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K100-forum.com » Technical, repair and troubleshooting » Electrical » Speedo /Taco Error

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1Back to top Go down   Speedo /Taco Error Empty Speedo /Taco Error Sat Feb 11, 2023 11:31 pm

Hamo42

Hamo42
active member
active member
Hi guys & girls, hope you can help. Restored a K5C with K75S final drive. Now taco shows 4750 RPM when at 100 KPH. I know the tyre sizes are different 130/90/17 on mine. 120/80/18 on a normal K75C. Is there anything I can do. It's obviously over reving. Instruments have been calibrated by qualfied shop.

Any assistance appreciated.

    

2Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 12:29 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
By my rough calculations, your tach and speedometer are within the normal speed error of these machines.  I am guessing your final drive is 32:10.

My K75RT does 75mph at 5700rpm which is approximately the same ratio as your 100kph(62mph) at 4750rpm.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

3Back to top Go down   Speedo /Taco Error Empty Speedo /Taco Error Sun Feb 12, 2023 5:31 am

Hamo42

Hamo42
active member
active member
Hi, Yes my final drive is a 32/10 but according to the riders manual it should be about 4100rpm at 100KPH.
I am looking at getting a K75C final drive with the brake shoes & the wheel to match. I really don't want to go to that expense.

Still open to sugestions Thanks.



Last edited by Hamo42 on Sun Feb 12, 2023 3:00 pm; edited 1 time in total

    

4Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 8:22 am

Rick G

Rick G
admin
admin
Hamo42 wrote:Hi, Yes my final drive is a 32/10 but according to the riders manual it should be about 4100rpm at !00KPH.
I am looking at getting a K75C final drive with the brake shoes & the wheel to match. I really don't want to go to that expense.
Those figures apply to a K100RT or RS the figures you state are fairly much right for a 32:10 final drive of a K75.
I also removed your other thread on the same subject, there is no purpose to putting it up twice.
Admin


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

5Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 1:06 pm

Laitch

Laitch
Life time member
Life time member
For those who might prefer affirmation from a gizmo rather than from experienced riders, there's this from the friendly folks at discount tire.com in Kansas, US of A.Speedo /Taco Error Scree230


__________________________________________________
1995 K75 90,000 miles
    

6Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 3:59 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Hamo42 wrote:Hi, Yes my final drive is a 32/10 but according to the riders manual it should be about 4100rpm at !00KPH.
I am looking at getting a K75C final drive with the brake shoes & the wheel to match. I really don't want to go to that expense.
The MaxBMW parts list shows the K75C having a 32:10 final drive ratio which is what you appear to have now. 

I'm getting pretty confused, which is not unusual.  Can you clarify what year and model bike you have?  that will help identify what the correct final drive ratio is.  Then, can you identify what rider's manual you have and where it specifies 4100rpm at 100kph?  I have looked at my rider's manual, and all it says is that the final drive is 32:10, there are no engine rpm to speed specifications that I can find. 

Last, is your taco beef, chicken or fish?  Personally, I prefer burritos, tacos give me a stiff neck.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

7Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 7:54 pm

duck

duck
Life time member
Life time member
Hamo42 wrote:Hi guys & girls, hope you can help. Restored a K5C with K75S final drive. Now taco shows 4750 RPM when at 100 KPH. I know the tyre sizes are different 130/90/17 on mine. 120/80/18 on a normal K75C. Is there anything I can do. It's obviously over reving. Instruments have been calibrated by qualfied shop.

Any assistance appreciated.

The stock tire size for the drum brake wheel is 120/90-18. 130/90-17 for the disc wheel. The disc tire is 1.1% smaller so will need only 1.1% more RPMs for the same ACTUAL speed. And of course the speedo reading will be 1.1% different since the smaller wheel will put out 1.1% more pulses for the same ACTUAL, not indicated, speed.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

8Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 8:08 pm

K75cster

K75cster
Life time member
Life time member
You should have a similar tyre circumference, a 130x90x17 is 2080mm tyre contact with road, so 100kph divided by 2080 x 3.2:1 x 1.67 (K75c gearbox 5th gear) divided by 60mins =4282rpm. A 120x90x18 is also 2080 on the road. So something is amiss with the final drive counter for the speedo. Try doing a speed check with a gps unit. your 4700 rpm is a ways higher in speed best to speed check it before the coppers do it for you.


