still working on odometer problems

[cruisin]

Well, my estimate (in another thread) of having the speedo within one or two mph was a tad off but did some more calibrating with the spiral spring. Now have access to a good GPS so will be checking against that this time. My next dilemma is the odometer. I did the fix on the brass gear as described on the airhead site even secured it better by cutting a slot in the end of the shaft and drilling some holes in the gear and made a keeper "staple" of sorts. Then glued it all together with JB weld. Now that gear is fine but something else lets it work for about 12 to 15 miles and quits again. I have had it apart numerous times and observed the movement of gears and wheels as I rotate it with the drill. I'm leaning toward saying there is too much side to side play in the main number bank allowing things to get out of whack and stop. But; before I go off half cocked and start trying things on my own, I thought I'd seek out more wisdom here first -- any ideas?

:whistle

[rpeckham136133]

Did you get the side gear back in place (the one that you loosen a screw to swing out of the way)? You want things to fit snugly, but not too tight.

I just this last weekend did the glue-the-gear-back-to-the-shaft repair, and it so far has been good. I had to dis-assemble once when one of the numbers was a half-number off. Those gears all need to fit snug together, pushing the "loose" gear onto the shaft. I don't remember that it could be so loose as to not bite.

You might want to put a vari-speed drill on it and just watch it all as you spin it...

Another thought: are you sure that you have properly re-engaged where the speedo drive first engages ... that is, the two white helical gears?

Again, just watch every part of it.

[cruisin]

everything turns fine when I use a drill, but if I reassmeble and reinstall, it will work great for 10,15 sometimes 20 miles then quit again. When I was working on the gear that normally slips, there didn't seem to be any give on sliding it farther onto the shaft and I didn't want to force it too hard and break something. I suppose I could remove what I've done and try again. Was just hoping someone had seen a similar problem and found a fix for the excessive side to side movement on the main number bank.

[rpeckham136133]

everything turns fine when I use a drill, but if I reassmeble and reinstall, it will work great for 10,15 sometimes 20 miles then quit again. When I was working on the gear that normally slips, there didn't seem to be any give on sliding it farther onto the shaft and I didn't want to force it too hard and break something. I suppose I could remove what I've done and try again. Was just hoping someone had seen a similar problem and found a fix for the excessive side to side movement on the main number bank.


If you have a lot of movement, that is probably the problem. Mine slipped on far enough so that there was very little play, and nothing could get moved or slide over.

[cruisin]

thanks for the insight. I'll see if I can figure out a way to press it all tighter without damaging anything; maybe use a vise or something. Any suggestions are certainly welcome.

[grumpyone]

Does your speedo/ odo slip then take off again or have to be disassembled to get it to going again. If it is intermittent you might have had a film of oil even from your hands on the shaft that lets the jb slip again. We chewed our shaft up with a dremel tool and then degreased the thing with acetone before applying the sealant. We used a sleeve epoxy from lock tite co instead of JB but JB is good stuff just didnt have any and had the other. Do know tho that clean little shafts are important to get a grip.
Good Luck
Jim and Esther

[cruisin]

only way to get it going again is to dismantle it. The way I fixed the slipping gear problem, would make it nearly impossible for that to still be the problem. I cut a slot in the shaft and then two small holes in the gear. Then made a "staple" shaped piece to fit over the shaft and into the holes. I set all of that in place with JB weld, so it's not very likely the gear is the problem. I plan to figure out a way to eliminate the side to side movement tonight; will report any significant findings or successes here as they occur in case anyone else might benefit from my experience. Also plan to take pictures along the way to share.

[cruisin]

Here's a pic of the "staple" I made with it sitting in the slot and turned down at the ends into the shallow holes.

[cruisin]

and then I used JB Weld to hold the staple in place. That's why I'm thinking the gear is not slipping; also can see the shaft turning when I use a drill to operate the whole unit. What looks like gray goo on the gear teeth and worm gear is moly-coat lubricant; it's sort of a semi liquid paste made from moybdinum and is extremely effective as a lubricant that will stay in place, not dry up and is not effected by heat or cold.

[rpeckham136133]

Uuuuuhhhh..... that's not the gear that slips, I don't think.......

Take a look at this website: http://www.airheads.org/content/view/160/98/


The one that slips is the one that is at the end of the pin that holds all of the numbers....

