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Bike cuts out when throttling... (Read 641 times)
MaxMayhem
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Bike cuts out when throttling...
11/15/11 at 23:20:00
 
Hi all.  

Bike info: 2007 s40, totally stock, not even raptor etc.

Well bike has been running fine as of late, and I rode into work today with no issues, but today when I went to go home, the following happened.

I have the petcock set to prime, as the notorious seal inside went not long after buying it, so I don't think that is my issue.

Turned key on, got green light on 'dash', headlights etc fine.
started bike, idling fine.
Bike stops...this happens sometimes when starting from cold and not using choke, so no biggy.

Start bike again, no issue, give throttle slight turn, bikes sputters till it cuts out.

Hmmm, give some choke, start bike, revs higher as you would expect, leave for 5 seconds or so, turn off choke.  Bike still idling fine.
Put into 1st, gently releasing clutch while applying throttle, bike sputters to a stop.

Start again without choke, as by now I feel there is more than enough fuel (can smell fuel so fear flooding bike), bike starts but even in neutral slightest throttle bike dies.

Try starting again without choke, but apply small amount of choke while idling to see if revs go up.
They do, so turn off choke, try throttle, bike begins to stutter again, so release throttle and bike idles a bit roughly but stays on.

After a bit of this expermenting, now even applying choke, it cuts out.

Got wife to pick me up in car and take me home, so bike is currently at work waiting till tomorrow to have a look in any free time.

I have checked all hoses to/from carb are secure, no evident leaking of any fluids anywhere.
I will remove spark plug in morning to see what condition that is in.

Any thoughts?
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verslagen1
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Re: Bike cuts out when throttling...
Reply #1 - 11/15/11 at 23:41:45
 
Carb... any work done on it?

I'd drop the bowl and make sure the main wasn't rolling around in the bottom.

may just need a good cleaning.
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MaxMayhem
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Re: Bike cuts out when throttling...
Reply #2 - 11/15/11 at 23:53:57
 
No work done to carb recently.

My thoughts were either carb or plug.
But what did you mean by 'main'? The main part of the carb?

Sorry I am by no means any kind of mechanic, but can follow instructions easily enough.

I have used clymer to strip carb down to individual parts not long after getting bike, when I first had the seal issue with the stock petcock, so I'm confident enough to do that again to clean the jets etc. That was over a year ago just so you know it wasn't something recent.
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Routy
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Re: Bike cuts out when throttling...
Reply #3 - 11/16/11 at 03:32:51
 
When the engines dies, loosen the drain plug on the bottom of the carb bowl, to make sure there is a continuous flow of fuel coming thru the petcock.....fuel line/filter.......and the needle valve float assy.
If very little gas runs out, it would mean that the main fuel flow to the carb is restricted somehow,.....either at the tank, or the needle valve/float.
If you have good continuous flow, it would seem you are into a restriction in the the carb circuitry itself, which would require cleaning.

If no fuel is leaking to the outside, I wouldn't suspect a flooding problem,.......unless like Versal said,....the main jet fell out.

Its always possible you have a coil/sparky problem.

on edit,.....
you speak of a nortorious seal problem,......care to explain that ?

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Rich
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Re: Bike cuts out when throttling...
Reply #4 - 11/16/11 at 05:53:42
 
 
Now Routy, come on now, our vac petcocks are NOTORIOUS for failing in 2-3 different ways over time -- didn't you know that?

Grin

This gentleman attempted to continue to use his stock vac petcock using the Prime trick for a while now (giving up his reserve function, but keeping the vac petcock body as a manual petcock).

He may be discovering a new vac petcock symptom that occurs when this Prime trick is done for a goodly amount of time, so we may all learn something new as we go through this one.  

He may have discovered failure mode #4 .....


==============


Seriously, now that I've finished teasing with Routy over his perpetual petcocky blind spot ....

First off, whack your float bowl 3-4 times smartly with a big screw driver handle -- this will jar free a stuck float and get you running again if this was you problem (yeah, I know -- but it is cheap enough to do and stuck floats do happen occasionally with folks using stock petcocks)

The main they refer to is the main jet, the one the needle runs through.  Yes, folks have had them unscrew when they weren't put in with the correct torque from a previous tear down.

"Totally stock" likely means no fine paper pleated in-line fuel filter -- you may want to consider adding that while you are in there fiddling with the hoses, etc.  

You may want to do this just to cut down on any future carb problems (especially if you find any sediment or trash when you go into the carburetor).

Another item you might want to check if you do take the tank off, is to unscrew the vac petcock unit and take a look at the screen -- I had mine varnish up closed and had to spray it with carb cleaner just to open up the little pores in the screen mesh so gas could get through.

fuel & spark -- spark is easy and cheap to check (replace the plug and check spark on the new one)   Don't forget to clean all the sand and grit out of the spark plug hole area before removing the plug -- don't want any of it going down the spark plug hole to score up your cylinder walls.

My betting money is going on a carburetor problem, not spark.   Spark doesn't come and go (it just dies) and it can't give you fuel/flooding smells ....  