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt 1992 K1100LT a blue one

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

9Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 8:31 pm

duck

duck
Life time member
Life time member
K75cster wrote:You should have a similar tyre circumference, a 130x90x17 is 2080mm tyre contact with road, so 100kph divided by 2080 x 3.2:1 x 1.67 (K75c gearbox 5th gear) divided by 60mins =4282rpm. A 120x90x18 is also 2080 on the road. So something is amiss with the final drive counter for the speedo. Try doing a speed check with a gps unit. your 4700 rpm is a ways higher in speed best to speed check it before the coppers do it for you.

A 120/90-18 tire has a circumference of 2,115 mm.

A 130/90-17 is 2,092 mm around.

https://www.calculator.net/tire-size-calculator.html


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

10Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 8:49 pm

92KK 84WW Olaf

avatar
Life time member
Life time member
I run 140 rear tyres on my Ks. No swing arm clearance issues.

Not difficult to change the final drive to a disc one 31/11 or 32/11.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

11Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 12, 2023 9:06 pm

duck

duck
Life time member
Life time member
92KK 84WW Olaf wrote:I run 140 rear tyres on my Ks. No swing arm clearance issues.

Not difficult to change the final drive to a disc one 31/11 or 32/11.

I run 150/70-17 radials. No clearance issues.

You give up some torque when you go from a 3.2 to a 2.82 or 2.91 final drive. (BMW put 32:10s on K75S for a reason.)


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

12Back to top Go down   Speedo /Taco Error Empty Speedo /Rev Counter Error Mon Feb 13, 2023 6:04 pm

Hamo42

Hamo42
active member
active member
Hi Guys, The bike was a bitza. A K75C frame 10/1986 Engine A Jap import K75 with gearbox 32/10 final drive from an K75S
Tyre size is 130 /90/17. Circumference 2080cm. I have had the Speedo/ taco calibrated  at a reliable motorcycle instrument shop. I check the speed with a GPS that was almost spot on. Currently I have taken the instruments back to shop to double check.


Hope this all helps.
Starting to pull my hair out now. ( Not much left )

    

13Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Mon Feb 13, 2023 7:49 pm

Laitch

Laitch
Life time member
Life time member
Hamo42 wrote:Hi, Yes my final drive is a 32/10 but according to the riders manual it should be about 4100rpm at 100KPH.
Because of your dedication to the data in this manual, it would be helpful to provide the date the manual was published, its title and the page where the data can be found so we can verify it. I haven't found those specs yet in my 1995 Riders Handbook but I realize formats and data in the handbooks have changed over the years.

Better yet would be for you to post a photo of the page.


__________________________________________________
1995 K75 90,000 miles
    

14Back to top Go down   Speedo /Taco Error Empty Hamo42 Mon Feb 13, 2023 10:50 pm

Hamo42

Hamo42
active member
active member
Hi Laitch, I have just been posted a copy of the K75 page in BMW-K motorcycle purists on FB. But when I

 have ridden it, the speed is ok at 100kph via a GPS but the thing revs at 4750PRM.



Last edited by Hamo42 on Mon Feb 13, 2023 11:01 pm; edited 1 time in total

    

15Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Mon Feb 13, 2023 10:56 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I went through my 1994 K75RT/S rider's handbook and couldn't find a reference in it.  I also went through my 1990 K75C/S rider's handbook as well.

