1974 R90/6 issue(s)

Issue with 1974 R90/6

I’ve recently started experiencing what I would term as “slight hesitations” when riding my bike,,,,by “hesitations” I mean it feels like there’s a momentary loss of power and by “slight” I mean that it’s a very light, (not noticeable via the tach) hesitation,,,similar to what one might call a misfire?.
These hesitations are occasional and not limited to one range of RPMs or gear….it really feels like the engine is starved momentarily for fuel. The hesitations can happen under acceleration and just cruising along at stable throttle setting.

Initially, I thought it might be some crappy fuel, so I discarded the remaining two gallons and purchased fresh gas from a station that is very reputable and popular (thinking their gas has a high turnover,,,) Changing the gas didn’t improve the situation.

I double checked the carb fuel level in the float bowls and both were at 23 mm as measured from the center of the bowl to the top of fuel.

I verified the floats still floated, removed the carbs and thoroughly cleaned the body and the jets and the passage ways. I checked the timing at idle and at 3500 rpms and it was spot on,,,,I verified the valve clearances were within spec then I doubled checked the balance of the carbs and only had to make some very minor tweaks to the throttle cable locking barrel,,,,issue still exists.

Some additional info: the bike has an electronic ignition (Motorrad Elektric Alpha Classic), a Dynatek dual tower 3.0 ohm ignition coil, enduralast III charging system with heavy duty diode board, new starter relay, new voltage regulator, new battery, new battery cables, new engine wiring harness (not the main harness). The contacts/connectors for the grounds and other electrical connections were cleaned and given a slight coating of no-ox-id when I was putting the bike back together earlier this past summer.

Also, after I got the bike back together and timed and carb balanced it ran really, really well for about 300 miles,,,this occasional “hesitation” issue has just recently cropped up.

So now I’m leaning away from carbs/fuel delivery but am not sure where to look next.

Any ideas/thoughts/guidance would be appreciated.

Wow. I will be watching this thread. I have a 1974 R60/6, and I have been fighting with this same issue for a long time. Runs great, then suddenly misfires/stumbles/hesitates (pick one), then returns to normal running. Just yesterday, it really gave indication like it was fuel starved. I checked both sides and I'm getting over 10 ounces of gas thru each carb in less than a minute.

A Possibility

Gas cap? The tank vents through the cap. Could be stopped up. Had it happen to me on my ‘74 R90. Slight miss, a little stumble, misfire, finally just engine shut down. Good luck with your diagnosis.

My two cents

Okay, I will chime in with my two cents and maybe or maybe not it might help. I don't have the bikes you guys talk about, my problem was with an 84 R80RT. LOL, I spent almost a year and a half chasing a slight hesitation while riding that became a complete shutdown of the bike while riding only to turn the ignition key off back on and everything would work fine.

Before you start thinking about swapping out parts and such, I can tell you, over the period I was looking for a clue, I swapped out the ignition switch, no joy, same problem put the old switch back in. The electronic ignition module and bean can, again no fix, old stuff went back in.

Somewhere down the long long road, the problem finally was determined to be a ground issue. LOL, don't ask me what particular ground wire, I had all of them apart, cleaned and tightened, just like all the hot wires.

I NEVER found a smoking gun that I could point directly at all I can say is clean terminals, check the grounds, do the cheap easy stuff first, don't get sucked into thinking it is an expensive item failing, it may not be. Good luck.

Intermittent crap is the WORST problem to chase down. When you want it to fail, it won't and when it does, it is at the worst possible time. St.

Grasping at carb-induced stumble threads - Make sure the carbs are level about a longitudinal axis when the bike is on its center stand. Probably not it but it is easy to do.

so far,,,,,

Thank you all for the feedback/advice. This morning I checked and cleaned all the ground wires attach points and the connections at the starter relay, voltage regulator, diode board, stator, electronic ignition, coils and connections inside the headlight shell (those I just verified were on and snug,,,to take all those connections off and clean the connectors is a nightmare for another life, for me, anyways). I had an older gas cap on the tank when this issue first arose but I swapped that gas cap out for a new one just a week or so ago, so I'm doubtful it's a venting issue.

I'll take it out for a ride a bit later after it warms up a bit. BTW, it started right up and idled great right from the start when I tested it the garage after this mornings efforts (that's been the norm for this bike since I got it back together)

Just crack the gas cap when out for the ride...or when you first feel the miss. Easiest way to rule the cap breathing out.

