Blaster runaway on initial start up only air leak or just lean from sitting?

mademan9

I ride a SuperFrk WannaBe
I had the same problem. it took a while but the air finally worked itself out. my brand new jetmaniac motor did this to me. With freshly built carbs and new fuel lines. I just keep checking everything over and over again. Put new zip ties and hose clamps on all the fuel lines. Primed up the motor a ton. And once I got it cleared that was it. Never happened again. My motor ran away from me about 3 times before I figured it out. It sure is a scary feeling when your new motor is reviving high as hell and wont shut off. LOL. At one point my ski was running on no battery and no spark plug boots. And she was still screaming. Good luck I hope you find it soon.
 

swapmeet

Brotastic
Location
Arlington TX
Well I went to the auto parts store at lunch and picked up a $10 tire gauge, took it apart and found that it has a 1/8" NPT nipple. Luckly they had a tap for that (when does that happen?!?) So tonight i'll put the gauge on the plate with some teflon tape and see what I can make happen. I'll report my results...

I gotcha. Hopefully this will help... You mentioned that you disassembled the carb and let it dry. When you do that you inevitably drain the majority of the fuel out of the fuel lines which has to be pumped back in. Plus you drained all of the fuel out of the carb which has to be pumped back in only after the fuel lines have been filled. In other words, you started up your engine and it started to runaway immediately and I imagine you shut it down immediately. That second or two of run time couldn't have gotten enough fuel in your lines and carb to maintain the proper fuel mixture so you're sucking air in from the top of the carb and sucking air in through the fuel lines and the engine runs away the second or third time. Then after that it should run right.

PS - Your setup looks ok but you may need a shut off valve between the pump and the gauge because your bike pump might leak a little bit of air. First rule of pressure testing is to spray soapy water on your test setup (valves, gauges, connections, blockoff plates, etc.) as soon as you pressurize the engine. This will save you hours of frustration of spraying the engine and not finding any leaks. Last thing I can think of right now is... I've never had any luck with block off plates so I use test plugs or freeze/expansion plugs. You can buy them in the pvc section of lowes or home depot or at an auto store.

Hmm... intresting.... I see what you mean. So is there any potential damage from letting the engine run at WOT for some period of time? Thats why I was killing it (the stop switch works,) because I thought it would damage the motor running like that. I had it on a beach stand so some water was going through the pump but the ski had jumped up the stand far enough that it was just getting some water, not enough to propel it.

I manually sucked fuel into the fuel lines (no homo) and there was no air when it was going into the carb. I pulled it back apart at the lake, (by your explaination creating the same problem again,) and it had fuel in it.

I looked at a plug at an auto parts store today that would have worked on my exhaust outlet. I didn't get it because I felt what I had would be adequate based on a grand assumption.



Thanks again for everyones input. I can't thank ya'll enough.
 
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swapmeet

Brotastic
Location
Arlington TX
So.... I finally did my test today and no leaks! I'm not sure if I should be happy. I really wanted to find something that helped explain my problem.
It held 10psi at the pulse port for 15min. Didn't drop at all, I had a inline gauge with the exhaust port and carb port blocked off. In the middle of the test I pulled the little aftermarket cap off the fly wheel cover and the pressure didn't change.
I assume this would give the same result as if I pulled the fly wheel cover itself?

Tomorrow i'm going to pick up some Yamabond4 and make new gaskets for the carb (if they don't have carb gaskets.)

After reading another thread, I made extra efforts tonight to 110% seal my tank. I'm trying to rule everything out, and it seems like a unpressurized tank can lead to the issues I had initally.


I don't feel like i've done anything, just taken things apart and put them back together. We'll see tomorrow if it did any good.
 

Dustin Mustangs

uʍop ǝpıs dn
Location
Holland, MI
If that doesn't clear it up look for issues with the fuel supply. Test run it with fresh pieces of hose from a gas can (new gas) straight to the carb. If it still does it you need to tear back into that carb or find a new one.

The vent is a long shot. I ran a bad one for quite some time w/ no issues at all.
 
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