1976 R90/6 intermittent, brief total shutdowns

[Darbarian]

I just rode my *new* R90/6 home from The Motorcycle Garage where they took off the heavy, unattractive Windjammer-style fairing, rewired to get the original lights working and mounted new tires.

Cass (the wizard) recommended an immediate fuel fillup, which I did. 

The throttle was really stiff and did not return on its own.  I loosened the tensioner which fixed that.  

It would no hold an idle.  I have yet to fix that, but expect a few minutes with a screwdriver will resolve the issue.

 

THE CONCERN: Around town and as I was rolling home minding my own business behind a pickup doing about 72 according to my speedo, every few miles the engine would stone-cold QUIT. 

Not for long. I would only lose a few miles an hour in 5 or ten seconds of what I consider to be no-spark-zones, but it is very concerning that my new steed will decide to do this for longer, more frequent, or for goodness sake continue do it at all. 

 

Seems a bit like a coil problem to me, but I don't even know if there is one, where it might be located or what to do about it.

 

Any R90 guys with suggestions?

[Skywagon]

Google Duane Ausherman. He has a lot of how to on air heads

[Michaelr11]

First thing to check would be the battery cables, under the seat. Make sure that the technician tightened the cables on the battery and the negative cable on the back of the transmission.

 

Next, hook up a voltmeter to the battery and next time you experience power loss, check the voltage display. I had an Airhead that would suddenly lose power. Turned out to be a battery with an intermittent internal break and it would go to zero volts.

[Lowndes]

My brother had a very similar problem on his old airhead. Fuel, ignition switch, coil, plugs, fuel filter, fuel tubing, battery, battery terminals, fuses - ALL were checked thoroughly, some many times.  Drove him nuts.

 

We'd be riding along and all of a sudden he would be slowing down with a dead engine while he'd be twisting and tweeking everything he could reach, then it would start and run beautifully for an hour/day/week/month.  No rhyme or reason.  He got real tired of that after a year or so and took it all apart to get to the wiring. 

 

It was an intermittent ground.  But, it wasn't the usual loose connection.  The ground wire from the battery to the rear of the engine was completely severed inside the insulation about 6 inches from the battery at the bottom of a U bend.  There was NOTHING visible on the outside.  Battery acid had worked its way down between the strands inside the plastic insulation and gradually corroded the copper almost completely in one place.  Vibration (some say boxers vibrate) would cause the wires to touch or disconnect, run or quit.  Ran well after that was replaced. 

 

Ohm your wires while moving them around.  Wires at the steering head are subject to fatigue and very difficult to find breaks.   Old ignition switches are highly suspect, old grease and worn contacts. A continuity tester with a bright LED and a buzzer will let you keep your eyes in the work.  In intermittent problem is THE worst.

 

Good Luck, AND LET US KNOW WHAT YOU FIND!!

 

 

[dirtrider]

15 hours ago, Darbarian said:

I just rode my *new* R90/6 home from The Motorcycle Garage where they took off the heavy, unattractive Windjammer-style fairing, rewired to get the original lights working and mounted new tires.

Cass (the wizard) recommended an immediate fuel fillup, which I did. 

The throttle was really stiff and did not return on its own.  I loosened the tensioner which fixed that.  

It would no hold an idle.  I have yet to fix that, but expect a few minutes with a screwdriver will resolve the issue.

 

THE CONCERN: Around town and as I was rolling home minding my own business behind a pickup doing about 72 according to my speedo, every few miles the engine would stone-cold QUIT. 

Not for long. I would only lose a few miles an hour in 5 or ten seconds of what I consider to be no-spark-zones, but it is very concerning that my new steed will decide to do this for longer, more frequent, or for goodness sake continue do it at all. 

 

Seems a bit like a coil problem to me, but I don't even know if there is one, where it might be located or what to do about it.

 

Any R90 guys with suggestions?

Morning Darby

 

The stuff mentioned in the posts above should be checked out. 

 

If nothing easy found then you might have to go under the fuel tank  (left side of the frame) then look closely at the  starter-relay area.

 

Poor wiring connections  (corrosion/resistance)  on the bottom of the relay are somewhat noted for causing a power loss or intermittent partial shutdown.  At least make sure the wiring it tight & the connection's are not corroded.

 

You might also have a fuel restriction or plugged tank venting issue  (especially if you rode the motorcycle at higher speed for while before the problem showed up). Your problem has some of the ear marks of a fuel restriction, or possibly a tank venting issue, except a tank venting engine cut-out issue typically doesn't go back to running normal until you stop & allow the tank pressure to equalize. (usually by allowing to sit for a while or opening the fuel cap)

[Darbarian]

Thank you all.  I came to the right place.

 

I have been running my subconscious on this and figure the wiring is most suspect.  Yeah, intermittent is the worst, particularly for a few seconds out of every five minutes. However the bad ground sounds like a great place to begin my search.

 

It has a voltmeter that I was watching for hints. It was staying well up throughout the ride, seemingly unaffected by the engine cutout. 

[Dennis Andress]

Do everything mentioned above, then clean the ignition switch…

https://www.bushpigperformance.com/amp/how-to-clean-and-lub-your-ignition-switch

[taylor1]

As Skywagon mentioned, Duane Ausherman has an excellent airhead web site that covers about anything you can think of. Snowbum also has one and is a great source of all thing's airhead.

[waltroman]

a go to for me is addressing the contacts in the kill switch. sometime just working the switch back and forth a hundred time is enough to clean up the contacts if they are not too far gone.  I also do not make a habit of shutting the off with the kill switch even though there is a relay involved.  If the bike refuses to start the relay is the first place to look.

[SDCRJohn]

On 8/25/2023 at 9:12 AM, dirtrider said:

Morning Darby

 

The stuff mentioned in the posts above should be checked out. 

 

If nothing easy found then you might have to go under the fuel tank  (left side of the frame) then look closely at the  starter-relay area.

 

Poor wiring connections  (corrosion/resistance)  on the bottom of the relay are somewhat noted for causing a power loss or intermittent partial shutdown.  At least make sure the wiring it tight & the connection's are not corroded.

 

You might also have a fuel restriction or plugged tank venting issue  (especially if you rode the motorcycle at higher speed for while before the problem showed up). Your problem has some of the ear marks of a fuel restriction, or possibly a tank venting issue, except a tank venting engine cut-out issue typically doesn't go back to running normal until you stop & allow the tank pressure to equalize. (usually by allowing to sit for a while or opening the fuel cap)

I had this exact issue on my ‘83 R100. The starter relay internal connector, had corroded to a blue/green color. This is the component that usually has been taped around the upper frame spar, after the tank is removed. Remember, these are decades old machines, and stuff corrodes, cracks and rust. Once you correct this issue, should be a nice rider.