revving dilemma...

[jef_46614]

This has happened 3 times now and I was hoping someone could give me some info on what could be going on.

I'll be riding and all of the sudden the rpms scream. All 3 times this happened in neutral. Also, it was freezing out. I thought maybe something froze up in the throttle line or carb or something was just getting hung up, but the weird thing is I turned the key off and the cut off switch to off and it still stayed running in high rpms.
I blipped the throttle and then finally the rpms come down and it dies... because the key and kill switch was off. switched them back on and kicked it over and it's back to running fine. How is this possible? The kill switch and key will kill the engine immediately any other time with no hesitation. I just don't get it.

[vondeister]

most likely you have a air leak on intake side of the carb. this will make it rev to the moon like that. when this happens it is really lean and it creates a hot spot (glowing piece of carbon) that acts as the ignition source instead of the bikes electronics. the best way to kill the engine in this situation is to hold the brakes and pop the clutch. I had this same issue a while back.

replace the intake / reed gaskets and check for a hole, tear, or loose carb inkake rubber.

good luck.

[jef_46614]

Thanks!
I'll look into that.

Could a leak like that also make the bike run sluggish at higher speeds? That's another symptom that's occurring, but I wasn't sure if it was related or not.

[vondeister]

yea, if it is leaning out?

[JAG Motosports]

you can use starter fluid to help locate the air leak

[jef_46614]

I've heard of that, but I'm not sure how it's done. Can you elaborate on that?

[adamson350r]

Had the same problem but the dude that sold us the blaster put a banshee carb lid on with lock tape. When it loosened up revved though the moon and the pump couldn't oil pump couldn't keep up. This caused the connecting rod bearing to go out and I haven't split the case to see if there is more damage.

[adamson350r]

I am still upset about that.

[JAG Motosports]

Originally posted by JAG Motosports
you can use starter fluid to help locate the air leak

Warm-up the engine and then with it running spray around intake, carb boot, base gasket, head etc... you will here a distinct change in the idle. Check the carb boot for cracks also.

You could also do leak down test, which isn't hard and is the best way.

Hope this helps

[jef_46614]

Thanks. I'll try that.