[Blaqkfox]

OK my fault for not reading the instructions fully there, I was in such a rush to get that installed before I went to the mountains with my friends.

anyways I messed with it today. I popped the old speedo cable in and rolled the bike forward one rotation of the front wheel. the speedo cable turned almost two times. so I guess its supposed to be set to two pulses. It wasn't quite two full rotations but then again I only moved the bike for one rotation because im a bit injured at the moment so I didn't drag it out of my shop.

which would make sense if im reading double like I was, so it should be pretty spot on now.

I have not attempted to test ride the bike and check yet. Unfortunately ive come down with costochondritis (hopefully thats all it is) assumedly from my long 6 hour ride through the mountains. So my chest has been killing me and im supposed to avoid strenuous activities such as getting the motorcycle out of the shop and riding it. Hopefully I can get back in the saddle soon, its finally not 100F out here anymore.

I do have the Circumfrence set to 2007. I am no longer on the Avon tires, I am on the dunlop K70 tires. factory sizes though. but anyways yeah I got 2006.6 when I measured (granted this was only one wheel rotation and unladen). But I should be awful close now. Cant wait to hop on the bike and see.

EDIT: my bad I just saw there was a lot of new replies in this thread since I last read it. Wish id seen Adrians post saying its 2:1 before I went to all the trouble of putting the old cable back on ha. I do like that mathematical approach Adrian laid out. what's interesting to me is the tire measurement for circumference y'all are suggesting- it would seem the Avons must have a taller sidewall or something? or maybe its the change from tire flex with the weight of the bike actually on it/tire pressure im running (I am running factory tire pressure). at any rate perhaps reality is slightly different than than the mathematical approach due to other variables like that.

[Adrian II]

I'm guessing the K70 and Avon will be close enough in diameter. When your strength is back, you could just get a tape measure, put the bike on it center stand and (with assistance if available) simply measure the circumference. Or am I oversimplifying?

A.

[viczena]

I also replaced the speedometer with the Acewell product, and it was quite easy to do. But I used the CA80-160RE, as I needed a km/h device. I had to use 2R1P.

https://www.g-homeserver.com/forum/royal-enfield-500-trials/388-tachometer

[Paul W]

The circumference of the inflated tyre tends to be slightly “longer” than twice its rolling radius. The difference is how the tyre compresses against the road due to the bike’s weight.

The latter is what the wheel revolves around on the road, so ideally that should be used for setting up the speedo. Measuring the distance run on the road takes the rolling radius into account if you want best accuracy.

[tooseevee]

The latter is what the wheel revolves around on the road, so ideally that should be used for setting up the speedo. Measuring the distance run on the road takes the rolling radius into account if you want best accuracy.

        That's why I've always suggested3 turns of the air valve with marks on the ground. It's probably a hair more accurate than just 1 turn & it doesn't take any longer. Make it 10; even better 

        I got two of the little (not Acewell) ones years ago. Omega? Sigma? I got them both to be very accurate.

[tooseevee]

I also replaced the speedometer with the Acewell product, and it was quite easy to do. But I used the CA80-160RE, as I needed a km/h device. I had to use 2R1P.

https://www.g-homeserver.com/forum/royal-enfield-500-trials/388-tachometer

      That's a gorgeous piece of advertising there.

       The whole thing wreaks of quality.

[Blaqkfox]

Yup still gotta mess with it. Rode the bike today, at two pulses it was much more accurate, but it’s still off. I need to roll it a bunch of times with my weight on it like y’all are saying. I was turning and burning in 5th gear at almost 4K rpms and it said I was doing 53mph lol should’ve been more like 65mph. So I’m closer now.

At first I was confused why viczena said he bought another unit for KMPH, because this unit can do both, but then I saw the unit he’s got actually has a KMPH face for the dial gauge so that makes sense, mine only displays KMPH digitally or you’re converting looking at the mph face. That’s cool I didn’t know they made that one. I really do like this unit I might have to put them on my next bike!

[tooseevee]

Yup still gotta mess with it. Rode the bike today, at two pulses it was much more accurate, but it’s still off. I need to roll it a bunch of times with my weight on it like y’all are saying. I was turning and burning in 5th gear at almost 4K rpms and it said I was doing 53mph lol should’ve been more like 65mph. So I’m closer now.

       My first experience with one of these digitals was in the early 2000s & I got same results; it's not quite right yet.

       That's when I did the 3 full turns of the tire, sitting on the bike rolling it backwards, making chalk marks on the driveway, measuring that distance, dividing by 3 & getting MMs from our friend Google.

       The number I got from that was a bit  different than the 1 turn result. I don't remember how much, I've lost track of the notes I wrote then. Seems to me one of the numbers (the last two digits of the 4 digit number in MMs) was in the very high 70s & the other in the very low 80s. 

        I'll predict that some day  there will be units that can be set up using smartphone apps that everybody loves these days.