Perhaps BMW North America doesn't include this information.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

16Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Tue Feb 14, 2023 3:48 am

robmack

robmack
Life time member
Life time member
Maybe run some numbers through this K-bike speed to rpm calculator.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

17Back to top Go down   Speedo /Taco Error Empty Speedo/Tacho error Tue Feb 14, 2023 8:38 am

daveyson

daveyson
Life time member
Life time member
I think your brick is probably OK, bricks just are high revving. 

My K75S is over revving compared with its rider's handbook, but so are my k100's. For some reason the graphs just don't match with reality. 

According to the graph on page 87 of my 1991 K75 rider's handbook at 4,000rpm I should be doing 100km/h in fifth, but it does 92km/h, for a K75S. The K75 graph is almost identical. 

On my k100RT the tacho and speedo needles are always parallel in fifth, so at 100km/h it does 4,000rpm, but the K100RT graph says it should be about 3,700rpm. 

If yours does 92km/h at 4,000rpm (pushing it)  it's the same as my K75 and I think OK. 

Speedo /Taco Error Img_2092


__________________________________________________
11/1985 BMW K100RT (late model)  Vin. 0090567
 ~120,000 km
    

18Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Tue Feb 14, 2023 11:17 am

Laitch

Laitch
Life time member
Life time member
Hamo42 wrote:I have just been posted a copy of the K75 page in BMW-K motorcycle purists on FB. But when I
have ridden it, the speed is ok at 100kph via a GPS but the thing revs at 4750PRM.
Take a screen shot of that K75 page and post it here, Hamo. I'll help you with that. Send me a pm if you have trouble.

If your instrument's speed display is the same as your ground speed then I see two strategies ahead. The first strategy is to check for clutch slippage. The clutch could be slipping at high speed but the slippage isn't noticeable at low speed. Goose it at high speed and observe if the revs jump faster than your neck snaps. If it's slipping, check the clutch adjustment. I rode with worn clutch disc that acted like that for 10,000 miles. I replaced it when fuel prices rose. Laughing

If the clutch is ok, the second strategy is to calculate your fuel economy over two or three fill-ups. If fuel economy isn't good, a compression test and general system check could reveal why it takes more revs to go the speed that your mysterious data source indicates it should. If it is good, there you go; cover the tach dial with an pleasant image or a symbol of spiritual well-being. Shift your preoccupation to personal health, politics or end-of-the-climate-as-we-know-it adaptation strategies. One of those should fill the void.


__________________________________________________
1995 K75 90,000 miles
    

19Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Tue Feb 14, 2023 4:38 pm

Laitch

Laitch
Life time member
Life time member
daveyson wrote:I think your brick is probably OK, bricks just are high revving.
You two should ride downhill on slab with tailwinds. That should bring them both into spec. Smile


__________________________________________________
1995 K75 90,000 miles
    

20Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Tue Feb 14, 2023 4:39 pm

Laitch

Laitch
Life time member
Life time member
daveyson wrote:I think your brick is probably OK, bricks just are high revving.
 Smile Thanks for posting that fable table, daveyson.



Last edited by Laitch on Wed May 03, 2023 9:21 pm; edited 1 time in total


__________________________________________________
1995 K75 90,000 miles
    

21Back to top Go down   Speedo /Taco Error Empty Speedo/Tacho error Tue Feb 14, 2023 7:12 pm

daveyson

daveyson
Life time member
Life time member
I'm thinking the books might be wrong, I think that might be at least a part of the reason.


__________________________________________________
11/1985 BMW K100RT (late model)  Vin. 0090567
 ~120,000 km
    

22Back to top Go down   Speedo /Taco Error Empty Speedo /Rev Counter Error Tue Feb 14, 2023 7:22 pm

Hamo42

Hamo42
active member
active member
Hi Laitch This is what I was meaning that graph Davidson Posted is what I mean. The one I have is for K75C
And you guys crack me up.
Also I can't seem to post the Image I have stored on my desk top it say post to long ?

Although when riding it really seems its reving its guts out compared to my K75 S I just sold.

