Vintage Dirt Bike Q & A

I am currently restoring a 75' MT125. I am not able to get spark and I am at a complete lose at to why this is. The coil/condenser has been tested and is good. I tested the stator for continuity and it is good. The points appear to be brand new and the gap is also to spec. The battery is fully charged. I have by passed the run/kill switch by just connecting the two wires. other than that the only thing it could be is the electrical peripherals such as the headlight turn signals and e.t.c. are not hooked up.

Where should I go from here? Any ideas?

This shorts the coil input to ground, killing the spark. Try unhooking these wires and see what happens; it may not fix it, but it will remove a big problem nonetheless.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I got spark! I enlisted the help of my local honda motorcycle guru and he got it done no problem. He's the man! I am still having trouble getting it started though. There is no fuel getting to the cylinder. I have cleaned the carb and replace all the necessary parts and so clogging is not the issue. I have checked A LOT. There seems to be good compression. When I pump it while placing my finger over the spark plug hole it gets pushed out with good force.

It seems to compress the air in the chamber with force but I am thinking there is not enough suction created on the down stroke of the cycle to pull fuel in. This is a complete guess. I do not know why there would be good compression with no suction. Does this sound right? I am at a lose once again. I have the airbox removed from the carb if that makes any difference.

Maybe unscrew the spark plug and pour a little gas down the hole. Put the spark plug back in. Kick it over and if there is spark it should fire a couple of times. If it does not fire then there is either no spark or there is something else wrong.

I got it going! It has been since mid Feb. since I bought it for about $250 with the engine close to being completely seized and it is a now a running bike. I split the cases, changed some seals out, repacked the engine bearings, new piston and rings, got the stator partially rewired, e.t.c and it is up and running. I still have some work to do but I took it around the block for the first time today. I am actually quite surprised how smooth the transmission was shifting through the gears. Now that it runs I see that the flywheel is not square at all which is the next thing on the list. After that is is mostly cosmetic stuff.