Airhead pieces all over!

My Dyna was on my /6 when I bought it five years ago, with 44K on the bike. Don't know how long or how many miles were put on the Dyna before I bought the bike. I just turned 80K recently, and the Dyna hasn't missed a beat. No points. Reliable. That Dyna has taken me every year across I-69 to Port Huron on my way back east. Couldn't be more pleased.

I definitely love the Dyna III on the /7. Set it and forget it. But don't forget how to go back to points...and be sure you have those parts with you at all times. DAMHIK! But when the Dyna works, it is very nice.

I love reading stories like this one...its that "Ah hah!" moment that sucks you in for life with these machines. Kudos to you.

ps. Is your front tire on in the proper orientation? From the pic, it looks like a Metzler Lasertec, but the tread looks backwards. On the sidewall, there is an arrow indicating the direction of normal travel. Maybe I am wrong, but yours looks reverse.

AnnapolisAirhead said:

ps. Is your front tire on in the proper orientation? From the pic, it looks like a Metzler Lasertec, but the tread looks backwards. On the sidewall, there is an arrow indicating the direction of normal travel. Maybe I am wrong, but yours looks reverse.

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Nope...they're fine. I have the same tires. Your first thought is that the "arrow" of the tread should be the other way, but the tire is mounted correctly.

20774 said:

Nope...they're fine. I have the same tires. Your first thought is that the "arrow" of the tread should be the other way, but the tire is mounted correctly.

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Yup, what Kurt said. The tread looks backwards to me, too, but the tire is mounted correctly.

Whew...I just had nasty unwrapping of the tread pictures floating around in my mind. I have Bridgestone Spitfire S11 on my bike. But that was my thought exactly, that the tread should point like an arrow.

Dyna III frustration

Due to time constraints, I was unable to take a ride over the weekend.

Feeling confident, I rode to work this morning. It was a beautiful morning to ride; cool, clear, and little traffic. The bike performed almost flawlessly. I got a little vibration between 4 and 5k rpm.

The ride home, on the other hand, was a different story.

Ambient temperature was in the low 90's. The bike started well, easier than I have ever had it fire up. I left work and less than a mile later stopped for gas. Continuing home, I started to notice more and more vibration. By the time I got home, almost 30 miles, the bike felt very rough, and was missing occasionally.

I checked the timing again with the timing light, and it was exactly where it was when I set it Friday. I checked for proper advance function, and it seemed spot on. I did not check carb balance, as it was beastly hot in the garage and I didn't want to mess with it.

I'm hoping to ride the bike a couple hundred miles this weekend to a Volkswagen TDI event in mid-Michigan, and I'd like to have her running smoothly.

So, I'm going to throw it out to the more experienced members of the forum:

What am I missing? How can the bike be running great in the morning and be running poorly in the afternoon? Is it carbs? Is it timing? Is it valves?

Any suggestions would be most appreciated!

If the thinking is that it is the Dyna III, I'm wondering about what you said that the timing was where you left it. Could it be that one of the cylinder firing points has drifted so far that it is not directly on top of the other cylinder and that it has drifted completely out of the window?

The basic timing is set by the donut that is screwed on the advance shaft/collar. Then, each cylinder is adjusted independently by moving the pickup coils on either side. My /7 broke down on me soon after I put the Dyna III on. Turns out I had not tightened sufficiently the two small nuts that secure the coils in place. One had drifted. I managed to get it back good enough to get home where I could fine tune it.

Are you certain that "both" S-marks are on top of each other? Did you watch the movement of the marks as you advanced the throttle? You might see another come into view. Or it could off the other direction and would not be visible at all and would further disappear as you advanced the throttle.

So, I'd check the position of the two coils to be sure that one hasn't moved. Of course it could be the carbs or valves!!

Good questions, Kurt. Sometimes it's hard to think of all the relevant information to put in a post.

I still see two distinct timing images, but they are nearly synchronized, probably less than 1 degree apart. As I increase the RPMs, I still see two images, and they are consistently the same distance apart. That leads me to believe that the donut and the pickups are exactly where I set them.

Problem solved....I hope

I got to spend a little quality time with the R90 this afternoon, since the heat wave broke and the humuggity is tolerable.

After checking the valve clearances (good), dropping the carb bowls to look for dirt (clean), I decided to once again check the carb balance.

Dead on at idle, can't get it right at 1500 rpm . Seems to be a cable pull issue. With the throttle at idle position, the right carb has a little slack, the left has none. The left cable has no adjustment left to give it slack. Hmmmm. Must be a cable routing issue .

