zombiepotatosalad
New member
I want to set the valve clearances right, but I saw in a video that part of the procedure is setting the timing mark correctly. How do I do that with this model?
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'77 R100: Achieving TDC
- Thread starter zombiepotatosalad
- Start date
Not sure I understand...setting the valve clearances and setting the timing are two separate steps. You set the clearances with the engine at the flywheel top dead center mark on compression stroke for each cylinder...the OT mark should be in the middle of the timing window. You set timing so that the points open up (ie, the spark plugs fire) when the flywheel S-mark is in the middle of the timing window.
Does that make sense with what you're trying to do??
So to set the valve clearances, the best way is to take the valve covers off and put the transmission in high gear...have the bike on the centerstand. Then stand over the rear wheel and pull on the wheel in the direction of travel and watch the valves on the left side. Watch the intake valve be pushed in and then watch for it to start to move out. You are now beginning the compression stroke. Sit by the side of the engine and watch the timing marks in the window. Start bumping the rear wheel around with your hand. Watch for the F-mark (full advance), then the S-mark (idle timing), finally watch the OT mark show up. At that point, the left side valves are ready to be set. 0.15mm intake and 0.20mm exhaust. Once that's done, you can repeat moving the rear wheel until you see the right side intake valve move in, then out. Back to the left side and watch the timing marks as you bump the rear wheel until you see the OT mark...now set the right side valves. OR...once you've done the left side valves, bump the rear wheel around so that the flywheel turns 360 degrees to the next OT mark...now set the right side valves.
Hope that makes sense.
Does that make sense with what you're trying to do??
So to set the valve clearances, the best way is to take the valve covers off and put the transmission in high gear...have the bike on the centerstand. Then stand over the rear wheel and pull on the wheel in the direction of travel and watch the valves on the left side. Watch the intake valve be pushed in and then watch for it to start to move out. You are now beginning the compression stroke. Sit by the side of the engine and watch the timing marks in the window. Start bumping the rear wheel around with your hand. Watch for the F-mark (full advance), then the S-mark (idle timing), finally watch the OT mark show up. At that point, the left side valves are ready to be set. 0.15mm intake and 0.20mm exhaust. Once that's done, you can repeat moving the rear wheel until you see the right side intake valve move in, then out. Back to the left side and watch the timing marks as you bump the rear wheel until you see the OT mark...now set the right side valves. OR...once you've done the left side valves, bump the rear wheel around so that the flywheel turns 360 degrees to the next OT mark...now set the right side valves.
Hope that makes sense.
zombiepotatosalad
New member
What I'm trying to do is set the distance between the end of the valve and the rocker arm.
pglaves
#13338
Rotate the engine until the OT mark on the flywheel is in the center of the timing window and one of the cylinders has detectable play at both valves while the other cylinder has no play with either valve. The timing window is the round hole, probably with a rubber plug, on the side of the engine case.
Then adjust the valve clearance on the side that had some free play to begin with. Use a feeler gauge between the end of the valve stem and the rocker arm.
When done with the first side rotate the engine exactly one full revolution until the OT mark is centered in the timing window. Repeat the clearance adjustments on the second cylinder.
Use the specifications for the clearances on your engine. These have changed over time and I am not sure what current wisdom for clearances are. I was always happy with .006" intake and .010" exhaust. There may be later Airhead wisdom about to be provided, I hope.
Then adjust the valve clearance on the side that had some free play to begin with. Use a feeler gauge between the end of the valve stem and the rocker arm.
When done with the first side rotate the engine exactly one full revolution until the OT mark is centered in the timing window. Repeat the clearance adjustments on the second cylinder.
Use the specifications for the clearances on your engine. These have changed over time and I am not sure what current wisdom for clearances are. I was always happy with .006" intake and .010" exhaust. There may be later Airhead wisdom about to be provided, I hope.
zombiepotatosalad
New member
Here's the thing... I don't see a flywheel behind the rubber plug.
Hmmm...a stock engine should have a visible flywheel through the hole. So, if you stick your finger in the hole, how far does it go in? On my bike my finger will go in about half between my finger tip and the first knuckle before it hits the flywheel.
