Please help. No spares on 2 back cylinders

[Dave 68]

Hello peoples, 

I’m a little bit stuck , 1997 Royal star 1300.

I have no spark on the back 2 cylinders and good spark on the front 2 , I have power going to the coils and have checked the leads, plugs and plug caps , swapped spark plugs and they are all in working order. 
The bike starts easily even only running on 2 cylinders. 
could it be the coil pack is it common for both to go at once. 
Any help would be greatly appreciated 

Thankyou Dave

[saddlebum]

Coil pack failures are less common then you may think as are TCI's. Ninety percent of the time the issue can be traced back to faulty or corroded wires and/or connectors. Having said that my favorite means of diagnosing is to start out by keeping things simple , rather than trying to get overly sophisticated (which can be overwhelming for some).

1. Pull the plug wire If you do not have a spark tester (which are cheaply purchased at most any auto parts sources) insert a small screwdriver that will stay in place and than holding the shaft of the screw driver about 1/2 to 5/8 of an inch away from the engine block crank the engine a good spark should jump from the shaft of the screwdriver to the engine block. If not go to step 2
2. Remove the plug caps from the plug wire and check resistance through the cap. Place one probe of the ohmmeter into the wire end and one into the plug end. You should get a reading of about 10k ohms. If not replace.
3. Remove and inspect all the connectors involved with the ignition system, specially the ones going to the TCI.. Even barely noticeable corrosion can be a source of electrical issue. Heavy green corrosion is easily noticed but if you look closely at the terminals you may notice what looks like a thin white or light green powder like coating on the terminals (this is known as fretting ) which believe it or not can interfere with  good electric conductivity. Clean this terminals up as best you can (thin slivers of sandpaper wrapped over the end of a tiny screw driver or other very thin and tiny metal object combined with a good electrical cleaner are most effective here. To prevent further corrosion spray with something like ACF50 (my personal favorite available through some bike shops and amazon) or thin coating of dielectric grease.

If you still don't have spark than you need to get into checking voltages and coil resistance.

1. Check the red black wire at each coil. With ign switch on you should have 12 volts
2. follow the checks in the attached PDF

ign system chk 96 -2001.pdf

Edited July 4, 2021 by saddlebum

[Dave 68]

Thanks mate , 
I’ve done all that and cleaned all terminals with CRC contact cleaner after pulling all the plugs from the connection blocks.  
Definitely no spark at the spark plug , and have unscrewed the spark plug cap and no spark from the copper wire in the lead . 
It’s got me a bit stumped rite now 

[saddlebum]

5 minutes ago, Dave 68 said:

Thanks mate , 
I’ve done all that and cleaned all terminals with CRC contact cleaner after pulling all the plugs from the connection blocks.  
Definitely no spark at the spark plug , and have unscrewed the spark plug cap and no spark from the copper wire in the lead . 
It’s got me a bit stumped rite now 

I updated my previous post and added a PDF as well to assist checking your ignition system. Check it out.

[Dave 68]

Thanks again , I’ll check it out next Saturday when I get home from work . I’ll be away all week again . 
Regards Dave