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Next: Road Tour Boots
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External
Since: Jan 05, 2005
Posts: 11
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(Msg. 1) Posted: Sat Mar 12, 2005 11:37 am
Post subject: Diagnosis?
Archived from groups: rec>motorcycles>tech, others (more info?)
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I have an 84 virago 700, got it about 2 years ago very cheap. The bike
has aftermarket pipes on it, (which i understand will increase airflow
due to reduced backpressure, and i'm not sure if the original owner
rejetted the carbs to compensate for this, or if it would be neccesary
in this case), but other than that i think it's stock. Anyway, in the
past i've had trouble running the bike at 60+ miles per hour for an
extended period of time. Generally after running at a higher rate of
speed for a while the bike pops and fizzles it's way down to nothing
and i end up sitting on the edge of the freeway for ten minutes before
it will start again. Lately it's also been extremely hard to start, it
has to turn over about 8 times before it will finally purr to life.
Any ideas what could cause behavior like this. Any input is much
appreciated.
-Mike |
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External
Since: Jul 18, 2003
Posts: 1653
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(Msg. 2) Posted: Sat Mar 12, 2005 2:06 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Mike wrote:
>
> I have an 84 virago 700, got it about 2 years ago very cheap. The bike
> has aftermarket pipes on it, (which i understand will increase airflow
> due to reduced backpressure, and i'm not sure if the original owner
> rejetted the carbs to compensate for this, or if it would be neccesary
> in this case), but other than that i think it's stock. Anyway, in the
> past i've had trouble running the bike at 60+ miles per hour for an
> extended period of time. Generally after running at a higher rate of
> speed for a while the bike pops and fizzles it's way down to nothing
> and i end up sitting on the edge of the freeway for ten minutes before
> it will start again. Lately it's also been extremely hard to start, it
> has to turn over about 8 times before it will finally purr to life.
> Any ideas what could cause behavior like this. Any input is much
> appreciated.
Check the valve clearances.
--
Mark '01 SV650S '86 GL1200A '81 CM400T '99 EX250-F13<!-- ~MESSAGE_AFTER~ --> |
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External
Since: Nov 16, 2003
Posts: 3251
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(Msg. 3) Posted: Sat Mar 12, 2005 3:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Mark Olson <olsonm.DeleteThis@tiny.invalid> wrote:
> Mike wrote:
> >
> > I have an 84 virago 700, got it about 2 years ago very cheap. The bike
> > has aftermarket pipes on it, (which i understand will increase airflow
> > due to reduced backpressure, and i'm not sure if the original owner
> > rejetted the carbs to compensate for this, or if it would be neccesary
> > in this case), but other than that i think it's stock. Anyway, in the
> > past i've had trouble running the bike at 60+ miles per hour for an
> > extended period of time. Generally after running at a higher rate of
> > speed for a while the bike pops and fizzles it's way down to nothing
> > and i end up sitting on the edge of the freeway for ten minutes before
> > it will start again. Lately it's also been extremely hard to start, it
> > has to turn over about 8 times before it will finally purr to life.
> > Any ideas what could cause behavior like this. Any input is much
> > appreciated.
>
> Check the valve clearances.
What he said.
--
Trophy 1200 (Doctored) 750SS CB400F CD200 ST70 DT50MX CB750F2
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Dec 10, 2003
Posts: 2728
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(Msg. 4) Posted: Sat Mar 12, 2005 3:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"The Older Gentleman" <chateauSPAMKILL.murray DeleteThis @dsl.pipex.com> wrote in
message news:1gtbsg9.7a9pyb1jng5a8N%chateauSPAMKILL.murray@dsl.pipex.com...
> Mark Olson <olsonm DeleteThis @tiny.invalid> wrote:
>
> > Mike wrote:
> > >
> > > I have an 84 virago 700, got it about 2 years ago very cheap. The
bike
> > > has aftermarket pipes on it, (which i understand will increase airflow
> > > due to reduced backpressure, and i'm not sure if the original owner
> > > rejetted the carbs to compensate for this, or if it would be neccesary
> > > in this case), but other than that i think it's stock. Anyway, in the
> > > past i've had trouble running the bike at 60+ miles per hour for an
> > > extended period of time. Generally after running at a higher rate of
> > > speed for a while the bike pops and fizzles it's way down to nothing
> > > and i end up sitting on the edge of the freeway for ten minutes before
> > > it will start again. Lately it's also been extremely hard to start,
it
> > > has to turn over about 8 times before it will finally purr to life.
> > > Any ideas what could cause behavior like this. Any input is much
> > > appreciated.
> >
> > Check the valve clearances.
>
> What he said.
Kinda hard to diagnose without actually seeing what it is doing.. Could be
that running the motorcycle for a while produces a kind of vapor lock ..
