bansh_88 Posted April 26, 2012 Report Share Posted April 26, 2012 A while ago there was a situation that I found myself in that I do not wish to have repeat itself with my 88 Banshee. The situation involves starting it up one day only to have it immediately rev up to about full throttle without any throttle input from me whatsoever. I have since had the engine completely rebuilt with a bore and a port job, and am very nervous about having this happen again when I start it up for the first time. The scary part is that while it was revving to about full throttle on its own, almost nothing would work to shut it down. The first thing I did naturally was to hit the engine run switch and key to the off positions, but it remained at a full throttle rev. After that failed, I pulled the spark plug boots off the spark plugs but it STILL remained in a full throttle rev! Now, being in a total panic at this point, I was just about to flip the quad upside down with the gas cap off to get all the gas out (yea I was in full panic mode at this point), but decided to first turn the round knobs on the back of the carburetors to one side as a last attempt to get this thing to stop revving uncontrollably. This actually WORKED and it finally shut down after a good couple minutes of near full throttle revving. My question is, how the heck did my engine remain revving even with the run switch, and key in the off position as well as the spark plug boots off the spark plugs? I dont get it at all! Before this all happened, I was playing with those knobs on the backs of the carburetors to get it to idle better. I now assume that I had adjusted them way off from where they should have been adjusted at. But anyways, can anyone tell me WHY this engine remained in a full throttle rev even with it shut down and without the spark plug boots on? I dont wish for this to happen on my new motor that has expen$ive work done on it. I also now have new carburetors that will be going on it and I will not be using the TORS setup. If anyone can explain to me what may have happened here that day, and how to avoid such an occurrence again, I would GREATLY appreciate it. It would absolutely make me SICK if this happened again to me with my new rebuilt/bored/ported motor. Thanks in advance for any info or advice. Quote Link to comment Share on other sites More sharing options...
zach45 Posted April 26, 2012 Report Share Posted April 26, 2012 Air leak... Did you do a leak down test?. Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted April 26, 2012 Report Share Posted April 26, 2012 yeah major air leak. i have seen this before i put it in gear and let the clutch out holding the brake. cut it right off.. do a leakdown test and be sure your carbs are adjusted and clean. Quote Link to comment Share on other sites More sharing options...
ClayAiken Posted April 26, 2012 Report Share Posted April 26, 2012 (edited) Did you remeber to tighten reeds or intakes? Sounds like a damn good airleak. Edited April 26, 2012 by Hyper Quote Link to comment Share on other sites More sharing options...
ClayAiken Posted April 26, 2012 Report Share Posted April 26, 2012 Did you remeber to tighten reeds or intakes maybe the crossover?? Sounds like a damn good airleak. Quote Link to comment Share on other sites More sharing options...
Phelps Posted April 26, 2012 Report Share Posted April 26, 2012 most of the time it's a sever lean condition, or a hung throttle slide. should have fixed it by popping the throttle. if that happens just pull the choke out or hop on and hold the brakes while popping it in gear. Quote Link to comment Share on other sites More sharing options...
bansh_88 Posted April 26, 2012 Author Report Share Posted April 26, 2012 Thanks guys for the suggestions here. I guess that the most common area to check for air leaks are around the intake area, right? This may be a stupid question, but would an air-leak around the exhaust also cause this occurrence? Thanks. yeah major air leak. i have seen this before i put it in gear and let the clutch out holding the brake. cut it right off.. do a leakdown test and be sure your carbs are adjusted and clean. That is a GREAT idea for shutting iit down if it occurs again. Thanks a lot for sharing that!! I will be 'sweating bullets' when I first start this new engine up but will be less nervous now thanks to your reply here, I intend to use your advice and actually have it in gear with the clutch in before I even start it up. This way, if it does rev up again, I wont have to slam it in gear while its revving to the moon since it will already be in gear. All that I will have to do then is just grab the brake and release the clutch. AWESOME advise, I REALLY appreciate that suggestion. Thanks! Thanks again everyone. If there are any other suggestions or advice etc, please let me know. Quote Link to comment Share on other sites More sharing options...
bansh_88 Posted April 26, 2012 Author Report Share Posted April 26, 2012 most of the time it's a sever lean condition, or a hung throttle slide. should have fixed it by popping the throttle. if that happens just pull the choke out or hop on and hold the brakes while popping it in gear. AH, the choke! Thats another AWESOME idea to shut it down! And being that I just replaced the throttle cable for a new one, I will be sure to make sure it isnt hanging up anywhere. I also have what I believe are fairly 'rich' jets that I will be installing into my new carbs which should guard against a lean condition I hope. GREAT ADVISE here, thanks!! Quote Link to comment Share on other sites More sharing options...
