I have good spark, compression, fuel and air. But no start :(
so i bought a dt 125 r, i have had the frame powder coated and built it from the frame up. The bike was not running when i first got the bike, however i never tried to start it. Long story short i have a good spark, 110 psi compression, and even if i spray brake cleaner in the carb it will maybe fire once if im lucky. The CDI is a 3RM-30 which from my knowledge is rare and hard to find a replacement or any information on. Could someone please give me advise. i have looped the circuit for the kickstand switch so there should be no reason for the bike not to start as far as i can tell.
I’ve never tried to run an engine on brake cleaner, don’t know if it will. I’ve just used it to test for air leaks...
Is the plug getting wet when you try and start it with petrol from the carb? Always try choke no throttle at first, then a blip of throttle if it doesn’t fire second kick...
I’d check the carb if it was me. If it’s clean in the bowl just remove the jets and blow through all the fuel and airways...
@spookdog Yeah brake cleaner 100% works, I've done it many times. so I've taken the carb of twice and cleaned it. The previous owner rebuilt the carb. I wasn't sure if he built it correctly so i have another dt 125r. i swapped the carb over and still nothing. the spark plug has fuel on it.
The neutral light does not come on, could this somehow be breaking a circuit?
@spookdog The only other thing i can think of is the CDI, this model has a 3RM-30 CDI and i cant really find any information about it. I also have a spare 3RM-20 CDI with all the wires cut. if i could re-wire this CDI. Could that work? or at least cancel out the CDI being a fault? ive never had a bike have compression, spark and a clean carb not run before.
@kylescave Don't use brake cleaner lol. It will wash the oil off the bore (bore wash) meaning you'll have no start up protection. It's not a wet lube system.
Yeah I've seen this before many times. Is it "good intermittent" spark? This is quite common when something like the neutral switch, side stand or kill switch is still pulled down. In other words, it will spark a few times but immediately die.
@calum Oh yeah i defo would not recommend using brake cleaner, but I'm very desperate to hear it fire up just so i can carry on the build . Okay i will check the neutral bulb when i get home, hopefully it is as easy as that.
This bike has been rebuilt by every nut and bolt. i cannot wait to finally give it a ride. My other full power dt 125 r gets 94mph which i thought was astonishing.
Fingers crossed this works.
@calum Could this be the neutral bulb? or does it have to be a switch to cause this issue?
@kylescave Won't be the bulb, but neutral switch/kill switch and side stand.
Usually it's the stand switch. 90% of the time.
@calum i've looped that with a plug so it cant be that i dont think, unless theres break in the wires somewhere in the loom. but i find that unlikely.
A good intermittent spark! Yep, sidestand circuit sounds guilty
Other CDIs won’t work. Yes the neutral switch is part of the sidestand kill circuit. The switch is by the gear change lever. The wire often breaks. I don’t know how the sidestand switch is bypassed, so can’t tell if a looped plug is good or not
I’d put it back to standard and see...
I think that there’s a black/yellow ~striped wire going to/from the CDI. I think This is the wire that earths the CDI. Try disconnecting it and checking your spark...
@spookdog " I don’t know how the sidestand switch is bypassed" <- This
IIRC it's something odd like that and looping it wasn't sufficient. Used to happen on an old DTR I had. It was the weirdest thing, it would start if you kicked it over whilst simultaneously switching the ignition from the "Off" position to the "On" position.
And never start with the ignition off and never start with ignition on. Always the combination of kicking it whilst it was off and switching the igniton whilst it's turning over. Weird fault.
Sounds like an under seat solenoid dilemma!
Actually 3rm 20 & 30 might be changeable, I was thinking of the earlier 3nc unit which is ‘standalone’ IIRC
What year is your bike? After 1997? I don’t think your problem is the CDI unit though. It does sound like a side stand or other ignition earthing problem ...
Check the neutral switch!...