[cruisin]

Interesting, the one I "fixed" was slipping because it wouldn't turn the shaft, but I never thought about the one at the other end also slipping. I may have misread the instructions from the airhead site. I'll try fixing that one next too as it will be easier than what I was planning. Good thing I got distracted with the season opener of House otherwise I may have done unnecessary work here.

thanks :thumb

[cruisin]

I'm happy to report problems solved. I tinkered with the odometer some more last night. First I got everything realigned and all the gears snugged up like they should be, fabricated and installed a bushing between the brass gear and frame to keep it that way, and then used the trusty dremel tool to cut a rounded quarter moon shape in the shaft and silver gear. I then filled that void with JB Weld and surrounded it all with another collar of JB Weld and let it set up. I also did some more tweaking on the spring that controls needle position at speed.

Final report: odometer worked perfectly for nearly 60 miles today. Using a GPS; the speedometer is spot-on at 45mph, +1 @ 65mph and +1.5 @ 70mph. That's close enough for me to not want to do any more.

I appreciate all the help -- :thumb

[20774]

That's close enough for me to not want to do any more.


Just wait until you change the rear tire...you'll be off again and have to start over. :laugh

Great persistence to finally get a handle on things...

[cruisin]

Just wait until you change the rear tire...you'll be off again and have to start over.

:drink please say it isn't so, wait; I thought the speedo cable ran off the front wheel. :scratch I'm so confused now.

[20774]

wait; I thought the speedo cable ran off the front wheel.

If if ran off the front wheel, then all us Airhead owners would be seeing wrong speeds because of all the wheelies we're doing...since we have no brakes and can't do stoppies, the pickup is from the rear wheel. :whistle

It plugs into the output of the transmission. It will always read the same "speed" for the same throttle setting, all things considered.

But consider this. You twist the throttle, open up the carbs, your in 5th gear, tranny turns the shaft which turns the final drive splines which finally turns the rear wheel. Up to that point, the rotational speed imparted to the splines on the wheel will always be the same for the same throttle twist.

Now, since the entire rear wheel will have the same rotational speed, that means that little spot where the rubber meets the road has to turn at the same rotational speed, but imparts a tangential velocity...ie, how fast you really go down the road. The bigger the rear tire, ie, the bigger the radius, the faster that small piece has to come around in order to keep up with the rest of the tire.

For a bigger radius, your speedo will read say 70, but the outside radius of the rear tire will be going faster. As the wheel radius gets smaller, the tangential speed will also decrease. If the radius approaches that of the splines on the rear wheel...well, you won't be going that fast.

So, a different sized rear tire changes your actual or ground speed, but the speedo may be registering a different speed.

[cruisin]

So; despite all the big words and explanations; who said I was changing the size of the rear tire? My plan is to keep it as close to stock as possible therefore I should never have to worry about adjusting the speedo again.

BTW: I was just foolin' around about the front tire/speedo thing. :stick

[20774]

So; despite all the big words and explanations; who said I was changing the size of the rear tire? My plan is to keep it as close to stock as possible therefore I should never have to worry about adjusting the speedo again.

BTW: I was just foolin' around about the front tire/speedo thing. :stick

OK...couldn't tell from how you posted...I thought your were being serious...now I'm confused...just kidding...:wave

I didn't suggest that you were changing tires now, but you will at some point. As has been posted on other threads, tires are like snowflakes, even within a manufacturer. All I was saying is that WHEN you changes tires, you might want to repeat your calibration of the speedo, either by GPS or using timing markers on the interstate. Depending on the change in radius of the rear tire, what you see might not be what you get!! Mr. Policeman might have something to say about that...

[cruisin]

I'm figuring that even with what slight variations seen in tires (sometimes within same brand and style) the difference won't be enough to go to the trouble to remove and recalibrate the speedo. Afterall, most beemer guys wonder around with the speedo at it's normal error of 7 to 10 miles per hour at 70. This one was off by 8 before I started calibrating, so having it within one or two is a god-send. :brad

I also just checked my '98 RT; it's off by exactly 5mph at all speeds (above 25) according to the GPS. So, next time I tear into the dash, I'm likely to do a little tweaking there too.

[20774]

the difference won't be enough to go to the trouble to remove and recalibrate the speedo.

As you suggest, I wouldn't want to go through the extremes of recalibration per what you've posted. But it doesn't take much to find a 5-mile section of the interstate, hold a constant speed over that section, time yourself, and compute your average speed. Compare to speedometer. When I'm bored going down the road, sometimes I do that in my head for something to do. You can also pre-calculate the number of seconds it will take you to cover 5 miles at several speeds like 60, 65, and 70. Just measure the seconds, check the table (or commit the table to memory) and see how things stack up. No biggee, really...

[cruisin]

As you suggest, I wouldn't want to go through the extremes of recalibration per what you've posted. But it doesn't take much to find a 5-mile section of the interstate, hold a constant speed over that section, time yourself, and compute your average speed. . . . . No biggee, really...


Tue that and then only hope the road crew that marked off the mile markers were sober when doing so. :buds :hungover