Starwriter Posted April 26, 2012 Report Share Posted April 26, 2012 What you had going on is that the spark plugs got so hot they were acting like glow plugs and lighting the fuel much earlier. Essentially, advancing the ignition timing. A lean condition creates extreme heat and then you have a runaway. It's much more common on alcohol motors. I had the exact same thing happen to me. Many years ago, you couldn't just go buy alcohol carbs. I decided I wanted to run alcohol on the dunes. I made a redneck main jet flow meter and figured out what size mains flowed twice as much. I chucked the needles in my electric drill and sanded them down. I put in larger pilots. I mixed up a batch of fuel and fired it up in my garage on the trailer. Warmed it up a bit and all of a sudden, WWWWWAAAAAAAAAAAAAA!!!!! Hit the kill switch, still screaming, yanked the plug wires off, still screaming. In a state of panic and disbelief, I winged the throttle and it died. The only thing I could figure out at the time was that the large amount of cold air going into the motor cooled off the plugs. I know exactly what you went through. The state of confusion that exists when the motor sounds like it's about to blow, inside your garage and you have already yanked the plug wires off. Quote Link to comment Share on other sites More sharing options...
bansh_88 Posted April 26, 2012 Author Report Share Posted April 26, 2012 What you had going on is that the spark plugs got so hot they were acting like glow plugs and lighting the fuel much earlier. Essentially, advancing the ignition timing. A lean condition creates extreme heat and then you have a runaway. It's much more common on alcohol motors. I had the exact same thing happen to me. Many years ago, you couldn't just go buy alcohol carbs. I decided I wanted to run alcohol on the dunes. I made a redneck main jet flow meter and figured out what size mains flowed twice as much. I chucked the needles in my electric drill and sanded them down. I put in larger pilots. I mixed up a batch of fuel and fired it up in my garage on the trailer. Warmed it up a bit and all of a sudden, WWWWWAAAAAAAAAAAAAA!!!!! Hit the kill switch, still screaming, yanked the plug wires off, still screaming. In a state of panic and disbelief, I winged the throttle and it died. The only thing I could figure out at the time was that the large amount of cold air going into the motor cooled off the plugs. I know exactly what you went through. The state of confusion that exists when the motor sounds like it's about to blow, inside your garage and you have already yanked the plug wires off. Yea, it sounds like you certainly know EXACTLY what I am talking about here! LOL. Its a FRIGHTENING experience to say the least when you have a Banshee motor SCREAMING full throttle out of control isnt it? Especially scary when you start accepting that the only solution of it shutting down is to wait for it to blow up! SCARY stuff indeed as you surely know as well! But thanks to the good folks here, I will be less nervous when it comes time to start it up for the first time after the rebuild and engine mods. The forums and members here are at BansheeHQ are absoltely stellar! Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted April 27, 2012 Report Share Posted April 27, 2012 Hahaha you were about to flip the bike and dump the fuel! That's a good one. That's happened to me. It scared the shit out of me!! Luckily it was only a blaster, I just grabbed the carb and ripped it out. Quote Link to comment Share on other sites More sharing options...
bansh_88 Posted April 27, 2012 Author Report Share Posted April 27, 2012 Hahaha you were about to flip the bike and dump the fuel! That's a good one. That's happened to me. It scared the shit out of me!! Luckily it was only a blaster, I just grabbed the carb and ripped it out. LOL, Yea, I was truly only a fraction of a second from flipping it when the thought came to me to twist those knobs on the back of the carbs! My hands were already in motion to begin flipping it upside-down, when the thought came to me. LOL scary situation! Quote Link to comment Share on other sites More sharing options...
troyzstang Posted April 27, 2012 Report Share Posted April 27, 2012 I just grabbed the carb and ripped it out. To funny . Rip that shit out Gotta love them Blasters Troy Quote Link to comment Share on other sites More sharing options...
03crawldaddy Posted April 27, 2012 Report Share Posted April 27, 2012 Grab a thick book and cover up the carbs. Cuts the air from the motor, no air thru carbs, no fuel into motor. If its diesel ing from a lean condition it'll shut off. And you'd have to have a hell of an air leak for it to keep running. I've seen this done with blocks of wood that we're stuffed over turbo inlets to kill run away diesel engines. Now that's scary, a diesel motor turning at 7k+, just waiting for parts to granade thru the block. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted April 27, 2012 Report Share Posted April 27, 2012 Grab a thick book and cover up the carbs. Cuts the air from the motor, no air thru carbs, no fuel into motor. If its diesel ing from a lean condition it'll shut off. And you'd have to have a hell of an air leak for it to keep running. I've seen this done with blocks of wood that we're stuffed over turbo inlets to kill run away diesel engines. Now that's scary, a diesel motor turning at 7k+, just waiting for parts to granade thru the block. I saw a diesel run away. Anything over 6000 is fucking scary. The guy had a stack of shop rags he just jammed into the turbo. Sucked them up like a paper shredder. Quote Link to comment Share on other sites More sharing options...
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