[Yamahawk]

Hey, I have a question about the Very Optimistic speedometer on my 1996 Bullet 500. It shows 20mph higher than my actual speed, and this is ALOT of error. I could see 5-10mph, but 20mph? Has anyone found a good fix for this? I thought perhaps it was just gummy lubrication in the needle drive, as they usually 'float' when this happens, so I tried ye olde clockmaker's trick of a cotton ball with an aromatic oil like kerosene or mineral spirits, but I didn't have either handy, so I used Kroil for the light lubricant, and stuck the cotton ball into one of the lighting holes, and let it sit in the sun for a day. That helped the wagging, but now it is verifiably 20mph fast on the clock... Is there another speedometer drive available, perhaps off of a 21" wheeled model that would give closer to reality in the speedometer? I am not liking the fact that I have to do the RPM math (625*speed) to get my actual MPH in RPM. But, it is what it is lol. So, if there is any alternative to get an accurate speedometer short of buying a $300 Koso GPS unit, let me know...
Charlie

[Stanley]

Online searches for a solution convinced me the easiest way was a $20 Sigma bicycle computer. I calibrated mine to match a roadside radar warning sign. Now I can see how slow I'm going, along with a clock that tells me how late I am. When I want to go faster the stock speedo obliges my speed lust.

[Arizoni]

I think the speedometer was calibrated wrong when it was made.

If it's really bugging you and you want to spend some money you could try to find a speedometer repair shop.  They usually have the tools to open it up and readjust it.  More importantly, they have the tools to put it back together so it doesn't look like a maniac messed with it.

Have you lubricated the drive cable?  If not, I suggest you remove the inner cable from the lower end (at the wheel drive) and apply a thick coating of Vaseline.   Getting the upper square end of the cable back into the speedometer can be a pain but if you try the "rotate it a bit and push" method it will eventually slip back into place.

[Yamahawk]

Thanks for the suggestions, fellas! I did some research and found some interesting videos as to how I can re-calibrate the speedometer. It is a magnetic drive, with a spring tension, that keeps the needle from moving all the way around, There is an aluminum cup and a magnet, and a spiral hairspring that governs how far it moves with the spinning magnet. After carefully uncrimping the bezel ring, you can remove the needle and tension the spring a couple more notches in the shaft/needle position, thereby giving more tension, and a slower moving needle... which, is what I need. (And most likely every Bullet owner)
So, now I have to see how easy it is to not destroy the crimp ring around the top of the speedometer, and then get it back together. One good thing, the speedometers are cheap on eBay lol...
And yes, Arizoni I have cleaned and lubed the speedometer cable at least once since I got the bike last year, I also reversed the cable so it doesn't drop out on the road when the lower ring nut comes loose lol... never could figure out why they always put the stop on the lower part of the cable instead of up on the speedometer side... 
Charlie

[Adrian II]

The Bullet uses an Indian copy of the old Smiths' 2:1 speedo drive gearbox (they used to be fitted over the rear wheel, and you can modify the rear hub very easily if you want to move it back for a more authentic look). Smiths also made them in 1.25:1 (also marked 15:12), 19:10 and 21:10, check any of the Brit bikes parts dealers as well as ebay, though beware those with larger holes than the Bullet front wheel spindle. Do the math, see if a 19:10 or 21:10 might save stripping down the speedo.

You could just try another speedo, of course, since they're cheap enough. The replicas of the Smiths chronometric are allegedly quite good.

The gold-plated option is a genuine Smiths chronometric speedometer correctly calibrated.

A.

[Yamahawk]

I have actually purchased a white face Smith's copy off eBay, and it was as bad as the original one.. at least 15 MPH off, and wags like a dog!! I believe it is the drive itself, as it is just the wrong ratio for the speedometer. If they made one for a 21" wheel, it would most likely be closer to the real speed, as a larger wheel turns slower and covers more distance per revolution.... or am I thinking backwards? Hmmm...
Charlie

[Adrian II]

A larger diameter front wheel/tire will rotate fewer times per mile.

Somewhere I have a spreadsheet of tyre circumferences vs. revolutions per mile or some such nonsense which lets you work out the correct calibration for a speedo based on whatever sized tyre and speedo drive gearbox you're using. The tire manfuacturers' web sites should have the specs for individual tyres including the circumference. If I can find it I'll send it to you or post it up here.

A.

[Kevin Mahoney]

The Smiths "repro's" are nothing more than a stock RE speedo with a new face. There is no such thing as an accurate speedo for an RE although the newest ones are likely to be better.

