CR Elec Experts

[PCMAX]

My 82 CR125 stopped suddenly at at recent meeting after completing 2 warm up laps with no problem at all. I finally got around to having a look at it yesterday and found a blockage in the pilot jet? Beauty I thought, easy fix.... put it back together and it wont start or run.
Tried several different spark plugs, no start
put a bit of petrol down the plug hole, no start
Checked the distance the spark would jump = 9-10mm
Tried a different ignition coil, stator coil, cdi, carby, still no start.
Checked the reed valve, pulled the head off & checked the piston/rings, still no start
Checked that the magneto was on solid and the marks still line up with TDC
Doesn't seem to have any leakage from the crank seals.
When i try to clutch start it (about 50 times so far) there is no sign of it actually firing just a few coughs and farts. It's as if it's firing at the wrong part of the stroke but that can't happen, can it?

[Lozza]

Checked  the timing marks on the flywheel and stator

[PCMAX]

Checked  the timing marks on the flywheel and stator

Yeah the TDC mark on the flywheel & stator lines up when the piston is physically at TDC. So presume that it is firing at the mark just before TDC. I have no way of actually checking that it is firing at this point though without the bike running and a timing light. That was the good thing about points ignition I guess.
Does anyone know of a way to statically check the actual firing point or is that impossible with a CDI unit?

[Noel]

when you check how far the spark would jump did you have the plug cap off,?
have you tried a different plug cap

Noel

[PCMAX]

when you check how far the spark would jump did you have the plug cap off,?
have you tried a different plug cap

Noel

Yeah Noel I tried it with a different ignition coil & cap. I have one of those spark gap testers that you can adjust from 1mm to about 20mm it was easily jumping a 10mm gap.

[Stewart Allen]

Hey Pete, youv'e got spark ( 10mm) & youv'e dropped fuel in, do you have the third requirement compression ?

[Noel]

If you can find the timing light,hook it up ,put bike in gear and get someone to spin the back wheel,
should be enough to see where it is firing, maybe

Noel

[PCMAX]

Hey Pete, youv'e got spark ( 10mm) & youv'e dropped fuel in, do you have the third requirement compression ?

Yeah Stuart It seems to be holding compression' it pops & sucks my finger when I put it over the plughole. I will borrow a mates gauge and check it next weekend though.

[PCMAX]

If you can find the timing light,hook it up ,put bike in gear and get someone to spin the back wheel,
should be enough to see where it is firing, maybe

Noel

Noel, genius!! I reckon that might work. I'll give it a go on the weekend, at least it will confirm or eliminate that suspicion. I have a couple of young fellas I can engage as wheel spinners......

[Lozza]

Ermm the safer way is to buy a hex to 3/8 or 1/2in socket adaptor put it in an electric drill set in reverse and turn the engine over with the plug out  and GROUNDED. CDI's do not like firing ungrounded. This will allow you to turn the engine over and check timing unaided.

[PCMAX]

All sorted now.......
Turns out that the rings had been nipped into the ring groove at the front of the piston, bugger all compression. Should have though of that earlier instead of chasing a non existent elec problem.