner move. Note the spring just below the tensioner. This spring is used to hold the tensioner in place while it is being adjusted. Once the tensioner is tightened in place, the spring is no longer used until the next time it is loosened.
61. With your fingers, gently slide the belt off the tensioner.
62. Move the belt above the tensioner to give it lots of slack.
63. Pull the belt free of the right cam pulley. Be VERY careful not to rotate the cam pulley while doing this. Rotating the pulley can cause the powerful valve springs to quickly and suddenly rotate the pulley, and cause a valve to hit a piston.
64. Pull the belt free of the crank pulley.
65. Pull the old belt free of the engine.
66. As you can see, this belt looks to be in perfect condition - no cracks or evident wear, despite having over 60,000 miles and being 12 years old.
67. To be able to remove the left belt from the crank pulley, the ignition pulse generators must first be moved. The lower pulse generator needs the lower bolt removed, and the upper bolt loosened.
68. Once the lower bolt is removed and the upper bolt loosened, slide the pulse generator away from the crank pulley.
69. The upper pulse generator must be removed. Remove both bolts.
70. The bolt on the left (closest to the right side of the bike) has a metal stay attached. Check the position of the stay so you can see how it fits back in, then remove it.
71. Gently pull the pulse generator out of the way.
72. Loosen the left belt's tensioner pivot bolt - break the bolt free, then rotate 1/2 turn.
73. Do the same with the slider bolt.
74. Pull the belt off of the tensioner.
75. Gently pull the belt free of the left cam pulley. Again, be sure not to rotate the pulley.
76. Pull the belt free of the crank pulley.
77. Remove the belt from the engine.
78. Check the tensioners for free play. They should spin freely and have no free play whatsoever. I would consider replacing tensioners at 100,000 miles regardless of their condition. The failure of a tensioner has the same consequences as the failure of a timing belt. Tensioners have sealed bearings and should NEVER be greased.
79. Timing belts can be damaged by oil and grease, so any oil and grease should be removed from the tensioner. My preferred method of oil/grease removal is brake cleaner - however, do NOT spray it directly onto a tensioner.
80. Spray some brake cleaner onto a shop towel.
81. Gently wipe the surface of the tensioners to clean them.
82. This is the Gates timing belt that I installed on my Goldwing - one belt per box. Before handling them, wash your hands of any oil or grease, or put on a new set of gloves.
83. The belts are delicate! Never bend the belt in a tight radius, as it can damage the internal fibers that make it strong.
84. We fit the left belt first. Fit the belt over the inner pulley of the crank.
85. Without moving the crank, pull the top of the belt taut so that there is no slack.
86. If you have managed not to move either the crank or the cam pulley, the belt teeth should slide perfectly into the cam pulley as shown.
87. Slide the belt up over the tensioner. Don't tighten the tensioner at this point.
88. Check to make sure the crank pulley is still lined up perfectly with the case mark.
89. Check to make sure the left cam pulley is still lined up perfectly with its case mark.
90. Replace the upper pulse generator, including the stay that fastens with the leftmost bolt.
91. Reposition the lower pulse generator, apply red Loctite to the bolts, then replace and tighten the bolts. Important: Make sure the wires for the pulse generators are routed correctly behind the stays, so that they cannot touch the belts when they are turning!
92. Slide the right belt in behind the frame.
93. Fit the belt over the outer pulley of the crank. Without rotating the crank, pull the bottom of the belt taut so that there is no slack.
94. If you have managed not to move either the crank or the cam pulley, the belt teeth should slide perfectly into the cam pulley as shown.
95. Slide the belt down over the tensioner. Don't tighten the tensioner at this point.
95. Check to make sure the crank pulley is still lined up perfectly with the case mark.
96. Check to make sure the left cam pulley is still lined up perfectly with its case mark. If you did not have the belt taut enough, the pulley can be off by a tooth, as shown here.
97. If you need to rotate the pulley in order to get it to line up, do NOT attempt to do it by hand - you will not be able to resist the powerful valve springs. Instead, drive two screws about an inch and a half apart into a piece of wood, as shown.