    

23Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Wed Feb 15, 2023 2:07 pm

92KK 84WW Olaf

avatar
Life time member
Life time member
A point not mentioned and one that does happen.....the speedo needle not moving fully due to the backing coming loose and obstructing the needle causing it to read slow......making the revs look higher. A gps check on the speedo will reveal this.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

24Back to top Go down   Speedo /Taco Error Empty Speedo /Rev Counter Error Wed Feb 15, 2023 2:31 pm

Hamo42

Hamo42
active member
active member
92KK 84WW Olaf wrote:A point not mentioned and one that does happen.....the speedo needle not moving fully due to the backing coming loose and obstructing the needle causing it to read slow......making the revs look higher. A gps check on the speedo will reveal this.

Hi Olaf, I have checked with GPS & a different Instrument assembly, Still 100kph /4750 revs  Thanks anyway.

Regards Geoff

    

25Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Thu Feb 16, 2023 1:28 am

MartinW

MartinW
Life time member
Life time member
I've just come back from a highway run and the speed of 100KPH on the speedo correlates with the  GPS at a 100KPH and the tachometer shows 4700 RPM + or -.
Regards Martin.


__________________________________________________
1992 K75s
    

26Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Thu Feb 16, 2023 2:04 am

Laitch

Laitch
Life time member
Life time member
OK! One more and we can start a support group.


__________________________________________________
1995 K75 90,000 miles
    

27Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Thu Feb 16, 2023 4:40 am

TacKler

TacKler
Life time member
Life time member
Laitch wrote:OK! One more and we can start a support group.

As one who has no interest in joining any more groups, if for no other reason than having met enough reincarnations of a one Mr Hitler, late of Berlin.  

My current speedo sits around 4,500 to 4,550 RPM for 100km/hr.



Last edited by TacKler on Sun Feb 19, 2023 10:09 pm; edited 1 time in total


__________________________________________________
Red 1991 K75S
    

28Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Thu Feb 16, 2023 11:20 am

Laitch

Laitch
Life time member
Life time member
TacKler wrote:As one who has no interest in joining any more groups, if for no other reason than having met enough reincarnations of a one Mr Hitler, late of Berlin. 
Maybe you'll be invited on as board chairman solely to direct the search for empathetic leadership from your saddle. Smile


__________________________________________________
1995 K75 90,000 miles
    

29Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Thu Feb 16, 2023 8:46 pm

K75cster

K75cster
Life time member
Life time member
the 3.36:1 f/d would do 48k at 100kph or 4th gear does about that on a 3.2:1 f/d. Is it definitely going into 5th?


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt 1992 K1100LT a blue one

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

30Back to top Go down   Speedo /Taco Error Empty Speedo /Rev Counter Error Fri Feb 17, 2023 2:37 pm

Hamo42

Hamo42
active member
active member
K75cster wrote:the 3.36:1 f/d would do 48k at 100kph or 4th gear does about that on a 3.2:1 f/d. Is it definitely going into 5th?
Yep  Laughing

    

31Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Fri Feb 17, 2023 8:39 pm

duck

duck
Life time member
Life time member
I have a taco error too!

Speedo /Taco Error GWAuDfd


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

32Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Fri Feb 17, 2023 9:46 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
You don't have that problem with burritos.  Nor any chance of getting "taco neck".

...and at my age, Speedos are ALWAYS AN ERROR.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

33Back to top Go down   Speedo /Taco Error Empty Speedo/Tacho error Sun Feb 19, 2023 6:18 am

Hamo42

Hamo42
active member
active member
Laitch wrote:
daveyson wrote:I think your brick is probably OK, bricks just are high revving.
You two should ride downhill on slab with tailwinds. That should bring them both into spec. Smile
I am not pursuing it any more. Just want to get my speedo back & fixed.