Check the gas tank vent hole.. If that puppy gets clogged, you might be
experiencing a vacuum build up in the tank which would cause the gas to not
flow from it.. Damned near drove me nuts, one time.. Sheesh.. I was ready to
commence a carb rebuild..
Bill Walker
Irving, Tx..
>
>
>
> --
> Trophy 1200 (Doctored) 750SS CB400F CD200 ST70 DT50MX CB750F2
> GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
> BOF#30 WUSS#5 The bells, the bells.....<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Mar 19, 2004
Posts: 22
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(Msg. 5) Posted: Sat Mar 12, 2005 5:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Mike" <hobbes17.TakeThisOut@mail.com> wrote
> past i've had trouble running the bike at 60+ miles per hour for an
> extended period of time. Generally after running at a higher rate of
> speed for a while the bike pops and fizzles it's way down to nothing
> and i end up sitting on the edge of the freeway for ten minutes before
> it will start again.
This sounds like a plugged fuel tank vent OR a restricted fuel line (i.e.
plugged filter or screen).
OTOH, it could be running WAY lean causing it to overheat on long runs.
That could be a factor in hard starting too.
If you got it real cheap, maybe it's time to invest a little $$$ in a good
mechanic.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Feb 27, 2004
Posts: 181
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(Msg. 6) Posted: Sun Mar 13, 2005 12:12 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Mike wrote:
> I have an 84 virago 700, got it about 2 years ago very cheap. The bike
> has aftermarket pipes on it, (which i understand will increase airflow
> due to reduced backpressure, and i'm not sure if the original owner
> rejetted the carbs to compensate for this, or if it would be neccesary
> in this case), but other than that i think it's stock. Anyway, in the
> past i've had trouble running the bike at 60+ miles per hour for an
> extended period of time. Generally after running at a higher rate of
> speed for a while the bike pops and fizzles it's way down to nothing
> and i end up sitting on the edge of the freeway for ten minutes before
> it will start again. Lately it's also been extremely hard to start, it
> has to turn over about 8 times before it will finally purr to life.
> Any ideas what could cause behavior like this. Any input is much
> appreciated.
The other suggestions were all good since this doesn't sound like a
jetting problem. For piece of mind about the jetting I would:
A) Read the plug. If you have any flakey white desposits then you are
running too lean.
B) Simple test is "How does it run with the choke slightly on?" If you
run better at 60 MPH with the choke on you are too lean. If you run
worse you are normal to rich which shouldn't cause overheating and the
problems you describe.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Mar 11, 2005
Posts: 4
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(Msg. 7) Posted: Mon Mar 14, 2005 5:40 am
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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>
> Kinda hard to diagnose without actually seeing what it is doing.. Could be
> that running the motorcycle for a while produces a kind of vapor lock ..
> Check the gas tank vent hole.. If that puppy gets clogged, you might be
> experiencing a vacuum build up in the tank which would cause the gas to
not
> flow from it.. Damned near drove me nuts, one time.. Sheesh.. I was ready
to
> commence a carb rebuild..
>
> Bill Walker
> Irving, Tx..
That was my first thought....fuel starvation due to blocked tank vent.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Dec 15, 2004
Posts: 133
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(Msg. 8) Posted: Mon Mar 14, 2005 8:12 am
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Mike wrote:
> I have an 84 virago 700, got it about 2 years ago very cheap. The
bike
> has aftermarket pipes on it, (which i understand will increase
airflow
> due to reduced backpressure, and i'm not sure if the original owner
> rejetted the carbs to compensate for this, or if it would be
neccesary
> in this case), but other than that i think it's stock. Anyway, in
the
> past i've had trouble running the bike at 60+ miles per hour for an
> extended period of time. Generally after running at a higher rate of
> speed for a while the bike pops and fizzles it's way down to nothing
> and i end up sitting on the edge of the freeway for ten minutes
before
> it will start again. Lately it's also been extremely hard to start,
it
> has to turn over about 8 times before it will finally purr to life.
> Any ideas what could cause behavior like this. Any input is much
> appreciated.
>
> -Mike
Do your problems happen mostly in colder weather? If so, it could be
carb icing. Cold, humid air enters the carb, condenses and freezes
(this can happen quite a bit above freezing, too, because fuel
evaporation cools down the walls of the carb to below freezing). This
buildup of ice blocks fuel from getting to your engine. When you pull
over and wait for ten minutes, engine heat eventually melts the ice and
the bike will start again.
Unfortunately there is no easy fix for this, but improperly set up
carbs can certainly make the problem worse.
-Gniewko<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Dec 09, 2004
Posts: 809
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(Msg. 9) Posted: Mon Mar 14, 2005 1:29 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Bill Walker wrote:
> Kinda hard to diagnose without actually seeing what it is doing..
Could be
> that running the motorcycle for a while produces a kind of vapor lock
...
