RM125 CDI - strong kickback
- Thread starter GGRider01
- Start date
motopsycho87
New member
You need to retard it a fair amount, 6-8 degrees to be precise, otherwise you'll burn your reeds. Rm cdi is amazing for low down grunt, but top end suffers badly unless you retard a lot
The opposite of what I want. I found pretty quickly that 2 out of the 3 slots on the plate wouldn't line up with the threaded holes with even a little bit of adjustment. I could elongate them, but figured the stock CDI will have to do. The low down grunt has never been exceptional, but neither has it been exceptional on the pipe. A lot of factors at play on my Frankenstein to sort.
motopsycho87
New member
If you're finding the bike a bit lacklustre it might be worth looking at the jetting, having the squish clearance sorted (raise the ports to the correct height with gaskets first, I had to use 1.5mm) and overall health, piston, rings, seals etc. The bike rips with any cdi. The RM one massively increases the low and mid, but yes you do have to file the holes out slightly. All depends what you want the bike for. Would suit enduro cross and supercross more than anything else
Exactly my thoughts.
Jakobi brought forward the idea that the 2013 jug on my 2000 bottom end could be throwing port timing out the window. I was so concerned with running as tight a squish as possible without a machinist that I just threw the thinnest gasket on I could. I popped the pipe off, rolled it over to BDC and behold, the piston sits nearly 1mm above the bottom of the exhaust port!
If I'm to measure squish and get it corrected, I'll have to stack some gaskets. Luckily I have two heads, so downtime is a non issue.
With the piston sitting high, I wonder if my compression ratio is through the roof. Piston looked perfect though, so that's one less thing to fret over.
motopsycho87
New member
I can't remember what my chamber volume was, but I did have to re machine it twice to stop it pre igniting. Taking a cc out at a time.
pscook
Platinum Level Site Supporter
FYI, the piston on my 2011 is about 1.2mm above the exhaust port floor, and the squish is 2mm+. Don't sweat it until you measure the squish, these bikes are notorious for having wildly varying gaps. You might be just fine, but again, you might not, but you have to measure first.
Just thought I'd add an update with a little background info. Over 4th of July I had the bike up at Taylor Park and noticed at very high RPMs the bike would miss occasionally. I thought maybe I was still a little rich in the main. It's progressively gotten worse since then, a little bit at a time. I'm now convinced it's not a jetting issue but electrical. It's neither sputtering nor bogging, it simply isn't sparking. I've made pretty much all the wiring in this bike and have been through it more times than I had ever hoped with the stators failing on me. Ignition coil has a good ground, stator is new and connections are sound. I must have a decaying CDI. I'll give an update if a replacement fixes it.
