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

[rfi]

hey guys i've got a dual carb yamaha 701 it runs great however if left to sit for a few days on the initial start up only it will sometimes runaway (diesel) need to pull the lanyard and hold the throttle open to kill it.
however if i prime it 1st and give it a couple of squirts of fuel it doesnt do it.
carbs look in sync i read this can be a problem.

only ever does it on the 1st start after that you rev the crap out of it doesn't do it again.
i swapped the carbs for another set i had and did the same thing.

opinions? is it just running lean from the fuel system not being primed or am i chasing an airleak? like i said after the inital start up it hasn't done it to me after riding all day pull it on the tap and rev it no probs just that 1st start of the day.

thanks rfi

 

[QJS]

Just sounds like its lean on start up to me, just make sure you prime it.
Chris.

 

[Waternut]

Totally normal...it's just air in the fuel lines leaning out the mixture.

 

[rfi]

thanks guys, i've owned a few skis and never had this issue.

 

[Boris]

Don't rev it to the moon when you fire it up.
There's no need for that at all.

 

[rfi]

mmm ok boris im guessing u miss read my post.
it runsaway by it's self.

 

[Waternut]

Don't rev it to the moon when you fire it up.
There's no need for that at all.

mmm ok boris im guessing u miss read my post.
it runsaway by it's self.

There's a legitimate point to Boris's comment though. Sometimes, the engine doesn't runaway by itself. In those cases, trying to rev the engine right after start up will cause the engine to shoot to the moon. Just an FYI...

 

[swapmeet]

Bumping this thread up so I don't have to start another.

Having a similar issue on a 61x 701. (Little background, incase it helps) I flooded the engine bay on my last trip, defintely ingested water into the engine. I pulled the carb, disassembled it, let it dry. Put it back on etc.

Sat it was difficult to get it to run, but once i got to start it ran like it was at WOT, bouncing off the rev limiter. I asked a jet ski tech who hangs out at the lake, he said air was getting in after the carb. I pulled the carb, made silicone gaskets, re-assembled and started again with the same results.

My next guess/step is to pull the top of the intake off and make/ replace the gaskets.

Where else could i be getting air in at? I know where the possibilities are, but what is the most likely place?

Hope ya'll can help, I havent been able to ride my ski for 3 weeks because of misc engine issues.

 

[Dustin Mustangs]

There really isn't a most likely place. Do a pressure test, squirt the engine w/ soapy water, and look for bubbles. No need to just go blindly replacing gaskets.

 

[Freakrider]

hey guys i've got a dual carb yamaha 701 it runs great however if left to sit for a few days on the initial start up only it will sometimes runaway (diesel) need to pull the lanyard and hold the throttle open to kill it.
however if i prime it 1st and give it a couple of squirts of fuel it doesnt do it.
carbs look in sync i read this can be a problem.

only ever does it on the 1st start after that you rev the crap out of it doesn't do it again.
i swapped the carbs for another set i had and did the same thing.

opinions? is it just running lean from the fuel system not being primed or am i chasing an airleak? like i said after the inital start up it hasn't done it to me after riding all day pull it on the tap and rev it no probs just that 1st start of the day.

thanks rfi

Primer is important and also turning the idle down until it's warmed up can help...the higher the idle the better chance of runaway...

 

[sjetrider]

you could have something not functioniung properly in the carb itself. Check diaphrams and needle and seat as well as the spring. If all good check the fuel pump side including carb filter.

 

[swapmeet]

I pulled the entire carb apart at the lake. Everything looked good.

I just read the thread on leak testing, incase anyone else is running into this issue and wants to try. http://www.x-h2o.com/threads/1303-Pressure-Test

I'll try to test it this week.

 

[Waternut]

+1 on the pressure test of the engine. Could've saturated a seal and caused problems. Could've blown a gasket when you hydrolocked it. Lots of things could've gone wrong and every point is an equally weak link so you have to go through the proper channel to make sure everything is working properly. However, before you go to all of that trouble even, make sure you have enough fuel in the engine and try to crank it again. When you open up the carb, you drain a lot of residual fuel out of the system. It usually takes me a couple potential runaways followed by additional priming before the engine will run normal again.

 

[swapmeet]

. However, before you go to all of that trouble even, make sure you have enough fuel in the engine and try to crank it again. When you open up the carb, you drain a lot of residual fuel out of the system. It usually takes me a couple potential runaways followed by additional priming before the engine will run normal again.

What?
LOL no really.... What?

 

[Dustin Mustangs]

FWIW I have never had a properly running engine run away on me. I would consider it a sign something is wrong, even if it only happens once in a while on startup.

 

[swapmeet]

Would a broken or cracked reed cause the engine to do this????



Anyone?

 

[Waternut]

What?
LOL no really.... What?

Laugh all you want. I'm just saying.... I can't tell you how many people I know that will have the slightest thing go wrong and won't touch anything until they have exhausted all possibilities on the internet...

 

[swapmeet]

I wasn't laughing at you, I was laughing because I didn't understand what you were saying.
Its an uncomfortable laugh. Damn internet does not relay inflection very well.
In other words, I'm laughing because i'm an idiot when it comes to engine problems.

 

[swapmeet]

*edit*

Does this look correct for a pressure test?

Black hose goes to a bike pump with a inline gauge.

 

[Waternut]

I wasn't laughing at you, I was laughing because I didn't understand what you were saying.
Its an uncomfortable laugh. Damn internet does not relay inflection very well.
In other words, I'm laughing because i'm an idiot when it comes to engine problems.

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.