Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2 weeks
so I decided to go out and enjoy the autumn sunshine. The last ride was
a 100km round trip on motorways and the bike was running fine when I
parked it under it's cover. Yesterday it didn't start too easily,
wouldn't idle and cut out under about 1500rpm. Lots of coughing and
farting which an "Italian tune-up did not cure. Thinking there might be
water somewhere it shouldn't be, I got it nice and warm, even filled up
with known "good fuel". All to no avail. I'm about to go out and start
taking things apart, soooo.............Place bets now please.

--
Geoff
NTV 650

On 20/10/2022 11:07, GeoffC wrote:

> Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2 weeks
> so I decided to go out and enjoy the autumn sunshine. The last ride was
> a 100km round trip on motorways and the bike was running fine when I
> parked it under it's cover. Yesterday it didn't start too easily,
> wouldn't idle and cut out under about 1500rpm. Lots of coughing and
> farting which an "Italian tune-up did not cure. Thinking there might be
> water somewhere it shouldn't be, I got it nice and warm, even filled up
> with known "good fuel". All to no avail. I'm about to go out and start
> taking things apart, soooo.............Place bets now please.

Think fuel, think electrickery. *sounds* like fuel, but. Whiskers (or
partially built-up whiskers can build up between electrodes on plugs, as
can eroding. First thing to check, I'd say.

In a standard type carburettor the needle in the main jet has been known
to drop from its clip on the slide - difficult to spot unless you take
the slide out. Pilot jet might be blocked.

Flake of paint from inside the tank (or other detritus) disturbed in
main jet?

Plug lead (both unlikely...) insulation breaking down?

--
Rusty Hinge
To err is human. To really foul things up requires a computer and the BOFH.

On 20/10/2022 11:07, GeoffC wrote:
> Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2 weeks
> so I decided to go out and enjoy the autumn sunshine. The last ride was
> a 100km round trip on motorways and the bike was running fine when I
> parked it under it's cover. Yesterday it didn't start too easily,
> wouldn't idle and cut out under about 1500rpm. Lots of coughing and
> farting which an "Italian tune-up did not cure. Thinking there might be
> water somewhere it shouldn't be, I got it nice and warm, even filled up
> with known "good fuel". All to no avail. I'm about to go out and start
> taking things apart, soooo.............Place bets now please.
>

If my recent experience is anything to go by, does it do the same thing
with the fuel cap loose?

Chris
--
The Deuchars BBB#40 COFF#14
Yamaha XV750SE & Suzuki GS550t
http://www.Deuchars.org.uk

On Thu, 20 Oct 2022 10:07:24 -0000 (UTC), "GeoffC" <me@home.nl> wrote:

>Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2 weeks
>so I decided to go out and enjoy the autumn sunshine. The last ride was
>a 100km round trip on motorways and the bike was running fine when I
>parked it under it's cover. Yesterday it didn't start too easily,
>wouldn't idle and cut out under about 1500rpm. Lots of coughing and
>farting which an "Italian tune-up did not cure. Thinking there might be
>water somewhere it shouldn't be, I got it nice and warm, even filled up
>with known "good fuel". All to no avail. I'm about to go out and start
>taking things apart, soooo.............Place bets now please.

If it's idling that's the problem rather than full power that is the
problem then I'd guess idle jet clogged or an air leak somewhere.
Assuming carbs, of course.

Can't absolutely eliminate ignition but in general weak ignition
symptoms show up at peak torque RPM (which is rarely peak rpm) when
the cc pressure is at its highest and the spark has a harder job
crossing the electrodes.

If the ignition is powered off its own coils then a fault here could
make for weak ignition, *possibly* at low RPM, because the voltage
could be lower when the alternator is turning more slowly. That is
much more of a guess though.

--

-Pip

RustyHinge wrote:

> On 20/10/2022 11:07, GeoffC wrote:
>
> > Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
> > weeks so I decided to go out and enjoy the autumn sunshine. The
> > last ride was a 100km round trip on motorways and the bike was
> > running fine when I parked it under it's cover. Yesterday it didn't
> > start too easily, wouldn't idle and cut out under about 1500rpm.
> > Lots of coughing and farting which an "Italian tune-up did not
> > cure. Thinking there might be water somewhere it shouldn't be, I
> > got it nice and warm, even filled up with known "good fuel". All to
> > no avail. I'm about to go out and start taking things apart,
> > soooo.............Place bets now please.
>
> Think fuel, think electrickery. sounds like fuel, but. Whiskers (or
> partially built-up whiskers can build up between electrodes on plugs,
> as can eroding. First thing to check, I'd say.
>
> In a standard type carburettor the needle in the main jet has been
> known to drop from its clip on the slide - difficult to spot unless
> you take the slide out. Pilot jet might be blocked.
>
> Flake of paint from inside the tank (or other detritus) disturbed in
> main jet?
>
> Plug lead (both unlikely...) insulation breaking down?

