The Airheads Beemer Club is a non-profit club reclaiming the 'Legendary Motorcycles of Germany'

Topic-icon Elevated Engine Idle RPM

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1 month 2 weeks ago #5303 by 895
Replied by 895 on topic Elevated Engine Idle RPM
The short-term fix is to install rubber bushings on the front motor mount. The rubber replaces the 5mm spacers located on either side of the engine block.
The tightening torque is lowered to 12 ft-lbs. The rubber bushing is sourced from motor mount off 57 Chevy. Alternately, use BMW /2 rubber motor mount bushings.

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1 week 5 days ago - 1 week 5 days ago #5474 by 895
Replied by 895 on topic Elevated Engine Idle RPM
We completed a 2100-mile, 6-day trip from Cape Cod to West Virginia. The Maryland Airhead's Last Days of Summer rally is so good that we're willing to travel 550 miles (one way) to attend this event. The R65 and my R75/5 LWB performed very well except the R65 battery began to fail on the second day. My R75 battery is apparently weak also because the starter "cricket" noise was present during engine-cold-start when it was unusually cold that morning. We found a best-fit replacement battery for the R65 in Cumberland, Maryland. The R65 engine was still difficult to start in the morning. It would fire on one cylinder repeatedly when cranked by the electric starter.

My R75 starter "cricket" went away when the morning temperature was above ~55 degrees. I used a voltmeter on battery terminals with engine running.
The R75 electro-mechanical voltage regulator would cut off charging voltage increase at ~13.2 volts. I increased the voltage regulator's spring pre-load tension a bit such that charging voltage would rise to ~14.2 volts before voltage regulator cut-off occurred.

The R65 would fire on only one cylinder engine-cold-start. We tried cleaning out the starting jet in the bottom of the float bowls. The engine has resistor spark plugs installed which is wrong. I advised my riding buddy to get non-resistor spark plugs installed ASAP. I also think the spark plug lead's resistance should be verified correct 5000 ohms. He thinks the ignition timing is not set properly.
Last edit: 1 week 5 days ago by 895.

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1 week 3 days ago #5477 by Wobbly
Replied by Wobbly on topic Elevated Engine Idle RPM
Replacing everything in the sparkplug circuit (wires, caps and plugs) will cost less than $20 per bike. It's the least expensive repair insurance you can buy for an Airhead. And all those parts, even the correct ones, eventually die from old age. So theories, conjecture, measurement and testing are really a complete waste of time, considering the low cost and ease of installation.

NGK 5K Ohm caps

Don't hide 'em, Ride 'em !!
#15150

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1 week 3 days ago - 1 week 3 days ago #5480 by 895
Replied by 895 on topic Elevated Engine Idle RPM
Thanks. What do you use for replacement spark plug lead wire?
Last edit: 1 week 3 days ago by 895.

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1 week 3 days ago - 1 week 3 days ago #5481 by Wobbly
Replied by Wobbly on topic Elevated Engine Idle RPM
It's called your local auto parts store. You walk in and say to the guy, "I need metal core spark plug wire by the foot. And while you're back there could you bring out 2 NGK BP7ES spark plugs, too ?"

He'll say, "How many feet."

Then you say, "3 feet, please."

It's really that simple.


If you don't like leaving your chair, then you can get pre-made wire sets from Motorrad Elektrik.

Don't hide 'em, Ride 'em !!
#15150
Last edit: 1 week 3 days ago by Wobbly.

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1 week 2 days ago #5486 by 895
Replied by 895 on topic Elevated Engine Idle RPM
After spending the weekend rebuilding the R65 carburetors (new O-rings, diaphragms), engine still exhibits poor cold-start capability. We've already tried cleaning out the starting jet in the bottom of the float bowls. Carbs are balanced at 5000 RPM and engine runs pretty smooth now.

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