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Old 11-23-2014, 03:26 PM   #1
OregonBob OP
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R100 valve clearance adjustment.

Why is the easiest thing so hard?

I bought an R100 (1983) last year. Lately it has been idling around 750 rpms and stalling out and I need to up the rpms at idle. When I bought it it idled above 1000 right where the gen light starts to flicker. All my reading says, adjust the valves and synch the carbs THEN adjust the idle. OK. Never done this before. Read the forum and looked at Youtube. Adjusted the port side with no problems. On the starboard side, the intake valve had a little freeplay and was adjusted. The exhaust valve was tight (no freeplay) and had no clearance. Turned the nut all the way out and all the way in and the rocker arm never came clear of the valve spring and could never get any clearance.

Where to go from here?
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Old 11-23-2014, 03:30 PM   #2
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Make sure before you adjust the carbs the engine is in OT (top dead center) for the side you adjusting. Then adjust the carbs to spec with your feeler gauges according to your climber. I think exhaust is .02 and intake .01. Don't quote me on that. If your already in OT then you might be looking at other problems. But sounds to me you just need to adjust and ride.
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Old 11-23-2014, 03:31 PM   #3
jclark83
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Did you rotate the engine 360 degrees before proceeding with the valve adjustment on the other side?
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Old 11-23-2014, 03:50 PM   #4
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Check your timing too. The F mark should be centered in the window at full advance. Valve adjustment, timing... then adjust carbs.
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Old 11-23-2014, 03:59 PM   #5
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Hi Bob I'm sure other will chime in but a great way to get the cam in the right spot is say this to your self on the side you are getting ready to adjust ...Inlet down, inlet up, then Top dead centre on that side. Check the clearances, then move across to the other cylinder then repeat, Inlet down, inlet up Top Dead Centre.

You can use a flashlight to see the piston falling and rising the bore, plus look for the T mark on the Flywheel in the litte timing hole on the left hand side of the bike. Then you know you have TDC on the correct cylinder that you are adjusting.

The push rods should be able to spin by hand. Cheers
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Old 11-23-2014, 04:10 PM   #6
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Quote:
Originally Posted by Dirt_Boy View Post
Inlet down, inlet up, then Top dead centre on that [one]
Been doing this for over thirty years and I may not say it out loud, but I still say it, whether it's a bike, car, tractor, or airplane (once).
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Old 11-23-2014, 04:49 PM   #7
disston
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I rotate the engine with a hex key in the alternator bolt. Spark plugs out, ignition off. Direction of engine rotation and the direction you turn it is clockwise, as looking at the front of the engine. I take the left side valve cover off, usually have a piece of paper or cardboard under the cylinder to catch that small amount of oil that will drip out when the cover is removed. I watch the inlet valve, after the inlet closes the next OT mark is TDC on the left side. Adjust left side valves at TDC.

Replace cover

Rotate engine 360* and stop when the OT mark is again in the window. Everything up to this point has been done sitting on my stool at the left side of the bike where the timing window can be seen. Now move over to the right side and take off cover, adjust valves.

Replace cover.

FIN

or whatever works for you. What is really important is understanding what is happening and knowing that the method, your method, works. The problem you had with one of the exhaust valves being tight, having no lash or gap? This on a running bike? Indicates a misunderstanding of the basic principle of your method. A valve that has no lash and can not be adjusted to have any lash is probably not on TDC. An engine can run with one valve too tight but it will run poorly. Poor idle is a symptom of this. But you should be able to adjust this valve. If it won't adjust then it is too serious a problem too run or you have not understood how to find TDC.
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Old 11-23-2014, 09:36 PM   #8
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Originally Posted by chollo9 View Post
Been doing this for over thirty years and I may not say it out loud, but I still say it, whether it's a bike, car, tractor, or airplane (once).
I'm glad that I'm not the only one.
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Old 11-24-2014, 06:45 AM   #9
CptImagine
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Valve recession ?

