The 2 stroke gremlin thread!

[motopsycho87]

Ok, I'm a happy owner of my 2 stroke death machine, but as with every other 2 stroke out there, they are finicky bastards to say the least. So in response to a PM I got asking about my RM125 CDI, I want to write those to stop anyone having the same problems as myself.

So, your bike is running like a piece of poop. It didn't, but suddenly, it hates you...

1 - Spark plug, always start here, take it out, look at it, if it's black, it's rich, if it's white, it's lean, if it's perfectly clean, you may have a water leak, if there are bits missing or extra bits, it's pre-igniting. Anyway, change the bugger. ENSURE YOU ARE USING A RESISTOR TYPE SPARK PLUG AND CAP, THIS IS SO IMPORTANT IT HURTS!!!!

DO NOT REJET AT THIS POINT!

It's worth noting the KTM EXC/SX300 and 250's use a BR7ES plug, honestly, I think KTM are a little better at technicalities, so I went with an Iridium BR7EIX.

DOES YOUR BIKE RUN HOW IT USED TO? IF NOT CONTINUE...

2 - THE CHECKLIST
Reeds - take them out, if they're ****ed, you'll know
Ignition coil - check resistances (the specs are in your manual)
Kill switch - Disconnect, does it start?
Stator coil - check resistances (the specs are in your manual, NO CABLE SHOULD EARTH, THESE ARE CLOSED CIRCUITS) *sometimes stators can read correctly when cold, but when hot begin to break up, keep this in mind, use your mum's oven maybe?... i've only had 1 go like this, and 3 earth out (on different bikes.. not just my gasser!)
Power valve - is it moving correctly? freely?
Exhaust - some of the silencers have a habit of imploding, check!
Engine / carb breathers - just blow through them...
Crank seals - is there oil on the stator side? are you getting a much heavier blue smoke upon first start that smells a bit funky compared to your insanely expensive strawberry flavoured yum yum? is there ANY float in the rotor or crank?
Carb float height - doesn't often come out of whack dramatically, but perhaps you have a big off and it shocked it enough
Jets - DON'T change them, your bike ran right before, just check they are clear of dirt, and if you don't have a fuel filter fitted, FIT ONE YOU TIGHT ****ARD!
Electrical connections - Ok, get a wiring diagram out, everything seems fine so far, so now start checking the condition of all connections, check continuity (use the resistance setting) the close to 0 from one end of a wire to the other the better.
Piston rings - still got 'em right?

I don't think I've missed anything, but if you have anything to add, please chip in.

Chances are, if you've got this far, your CDI is shagged, and no-body wants to buy a new one, have a look at the image below, it will give you an idea of what you can fit.

Ok, so the RM125 CDI, if you go on electrex world, you can see how I came to this conclusion (attached image). The KTM CDI's will fit too.

I fitted the RM125 CDI because it looked the same, quite frankly that was it. It's important to note that the GASGAS has a shared earth with the lighting etc, take the earth's from the CDI, cut them, and make a new earth direct to the frame.

Literally, almost any kokusan cdi will fit as long as they use the same stator, make sure you get the wiring plug that goes into it, the wire colours are the same, but may fit the plug differently.

I've found RM125 CDI's from 1995 all the way to 2004 are almost identical, they have different part numbers, but the same plug, same wires, same stator.



Sorry this is quite fractal and rushed, I'm moving house today. I'll get everything neat and itemised and detailed as hell soon..

[Harry]

Thanks for the write up. You answered a number of my questions re. the RM125 cdi.

[swazi_matt]

Nice write up, The one GG-specific gremlin to also check under the circumstances above is to check that the cable-choke is not engaging by itself

[motopsycho87]

More info re: rm125 cdi.

Originally Posted by Selvagem

Hello.

First I want to ask early apologize for my English, I use google translator. I was very intrigued by the subject of the CDI of RM 125, and I'm almost buying one for me. My bike works superbly after setting Squish (1.0mm). You indicate me the exchange of CDI? The change is very noticeable? I'm looking at the CDI of a RM 125 year 2004, the exchange of CDI is plug and play? It has to advance or delay the static point?

Sorry for so many questions.

Best Regards.

Leandro Lindemann.

Hi. To the best of my knowledge my RM125 cdi is 2004, I also have a 1998 cdi which has the exact same connectors, and feels the same to ride, despite different Suzuki part numbers.

The wires to the plug use the same connectors, though the Suzuki CDI has an extra earth, I joined the 2 earth's together and fitted an eyelet to the frame closer to the CDI as I didn't like the CDI sharing an earth with the lighting circuit.

The stator I originally retarded to be safe, but have since returned it to the original position with no problems.

The power difference is very noticeable, the bottom end barks and breaks away where it would normally be very smooth and grip. There seems to be less of a transition between low to mid, with more power at the low end going into similar mid range. On full throttle the power is very sharp and relentless, there is a little less over rev, but feels as though the power gained definitely outweighs the 500 or so rpm lost.

So in short

Very noticeable change
Easy to fit
No stator adjustment

[socalscott]

Worn float-pin post hole. Mid-range vibration shifted the float position, which allowed fuel to dump into the bowl.

[motopsycho87]

Originally Posted by socalscott

Worn float-pin post hole. Mid-range vibration shifted the float position, which allowed fuel to dump into the bowl.

That's an interesting one, mine is worn and slides too freely, but the shape of the bowl stops it moving anywhere far enough to cause a problem...?