Sounds like a plan.

--
Geoff
NTV 650

chrisnd @ukrm wrote:

>
> If my recent experience is anything to go by, does it do the same
> thing with the fuel cap loose?
>
> Chris

Yes that did occur to me, open cap didn't make any difference. Also
it's got an electric fuel pump.

--
Geoff
NTV 650

Pipl wrote:

> On Thu, 20 Oct 2022 10:07:24 -0000 (UTC), "GeoffC" <me@home.nl> wrote:
>
> > Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
> > weeks so I decided to go out and enjoy the autumn sunshine. The
> > last ride was a 100km round trip on motorways and the bike was
> > running fine when I parked it under it's cover. Yesterday it didn't
> > start too easily, wouldn't idle and cut out under about 1500rpm.
> > Lots of coughing and farting which an "Italian tune-up did not
> > cure. Thinking there might be water somewhere it shouldn't be, I
> > got it nice and warm, even filled up with known "good fuel". All to
> > no avail. I'm about to go out and start taking things apart,
> > soooo.............Place bets now please.
>
> If it's idling that's the problem rather than full power that is the
> problem then I'd guess idle jet clogged or an air leak somewhere.
> Assuming carbs, of course.

Yep, 36,5mm Keihin

>
> Can't absolutely eliminate ignition but in general weak ignition
> symptoms show up at peak torque RPM (which is rarely peak rpm) when
> the cc pressure is at its highest and the spark has a harder job
> crossing the electrodes.
>
> If the ignition is powered off its own coils then a fault here could
> make for weak ignition, possibly at low RPM, because the voltage
> could be lower when the alternator is turning more slowly. That is
> much more of a guess though.

Interesting, thanks. Yes it is definitely a low rpm problem. A good
dose of throttle gets things going ok although I'm not sure it's quite
right even at full pelt. No missing or breaking down though.

--
Geoff
NTV 650

Pipl wrote:

> On Thu, 20 Oct 2022 10:07:24 -0000 (UTC), "GeoffC" <me@home.nl> wrote:
>
> > Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
> > weeks so I decided to go out and enjoy the autumn sunshine. The
> > last ride was a 100km round trip on motorways and the bike was
> > running fine when I parked it under it's cover. Yesterday it didn't
> > start too easily, wouldn't idle and cut out under about 1500rpm.
> > Lots of coughing and farting which an "Italian tune-up did not
> > cure. Thinking there might be water somewhere it shouldn't be, I
> > got it nice and warm, even filled up with known "good fuel". All to
> > no avail. I'm about to go out and start taking things apart,
> > soooo.............Place bets now please.
>
> If it's idling that's the problem rather than full power that is the
> problem then I'd guess idle jet clogged or an air leak somewhere.
> Assuming carbs, of course.
>
> Can't absolutely eliminate ignition but in general weak ignition
> symptoms show up at peak torque RPM (which is rarely peak rpm) when
> the cc pressure is at its highest and the spark has a harder job
> crossing the electrodes.
>
> If the ignition is powered off its own coils then a fault here could
> make for weak ignition, possibly at low RPM, because the voltage
> could be lower when the alternator is turning more slowly. That is
> much more of a guess though.

Update: Got the tank off eventually yesterday and had a look at the
plugs. Tellingly, the ones from the front cylinder were ok (although
one was seeping slightly around the seal. The back ones however were
both very sooty, but dry. Looking at where the choke cables entered the
carbs, the one for the rear cylinder was seeping a bit of gunge.
Removed both choke plungers and neither was particularly clean but the
one for the rear cylinder could definitely do with a clean up.
So, the plan is, clean up the choke plungers, treat the engine to a set
of shiny new plugs and see if that helps.