The instruments I borrowed the speedo now doesn't work What a pain in the B____. Speedo /Taco Error 8157 Speedo /Taco Error 8157

    

34Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Sun Feb 19, 2023 7:42 am

Laitch

Laitch
Life time member
Life time member
Hamo42 wrote:I am not pursuing it any more.
Speedo /Taco Error 177381


__________________________________________________
1995 K75 90,000 miles
    

35Back to top Go down   Speedo /Taco Error Empty Speedo/Tacho error Mon Feb 20, 2023 3:28 am

Hamo42

Hamo42
active member
active member
daveyson wrote:I'm thinking the books might be wrong, I think that might be at least a part of the reason.
Well back to square one. I tested it with the K75C final drive & basically its the same. So I'm putting my Disc

final drive back on with the 130/90/17 tyre & I will put it down as a learning experience.

Thank you all again for your help & hints.

Cheers from Brisvegas

    

36Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Mon Feb 20, 2023 3:43 am

daveyson

daveyson
Life time member
Life time member
Hamo42 wrote:
Although when riding it really seems its reving its guts out compared to my K75 S I just sold.

Haven't checked bricks, but every car I checked at those speed checkers along the freeways, when the speedo said 100km/h they were actually doing 95 or 96km/h. Since your latest brick has been calibrated for accuracy, that might be why it's revving higher.

My handbook doesn't have a graph for K75C bricks, I think they were no longer in production then, but there's a graph for the K75 (page 85) I think it might be the same, since you say at 100km/h it looks about 4,100rpm.

Speedo /Taco Error Img_2093


__________________________________________________
11/1985 BMW K100RT (late model)  Vin. 0090567
 ~120,000 km
    

37Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Mon Feb 20, 2023 9:45 am

Laitch

Laitch
Life time member
Life time member
Hamo42 wrote:Well back to square one . . .
Viva Brisvegas!


__________________________________________________
1995 K75 90,000 miles
    

38Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Mon Feb 20, 2023 10:13 am

Dai

Dai
Life time member
Life time member
daveyson wrote:every car I checked at those speed checkers along the freeways, when the speedo said 100km/h they were actually doing 95 or 96km/h
If you're talking about modern stuff i.e. < 20 years old, they're all calibrated to read fast. In the UK the speedo reads 2mph faster than you're actually doing. It's supposed to help stop you speeding.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

39Back to top Go down   Speedo /Taco Error Empty Re: Speedo /Taco Error Mon Feb 20, 2023 10:48 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Low reading speedometers must be a European thing. 

Having done years of timed rally and enduro events I am really picky about speedo and odometer accuracy especially since I used to do 50-60,000 miles a year as an industrial sales rep and didn't need speeding tickets in strange towns.

I periodically test my cruise control and speedo accuracy by recording the time it takes to cover a marked distance on the interstate with a stop watch.  On a long flat section I would set the cruise for 10mph over the posted limit and watch how much time it would cover a distance of 5 or more miles.  Seconds per mile is calculated by dividing 3600 by the speed in mph.  For example,  at 75mph it takes 48 seconds to cover a mile. 

My experience with Honda and GM vehicles over the past 30 years is that with the OEM tire sizes the speedometers are accurate to less than 1mph error, which is probably more a function of how accurately I can read the speed on the analog meter.

The low reading speedos on my bricks are annoying because I like to run at the limit of what the police will let you get by.  I also keep a running schedule in my head when touring, and the speedo error forces a lot of fudging.  I usually go by engine rpm now when I'm on the interstate and eating lots of miles.  I have a pretty good idea of where the tach needle is at 65 and 75mph and that is what I watch. 

I did do a calibration with Karamba on my RT, but even with the adjustment max'd out, the speedo still read a little low.


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Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

40Back to top Go down   Speedo /Taco Error Empty Over/under revving Wed Feb 22, 2023 4:31 pm

davemadsen

davemadsen
Silver member
Silver member
If you feel the tach is reading higher or lower than it should (or than you would like), a simple solution is to adjust the “pot” (potentiometer) behind the tach. In this way, you can have the tach show whatever you want it to show.


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Dave
    

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