[Paul W]

I’ve just noticed an error in my earlier post. I should written that the diameter of a tyre (not the circumference) is a bit longer than twice the rolling radius.

Sorry, old age and stupidity kicking in.

[Blaqkfox]

hmm. more troubles today. or disappointment rather.

I rode to the nearby church to borrow their parking lot while nobody was around (its the only large paved area out where I live).

I parked the bike with the valve stem as close to bottom dead center as I could and marked the pavement with chalk.

I hopped on the bike started it up and rode slowly with all my weight on the bike counting the tire rotation...1...2...3.

parked the bike with the stem as close to BDC as I could and marked with chalk.

pulled out the measuring tape. 234 inches. divided by 3 thats 78 inches.

perfect I thought.

converted to mm for a grand total of 1981.2mm

I thought, thats awful small compared to the figures of 2068 or whatever y'all were giving me.

so I did it again. 4 full rotations this time.

came up within 1mm of the same number.

must be correct.

take off to ride the bike back home.

I'm screaming at 4k rpms in 5th gear and my speedo says 55mph. not a lot of throttle left either. odd... usually with the old factory speedo it would be reading around 65mph right now.

I give it full throttle, pushing it to its limit. it slowly creeps up 56, 57, ... 60mph absolute top speed. probably burning around 4.5k+ rpms in 5th at this point.

"No", I tell myself, "I know these bikes are pretty freaking slow, but the old gauge I topped out multiple times before at 70-75mph. I always cruise 60-65mph on the backroads home from work and have a solid 1/4 throttle left to give. This can't be correct."

So I ride back to the church and do the test for a 3rd time. 233inches. thats 77.7in. thats 1973.6mm roughly

so I plug that number in.

a little better, 55mph cruising speed, still a slow climb to 60mph though. honestly not much different than it was before. maybe gained 2mph or so but thats it.

bike was fully warmed up, conditions were good. I don't know why it reads slower than the oem gauge was. I was using the digital mph readout as I have the needle doing tach, but I can't imagine they'd be different. But ill try tomorrow and see. maybe the old gauge was just off some. id be curious to have a friend drive next to me and see how fast his car says were going. When I went on that long ride with my buddies we had a guy in a newer Audi RS7 behind me the whole way. I asked how fast we were going, and he said usually around 55mph. so maybe its not off. my other buddy leading the pack said we were doing about 65 at another point in the day when I was keeping up with them, but he also said his speedo was probably off some.

and ive always heard the old "55 all day, 65 for awhile" saying with these bikes, but that was for the old 4 speed iron barrels. I figured the 5 speed AVL lean burn here would be capable of more like "60 all day, 70 for awhile". And thats how it seemed with the oem gauge. so now im confused on what's correct. its only 5mph, but still.

Thinking the math must be correct. perhaps ill go back another day and try for about 10 rotations or something see if I get the same numbers.

OR maybe its just not tuned to its peak performance. By that I mean, I have things running a hair on the rich side (I think, thats a whole other story) with my BSA exhaust, hot tube mod, and up jetting the bs29. my chain probably has a hair too much slack in it too, but thats honestly negligible. everything else is in perfect working order though.

Also I may very well switch to an 18 tooth sprocket at some point. try and bump that top end up just a bit. if I could maintain 65mph on this bike id be a happy camper.

[tooseevee]

quote author=Blaqkfox link=topic=33338.msg413962#msg413962 date=1656286708]

hmm. more troubles today. or disappointment rather.

     ****Imogee for Oh No.

I parked the bike with the valve stem as close to bottom dead center as I could and marked the pavement with chalk.

     ****Not "as close to". Run a straight chalk line down the tire & measure exactly.

I hopped on the bike started it up and rode slowly with all my weight on the bike counting the tire rotation...1...2...3.

     ****Don't start it up & ride it. The bike's not heavy. Sit on it & Push it backwards In A Straight Line.

parked the bike with the stem as close to BDC as I could and marked with chalk.

      ****Again. Exact measurement.

pulled out the measuring tape. 234 inches. divided by 3 that's 78 inches.

converted to mm for a grand total of 1981.2mm

I thought, thats awful small compared to the figures of 2068 or whatever y'all were giving me.

     **** Forget those other numbers people were telling you. MEASURE Your Own number Yourself!

so I did it again. 4 full rotations this time.

came up within 1mm of the same number. must be correct.

I'm screaming at 4k rpms in 5th gear and my speedo says 55mph. not a lot of throttle left either. odd... usually with the old factory speedo it would be reading around 65mph right now.

    **** With a 17 tooth

        ** 50=3207 
        **  60=3855
        ** 70=4498

         ** (Adrian?)

I give it full throttle, pushing it to its limit. it slowly creeps up 56, 57, ... 60mph absolute top speed. probably burning around 4.5k+ rpms in 5th at this point.