88bmwjeff
SF Bay Area
On my 88 R100 RT, it depends on how and where you are looking. The flywheel teeth are barely visible at the front of the hole, and the OT/S mark and Z/F mark (Kurt called it the F mark, but it's a Z on my bike) are only visible when directly in front of the hole. I don't know how you're rotating the engine, but those markets can go by fast if you're not paying attention. It's best to go slow while watching the timing hole. As others have mentioned, bumping the wheel works well too. Also, I'm assuming you have the spark plugs out, since it makes rotating the engine much easier. I know when I first started, I would see those marks go by the window fairly quick and it took me a while to learn how to go slow enough so that I could stop at the right point.
Right, but it seems to me that the rear wheel rotation to get the marks visible in the hole is not the best. My choice, put the bike on the center stand, take the front cover and valve covers off, put a key in the crankshaft, take out the spark plugs, put the bike in neutral and put a brigh light on the inspection hole. Turn the crankshaft slowly with the key until the timing marks appear in the hole, take a small paint brush and some white paint an paint the F, Z and OT marks. Then figure out which cylinder has both valves closed at OT. Adjust it, then 1 full rotation to the next cylinder and do it. You can use a timing light to indicate when the valves open and the F and Z marks will show you that. No?
88bmwjeff
SF Bay Area
zombiepotatosalad, in case you didn't know, you must disconnect the battery (just the negative will suffice) before you take off the front cover if you decide to go that route.
Felaw, I've done both. With some practice, it's not that difficult using the rear wheel. It takes some practice and the key is learning to do small bumps with rear wheel to avoid going past. For me, with an RT, it's way too much effort to take the lower RT panels off, move the oil cooler out of the way, disconnect the battery, then the front cover (plus, I have to reverse the step to reinstall). I found it easier, and quicker, to learn to use the rear wheel. However, if you have a naked bike with no oil cooler, then the time it takes to remove the front cover is dramatically reduced.
88bmwjeff
SF Bay Area
That's a good tip. I just may have to use that next time (assuming I remember it next time I go to adjust/check things).
zombiepotatosalad
New member
I can't see the flywheel when I look inside the hole.
pglaves
#13338
The rotation markings - OT, F, etc, are on tabs that will be visible when aligned with the hole. When turning with the rear wheel they may fly past almost undetected. My preferred method is to:
1. Disconnect the battery ground wire
2. Remove the front cover
3. Remove the spark plugs (optional for easier turning)
4. Rotate the engine clockwise facing the front of the engine
using the center bolt in the alternator rotor.
You can sit beside the engine and reach to the front and slowly turn the engine over until you see the OT mark in the window.
And, you have to have a flywheel if the starter turns the engine over.
ccolwell
Member
Make sure it's a long dowel. Lost a stub inside the Gold Star cylinder using that method. Damn, that was a long time ago; my dad was teaching me that method at the time.
I have actually moved to using Delrin plastic for a lot of these “odd” chores. I posted about a wooden dowel as most have easier access to wood. It also helps that I scavenged about 50 pieces, an inch square, 18 inches long that I can machine into most anything.
Of course they need to be long enough but with wood, there are fairly easy ways to remove due to easy workability.
OM
That would be a quick and easy solution/tool. I can’t operate them for anything else.
OM
pglaves
#13338
That would be a quick and easy solution/tool. I can’t operate them for anything else.
OM
They work pretty well for skewering olives or pickles at the bottom of the jar.
kbasa
Well-known member
I prefer to use the rear wheel in a low gear because I don't have to disconnect the negative ground, I don't have to rely on a hex key to move the fairly heavy rotating assembly and I don't have to open the front of the bike at all.
Mostly, by using the rear wheel, it means fewer things to take apart and then have to put back together and completely negates any requirement to touch the electrical system at all.
+1 on the paint marks on the flywheel.
When I learned to do valve adjustments on VW Bugs in the late 70s, I used the "pull plugs, rotate via crank bolt", but motorcycles give you a handy rotating wheel with pretty decent leverage.