--
Geoff
NTV 650

On Thu, 20 Oct 2022 10:07:24 -0000 (UTC), "GeoffC" <me@home.nl> wrote:

>Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2 weeks
>so I decided to go out and enjoy the autumn sunshine. The last ride was
>a 100km round trip on motorways and the bike was running fine when I
>parked it under it's cover. Yesterday it didn't start too easily,
>wouldn't idle and cut out under about 1500rpm. Lots of coughing and
>farting which an "Italian tune-up did not cure. Thinking there might be
>water somewhere it shouldn't be, I got it nice and warm, even filled up
>with known "good fuel". All to no avail. I'm about to go out and start
>taking things apart, soooo.............Place bets now please.

<old joke>

Shit in the carb?
--
Champ
neal at champ dot org dot uk

I don't know, but I been told
You never slow down, you never grow old

On 21/10/2022 11:41, Champ wrote:
> On Thu, 20 Oct 2022 10:07:24 -0000 (UTC), "GeoffC" <me@home.nl> wrote:
>
>> Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2 weeks
>> so I decided to go out and enjoy the autumn sunshine. The last ride was
>> a 100km round trip on motorways and the bike was running fine when I
>> parked it under it's cover. Yesterday it didn't start too easily,
>> wouldn't idle and cut out under about 1500rpm. Lots of coughing and
>> farting which an "Italian tune-up did not cure. Thinking there might be
>> water somewhere it shouldn't be, I got it nice and warm, even filled up
>> with known "good fuel". All to no avail. I'm about to go out and start
>> taking things apart, soooo.............Place bets now please.
>
> <old joke>
>
> Shit in the carb?

<old answer>

But won't that block the jet?

--
Rusty Hinge
To err is human. To really foul things up requires a computer and the BOFH.

Champ wrote:

> On Thu, 20 Oct 2022 10:07:24 -0000 (UTC), "GeoffC" <me@home.nl> wrote:
>
> > Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
> > weeks so I decided to go out and enjoy the autumn sunshine. The
> > last ride was a 100km round trip on motorways and the bike was
> > running fine when I parked it under it's cover. Yesterday it didn't
> > start too easily, wouldn't idle and cut out under about 1500rpm.
> > Lots of coughing and farting which an "Italian tune-up did not
> > cure. Thinking there might be water somewhere it shouldn't be, I
> > got it nice and warm, even filled up with known "good fuel". All to
> > no avail. I'm about to go out and start taking things apart,
> > soooo.............Place bets now please.
>
> <old joke>
>
> Shit in the carb?

It's the way you tell'em.

--
Geoff
NTV 650

GeoffC wrote:

> Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
> weeks so I decided to go out and enjoy the autumn sunshine. The last
> ride was a 100km round trip on motorways and the bike was running
> fine when I parked it under it's cover. Yesterday it didn't start too
> easily, wouldn't idle and cut out under about 1500rpm. Lots of
> coughing and farting which an "Italian tune-up did not cure. Thinking
> there might be water somewhere it shouldn't be, I got it nice and
> warm, even filled up with known "good fuel". All to no avail. I'm
> about to go out and start taking things apart,
> soooo.............Place bets now please.

Update (2). Removed and cleaned both choke plungers, re-routed the
choke cables so they are not wrapped around the throttle cable. Put it
all back together and............still the same. Plugs on the rear
cylinder are both sooty. I'm starting to think about the float/needle
valve now.

--
Geoff
NTV 650

On 23/10/2022 20:32, GeoffC wrote:
> GeoffC wrote:
>
>> Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
>> weeks so I decided to go out and enjoy the autumn sunshine. The last
>> ride was a 100km round trip on motorways and the bike was running
>> fine when I parked it under it's cover. Yesterday it didn't start too
>> easily, wouldn't idle and cut out under about 1500rpm. Lots of
>> coughing and farting which an "Italian tune-up did not cure. Thinking
>> there might be water somewhere it shouldn't be, I got it nice and
>> warm, even filled up with known "good fuel". All to no avail. I'm
>> about to go out and start taking things apart,
>> soooo.............Place bets now please.
>
> Update (2). Removed and cleaned both choke plungers, re-routed the
> choke cables so they are not wrapped around the throttle cable. Put it
> all back together and............still the same. Plugs on the rear
> cylinder are both sooty. I'm starting to think about the float/needle
> valve now.
>

That was going to be my next suggestion.
The major clue to my own misfiring problem, reported up there^^^, was
that I suddenly realised the float level was different when the bike was
running compared to when it was not!