Assuming you had it at TDC, what kinda miles ? That era has been problematic since lead left gasoline . In Oct. my buddys 84RT was running like a top, 400 miles later at a rally it would not idle . One exhaust was as you described . Adjusted valves got him home . He needs a valve job . No need to remove front cover as suggested . Rear wheel off ground, MC in gear, turn the rear wheel, watch the rockers and timing mark .
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Old 11-24-2014, 07:00 AM   #10
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Originally Posted by OregonBob View Post
All my reading says, adjust the valves and synch the carbs THEN adjust the idle.
There is a good reason for this order of things and it's not just in case one or more valves might have no clearance.

When you adjust valve clearances you are also making very small changes to the valve timing. Opening up clearances reduces the length of time the valves are open and particularly important with respect to idle it reduces valve overlap. That effectively richens the idle mixture which can increase the idle speed. For the same reason if you tighten up loose clearances it will increase valve overlap and the idle speed can drop.

These are small effects but real and they will be more noticeable if the idle mixture is correctly set i.e. only as rich as it needs to be and no richer.
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Old 11-24-2014, 12:00 PM   #11
OregonBob OP
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R100 Valve Clearance Adjustment

Thanks for all the replies. This machine has 82,000 miles. I got it at 78k from a certified airhead nut who seemed to be very into maintenance, and seemed to be running smoothely until lately.

When I attempted this, I had the rear wheel off the ground, in top gear, spark plug removed, and rotated the wheel until I saw the "OT" in the viewing hole on the port side. Adjusted port side (.2mm exh. and .1 intake), then rotate until "OT" comes up again, then move to starboard side and repeat. It was there that I ran into trouble. The intake would adjust, but the exhaust would not. That is, by turning the adjusting nut, I could observe the gap between the rocker arm and the valve stem increasing or decreasing on the other three valves. On this particular valve, however, I turn the nut fully in or fully out and it never separates and creates a gap. When I am turning it out, you can see the spring following it out.

Does this mean there is some problem with this valve? If so, how do I tell? And if so, is the solution to pull the head off and then what? Replace valve, or head, or...?

I am going to go down to the shop and repeat everything I did yesterday which prompted my post. Meanwhile waiting for more guidance if anybody has any.

Part of the deal on getting the airhead is that I should be able to do the basic maintenance myself. I have no experience as a motorcycle mechanic, but have been working on boats and cars for a long time, so I should be able to noodle this out with some help.

Fortunately, I have a shop and a lift where I like to hang out and work on things, and am retired and have the time. But, riding is better than working on them. Need to get this fixed.
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Old 11-24-2014, 01:08 PM   #12
Stan_R80/7
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It sounds like the cylinder for which you are attempting to adjust the valve clearance is not at top dead center (OT). As mentioned before, top dead center occurs just after (or when) the intake valve closes. Pay close attention to the intake valve position along with the flywheel markings. Both the intake and exhaust valves will have some valve clearance at top dead center. Also, the piston can be seen through the spark plug hole using a flashlight when it is at top dead center. Good luck!


p.s. along with reading (or re-reading) the manual on adjusting the valves, here is some more light reading on this topic: http://bmwmotorcycletech.info/setvalves.htm
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Old 11-24-2014, 01:45 PM   #13
JimGregory
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If the valve had receded enough to not have enough threads to get play into it, then the engine would NOT be running on that cylinder most likely at all. You would have known something was amiss long before now.
I figure you have got something wrong in getting the starboard side to TDC.
Revisit with a fresh rested brain.

Edit: Or not. I may be wrong for sure. These bikes do want to run no matter what. FWIW I keep my idle around 1100 or a tad higher.
Maybe the PO knew the valve seat was on the way out. Was there a lot of threads showing when you first looked at it?
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Old 11-24-2014, 02:03 PM   #14
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Assuming the engine is at TDC for that cylinder and you cannot get clearance, you may have a very recessed valve. I ran into recessed valves with a bike that ran, but not well. Both valves were recessed but the exhaust was the worst. Even the intake adjuster was nearly bottomed out. Once you are sure you've done everything correctly, you may need to disassemble to fully inspect. You don't want any of it to break.


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Old 11-24-2014, 04:14 PM   #15
chollo9
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This was how close one of mine was when I took it apart to have the heads done. I could still get proper clearance, but it wasn't going to be long before I wouldn't.

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