98. Remove the belt from the cam pulley. Insert the heads of the screws into the pulley holes and use the leverage of the wood to slowly rotate the pulley until its marks line up once again. Then re-fit the belt to the pulley and check the alignment again.
99. Fit the socket to the crank pulley and rotate the crank 90 degrees (one quarter turn) clockwise, then 90 degrees (one quarter turn) counterclockwise. Re-check that the alignment marks on all three pulleys are aligned.
100. Apply red Loctite to the threads of the tensioner bolts. Tighten the bolts on the tensioners - tighten the slider bolt first, then the pivot bolt. Don't torque them at this point, just snug them up so that the tensioners won't move.
101. To properly tension the belts, I use a small luggage scale.
102. I fashioned a hook out of a coat hanger, to allow me to pull the belt without damaging it.
103. The belt tension is measured on the side away from the tensioner. Place a ruler next to the belt so that the top of the ruler's scale is level with the top of the belt.
104. Apply 4.4 lb of pressure to the hook over the belt. Look at the belt on the ruler - with 4.4 lbs of pressure applied, the belt should be deflected 5-7 mm (I set mine to 5 mm). If the belt deflection is less than 5 mm, then the belt is too tight. If the deflection is greater than 7 mm, then the belt is too loose.
To adjust the tightness of the belt, first loosen the pivot bolt of the tensioner, then very slightly loosen the slider bolt. Adjust the tensioner up or down to tighten or loosen the belt as required, then tighten the slider bolt. Finally, tighten the pivot bolt and re-check the belt tension.
When I did this procedure on my GL1100, I found the tensioner springs were quite weak, and did not apply anywhere near enough tension to the tensioners, resulting in belts that were too loose. When I did this on my GL1500, I found that the tensioner springs were just about perfect - allowing the springs to apply tension to the belts, then snugging up the tensioners, gave me exactly 5mm of deflection with 4.4 lbs of pressure applied.
Once you have tensioned the left belt, repeat the process on the right belt.
105. Using a torque wrench, torque the bolts on the tensioners to 19 ft-lb.
106. Make one last check of all three pulleys to ensure that they are perfectly aligned. This is the moment of truth! Affix your socket to the engine crank, and slowly turn it counterclockwise. You want to make at least two (preferably more) complete rotations. You are checking to ensure that you have done everything correctly, and that none of the valves will touch any of the pistons.
If at any time you feel sudden resistance or pressure, STOP! Rotate clockwise back to the alignment marks and re-check your work.
107. The friendly Gates people include a sticker for you to stick on your timing belt cover, to remind yourself (or perhaps the next owner) when the timing belts were last changed. If your belt doesn't have a sticker, use a marker or other reasonably permanent method to mark the mileage and date of installation.
108. As my timing belt cover gaskets were in sad shape, I pulled them out and installed my new gaskets. Had I known how hard and brittle the old gaskets had become, I would have ordered these in advance, rather than waiting until I had things taken apart to order them.
109. Slide the left cover into place. Check the entire cover (especially the right side) to make sure the gasket hasn't peeled out of its channel, and is correctly in place against the engine. Replace the bolts and tighten them.
110. Slide the right cover into place, again making sure the gasket is in the correct position before bolting it into place.
111. Replace the crank cover, ensuring the "UP" is facing upward, and bolt it into place.
112. (SE only) Feed the heater hose down behind the frame as shown.
113. (SE only) Pull the heater hose to give you some slack.
114. (SE only) Fasten the heater hose in place with the orange rubber skirt.
115. Slide the coolant tubes over the radiator tubes.
116. Slide the band clamp in place and tighten it. Repeat on the other radiator tube.
117. Route the smaller coolant tubes behind the frame and push them gently onto the water pump pipes.
118. Compress the clamps and slide them into place over the outlets.
119. Feed the oil pressure switch wire down to the oil pressure switch. Connect and tighten the lug onto the switch.
120. Slide the rubber boot over the switch.
121. Time to install the new spark plugs. Spark plugs should be gapped to 0.031 to 0.035 inches - although it has been a long time since I saw new plugs from the manufacturer that weren't already gapped correctly.
