I have been having a strange "missing problem" every so often I get a total power cut-off miss while rolling up the revs. first thought was a fuel/jet problem but a check of my plug showed a nice even tan throughout. raptor ignition is a mystery to me does anyone know of an ignition problem that would cause this? or have any other suggestions? thanks
I have a biggun exhaust, aftermarket air filter and a medium webcam cam

 

try disabling the rev limmiter and see if that helps .

 

Ignition timing can be done with a timing light and the timeing mark accessing screw is on the left side, the smaller screw on the case above the shifter, I dont think there is an adjustment, if out of range check the pulsar coil assembly. Yamaha has an elaborate method for checking the spark plug, its just easier to replace it. on the ignition coil check the resistance by connecting an ohm meter set at x1 with th e+ lead on the orange lead and the - lead on the ignition coil base the coil resistance should be at 0.18->0.28 ohms at 68 degrees, you can also check the plug cap resistance which should be at 10k ohms
hope some of this helps

 

1rap,

I suspect that your problem is really a rich fuel condition. The craptor needs alot of fuel at low speed and early mid but high mid and top in must be really lean. When you rev up and the engine cuts out like an electrical misfire, it is too rich.

Check you jetting, needle position and float levels.

 

720
I rejetted about 2.5 weeks ago after finding my plug was running pretty dark, I dropped from 144/146 to 142/144 on the mains put in a new plug which is a nice tan color now. the problem did not start till last weekend which is why I was thinking ignition rather than fuel, but it is possible my filter needs cleaning leading to a high altitude rich condition, my confusion is the nice tan plug
vraptor
thanks for the specs on the ignition that should be easy to check out at the same time, might as well cover all bases

 

I have run a Raptor without main jets and found the plug to be white (lean). When I corrected the jetting to remove what appeared to be an electrical misfire, the plug remained white but the performance increased substantially.

You may also want to try reducing your plug gap .002"

 

One last thing to check is the emergency brake safety switch. I recommend disabling it by following the wires down behind the radiator. You will see the connector.

/NotuRaptor

 

thanks everyone for the help, one last question for biggy or anyone: how do you disable the rev limiter? or even where is it?

 

Why worry about the rev limiter???? Unless you miss a shift you will never hit the limiter.

 

I've had an annoying miss that sometimes results in the engine stopping altogether, but generally is a miss under acceleration, turns out to be a poor connection at the ignition switch plug in the wiring, built up resistance, miss miss miss...... frustrating......

I'd check the plug cap resistance also, if it is "high" then hard staring and poor low end running could be caused by the plug not getting enough current (excess cap resistance).

Raptor 720, man I curious about your "running with out main jets" comment but you have a heavily built engine right??

Certianly agree with your comments on low end jetting, we found a huge jump in low end torque by richening the low end jetting / needles, the engine was running fine, but my dyno tech though the air/fuel was just a touch off, instant 20 % torque gain !!!. Top end jetting with the dyno jet kit, go small, most guys over jet them to hell.....

On the MZ pages (MZ 660 engine is manufacturered by Yamaha, same top end, different low end / tranny) several guys claimed big power increases on built engine with the FCR 36/39 carbs. Could be a good mod for a heavily built Raptor engine ??

kiwi