[RE350]

First verify that the odometer is giving accurate readings. If so the gearing is correct and the high speed reading is due to the speedometer speed unit. Changing the gearing to lower the speed will lead to incorrect distance readings. If the odometer is reasonably accurate cheapest solution is to simply replace the speedometer with a factory unit. They are available at reasonable prices.

[Yamahawk]

Yep, you are correct. I am thinking about how the magnetic speed cup works, and whether the cable, sticking up into the speedometer, may lift the cup too high, and skim the piece that it is supposed to not touch. I reversed my cable, with the brass stop up in the top of the cable, and I am thinking that this may push the cable into the drive part inside the speedometer, causing it to scrape or hit the part it is supposed to magnetically drive. I am going to try reversing the cable back the way it came, and see if it helps the accuracy. I have a white face Smiths copy with the 'upside down' face, and it did the same thing. It would skip and wag back and forth, the faster you drove. I will do that this morning, and see what happens!. Also, I will do a distance test to see if the odometer is correct.
Charlie

[solg]

This is how I corrected the OEM speedo issue https://forum.classicmotorworks.com/index.php/topic,18628.msg202961.html#msg202961

[Yamahawk]

First verify that the odometer is giving accurate readings. If so the gearing is correct and the high speed reading is due to the speedometer speed unit. Changing the gearing to lower the speed will lead to incorrect distance readings. If the odometer is reasonably accurate cheapest solution is to simply replace the speedometer with a factory unit. They are available at reasonable prices.

It is close, when I was on the expressway I would see the mile markers, and when I has 1 mile turn over on the digit, I would see where I was in relation to the mile markers, and it is within 100 yards or less from where I started the measurement. So, I would say it is close to being right, although I believe it is counting more miles, slightly, than my wife's bike. After a 100 mile ride with her, our odometers are off by 5 or 6 miles, with mine showing more miles.

Yesterday, I noticed that I had already flipped the cable around like it was when I got it, with the brass ring at the bottom by the speedometer drive. So, I clipped about 1/8" off the end by the top of the cable where it goes into the speedometer and then carefully stuck it back in and tightened the nut. I took it for a ride, and it is still 15mph faster than what I should be showing. It wags less, but still has a needle wag at certain speeds. I would just like a reasonably accurate speedometer, with no needle wag, if possible. I am going to replace the whole cable next, and see if that will help.
This is how I corrected the OEM speedo issue https://forum.classicmotorworks.com/index.php/topic,18628.msg202961.html#msg202961

[/color]
This IS a nice speedometer... now, in the last post of your link, you mentioned 'calibrating' it. How do you do that? Is there an external adjustment that you can do to 'adjust' the Smiths speedometer?
Charlie

[solg]

 the speedo comes with a grounding wire that is used to calibrate (program) it by entering the program mode then driving a pre
measured mile. Its explained in more detail in the instruction manual.

[RE350]

The original speedo like most magnetic speedos has a spiral "hair spring" attached to the small shaft that the pointer is attached to. This controls tension on the pointer movement. Higher tension will result in lower speed readings, and the opposite if weak tension. Most speedos have provision to adjust tension with the spiral spring mounted in such a way that it can swiveled CW or CCW to adjust tension. A weak hairspring can cause high readings especially in the lower range. So can an overcharged magnet. In cases with an overcharged magnet not much can be done without special equipment, but INCREASING the spring tension to a compromise tension could help. Of course the bezel  ring  lip would need to be peeled or pryed up to get inside. For your information I worked a few years in a speedometer shop before electronics took over mostly on Stewart Warners and AC. Never had an Enfield speedo apart, but the principle of operation on magnetic speedometers are the same. As for a too long  cable end pushing up on speedo magnet shaft the stress  would cause excessive end play on the magnet shaft and force the magnet shaft to wear upward and bind the speedcup causing it with the attached pointer to dance around wildly (usually). It would be immediately apparent externally with excessive end play at the speedo magnet shaft (where the cable attaches to the speedo).   

[Yamahawk]

The original speedo like most magnetic speedos has a spiral "hair spring" attached to the small shaft that the pointer is attached to. This controls tension on the pointer movement. Higher tension will result in lower speed readings, and the opposite if weak tension. Most speedos have provision to adjust tension with the spiral spring mounted in such a way that it can swiveled CW or CCW to adjust tension. A weak hairspring can cause high readings especially in the lower range. So can an overcharged magnet. In cases with an overcharged magnet not much can be done without special equipment, but INCREASING the spring tension to a compromise tension could help. Of course the bezel  ring  lip would need to be peeled or pryed up to get inside. For your information I worked a few years in a speedometer shop before electronics took over mostly on Stewart Warners and AC. Never had an Enfield speedo apart, but the principle of operation on magnetic speedometers are the same. As for a too long  cable end pushing up on speedo magnet shaft the stress  would cause excessive end play on the magnet shaft and force the magnet shaft to wear upward and bind the speedcup causing it with the attached pointer to dance around wildly (usually). It would be immediately apparent externally with excessive end play at the speedo magnet shaft (where the cable attaches to the speedo).

