701 fouling one plug fouling

[jgstarry31]

Newbie looking for help. My 61x 701 with a factory b pipe and ada head with 36cc domes and everything else stock (stock prop and cdi) will run good if i stay on flat water and cruise but if I get into waves and am jumping and hitting rev limiter it will eventually start to misfire occasionally then continue to get worse until it fouls one plug (so far it has always been the front/mag side plug) . It is set at FP carb settings and is a single carb and has only ever fouled one plug so I do not believe it is a carb issue. I replaced the reeds and it still does it. Does anyone have any ideas on what it could be? I am thinking possibly coil or cdi but it doesn't make sense why it runs good for a little while. It doesn't appear to be a heat dependent because as soon as i put new plugs in it runs fine for a while. I run BR8es with the stock gap, could it be as simple as too big of spark plug gap for the higher compression (175 psi). Open to trying anything but don't want to order a coil or cdi if that's not the issue. Thanks in advance.

 

[newbee]

I would cut the plug wire down on the boot side and see if that helps. Also closing the gap couldn't hurt there some post on here about that or how much to close it.

 

[Freakie]

have you checked the compression in both cylinders....are they the same ?......next idea is to trim back the spark plug leads to ensure proper connections are made

 

[SXIPro]

I would cut the plug wire down on the boot side and see if that helps. Also closing the gap couldn't hurt there some post on here about that or how much to close it.

0.024"

 

[jgstarry31]

Compression is 175 mag 170 pto so I do not believe that is the issue. I will try trimming back the wire and re attaching the caps and setting plug gap to 0.024” . Thanks

 

[jgstarry31]

Trimmed back wires and installed new caps with new BR8ES gapped to 0.024" and it is doing the same thing. Ran great for 10 minutes then after jumping waves and hitting rev limiter it started to miss and eventually fouled a plug. Any other ideas? Coil or CDI?

 

[Harbor]

I have a Cdi that I bought used, it lasted 1 ride then started to develope a sharp mis on wide open and the after about 10 to 15 minutes it started misfiring when I jump wakes. Removed it and that issue went away...

 

[Harbor]

Why are you running Extended Spark Plugs? All 701's use BR8HS or B8HS. Best to buy the Solid Tip NGKs. Try these Spark Plugs first.

If the correct Spark Plugs don't fix it, then it's probably a Stator Coil with a "Layer Short", that is, a break in a Strand of the Copper Winding.

When Stator Coil is Cold, the broken wire ends are in contact with each other, allowing for a good circuit. But when the Stator Coil warms up, like it does after 10 minutes of Engine operation, the thermal expansion causes the broken copper wire ends to separate. breaking the circuit.

With an Ohm-Meter , test the all the Stator Coils cold, then with a Hair Blow Dryer or Heat Gun, warm up the Stator Coils and then re-test.

Do a Search to find the Coil resistance specs for reference.

Might as well test the Ignition Coil while you're at it.

Also, if you can borrow a known good CDI, install it and see if that changes anything.

He running an ADA head so long reach is needed

 

[jgstarry31]

Update for anyone that is curious or having a similar issue. I sent my coil out to JSS and had them redo the wires and it fixed the issue! I had the coil back 3 days after shipping. Great turnaround time and solid work.