Rs

My RS had a gas cap venting problem, no matter how much I tried to clean the vent, it would hiccup from time to time. St.

'Intermittent' reeks of electrical issues, a ground sitting high on the list.

so far,,,,hesitation still present

after yesterday's efforts of checking grounds and cleaning contacts and so forth I went for a ride,,,,issue still present. I tried to be more observant on this ride,,,what I noticed is it took about 5 miles of riding at moderate speed to have the hesitation(s) appear, but once they started (still occasional and very fleeting) they were prevalent for the rest of the ride (a total of about 15 miles or so). The bike still idles well at stop signs and sitting still in the garage,,so now I'm wondering if it's something "mechanical"? as opposed to electrical or carburation? I did try the open-the-gas-tank-cap on the ride but that didn't prevent the hesitations.

When it happens during a ride I would pull the clutch immediately and rev the motor up-and-down to ~5,000 RPM.

If the motor runs 'clean' at that point I would then look at fuel supply.

I put one of the early versions of the Alpha Omega ignition system on my '89 R100GS. It wasn't working perfectly. Motor started well but riding the motor 'stuttered'.

At that time I put the old ignition module and 'bean can' in and no problems.

I reported the problem to the seller and a few weeks later I got an email from someone in Taiwan who claimed to be the engineer on the Alpha system. I got two more sets of the Alpha Omega systems to try out and the last one worked correctly.

And my point...it could be the ignition system.

Guenther said:

When it happens during a ride I would pull the clutch immediately and rev the motor up-and-down to ~5,000 RPM.

If the motor runs 'clean' at that point I would then look at fuel supply.

I put one of the early versions of the Alpha ignition system on my '89 R100GS. It wasn't working perfectly. Motor started well but riding the motor 'stuttered'.

At that time I put the old ignition module and 'bean can' in and no problems.

I reported the problem to the seller and a few weeks later I got an email from someone in Taiwan who claimed to be the engineer on the Alpha system. I got two more sets of the Alpha to try out and the last one worked correctly.

And my point...I could be the ignition system.

Click to expand...

thank you for the input, I am tempted to put the points back in just to see what happens. The first time the engine hesitated it was after about 20 miles into a ride,,,,it happened only a couple more times that ride (total ride about 60 miles), then it started to happen with more frequency and much earlier into a ride such that now within just a few miles it starts and will repeat it quite a few times in just the first 10-11 miles

It won't hurt

To be honest, it wouldn't hurt to put the points back in and give it a try.

I have to admit, I have an Alpha system on my 84 R80RT and have never had a problem with it. LOL, I fell for the hype about improved performance and found I could have kept the stock electronic ignition and saved money. I can't see any advantage of the Alpha over stock.

And as I said, the intermittent problem I was having didn't go away with swapping out parts. I disappeared after a lot of contact and ground cleaning.

Over the winter, I installed a Wedgetail system on my 78 R100RS, now I could see performance gains with that system and I was very happy with spending the money on it. It was far better than the Dyna system I had in place. Sadly, I only put 1000 miles on it when Monday, I rear ended a stopped car because I took my eyes off the path to wave at a group of bikers on the side of the road.

The RS is pretty badly damaged, not sure if the frame is bent but I know I won't be rebuilding it. So I guess I won't be able to give long time report of the Wedgetail system performance. St.

STEVENRANKIN said:

To be honest, it wouldn't hurt to put the points back in and give it a try.

I have to admit, I have an Alpha system on my 84 R80RT and have never had a problem with it. LOL, I fell for the hype about improved performance and found I could have kept the stock electronic ignition and saved money. I can't see any advantage of the Alpha over stock.

And as I said, the intermittent problem I was having didn't go away with swapping out parts. I disappeared after a lot of contact and ground cleaning.

Over the winter, I installed a Wedgetail system on my 78 R100RS, now I could see performance gains with that system and I was very happy with spending the money on it. It was far better than the Dyna system I had in place. Sadly, I only put 1000 miles on it when Monday, I rear ended a stopped car because I took my eyes off the path to wave at a group of bikers on the side of the road.

The RS is pretty badly damaged, not sure if the frame is bent but I know I won't be rebuilding it. So I guess I won't be able to give long time report of the Wedgetail system performance. St.

Click to expand...