I have watched a few YouTube videos on repairing speedometers, and actually one on the Enfield type. I am thinking of carefully prying the bezel ring with a small screwdriver, and then removing the needle to increase the spring tension. I am not sure if the Enfield Speedometer has a spring adjustment or not, but if not, what do you think of the idea of removing the needle and increasing the tension (i think CCW) before replacing the needle and returning it to the needle stop? It wouldn't take a whole lot more tension i think, to correct the speedometer 15mph. I think it may be a trial and error thing also. The speedometer is consistently 15MPH higher through the whole speed range. 25 is 40, 60 is 75, etc. After doing the cotton ball in the lighting hole, soaked in Kroil, and set in the sun, it stopped wagging a lot, but it still does it a bit. I am going to order a new cable soon, I have seen them on eBay along with a speedometer drive, and sometimes a complete set with speedometer too, for rather modest price. The digital speedometer that Solg showed me is very Nice but the price is very High lol... It would be a great choice, though if I could afford it. I would get my NJB shocks first and an inexpensive speedometer kit before I considered that other digital speedometer.
Charlie

[Arizoni]

Here are several links to topics on this forum that talk about fixing the RE's speedometer.

Once you get into them be sure to look at all of the pages.  There's a lot of interesting information there.

https://forum.classicmotorworks.com/index.php/topic,23491.msg270161.html#msg270161

https://forum.classicmotorworks.com/index.php/topic,17430.0/all.html

[Yamahawk]

Thanks for the links, Arizoni, it gave me the confidence to remove the bezel ring and see what's what! I found the hairspring has one end staked through a hole, with a tiny brass pin. I pulled the pin, and then grabbed the spring end, pulling it further through the hole about 1/4", and re-staked it with the teeny tapered pin. I now have more spring tension, and have yet to try it. As I started the bike, it ran for 10 seconds, then quit, and I haven't been able to start it since... so, my speed test to see if I am close, will have to wait until the bike starts and I can ride it lol...
Charlie

[Yamahawk]

PROGRESS>....
    I have dismantled the speedometer, adjusted it, and took it for a test drive. I regained 5mph from the 20mph over-speed it was reporting. I 'should' have left it with the greater tension I had when I first pulled the spring through the hole, but I thought it would be too much, and slackened it off. Now, I have to repeat my process, and give it more tension, but I am on the right track! Stay tuned!
Charlie

[Stanley]

While following the method of refitting the needle with more spring tension, I think I did a passable job of re-calibrating my speedo until I was putting the bezel into place. I cracked the lens and just spent time searching the Interweb for a replacement. Does anyone know of a source for 3 inch lenses? I found various other sizes and will keep looking. I may have to turn some plastic on the lathe, but it's hard to find thin Lexan.
Boogers!

[hpwaco]

Try a clock supply place like Timesavers in AZ.

[Stanley]

Thanks, but the clock glass isn't available in 3 inch, so turned a piece of Home Depot Lexan on the lathe.
My speedo is now as accurate as can be. It was reading a consistent 12 MPH fast. Other than removing the bezel and glass, the rest is easy. I simply pulled off the needle and replaced it CCW the same number of degrees it was reading higher than than it should.  I simply bent it up slightly to settle above the stop peg. Testing was a simple ride with the glass off, stopping to fine-tune the needle angle until it matched my bicycle speedometer at different speeds. Easy peasy. No need to even remove the speedo face or housing. I rode home to remove the speedo, crimp on the bezel and Bob's now my uncle. Now I can use that bicycle speedo as a tach on my lathe.

[Yamahawk]

Cool Stanley! What year is your Enfield? Mine's a 1996, and for the life of me, I couldn't get the needle to pull off the shaft. So, mine has a brass tapered peg (VERY small) in a hole that stakes the outer end of the 'watch' coil spring on the needle shaft, and I added tension by pulling the spring a little more through the hole, and then re-pegging the spring with the brass tapered peg. I am now down to 10 mph instead of 20 mph, so I will try it again when I get the chance to do so.
Charlie

[Stanley]

I have a 2000 IB. After I decided to risk a bad outcome, I evenly heated the disk of the needle with a light soldering iron and pried it off with two screwdrivers against the two face-attaching screws.  Once it was off, it went on and off with firm pressure. Small soft leather pads protected the face from scuffs.

That hairspring looked too dainty for me to touch. Kudos to you!