      **** "Probably" "Around" 4,500?

       ****Isn't there a tach on that thing? You can't be guessing at RPM OR speed.

        **** You just have to get that tire rotation number as accurate as possible & then TRUST the number & then you have to quit guessing what your RPMs are.

        **** I think the only way you're going to believe your speed indication is to verify it with GPS. I hear you can use a telephone now as a speedometer.

        **** What will they think of next?

        **** (Well, I EFed that up pretty well, didn't I? How the hell do you insert a response WITHIN the quoted poster's text?)

[/quote]

[Paul W]

Interesting!

I know that the original speedo on my 350 reads approximately 10% fast, even though the final drive gearing is very slightly taller than standard (18/42 rather than 16/38). I do have a GPS speed “app” on my phone but so far I’ve not found a way of fastening it to the bike where I can see it to get a “real world” speed reading.

I occasionally ride on the motorway where the heavy goods vehicles generally travel at their governed maximum speed of 56 mph (some can now do 60 mph, depending on whether they are governed to European rules, or the more recent U.K. rule).

The bike will easily overtake them all but although it’s revving hard at those speeds I don’t think it’s outrageously so.

I suggest you try a phone app if you can safely do so. If you find the speedo is reading incorrectly you can then “fudge” the number you programme in, to make it work more accurately.

Edit: Your idea of “screaming revs” at 4,000 might be a fair bit lower than mine… 

[Blaqkfox]

Yeah 2cv, I just eyeballed the valve stem for BDC. And marked with chalk on the pavement. I figured if i was off a millimeter or two no big deal there. No sense in marking the tire, these sidewalls are not thick, I know I marked the pavement exactly in line with the valve stem, granted the valve stem could’ve been 1mm off of a true BDC. I could’ve used a pendulum to get super exact I guess, but I can’t imagine I was more than 1-2mm off at most.

I don’t think it matters if I ride slowly or walk it, but I am curious why you go backwards instead of forwards lol

As far as tac readings go, I was too busy watching the car in front of me at that moment, all I know is I was turning a little over 4K rpms at 55mph, so to be at 60mph I’m sure I was up there close to the limit

[Adrian II]

As for Electra-Xs and disappointing performance, it may well be time to lose that stock carb, plenty of advice available for something sportier. You've already gutted the exhaust downpipe and sorted a freer-flowing muffler, so that's one factor less to take into consideration.

A major limiting factor with these engines is the AVL cam design, you get valve bounce setting in at 5,800 rpm with these. THE solution is a set of original late 1950s Redditch Bullet "S" cams (try your swap meets), Bullet Whisperer lent me a set of well-used ones some years ago, and they transformed the top-end power, but good results have been had from a set of "R" cams from Price Part Motorcycles in the UK too.

The UK Electra-Xs had an 18T gearbox sprocket as stock, with my height and er... build I found it over-geared and dropped down to a 17T for a much happier bike, BUT if you're lighter, slimmer and maybe shorter than I am, 18T might be better suited to you for higher cruising speeds, at the cost of some acceleration.

A.

[AzCal Retred]

Find a piece of straight State or county road marked with mileage signs. Hold a constant speed (or constant RPM in 5th, you have a tach) over a two mile section, record the time and just do the math, that will be accurate. Adjust the speedo conversion factor until it gives the correct reading at that RPM. You don't really care exactly what the conversion number is, or why, it just needs to work.

The "55 all day, 65 for awhile" is related to power output, not whether or not there is a 4 or 5 speed in there. The top cog of the 5 speed is 1:1 also, so no real difference. The "mantra" relates to flogging the engine at max power output. The roller crank is normally better for making power UNLESS you have a known good custom fitted Bushing/Rod/Piston combo in there like Chumma can build. It takes maybe 30 HP to blast along at 75 or so; regular unfaired machines with an "upright rider" are pretty draggy. These Old School engines max out at maybe 25 HP, so there you are, it takes WFO effort on the Bullet motor to maintain those speeds - there's no reserve left. Almost every modern 500 engine is pumping out 40-50 HP. The Bullet engine can also reliably make 35-40 HP, but definitely not as a stock powerplant. If you are ready & willing to "Run to Failure", maybe start collecting bits for building that high performance engine now. You are about $3500 away from the performance you want, about the cost of a nice, modern, used 650cc - 1000cc motorcycle that will easily run those speeds. If the crank or rod lets go in the mean time it'll likely frag the cases, an expensive additional purchase.

https://accessories.hitchcocksmotorcycles.com/accessory-shop/Modified-5-Speed-Gearbox-Standard-Indian-Made
4 Speed ratios: 1st = 2.78:1, 2nd = 1.84:1, 3rd = 1.36:1, 4th = 1:1
5 Speed ratios: 1st = 3.06:1, 2nd = 2.01:1, 3rd = 1.52:1, 4th = 1.21:1, 5th = 1:1