What causes weak spark?

[sdhunter123]

i have a 750 sx that i want to sell, so i posted a thread on here. shortly after i figured i better go to my parents house ( where i keep the ski in the garage during the winter) and make sure it fire it up and make sure averything is all good. well it wouldnt fire up. It turns over nicley but i didnt even get a "pop" like it was trying to start. I have fuel gettin in there and i have spark. I was thinking that maybe it was just a little to cold to start, but i when i check the spark it seems to be a bit weak. i dont know if it is or not but i would imagine that it would be a bit stronger. is this a common thing and what would cause this? they are brand new plugs. its prob something stupid and easy but any input would be appreciated.

 

[fishinrod]

try diff plugs my sj wouldnt start then put diff plugs in and it worked perfectly

 

[Waternut]

The stock spark on a 750 isn't exactly strong in the first place. Generally if you have fuel and spark and still not getting it start, you may want to check your compression. I'm guessing the ski hasn't been touched since last season and you're certainly far enough north that water could've potentially frozen in the engine and cracked the cylinder.

If the compression is good, it could be the spark plug wires and they've corroded or broken and aren't carrying the current like they should. You can just trim those back some. Make sure the plugs are gapped properly as well since they're new.

 

[sdhunter123]

thanx guys i appreciate it ....im gonna head there tomorrow to see if i can figure this out..ill check what you guys said and let you know the findings

 

[WaveDemon]

if your spark is white/blue it's strong. if it's yellow/orange it's week.

the spark strength can degrade because of a bad coil, wires, plugs, plug gap, ground.

 

[cosander]

how old is the gas?

 

[sdhunter123]

the fuel is about 4 months old

 

[SJBrit]

Check the wires first though - that's easy to do, free, and a very common cause of weak spark. They corrode at the plug end. Pull the cap off and take a look - you may have to cut them back quite a bit to get back to good copper. When I did this I had to go back about 2 inches to find fresh copper.

 

[sdhunter123]

thanx fellas. i replaced the positive and negative wires and cleaned up the terminals real nice.. fired right up... shes running real perty like...so does anyone want to buy a 750sx ( that runs now) lol