Water box exploded

[Chandleracman]

My 96 b1 blew out my water box , blew the hoses off as well.
Trying to figure out what caused it , pulled cards and went through them and rebuild them at the same time . Everything looked good , no issues. Before I pull the motor to go through it any ideas ?

 

[WFO Speedracer]

Usually a leaking needle and seat cause this .

 

[kevbo]

A strong after fire generally requires an overly lean carb setting. It most commonly happens when you rev a cold engine. I still use composite water boxes and have blown one up once. I’m a lot more careful when the engine is cold now.

 

[Myself]

Anything that can allow extra gas to pool in the exhaust can do it. Leaky seat o'rings for sure. Also a badly misfiring ignition, one bad spark plug, engine runs very poor eventually dying out. Owner figures out the spark plugs were shot, gets new ones put in, cranks and cranks not knowing it's flooded with unburnt fuel that is floating on top of the water INSIDE the waterbox. It finally fires off and BOOM !!.......lights off the unburnt fuel in the exhaust.

 

[JC-SuperJet]

What Myself said plus the aged Fiberglass Waterbox develops Air Leaks via Rivets that have dropped their Mandrels. This gives it the perfect Air/Fuel mixture for a loud Boom just when you have your face right above the Waterbox.

That's why it's called a Blaster

 

[Chandleracman]

I had just rebuilt carbs before this happened and pulled them after and rebuild them again just to be safe. I use mikuni rebuild kits ( not cheap ones) but I heard you say kevbo a lean start up , now I'm looking for a air leak . Scared the poop out of me when it blew up . Was on the trailer with hood up . Like I said just rebuilt the carbs and switched from choke to primer set up . I'm also worried about my reeds now , like maybe they got cracked.
I had started and was running, I came back 5 minutes later and went to start , didn't want to , then boom goes the dynamite in my water box , It is a jm box , I got it fixed but I'm a little shell shocked before I try to start it again I want to double, triple check everything and eliminate any possible causes. Don't want it to happen again.

 

[Myself]

You had needles not seating or something. Did you check lever arm position and popoff? It was flooding badly but running..........5 minutes later the rest of the fuel in the carbs had leaked into the engine. A little bit of cranking pushed enough of it OUT to actually light off.......and then the raw fuel spit out while cranking ALSO lit off.......BOOM!

 

[WFO Speedracer]

I had just rebuilt carbs before this happened and pulled them after and rebuild them again just to be safe. I use mikuni rebuild kits ( not cheap ones) but I heard you say kevbo a lean start up , now I'm looking for a air leak . Scared the poop out of me when it blew up . Was on the trailer with hood up . Like I said just rebuilt the carbs and switched from choke to primer set up . I'm also worried about my reeds now , like maybe they got cracked.
I had started and was running, I came back 5 minutes later and went to start , didn't want to , then boom goes the dynamite in my water box , It is a jm box , I got it fixed but I'm a little shell shocked before I try to start it again I want to double, triple check everything and eliminate any possible causes. Don't want it to happen again.

You said you rebuilt the carbs, needle and seats don't come in the Mikuni kits , did you replace them or check the popoff pressure to make sure they were not leaking ?

 

[Chandleracman]

Yes I had ordered new needle and seat and replaced it and yes checked pop off. When I replaced they looked good but still put news ones in . Well I just replaced everything again, but before I try again just wanted to see if any other ideas on what could cause it to put fuel down my exhaust. Over pressure? Running lean from a air leak . Or am I just over thinking this

 

[way2manyhobbies2keep]

Yes I had ordered new needle and seat and replaced it and yes checked pop off. When I replaced they looked good but still put news ones in . Well I just replaced everything again, but before I try again just wanted to see if any other ideas on what could cause it to put fuel down my exhaust. Over pressure? Running lean from a air leak . Or am I just over thinking this

bad primer could too, if your fuel system is pressurized especially on a hot day, or elevation change it could run through the primer line, or the needle and seats. i have a stock waterbox id sell if you are looking,