RPM gone crazy

[petron]

I think I have a serious issue here and really need your help.

My ski has been running great since the start of the season.

Today, I was flushing it and upon giving it some throttle at approx. 6500 RPM then letting off the throttle she just peaked to maximum RPM and wouldn't stop.

I shut off the water, pulled the laynard off and it would'nt stop. The only way she'll stop is to hold down on the throttle and it'll go into a stall mode. Nothing wrong with the throttle cable, at all.

Possibly a serious issue because if it happen's out on the water who knows? I ohmed out my start/ stop switch and it rang out fine.

I have all new fuel lines, carbs recently rebuilt, new gaskets, filters etc.

I really need your input on this matter, greatly appreciate it.

[dsolie]

Re: RPM gone crazy

It's called a run-away.. Caused by a few things.. Fist off, what ski again, and what mods?
1) You have an airleak somewhere below the carbs, causing a lean condition and a glow-plug effect, causing the ski to rev to the moon..
2) Your low speed adjusters are a hair lean, open them up 1/4 of a turn, see if it's still there.

Now to the quick basics.. What you did was correct. You turned off the water then killed the ski by opening the throttle. This or pulling the choke is the only way to stop the runaway.. Scary though huh!!

Let us know the ski and mods and I can point you to motor specific causes of runaway..

[dsolie]

Re: RPM gone crazy

oh yhea.. it'll never happen on the water.. The load on the motor won't allow it to happen, so don't freak out lol..

[petron]

Re: RPM gone crazy

Dan, I have a 96 GSX 787, everything is stock.

Scary though huh!!

Not going to lie, **** my pants, thought the engine was going to blow up.

Like I said, I just rebuilt carbs, changed all fuel lines & ski has been running great since beginning of the season. In the last 24 hours I started noticing while giving it some gas (while flushing) the RPM wouldn't come back to idle as quick, then the run away.

[petron]

Re: RPM gone crazy

...also, my high and low speed adjusters are set per manual.

High speed slightly seated and low speed around 1 turn away from a slightly seated position. Yes I tweaked my low speed and went clockwise about 1/4 turn a few weeks ago.

I've also noticed in the last few days upon startup it'll take a few extra moments to come up to idle (out of the water 3000 RPM) and if I give it some throttle it'll almost want to stay at that RPM before deciding to come back down to idle. Once it reached 6500 RPM I'd experience run-away.

[dsolie]

Re: RPM gone crazy

Try opening your low speeds a tad more, see if you can re-create (yes, I know.. do it again?!?!?)..

It could be your plugs, gapped too tight, a warm motor likes to do it easier than a cold motor etc...

I am going to bet on it NOT being an airleak (good news, no cracks in the cases).. Usually an airleak will pin the RPM instantly on startup.

My 94xp does it.. but not all the time.. My Twin Pipe XPL did it all the time, modded 951's like to run...

[petron]

Re: RPM gone crazy

Try opening your low speeds a tad more, see if you can re-create

I will. Like I said I know I've been going clockwise a little, maybe I should just go back (open) and leave it. I'll give it a try.

It could be your plugs, gapped too tight, a warm motor likes to do it easier than a cold motor etc...

I am going to bet on it NOT being an airleak (good news, no cracks in the cases).. Usually an airleak will pin the RPM instantly on startup.

Yesterday I checked my plugs, they looked dark chocolate, with a hint of black, they were gapped at approx 0.026" (specs call for 0.020 - 0.024") I just purchased new plugs and I'll gap it to 0.022" & give it a try.

She'll start up, idle for ever if I allow it, but once I WOT at 6500 RPM she'll run-away. Everythings tight and no real signs of air leaks (but not ruling it out)

[dsolie]

Re: RPM gone crazy

Take your lows back to 1 or even 1-1/4.. If it still does it, crack your highs open 1/8th

[petron]

Re: RPM gone crazy

Dan Solie, Just wanted to inform you that your diagnosis was on the money.

I backed off about 1/4 turn on the low speed, I ever so slightly opened up on the high speed, I ended up changing my plugs and gapped them perfectly.

I found my allen screws loose where it holds down on the flame arrest housing so I disassembled it, applied a coat of Loctite 518 and installed it back on - It was the closest thing that may of resembled an air leak, carbs were tight.

I started her up, idle was perfect, gave it some gas and she'd go back to idle perfectly, hit 6500 RPM and no run-away, right back to idle.

Thanks pal.

[dsolie]

Re: RPM gone crazy

Nice! now go ride!