DR750 max 4000 RPM (solved)

[Radek]

Hi, after installing Sixo on my old bike I have issue with rev counter. Everything works perfectly to 4000 RPM, above this value Sixo start to show 0, even if the engine keeps reeving higher. Everything else (indicator, pressure switch, temperature sensor, speed sensors, buttons etc works perfectly). My Sixo is # 181 and soft 3.1.6
What I did:
1. Verifying Sixo setup. My current setup is AfricaTwin, because I am using oil pressure switch.
a. CCF setup to 1/1 ( 4 stroke single cylinder engine that generates spar every crank rotation)




2. Verifying connection:
1 RPM+ IN Timing signal (ignition coil input blue/white cable)
14 RPM- IN Timing ground (connect to ignition coil ground +motorcycle ground (black/white))
3. Replaced CDI
4. Replaced ignition coil
5. Replaced stator - there was damage of one of coils so I had to do it anyway
6. New electrical harness - I decided to simplify my electrical harness so I made it designed for Sixo. Sixo inputs made with UNITRONIC LiYY 0. 34 mm2 cables. All new plugs etc. Base on: https://www.bollertante.de/rur/kabelbau ... t-0003.pdf

After all that changes no improvement. I have no idea what to check next, since Sixo was proven to work on DR750 without problems.

[Arnold]

Hey Radek,

it's a pity that it doesn't work out of the box sometimes. I am always wondering why it is so hard for me to built a pickup that is working for _any_ ignition out there...

This is for me to get into it - and for you to read through, so that we don't miss anything:

- I'm assuming "readings correct up to 4000 RPM" means "up to _about_ 4000 RPM". (So it's some "analog" stuff, not software that is cutting away at _exactly_ 4000 RPM.)
And I'm assuming there is a range where the displayed RPM is "jumping" between low and high values.
- In the Settings of the SIxO the K-factor is 1/1. It's a 4 stroke engine with one of the ignition pulses into the already burned mixture. At 4000 U/min there is an ignition pulse all 15ms.
- You got your SIxO mid 2017. It is already prepared for negative ignition pulses (1nF/400V instead of R11). MC14538 for higher resistance to interferences.
I had a look again at the input filter characteristics. In the interesting range it get's better (lower damping with higher RPM).
Also the monoflop (T=R*C=3.3ms instead of T=0.7*R*C with MC14538) is far away from limitig the RPM.
- According to the schematics you referenced:
SIxO Pin 1 RPM connected to primary side of ignition coil (not to a separate low-voltage output of the CDI)
SIxO Pin 14 RPM return connected to vehicle ground near ignition coil

This is all correct.

I think that the signal amplitude from the CDI is simply lower at higher RPM. I always hesitate to make the input resistors smaller without measuring first (see next post) since this can possibly damage the SIxO. But anyway: Try to lower the value of R6. 15K instead of 22K should be ok.
At least you should get higher readings than 4000 RPM. So that we see an improvement.

Best Regards,
Arnold

[Arnold]

To measure the voltage level:
Connect ground of an oscilloscope probe to vehicle ground. Connect tip of the probe to the primary winding of the ignition coil.
(Be sure that the probe can withstand the high voltages - usually several hundred volts.)

The waveform looks like VM2 in http://www.sixo.de/EXCHANGE/pos13_wav.jpg. (With some ignitions the waveform is inverted.)

If the ignition pulse is lower than 100V, the value of R6 can be decreased.
Decreasing R6 is the last step. Everything else has to be checked before. Only do this if you are sure that the problem originates from the voltage level of the ignition pulse.

/Arnold

[Arnold]

[Radek]

Arnold,

you are right. RPM readings are not cut exactly at 4000, it goes a bit up and than very fast to 0.
Something like this:

I will arrange oscilloscope and do the recommended measurements.
Thanks for help!
Radek

[matzejochen]

Hey ho.

Radek, my little Pony is a DR 800. SR 43 A, 1992.
My Plan i have created with staubig. He also created most of the other plans -with Stefan Hessler and Resi (Bollertante).
So, if this can help you, have a look to: https://nc.fusem.de/index.php/s/jaa4PLLesp9bFj8
Also, HERE the SIxO on my DR 800.

Matze

PS: Sorry, my english is much more terrible than my german.

[Radek]

I took some time, but the issue is SOLVED!
Arnold was right with R6. After changing to 15k rpm meter is working correctly.
Why? My opinion is that: I am running DR750 (SR41) which has different ignition system vs DR800 (SR43). Differences are CDI, number of ignition coils on the stator (SR41 has 1, SR43 has 3) and different pickup unit of rotor. Signal was to week on SR41 this is why it was not working correctly on original R6.
Details of the systems can be found here: http://bollertante.de/site/index.php/de ... e-in-farbe

[Ralf]

Sounds good.

And thx to share your results with us!