James,
Here's the differences:
17. Loosen the locknut on the idle stop screw. Adjust the idle stop screw until the bottom edge of the throttle cam is aligned with the edge of the front corner of the throttle stop screw boss.
Do NOT install the throttle cable at this time.
On the XR4, the throttle cam lever is angled upward toward the back. This adjustment is to put the aft/lower edge of the throttle cam 1/8 inch from the forward edge of the throttle stop screw boss. (I use a 1/8 inch drill bit as a gauge.)
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19. While the engine is being cranked, adjust the throttle primary pickup screw until the specified throttle primary pickup mark on the timing decal is aligned with the timing pointer. See the Specifications in the General Engine and Tune-Up chart for the correct setting.
11 degrees ATDC, according to the Murkery manool.
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23. With the lever in this position, move the roller arm until the roller just makes contact with the throttle cam. Without moving the roller arm, tighten the three carburetor synchronizing screws to hold the adjustment.
Maximum Advance Timing
This is accurate, not the spacing I had "remembered".
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26. Loosen the locknut and adjust the maximum spark screw until the maximum spark advance timing mark is aligned with the timing pointer.
AN EXPLANATION: This adjustment will result in a spark advance reduction of 2? at maximum rpm, due to the spark advance characteristics of this ignition system
18 degrees BTDC, acording to the Manual. Go 23 degrees
IF you discard the "advance" module.
Whether or not you use the module is a toss up. If it works, it'll keep it idling under adverse conditions, and mid range timing will be a bit slower and easier on the engine. If it catastrophically fails at WOT, it'll hit you in the back of the head with a rod cap. (Theoretically, I haven't heard a lot of incidents)
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32. Use a feeler gauge and check the clearance between the roller and the throttle cam at WOT. This clearance should be 0.010-0.015 in. (0.25-0.38mm). Tighten the locknut to hold the adjustment.
This isn't rocket science, and needn't be real precise either. The object is to insure that there is a
little free play in the carb linkage so you don't damage carbs when you mash the throttle.
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46. Install the powerhead cowling.
If sufficient throttle cable barrel adjustment is not available, a check MUST be made for correct installation of the link rod (located between the throttle lever and the throttle cam). Each end of this link rod must be threaded into its plastic barrel until it bottoms against the throttle lever or the throttle cam casting, and then backed out from this position ONLY far enough to obtain correct orientation of the link rod. The link rod must be backed out LESS than one turn. All timing adjustments must be reset after this procedure has been completed.
If you even remotely suspect an ace (spelled with a double s) mechanic has been here, I'd check this link rod as a first step, to avoid repeating all the other steps. On the other hand, maybe you enjoy it so much you want to do it twice.
I'm going back to bed.
hope it helps
John
