Running on one cylinder; what order would you go?

[Benjamin Temchine]

Last week I was riding in the rain/mist and of a sudden the bike transformed: different engine noise, exhaust smelled like gasoline; had to open up the choke to keep it from stalling and when i gave it some throttle, revs dropped.

I figured that this meant I had lost a cylinder. Before I go any further, what do you all think of that hypothesis?

Now, I am setting about fixing this condition. I know all a motor needs is three things: gas, fire and air, and if the thing isn't firing, one or more of those things is wrong. But to systematically check things out, what would your decision tree look like? Obviously the first thing to check is spark (loose wire, non-functional plug etc.)

But then what?

All help would be greatly appreciated.

Ben
99/02 SV650

[Jim Stewart]

On 11/28/2011 11:11 AM, Benjamin Temchine wrote:
>
> Last week I was riding in the rain/mist and of a sudden the bike
> transformed: different engine noise, exhaust smelled like gasoline;
> had to open up the choke to keep it from stalling and when i gave it
> some throttle, revs dropped.
>
> I figured that this meant I had lost a cylinder. Before I go any
> further, what do you all think of that hypothesis?
>

Yep. And the usual culprit is spark.

Riding in the rain, eh? You may have the front spark plug well filled
with water. There's a drain hole at the bottom right of the cylinder
that sometimes gets plugged up. You can clean it out with a stiff wire:
http://www.strappe.com/pics/sv650/sv_drain_hole.jpg

To determine which cylinder isn't firing, just feel the exhaust pipes.

Check the primary connections to the spark coils - the front coil's
primary wire likes to fall off for some reason.

If all seems OK with the connections, check for voltage at the coil with
your multimeter (ignition on, not running). Should be about 12 volts at
one terminal of each coil.

You can check spark at the plugs by removing them and touching the plug
shell to the head while cranking the engine.

An alternate way to find out which cylinder is off is to inspect the
plugs. The bad one will be wet.

----------

It is possible that your problem is fuel or compression related. Since
you smell raw gas, you're not looking for a plugged jet so the carbs are
probably not involved. Compression-related problems such as a holed
piston or dropped valve are rare.

Let us know what you find, hmmm?

-js

[Rob Bandler]

This is a very common issue with SVs and DLs when riding in the rain.  The problem was most likely with the front cylinder.  The spark plug recess has a drain hole.  That hole gets plugged with junk, then water collects there and shorts the spark plug and the cylinder cuts out.

Clean the drain hole out with a wire or toothpick and spray some WD 40 in there.

Rob

http://motopumps.com

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[BenTemchine]

Thank you both. Turned out to be a completely gunked up fuel system.
A little sea foam did the trick. And the weird surging? A toasted
chain. two east coast winters and a little absent mindedness on my
part.

Ben

On Nov 29 2011, 12:59 pm, Rob Bandler <r...@cornell.edu> wrote:
> This is a very common issue with SVs and DLs when riding in the rain.  The
> problem was most likely with the front cylinder.  The spark plug recess has
> a drain hole.  That hole gets plugged with junk, then water collects there
> and shorts the spark plug and the cylinder cuts out.
>
> Clean the drain hole out with a wire or toothpick and spray some WD 40 in
> there.
>

> Robhttp://motopumps.com

>
>
>
>
>
>
>
> On Mon, Nov 28, 2011 at 2:42 PM, Jim Stewart <j...@strappe.com> wrote:
> > On 11/28/2011 11:11 AM, Benjamin Temchine wrote:
>
> >> Last week I was riding in the rain/mist and of a sudden the bike
> >> transformed: different engine noise, exhaust smelled like gasoline;
> >> had to open up the choke to keep it from stalling and when i gave it
> >> some throttle, revs dropped.
>
> >> I figured that this meant I had lost a cylinder. Before I go any
> >> further, what do you all think  of that hypothesis?
>
> > Yep. And the usual culprit is spark.
>
> > Riding in the rain, eh? You may have the front spark plug well filled with
> > water. There's a drain hole at the bottom right of the cylinder that
> > sometimes gets plugged up. You can clean it out with a stiff wire:

> >http://www.strappe.com/pics/**sv650/sv_drain_hole.jpg<http://www.strappe.com/pics/sv650/sv_drain_hole.jpg>

>
> > To determine which cylinder isn't firing, just feel the exhaust pipes.
>
> > Check the primary connections to the spark coils - the front coil's
> > primary wire likes to fall off for some reason.
>
> > If all seems OK with the connections, check for voltage at the coil with
> > your multimeter (ignition on, not running). Should be about 12 volts at one
> > terminal of each coil.
>
> > You can check spark at the plugs by removing them and touching the plug
> > shell to the head while cranking the engine.
>
> > An alternate way to find out which cylinder is off is to inspect the
> > plugs. The bad one will be wet.
>
> > ----------
>
> > It is possible that your problem is fuel or compression related. Since you
> > smell raw gas, you're not looking for a plugged jet so the carbs are
> > probably not involved. Compression-related problems such as a holed piston
> > or dropped valve are rare.
>
> > Let us know what you find, hmmm?
>
> > -js
>
> > --

> > This is the SV/DL Riders mail list. Moderators: Beth <hacktas...@gmail.com>,

> > Jim <j...@strappe.com>
>
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[Chris Weiss]

Good old threads never die...

I'm in a similar boat as Ben - except in my case, it's the rear cylinder on my '02 with ~30k/mi.

Very long story short, I'd installed a new-model K&N and full micron exhaust. The bike was already re-jetted for the old style K&N but I asked a local shop to check it out anyhow because it was running poor - they said the valves were far out of spec and fixed that. I moved away from the shop before I got a chance to seriously ride it.

After sitting for a while, I finally got a chance to commute on her again. She ran fine for a month or so, then the rear cylinder seemed to go dead (based on weak power, and only-warm-to-the-touch exhaust header).

Plug is dirty and wet. Exhaust smells a little funky. There's no smoke indicating head gasket or ring issues.

Next steps - Check for spark - Anything I should know before doing that - just grounding the plug against the cylinder head while turning the bike over should do it? Any concerns about vaporized gas blowing out the plug hole into the spark and me losing what little hair I've still got? I'll wear some welding gloves to make sure I'm not the path of least resistance.

After that, it'll be pulling the tank to do a visual inspection. My understanding is you unplug the fuel line at the end opposite the petcock (not sure what the part is - it's bolted to the frame on the right side) as it's easier to re-connect than fiddling with the petcock end. Do I need to pinch it off or drain the tank first?

Since this is an '02, is it worth swapping out the fuel lines? They look to be in decent shape.

What else should I look into? I'm going to assume the air filter's clean as the front cylinder seems to be firing fine. Likewise, the jetting should be OK.

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[Milktree]

I can tell you now you don't have spark.

Fuel isn't the issue unless the rear is running *so* rich it can't
fire.

Don't stress about the volts, it wants to jump to the frame ground, so
if you're holding it against the frame or engine block with any force
at all it'll go there before going through you.

-Will

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[Chris Weiss]

Just a follow up - I swapped the plugs, wiggled all the connectors, and she fired up and runs fine. Actually much nicer than before - especially when cold. Maybe something was loose or maybe the plugs were just That Bad(tm). I think they had ~15k on them (sadly, lost the early service records in a Google screwup).

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-Chris

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