> Check the gas tank vent hole.. If that puppy gets clogged, you might
be
> experiencing a vacuum build up in the tank which would cause the gas
to not
> flow from it.. Damned near drove me nuts, one time.. Sheesh.. I was
ready to
> commence a carb rebuild..
That and the fuel filters.
If you can loosen the cap and it gets better it's the vent.
You can also disconnect a fuel line, put a quart bottle under
it, turn on the tap and measure how long it takes to fill the
bottle. You ought to be able to fill a quart bottle in maybe
5 minutes or quicker.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Jan 05, 2005
Posts: 11
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(Msg. 10) Posted: Mon Mar 14, 2005 1:47 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Thanks to you all for your input so far, this usually happens
midsummer, or after the bike has warmed up a lot. It could be a
problem in the fuel line as you have suggested, or possibly in the
venting, i went ahead and changed the fuel filter, and we'll see what
that does, i'll take a look at the fuel cap for proper ventalation this
afternoon too. As far as the hard starting goes, that may have
improved with new plugs torqued to the correct specs. That was a new
issue just this spring, hadn't had any trouble in the past. Thanks
again. Any more advice is appreciated. >> Stay informed about: Diagnosis? |
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External
Since: Dec 09, 2004
Posts: 809
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(Msg. 11) Posted: Mon Mar 14, 2005 3:01 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Mike wrote:
> Thanks to you all for your input so far, this usually happens
> midsummer, or after the bike has warmed up a lot. It could be a
> problem in the fuel line as you have suggested, or possibly in the
> venting, i went ahead and changed the fuel filter, and we'll see what
> that does, i'll take a look at the fuel cap for proper ventalation
this
> afternoon too. As far as the hard starting goes, that may have
> improved with new plugs torqued to the correct specs. That was a new
> issue just this spring, hadn't had any trouble in the past. Thanks
> again. Any more advice is appreciated.
Besides any in-lin filters, there's probably a screen inside the
tank that ought to be looked at.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Feb 01, 2004
Posts: 1744
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(Msg. 12) Posted: Mon Mar 14, 2005 4:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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External
Since: Nov 16, 2003
Posts: 3251
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(Msg. 13) Posted: Mon Mar 14, 2005 5:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Bownse <bownse.RemoveThis@swbell.net> wrote:
> depending on the age of the bike, your fuel feed lines might be old
> enough to collapse some when under pressure.
It's an ancient Virago with a gravity fuel feed, so this can be ruled
out.
--
Trophy 1200 (Doctored) 750SS CB400F CD200 ST70 DT50MX CB750F2
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Jul 18, 2003
Posts: 1653
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(Msg. 14) Posted: Mon Mar 14, 2005 6:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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In rec.motorcycles.tech Mike <hobbes17 DeleteThis @mail.com> wrote:
> Thanks to you all for your input so far, this usually happens
> midsummer, or after the bike has warmed up a lot. It could be a
> problem in the fuel line as you have suggested, or possibly in the
> venting, i went ahead and changed the fuel filter, and we'll see what
> that does, i'll take a look at the fuel cap for proper ventalation this
> afternoon too. As far as the hard starting goes, that may have
> improved with new plugs torqued to the correct specs. That was a new
> issue just this spring, hadn't had any trouble in the past. Thanks
> again. Any more advice is appreciated.
Again. Check the valve clearances. Your additional input that the
problem is more likely to manifest itself on warm days or when the bike
has warmed up a lot, is a further clue that tight valves are causing
the engine to lose compression when it gets warm.
--
Mark '01 SV650S '99 EX250-F13 '86 GL1200A '81 CM400T<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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External
Since: Nov 16, 2003
Posts: 3251
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(Msg. 15) Posted: Mon Mar 14, 2005 6:40 pm
Post subject: Re: Diagnosis? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Mark Olson <olsonm.RemoveThis@tiny.invalid> wrote:
> In rec.motorcycles.tech Mike <hobbes17.RemoveThis@mail.com> wrote:
> > Thanks to you all for your input so far, this usually happens
> > midsummer, or after the bike has warmed up a lot. It could be a
> > problem in the fuel line as you have suggested, or possibly in the
> > venting, i went ahead and changed the fuel filter, and we'll see what
> > that does, i'll take a look at the fuel cap for proper ventalation this
> > afternoon too. As far as the hard starting goes, that may have
> > improved with new plugs torqued to the correct specs. That was a new
> > issue just this spring, hadn't had any trouble in the past. Thanks
> > again. Any more advice is appreciated.
>
> Again. Check the valve clearances. Your additional input that the
> problem is more likely to manifest itself on warm days or when the bike
> has warmed up a lot, is a further clue that tight valves are causing
> the engine to lose compression when it gets warm.
I'm *still* with you on this one.
--
Trophy 1200 (Doctored) 750SS CB400F CD200 ST70 DT50MX CB750F2
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Diagnosis? |
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