I try several different ways of routing the left throttle cable, and can't seem to come up with a way that does not "shorten" the left cable too much. Finally, I run the cable through the steering head and outside the frame. Finally, I get slack. A lot of slack. Whatever, I can now get the carbs to balance both at idle and at 1500 rpm.

So, it was most likely a cable routing issue that has been causing my problems. I'm riding her a couple hundred miles tomorrow, so I will see how it goes.

In the meantime, can anyone describe for me, or give me a picture of, a succesful left throttle cable route?

Try left carb adjuster with nut underside of carb top instead of on top
to get slack needed

Kevin, are the carbs in sync at 3000-3500? I usually do them at idle, then hold the revs to 3000-3500 and fine tune them in there. Make sure you have a fan blowing on the cylinders and take it for a 10 mile ride before you balance the carbs (I know you know this, just stating the obvious for future thread searches).

I figure at 3500 if they are in sync (and in synch as the RPMs creep up from idle to 3500), then they are likely to be in synch at cruising RPMs (4400-5000 for me). 1500 may be a bit low to set them.

AnnapolisAirhead said:

I figure at 3500 if they are in sync (and in synch as the RPMs creep up from idle to 3500), then they are likely to be in synch at cruising RPMs (4400-5000 for me). 1500 may be a bit low to set them.

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Here's what Snowbum says about making the adjustments just off idle:

"This is BEST done at a low rpm, an rpm above the idle rpm, but not too far above. The farther above the idle rpm, the less sensitive the adjustments and the harder it is to then get it right for the more critical area, the 'off-idle' position. Because of this, I recommend 1300-1500 rpm. You can lock the throttle if you have the factory friction screw at the bars, or, just hold the throttle."

You still want to check at higher RPMs, but adjustments when the butterflys are just opening meanst that small changes can be readily noticed. Ideally, once the throttle cables are under tension, they should remain at the same relative tension throughout the range. If that tension should change, for whatever reason, you'd never get the carbs balanced and it would be best to figure that out before moving further along.

Of course there is something to be said for balancing the carbs at the position where you spend most of your time!!

20774 said:

Of course there is something to be said for balancing the carbs at the position where you spend most of your time!!

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Duane Ausherman mentions that. He feels it is not possible to perfectly synchronize these engines across all rpm ranges, and that you will drive yourself crazy trying to do it It is better to get the engine running as smoothly as possible in your favorite cruising rpm range, and live with it otherwise

Yeah, Duane even espouses adjusting the carb as you're running down the road! He mentions getting the carb balanced at idle as well as the mixture and then ensure some slack in the cables. Then with the right carb adjuster locked, loosen the left carb adjuster and put the 10mm wrench in your pocket. After the bike has warmed up and you're at the cruising speed, reach down with the left hand and begin adjusting the carb in steps. When you find a position that seems good, stop the bike, tighten the adjuster nut, and verify that all is OK.

It's important to remember not to tighten the left adjuster any more than the initial slack otherwise you will mess up the idle balance. Typically in order to find proper synch point, you would want to only loosen or reduce the tension in the left cable.

It's also very important to do this on a deserted road and to be very careful. Reach down to adjust the carb takes your eyes off the road and splits your attention.

Hm. I think I'll do my carb adjusting on the center stand in the garage. That whole reaching down and fiddling with the carb while riding thing sounds a little, um, nuts

geisterfahrer said:

Thanks, Phil. Sealant it is. I was pretty sure the entire engine was original, but thought I'd specify everything since beemerguru had asked. What did the interior of your cylinders look like? The more I look at mine, the more I think they are just glazed. I'm thinking maybe a ball hone before I put it back together. Anybody have any advice there?

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You didn't mention having the pistons and bore measured. Might be that the bore is at the spec limit. I wouldn't want to put it back together without knowing.

Engine and Frame

I just now looked into this thread and early on there was a bit of discussion on removing/ installing the engine from/ into the frame. Yeas, the engine/ trans is the heaviest part of the whole bike and handling it requires a lot of strength, particularly when putting everything back together with new paint to protect.

One thing I have done over the years with dozens of different size and brand of bikes that seems to work on every make I have tried it on.... If you are dealing with just the bare frame and engine/ trans (no fork, etc.), simply place the engine onto a simple stand like a sturdy five gallon bucket or improvised fixture to hold said engine with the appropriate side/ cyl. downwards. Two persons of only moderate strength can then very easily hold the frame sideways and drop the frame over the engine to get everything aligned properly and back together. The frame is much lighter to manipulate around the engine than vice versa. Reinstalling it is a snap. Put a mounting bolt or two into place, hand tighten and when done, move the engine/ frame assy. back to its normal vertical attitude, finish the engine mounting hardware assy and there you have it. No straining, no scratched paint and no one with an injured back.

Try it, you'll like it!