Float sticking can come and go and it can starve you if it sticks up, and it can flood you if it sticks down.   I'd carry a big screw driver with you for applying the 3-4 float bowl whacks until you get this thing all worked out.
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Stock silver 2002 ls650 with small saddle bags. Looks like Granny's old worn out bike, nothing special to it at all.
(all mods except BIG piston and carb change have been done, but do not show)
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Routy
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Re: Bike cuts out when throttling...
Reply #5 - 11/16/11 at 06:27:49
 
I had never heard of a "nortorious seal" problem w/ the petcock. I thought the question deserved just a simple answer,......and from the OP that posted it !
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Rich
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Re: Bike cuts out when throttling...
Reply #6 - 11/16/11 at 06:42:22
 
 
Routy, let's get the poor man's bike running before we play "petcock war" again ....

I think Max understands all about petcock failures already as he has already had one already and has dealt with it.

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Stock silver 2002 ls650 with small saddle bags. Looks like Granny's old worn out bike, nothing special to it at all.
(all mods except BIG piston and carb change have been done, but do not show)
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justin_o_guy2
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What happened?

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Re: Bike cuts out when throttling...
Reply #7 - 11/16/11 at 06:59:12
 
I have the petcock set to prime, as the notorious seal inside went not long after buying it, so I don't think that is my issue.

Ive never hear of the diaphragm referred to as a seal either, but the context & knowledge of what IS inside the petcock made it simple enough for me. The diaphragm is notorious for causing problems, by leaking or being stiff & restricting fuel flow. I suspect its a cheap rubber being used. Seems to me the older models ran further on the factory cam chains & had fewer petcock failures.
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Re: Bike cuts out when throttling...
Reply #8 - 11/16/11 at 07:22:22
 
What happens if you run it with the choke on? My brothers bike generally has to have the choke on for a few miles before he even tries to click it off (it surges a lot if he doesn't).
He rides very little and doesn't even want to mess with swapping out to larger jets so I figure it's his bike, he can do what he wants.
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'06 lt Blue, Dyna Power pipe, air screw 2 1/4 turns, 52.5 pilot w/ bleed holes, 150 Main, 2/3 spacer, Pirelli MT66 tires, Raptor petcock, 412-4006 Progressive shocks
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OK.... so what's the
speed of dark?

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Re: Bike cuts out when throttling...
Reply #9 - 11/16/11 at 08:39:40
 
Max,... you run with the petcock set to prime... but, you need to remove the vacuum line, and cap off both taps, (at petcock and right side carb)...
You likely have fuel leaking down that line, causing flooding...
Wink...
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Ludicrous Speed !... ... Huh...
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MaxMayhem
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Re: Bike cuts out when throttling...
Reply #10 - 11/16/11 at 09:01:46
 
Morning.

Thanks for the comments ppl.

Routy - I did mean the diaphram not seal issue, that is my non-mechanic term sorry.

Bubba - Tried that, died as well once throttle is twisted to take off.

Oldfeller - Will try 3-4 slaps with a screwdriver first see how that goes.  Cheapest option first eh Smiley

Serowbot - It's been running fine for well over a year with just the petcock set turn prime.  Could it just suddenly decide it needs vac line removed etc?

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Re: Bike cuts out when throttling...
Reply #11 - 11/16/11 at 10:20:48
 
since it starts, the idle jet is fine.

my thinking is you twist the throttle, you either flood it out or stave it for fuel.

Flooding out could be caused by the main jet unscrewing and falling into the bowl.
Starving could be caused by a blocked jet.

drop the bowl off the carb and take a look at the main jet.
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OK.... so what's the
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Re: Bike cuts out when throttling...
Reply #12 - 11/16/11 at 10:37:55
 
MaxMayhem wrote on 11/16/11 at 09:01:46:
Serowbot - It's been running fine for well over a year with just the petcock set turn prime.  Could it just suddenly decide it needs vac line removed etc?


Yup,...   block off those taps...  Wink....

Then, you will be completely bypassed from the vacuum circuit... if that don't fix it,... go on from there, but do that first...
If, either the diaphragm or the line starts to leak, just being on prime won't fix it...  you must block off that hose to prevent air or fuel leak......

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Ludicrous Speed !... ... Huh...
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Re: Bike cuts out when throttling...
Reply #13 - 11/16/11 at 12:43:39
 
 
Serowbot, you are describing an issue we already know all about.

-- the vac line being split wide open can supply extra air (an air leak)

-- the diaphragm cracking/leaking can supply extra fuel

These are both known failure modes.  Are you are saying because Max didn't block off or remove his vac line he set himself up for stage 1 and stage 2 and stage 3 of vac petcock failures to come see him on the known, well documented and properly appointed schedule?

Makes sense.   Don't mean it is what happened, but it makes sense.


===============


Is this where I say "Max -- if Serowbot proves out to be right, you know what you might need to do about it (if you want to get your reserve function back anyway?)".   Plus, if you don't, you may well eventually discover that new failure mode #4 whatever it might be.

Ask Verslagen .... he is still assiduously avoiding acknowledging any of the further ways a vac petcock might could do your engine dirty.  


Grin    Grin    Grin    Grin


The reason we call it failure mode #4 is that is Verslagen's current engine rebuild/replacement number that he is currently working on.

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Stock silver 2002 ls650 with small saddle bags. Looks like Granny's old worn out bike, nothing special to it at all.
(all mods except BIG piston and carb change have been done, but do not show)
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Re: Bike cuts out when throttling...
Reply #14 - 11/16/11 at 13:23:57
 
This may be a newb question, but is it possible he's just running out of gas?  With the petcock set on prime, you never know when you're out of gas.
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