Holy smokes ! I hope you're ok, and that your bike can be fixed! What a bummer. Dang

Walking an talking

Oh I am walking and talking thank God, cracked a vertebra in my neck, lots of pulled muscles and bruising. Not bad for a 35ft flight at 6ft 45mph hard landing. Thank goodness I had a great helmet and gear. It could have been much worse. St.

STEVENRANKIN said:

Oh I am walking and talking thank God, cracked a vertebra in my neck, lots of pulled muscles and bruising. Not bad for a 35ft flight at 6ft 45mph hard landing. Thank goodness I had a great helmet and gear. It could have been much worse. St.

Click to expand...

Gracious ! Light a candle in thanks. Well at least you have the R80RT to ride when you get back to feeling up to it. I once owned a 1982 R80RT while I lived in Madrid,,,,best bike I ever owned by far,,,,I should have gone through the hassle and expense of importing it into the US when I moved back here,,,I would still be riding it

84

I keep the girl on the road now, just about 238,000 miles on her. She is my favorite bike by far. I liked the RS and always wanted one, now that I have had one and wrecked twice on it, I am done. LOL. St.

update (and hopeful resolution)

So, today I got back at it,,,I removed the diode board and tested it per the instructions EME graciously provided me. The diode board tested fine,,,the reason I wanted to test the board is due to something I read about installing an electronic ignition,,,they need a minimum voltage to operate properly and I wasn't sure if that was happening (I have had issues with what I thought was the charging system,,,I posted a series of messages about my issues earlier this year). Anyways, while riding the gen light would illuminate a bit (granted, with a KATDASH instrument and console light upgrade I came to understand that the gen light might stay lit a bit more than with stock console bulbs because the LEDs draw so much less power?). So, after awhile I pretty much ignored the gen light illumination (it was pretty mild).

When I removed the diode board I once again cleaned all the contacts and connectors and grounds before I reinstalled it. I also checked the starter relay,,,,and when I tried to remove the wire that goes to post 85 the plastic shield cracked and crumbled in my hands,,,,so, I replaced that connector (which showed quite a bit of corrosion under the metal connector). Per the wiring diagram I have Post 85 doesn't seem to have any relationship to charging or powering the coils . Since I had a spare starter relay I replaced it and double checked the rest of the connectors. I had planned to check the voltage regulator and stator and alternator per the instructions I received from EME, but thought I've changed somethings already,,,I'll put the bike back together and test ride it.

I took it out for a 30 mile ride and did not experience any of the hesitations I had been experiencing (and recently the hesitations would start showing up (sporadically) after about 5 miles or so and continue throughout a ride).
And, the gen light only flickered at idle (right about 1,000 RPMs) the instant I came up off of idle the light would go out. I took that as a positive sign.

When I got back to the garage the battery showed 13.04 VDC with the engine off.

So, at least I had a 30 mile ride without hesitations,,,,I'll see how things go on a longer ride later this week, but for now, fingers crossed, it runs much better.

Good find

I always advocate looking at the simple things first before going deeper. A ten cent terminal is better to replace than a high priced ignition module or what not. Glad you may have found your problem and have it fixed. Enjoy the riding. St.

another update,,,,,

Well, I thought I had solved the hesitation issue but I had not. For a brief spell, after double checking grounds and connections (changing those that looked sketchy), I was able to ride about 90 miles total in 3 rides without the hesitations,,,,then, they started appearing again and became even more pronounced and prevalent than before.

I talked to Rick at Motorrad about my ignition system (an Alpha Classic). The ignition system was with the bike but not installed when I inherited it,,,,so the system was about 3 years old, more or less. I described the symptoms and what I had tried to do to address the issue. He recommended (as others have on this forum) to go ahead and removed the system and reinstall the points. So I got some new points and AU return springs and installed those this morning,,timed the bike and took it for a ride.

It ran great. Granted, it was only about 25 miles (prior to replacing the points the bike would have started hesitating long before 25 miles) but there were no hesitations occurring anywhere in the RPM ranges/gears.

So, came back home, rebalanced the carbs, rechecked the timing with a strobe light,,,,all is good,,so far.

Rick thought it was possible the module was starting to go bad and that the age of the system put it around the time there had been some issues.

So, a Wedgetail is on order and should be here in Nevada in a couple of weeks !

I'll post an update when I get that installed, Thanks to everyone that read my posts and offered insight/advice/guidance and ideas,,,,very very much appreciated.