Can't start issue - is it stator

[Strummer10]

Guys banged a newly built engine in the scoot yesterday and ready to set up the timing BUT although I have a spark it is not firing up ?? On checking the ohms values to the stator plate (as per Stickys book) the values I have are 93 (to Stickys 95) and 390 (to stickys 450-540) so am presuming the stator's knackered on that basis.

Do the low values mean the spark will be intermittent maybe, not strong enough or does this mean one of the coils is defective ??

Thanks

[coaster]

The pickup resistance is close enough but the LT coil resistance is way too low to give a strong enough spark under compression . I would advise trying a different CDI though but even if it runs I would definitely change the stator or the LT coil at least as it is definitely failing, the low resistance indicates that the insulation on the coil windings is breaking down.

Colin

[Daggs]

When you say "you have a spark" do you mean at the sparkplug? If so i would be surprised that the engine doesn't fire due to the spark quality.
However i do agree with 'Coaster' the LT reading is rather low. The simple answer is to change the coil or borrow a stator.

[coaster]

When you say "you have a spark" do you mean at the sparkplug? If so i would be surprised that the engine doesn't fire due to the spark quality.
However i do agree with 'Coaster' the LT reading is rather low. The simple answer is to change the coil or borrow a stator.

I was thinking that a weak spark might not fire easily under compression. I had a similar thing with one of mine a couple of years ago although it had previously been running fine, it decided not to start after standing for a few hours, kicked it for ages, checked spark and it had one so decided to bump it and it fired up but was running like shite. That was the LT coil on that occasion.

[Daggs]

Yeh! I wasn't really arguing against what you typed. I was just wondering if 'Strummer10' had another problem simultaneously.
Best to change the LT first, to remove that possibility.

[sunrisemac]

Have you checked compression. Try a small squirt of engine oil down plug hole and spin engine over a couple of times (to seal rings) before putting plug back in, then try a kickstart.

[Muppet]

carb? is choke working?

[Strummer10]

Thanks for responses. Ordered a new stator and CDI to try a change over. Yes it was sparking at the plug and maybe the issue was always there. We rebuilt the engine because the flywheel was 'chaffing' against the bottom of the mag flange, so believed the issue might have been air being drawn into the mag flange, but reckon from you responses the stator or CDI might be at fault........both been on the bike for 12 years so done well !!