122. Use a gapping tool to adjust the gap if necessary.
123. Always apply anti-seize to the threads of the plug before installing it. This will keep the steel plug from seizing in the aluminum head of the engine.
124. Rub the anti-seize around the circumference of the threads.
125. Insert the spark plug into the well and start threading it in by hand until you are sure it is not cross-threaded. Cross-threading a plug in an aluminum head has dire consequences!
126. Place the spark plug socket over the plug and continue to thread it in by hand until it is finger-tight.
127. Using a socket wrench, tighten the plug exactly 1/2 turn. This will compress the crush washer and correctly torque the plug. Note: This is for NEW plugs only - if you are replacing old plugs, the crush washer will have already been crushed, and tightening a full half turn past finger tight is a good way to break a plug off in the head. In this case, use a torque wrench and torque the plug to 12 ft-lb.
128. Replace the spark plug boot over the plug and push it into place. Make sure you put the correct boot over the correct plug!
129. Any non-silicate coolant can be used in Goldwings, but the Honda OEM coolant is guaranteed right, and it's reasonably cheap. You'll need four quarts of it.
130. Using a funnel, slowly pour in as much coolant as the bike will allow. You will likely only get 1 1/2 or 2 quarts in before it fills up to the neck - so be ready for it! Once it does fill up to the neck, let it sit for a minute until the bubbles of air work their way up, then add some more. Repeat this until you've got at least two quarts of coolant in. Turn the ignition on and crank the engine briefly. This will move coolant through the engine and radiators. You should be able to get another quart of coolant in cranking the engine like this.
131. Start the engine and let it idle. You will see bubbles start to come up the radiator neck, and the coolant level will go down as the bubbles come up. Immediately as the coolant goes down, add more coolant to keep the level at the radiator neck as shown. Keep doing this as the engine warms up, until you've got all of the fourth bottle of coolant in the engine.
132. While the engine is running, install the radiator cap and make sure it is tightened all the way. Allow the engine to warm up to normal operating temperature - at least until you hear the radiator fans come on.
133. Remove the coolant reservoir cap.
134. Check the level of coolant in the reservoir. When the engine is at operating temperature, it should be between the two holes on the dipstick. If it is low, you should add coolant to the reservoir (not the radiator). Shut the engine off.
Reassembly
135. Place the lower cowl back into position. Ensure the innermost tab (with the hole in it) fits behind the black tab protruding down from the radiator grill mentioned in step 4. This holds the front of the lower cowl in place.
136. Replace your side marker light and trim, and screw it into place.
137. Replace your screw caps (if you have them).
138. Replace the lower cowl deflector. Insert the front tab first, then the top tab, then slide the deflector to the left to line up the screw holes.
139. Tighten the lower cowl screw.
140. Replace the lower cowl screw cover - insert the tab first, then press fit it over the screw head.
141. At this point you would repeat the procedure to install the lower cowl on the other side of the bike. Once that is complete, lift the under cover into place.
142. Insert the center screw to hold the under cover in place.
143. Ensure the posts at the front, on the bottom of the lower cowls fit into the holes on the top of the under cover (visible at the front edge where the lower cowl and under cover meet) - on both sides! Once the posts are in place, replace and tighten the screws on either side.
144. Make sure the tabs at the bottom of the front cover fit behind the ridge of the under cover, and that the tab on the bottom center of the front cover fits into the slot in the under cover. Align the front cover, then press the posts on either side into their respective grommets.
145. Insert the forward tab of the left top inner cover into its slot in the dashboard.
146. Work your way around the top inner cover, inserting the tabs into their slots, until you finish up with the tab on the inner part of the fairing top. Repeat to install the right top inner cover.
147. Insert the top tabs of the ignition switch cover into the dash, and press the posts down into their rubber grommets.
148. You're done! Go have yourself a cold one, you deserve it!
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