DR125 no spark

Hello, I've got a 1988 DR125 with no spark. I put in a brand new plug, checked connections and still nothing. Pulled out a few bits to test resistances etc. stator was fine but the HT lead resistance was a bit lower than recommended (about 2000 ohms under recommended) so I've ordered a new one. Prior to this the bike had a few instances where it shut off from what appeared to be overheating leading to no spark. Is there anything else that could be the problem based upon the fact it was overheating, such as the CDI?

Also on a slightly unrelated note, what do people find is the best method of setting the engine timing correctly on these single cylinder jap bikes? I usually manage it but with great difficulty.

Thanks

Also, here is a picture of the stator, not entirely sure what to be looking for in terms of damage, but does it look at all melted/corroded to a point where it will no longer work?

There's the manual https://www.dropbox.com/s/sx1whybr3rv7k64/DR125%20%26%20SP125%20Service%20Manual%201986-1988.pdf?dl=0

Shows the electrical system on page 5-1. It's the older CDI system with no reg/rec. I've never had one of them but it's just the stator, pick up coil, CDI, ignition coil, spark plug, kill switch and the connectors. You have probably already done it but you can check the resistance of the stator, pick up coil, ignition coil and compare it to the manual. Check for continuity and corrosion in the kill switch. Check all the ground connections. Check all the connectors and wiring for opens or high resistance. In my experience electrical faults are often just bad connections. If that all checks out ok I'd be thinking the CDI.

Setting the timing is on page 3-57. On the stator you're looking for high resistance or a short to ground

If you want a description of how a CDI system works have a look at page 23-5 of this manual https://www.themotorbikeforum.co.uk/viewtopic.php?f=27&t=72619

Thanks for your response, fit a new ignition coil/HT lead last night and bike fired right up.

Thanks for your response, fit a new ignition coil/HT lead last night and bike fired right up.

Nice one. You said you had a low resistance reading on the HT lead? Did you take that measurement from the positive of the ignition coil to the spark plug cap like it shows in the manual on page 5-3? If you did and you got a lower resistance reading than expected I think that shows there is a short in the secondary side of the ignition coil. That would cause a weak spark or no spark. I think it happens because the insulation in the secondary coil fails so the coil touches off itself so the current has a shorter path to travel so less voltage is created at the spark plug.

One more thing just in case someone finds this in the future. I think if you had a test light you could have tested if the CDI was working. Attach the clamp on the test light to battery negative and touch the other end of it to the output of the CDI which is W/Bl and the test light should flicker when the engine is turning over. That would show that the CDI is sending power to the ignition coil.

Seems to have done the same thing again, took off and cleaned the carb and the bike wouldn’t start. Checked the spark and there wasn’t one, swapped out the HT lead for another and it sparks now but still won’t start, just gives a loud pop/backfire every kick, but there is a small hole in the exhaust.

On another note, kickstart seems to have gone slightly stiffer?

What does the spark plug look like after you try to start it? Is it wet or dry

It’s coming back slightly wet with what smells like fuel, not oil

Seems like you might have a weak spark or you're losing spark. Sometimes you can have spark at atmospheric pressure by not under compression. You can get one of these spark testers. That will tell you how strong your spark is. If you get one make sure it has the stud type connector on the end. The other ones only fit car spark plugs. https://www.ebay.co.uk/itm/Adj-Ignition-Spark-Plug-Tester-Inline-H-T-Test-Lead-Diagnose-Car-Engine-4121-A32/363010081019?hash=item54851640fb:g:M2oAAOSwlsde1TwY

Do you have a fully charged battery attached to the bike ?

Thank you for your replies, I will invest in a spark tester

There is no battery currently attached to the bike, shouldn’t need one to run tho should it?

There is your problem.

Yes it needs a battery hence why its burnt your stator out.

They are not designed to work as the main continuous source of ignition/power source

Okay, I had a battery previously and hooked it up and all was fine, I would turn on the ignition and the dash would light up, lights work etc. Then upon starting the bike however, all lights and electrics seemed like they were running off the engine, and not the battery (lights would fade and brighten slightly with the rev of the engine). After restarting the bike, it would run as though there was no battery attached at all. Could this be due to a bad regulator?

Stator/Alternator provides x amount power

Arguements sake 12.5v

Nothing turned on engine running the ignition system has full use of that 12.5v

Now you use lights that 12.5v is being shared everywhere

This is why you need a battery to store power that can be distributed smoothly and consistently across the electrical system .

Charging systems are designed to replenish power in the battery and if its not there it causes damage to the charging system which over time will cause it to fail and not provide sufficient power .

Light fluctuations can be a sign of poor battery condition ,charging or could be how the charging system operates and not provide any relevant output until a certain rev range .

Old school bikes with points could work without batteries easily but newer still bikes with cdi 's , electronic ignition require a battery .

If you look in that manual it shows no battery and no reg/rec for a DR125. It's just AC from the stator going to the cdi. If he has a reg/rec and a battery it must not be a DR125 it must be a SP125G

Manual shown is for dr125g (1986) though

Parts fiche shows battery and reg

https://www.cmsnl.com/suzuki-dr125s-1988-j-united-kingdom-france-finland-e02-e04-e15_model13161/partslist/

Yeah maybe there's a few different version of it. I just went by that Suzuki manual

This bike definitely has the slot for a battery, and also has a regulator rectifier. So this means it’s not a DR125 but a SP, which means it requires a battery? It has run without a battery before but this may be what caused the HT lead to go bad in the first place. I also noticed it has the mikuni carb found on the GS125 whereas usually the DR usually has a teikei carb as standard.

I will have to pinch the battery off my xlr and give it a go, but the loom on this bike is in sorry state

This bike definitely has the slot for a battery, and also has a regulator rectifier. So this means it’s not a DR125 but a SP, which means it requires a battery? It has run without a battery before but this may be what caused the HT lead to go bad in the first place. I also noticed it has the mikuni carb found on the GS125 whereas usually the DR usually has a teikei carb as standard.

Yeah if it has a battery and reg/rec put a battery in and see if that helps. The Suzuki manual I put up for a 1988 DR125 only showed it having a basic electrical system with no battery and no reg/rec so I thought that's what you had. TimR put up a link to a DR125 from 1986 with a full electrical system so there must be two types of DR125 at that period.