HTH, Chris

--
The Deuchars BBB#40 COFF#14
Yamaha XV750SE & Suzuki GS550t
http://www.Deuchars.org.uk

chrisnd @ukrm wrote:

> On 23/10/2022 20:32, GeoffC wrote:
> > GeoffC wrote:
> >
> > > Until yesterday I hadn't ridden the bike ('97 NTV650) for about 2
> > > weeks so I decided to go out and enjoy the autumn sunshine. The
> > > last ride was a 100km round trip on motorways and the bike was
> > > running fine when I parked it under it's cover. Yesterday it
> > > didn't start too easily, wouldn't idle and cut out under about
> > > 1500rpm. Lots of coughing and farting which an "Italian tune-up
> > > did not cure. Thinking there might be water somewhere it
> > > shouldn't be, I got it nice and warm, even filled up with known
> > > "good fuel". All to no avail. I'm about to go out and start
> > > taking things apart, soooo.............Place bets now please.
> >
> > Update (2). Removed and cleaned both choke plungers, re-routed the
> > choke cables so they are not wrapped around the throttle cable. Put
> > it all back together and............still the same. Plugs on the
> > rear cylinder are both sooty. I'm starting to think about the
> > float/needle valve now.
> >
>
> That was going to be my next suggestion.
> The major clue to my own misfiring problem, reported up there^^^, was
> that I suddenly realised the float level was different when the bike
> was running compared to when it was not!
>
> HTH, Chris

Update (3). All sorted now. Fitted 2x new float valves. Never seen
valves like it, rubber tips at the pointed end and a spring loaded
plunger at the other(maybe all float valves are like this these days?).
One of them seemed to be quite corroded, with a white powdery deposit,
dislodging the rubber tip and seizing the spring loaded plunger.
While I was at it, I removed and lubed the throttle cable hopefully
with better routing and replaced a seeping coolant seal.
The engine is running distinctly better now, I think this problem had
been building up for a while. Full blast has always been OK but it's at
lower revs I notice the improvement mostly. It's a totally different
engine now.

--
Geoff
NTV 650

GeoffC wrote:

> Fitted 2x new float valves. Never seen
> valves like it, rubber tips at the pointed end and a spring loaded
> plunger at the other(maybe all float valves are like this these
> days?).

The Dellortos on my 70's Guzzi have the same type of valves.

I don't think it's a new thing (I'd be surprised if there's been a huge
amount of R&D on carbs recently).

--
Simon

sweller wrote:

> GeoffC wrote:
>
> > Fitted 2x new float valves. Never seen
> > valves like it, rubber tips at the pointed end and a spring loaded
> > plunger at the other(maybe all float valves are like this these
> > days?).
>
> The Dellortos on my 70's Guzzi have the same type of valves.
>
> I don't think it's a new thing (I'd be surprised if there's been a
> huge amount of R&D on carbs recently).

I think you're right. I've only ever seen ones with a metal point and
maybe an embedded steel ball where it acts on the float tang. Or the
integral type which use a steel ball instead of a cone. But then I
haven't seen all that many.
In my case I'm curious why only one of the two valves was encrusted
with white powder dislodging the tip and seizing the plunger. I'm
assuming some kind of fuel contaminant (probably water) caused the
corrosion, but how did it reach only one carb?

--
Geoff
NTV 650

On 31/10/2022 10:38, GeoffC wrote:
> sweller wrote:
>
>> GeoffC wrote:
>>
>>> Fitted 2x new float valves. Never seen
>>> valves like it, rubber tips at the pointed end and a spring loaded
>>> plunger at the other(maybe all float valves are like this these
>>> days?).
>>
>> The Dellortos on my 70's Guzzi have the same type of valves.
>>
>> I don't think it's a new thing (I'd be surprised if there's been a
>> huge amount of R&D on carbs recently).
>
> I think you're right. I've only ever seen ones with a metal point and
> maybe an embedded steel ball where it acts on the float tang. Or the
> integral type which use a steel ball instead of a cone. But then I
> haven't seen all that many.
> In my case I'm curious why only one of the two valves was encrusted
> with white powder dislodging the tip and seizing the plunger. I'm
> assuming some kind of fuel contaminant (probably water) caused the
> corrosion, but how did it reach only one carb?

Only one trickle of water?

--
Rusty Hinge
To err is human. To really foul things up requires a computer and the BOFH.