No spark

C

critter39

Junior member
Hi needing some help have a 750sf2 been sitting for 4 months previously fully rebuilt by Redax , new battery but no spark is fitted with a Sachse ignition have been all over the wiring, checked fuses, it's getting fuel wet plugs just no spark all input appreciated
 
I'm not familiar with the Sasche unit but believe it has a test facility. Turning the selector switch to 0 fires the plugs continuously with ignition on -

Test Mode
The ignition box features a test mode. This mode make the spark plug(s) fire continuously
without the engine running. This tests the power supply, wiring, coils and the ignition box.
However, it does not test the pickup. For a working ignition test mode has to succeed.
To use test mode, unscrew the spark plug(s) and place them back into the plug caps,
so the spark can be observed. Then switch the 10-way hex switch on the side of the box
into position ’0’. Then turn on the ignition. You should get a continuous spark. If that’s
not what’s happening, check the voltage between ground (pin 2) and pin 8 if it reads 12 V.
Sometimes it is required to turn the ignition off and on again to engage test mode.
 
critter39 said:
Hi needing some help have a 750sf2 been sitting for 4 months previously fully rebuilt by Redax , new battery but no spark is fitted with a Sachse ignition have been all over the wiring, checked fuses, it's getting fuel wet plugs just no spark all input appreciated
Click to expand...
Fully rebuilt by Red for sure means it has run before. What plugs are used and have you changed them? I had several times the issue that cold starting with to much choke killed spark plugs. mostly just one, but who knows.

Earth is a very good hint, had that with a cable coming lose under the regulator... Sometimes - even if well experienced - crimping connections fail. Had that also when I hooked up my DMC 30 years ago. First time I just hooked it up with long cables and bike was instantly running. Then I shortened the cables and obviously the crimping of the earth cable wasn't good. Bike did not fire up. searched for two full hours, not finding the fault. Braught the bike to Uwe Witt's workshop and they found and fixed it...
 
Vince said:
Tried new plugs, high-tension plug leads connecting plug caps. If both don't spark, that's a good indicator of a common issue. Make sure your earths are nice and tight.
Click to expand...
Checking earths new plugs tomorrow ( Bosch in case it's dodgy NGK's )
Rob said:
I'm not familiar with the Sasche unit but believe it has a test facility. Turning the selector switch to 0 fires the plugs continuously with ignition on -

Test Mode
The ignition box features a test mode. This mode make the spark plug(s) fire continuously
without the engine running. This tests the power supply, wiring, coils and the ignition box.
However, it does not test the pickup. For a working ignition test mode has to succeed.
To use test mode, unscrew the spark plug(s) and place them back into the plug caps,
so the spark can be observed. Then switch the 10-way hex switch on the side of the box
into position ’0’. Then turn on the ignition. You should get a continuous spark. If that’s
not what’s happening, check the voltage between ground (pin 2) and pin 8 if it reads 12 V.
Sometimes it is required to turn the ignition off and on again to engage test mode.
Click to expand...
Thanks Rob on to that tomorrow great information
 
Laverdalothar said:
Fully rebuilt by Red for sure means it has run before. What plugs are used and have you changed them? I had several times the issue that cold starting with to much choke killed spark plugs. mostly just one, but who knows.

Earth is a very good hint, had that with a cable coming lose under the regulator... Sometimes - even if well experienced - crimping connections fail. Had that also when I hooked up my DMC 30 years ago. First time I just hooked it up with long cables and bike was instantly running. Then I shortened the cables and obviously the crimping of the earth cable wasn't good. Bike did not fire up. searched for two full hours, not finding the fault. Braught the bike to Uwe Witt's workshop and they found and fixed it...
Click to expand...
I have changed them a couple of times previously with the same complaint ( failed plugs NGK's ) I did renew the earth connection to the wiring as it just didn't feel good, charging the brand new battery overnight and I'll put all the great advice to work tomorrow
 
Are the LED lights on the trigger board flashing when turning engine on with starter? If not no power to black box, or rotor that triggers the sensors on trigger board has moved.
Andy
 
critter39 said:
I have changed them a couple of times previously with the same complaint ( failed plugs NGK's ) I did renew the earth connection to the wiring as it just didn't feel good, charging the brand new battery overnight and I'll put all the great advice to work tomorrow
Click to expand...
If you have to change plugs often due to cold start fooling, you might want to consider a change on your start-up procedure and/or check your float hights and float valves (later one to close completely once the float is filled to the right level), sync the carbs and especially the choke plungers (they need to be equally high, moving at the same time and close completely when you close choke, please). Choke plungers synchronization is mostly disregarded but makes a hughe difference if out or correct.

I visited a british Laverda owner several years ago who was living in California in a lovely house right at the seefront who had an issue with his Jota. It started fine, but in idle it died after just 10 - 15 Sec.. I asked him what he had done and looking at the bike, I strongely believed him that he completely rebuilt the bike. Also the carbs looked brand new. I asked him if he had synchronized them and adjusted it to the right specs, which he assured me he had done. I took a small screw-driver and checked the air mixture screws. Left was 1 turn out, center 1,5, right side was 2 out.... As the bike was ideling smoothly with not many vibrations, I took off the rubber hoses connecting the carbs with the airbox to see if all 3 sliders were going up and down equaly, wich they indeed did. Right away though I recognized that on the left carb, the choke slider was several milimeters open, while the center one was almost closed and the right one was closed...

I asked for the right tools, slid the rubber up that hides the adjustment screws (where the choke cabel goes into the carb) on all 3 and opened the choke just so that the middle choke plunger barely opened up. Now I adjusted the other two to the same level and made sure that all 3 close completely and open at the same time. I adjusted the mixture screws to 1,5 out, put the rubbers back in place and started the bike, which now constantly ran for the next minute without dying... ;-) Easy fix, rewarded by a good cold beer afterwards and one of the nicest sea-food dinners I have ever had!
 
If it was running but just left for months it will be something lose, snapped , unplugged, switched off etc - very unlikely a component failure.
Have you dislodged something taking the tank off? 12 v at coils? Earths - undo and redo all earths especially if it has powder coated frame.Ignition switch block connector- Something simple….🤔
 
Not thinking it is that easy, but... The SF2 has ND switches, right? is maybe the kill switch put to OFF? else check also the ignition key switch. The cables on the back might have lost conection...
 
Rob's Sachse test is a good start - if no result, grab a multimeter and start from the source of power to the ignition-coil system, checking for at least 12v at every step (eg, from the fuse in, fuse out, to RH kill switch, from RH kill switch, at coils). Just contact the red + of your multimeter to the lead/connector and black - to earth. You can check earths by using a test wire to a known strong earth source (eg, motor). Eventually you'll find the problem - obviously you try new plugs but I'll bet my left knacker it's not that.
 
critter39 said:
Thanks everyone for your great advice the problem was a dodgy earth wire from the battery to the wiring harness, again thanks brains trust for all your input cheers Chris
Click to expand...
Good to hear.

Battery to harness? The only leads I run from my battery neg to earth are heavy wires/cables going to frame and engine. The rest of the components have their own earth to complete a circuit, except things like neutral and horn switches that have + feed directly to the component and earth when triggered.
 
Old story, I had a slight tipover doing a U-turn on a hill, and my battery hold-down strap snapped, and the wiring got a good stretch. For the next 2 days, heading home, the bike would cough and die and then refire, not fun. Anyway, what was found later was a snapped earth wire to the ignition box, 50mm up under the insulation. Good battery hold-down is important.
 
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