Instant rev with no throttle

[Noodes7792]

701 motor will start and run then instantly rev up with no throttle. Thinking intake leak but I see nothing. Ran fine previous until my b pipe head pipe bolts worked themselves loose and I blew a gasket. Has msd ignition and coils if that matters. Thoughts

 

[eastcoastjumper]

Its an air leak from somewhere, and there aren't many places to check. Start with your throttle plate. Check if the brass plate is worn on the sides. Then check the throttle shaft. If the carb checks out you're left with crank seals or your intake gaskets.

 

[eastcoastjumper]

Make sure your throttle cable isnt pulling the throttle plate and its sitting against the idle screw. turn your idle down and make sure the throttle plate seals

 

[wanderer1]

What are you reviewing here?

 

[SuperJETT]

Moved.

 

[Noodes7792]

Carbs had crap in them. Gas looked to have water in it. I have an idea how I can easily leak test the intake. Can I use pilot nipple to pressurize or can I make a apparatus to plug and pressurize intake. Thanks

 

[Noodes7792]

Oooorrrr if my crank seals are bad does cause an air leak to lean out aannnnddd water in my carb..... Fml

 

[Noodes7792]

Crank seal behind the flywheel is leaking. Score. Looks like I know what I am doing this winter.

 

[Quinc]

Take off your flame arrestor and make sure your throttle shaft isn't open. I had a screw fall out of mine last season and cause it to rev... Pull off the exhaust pipe and do a leak down test. I use the vacuum nipple on the intake.

 

[Quinc]

Crank seal behind the flywheel is leaking. Score. Looks like I know what I am doing this winter.

JM has bogo on OEM crank seals and gaskets right now. Cheapest you are going to find them.

 

[Noodes7792]

Fabbed two plumbing sewer caps and plugged the intake and the manifold. Used a tire pump to the pilot nipple. Just needed a few pumps. Didn't go over 9 psi and I could hear it behind the flywheel. Looks like a flywheel puller, coupler tool, and gasket kit is in my near future. But with the motor out...... Do I dare buy an am hull or bore cylinders. Options are endless. 61xcase and upgrade to 62t cylinders dual carb intake. Santa has a big list coming his way

 

[FlightPlanDan]

The "spray method?"

It's not completely scientific, but spraying wd-40 or carb cleaner around the exterior of the motor while running will usually make a notable change in RPM when an air leak is sucking it in.
If the crank seal behind the flywheel is bad, then your flywheel cover gasket, or starter seal was bad as well.