Posted by beatyerbrainsout on December 7, 2009, 5:27 am
On Dec 4, 6:36 am, âÍÁ Á³Õ »Ñ·àÁ ËØÁ <macmi..=
.@gmail.com> wrote:
> > It goes along with the fact that you always get a gas smell
> > after trying to start it, as if it's flooding. That ought to tell
> > someone in the know something.
> This problem, whatever it is, is probably not electrical at all, it's
> probably a carburetor problem, combined with a lack of understanding
> of how constant vacuum carbs work.
> Maybe you have a sticky/leaky float valve on one carb. I know that my
> Yamaha FZR1000 has at least one sticky/leaky float valve because of
> the backfires when I start the engine the first time in the spring and
> also when roll off the throttle the first few rides of the year.
> I live in an area where the temperature gets up to 100 degrees every
> day for half the year, and the other half the year it's cold and foggy
> and riding is no fun at all.
> So my carbs plug up if I don't ride for a few months.
> I add fuel stabilizer to the gasoline before storing the bike for the
> winter and I also add about five ounces of Berryman B12 Choke and
> Carburetor Cleaner to a full tank of gasoline every spring.
> B12 contains solvents like acetone, toluene, methyl ethyl ketone and
> xylene which dissolve gum and varnish quickly.
> But I will often hear one or two really loud and scary backfires when
> trying to start the engine for the first time. And I get the smell of
> unburned gasoline, but nothing runs out the float bowl overflow hose.
> (If a backfire actually causes the engine to rotate backwards a
> fraction of a turn, this can jam up the starter clutch and that would
> be a major disaster for my engine, because the starter clutch is
> buried deep inside the engine and I would need to remove the engine
> and split the crankcases to repair it. Your starter clutch is much
> more accessible.)
> Berryman B12 comes in both liquid and aerosol cans so it can either be
> added to the fuel directly or used to clean out the jets and passage
> directly.
> Your carburetors probably have a small hole in the intake bellmouth,
> and, if you
> squirt B12 (or GumOut or STP or other clear carburetor cleaner) down
> the smaller of the two holes, that will clean out the idle mixture
> circuit.
> The larger of the two holes in the intake is the "choke". Actually you
> don't have a flat plate type choke like a car's carburetor used to
> have.
> The cold starting enrichener circuit has a little valve that allows
> air to bypass the throttle butterfly and the air rushing through the
> air passage sucks gasoline directly out of the float bowl.
> When you start an engine that is equipped with a cold starting
> enrichener, the drill is to move the "choke" lever or knob to the full
> on position and leave the throttle twist grip alone and push the
> starter button until the engine acts like it wants to start.
> Then you can help the start by twisting the throttle grip a little
> bit. What you're actually doing when you twist the throttle is adding
> AIR to the excessively rich mixture, so it's not surprising that you
> smell raw gasoline for that reason.
> An old trick to starting a stubborn engine is to turn the master idle
> speed control knob all the way counterclockwise until the throttle
> butterflies are completely closed.
> When you crank the engine with the electric starter you get MORE
> engine vacuum to suck fuel through the idle jets and passages and
> through the cold starting enrichener because the throttle butterflies
> are fully closed.
> Then, when the engine starts, you can twist the throttle and hold it
> open until the engine warms up and then you can turn the master idle
> knob clockwise to adjust the idle speed to normal.
> There's another thing to understand about the smell of unburned
> gasoline after starting.
> The engine needs a rich fuel air ratio to start, and if the carbs are
> plugged up (or a float valve is stuck shut) the affected cylinder will
> only fire every eighth stroke (four turns of the crankshaft) instead
> of every fourth stroke (two turns of the crank) and it will blow
> unburned gasoline out the exhaust pipe.
Good info that I'll keep in mind. Unfortunately, as you will find in
the original post, I not only added carb cleaner early on but tore
down the carbs. They were absolutely clean. No varnish or plugging
at all and the floats appeared to move just fine. I was disappointed
to find that a float tang angle was not included in the manual for
proper adjustment of the float levels. This was always the way to
adjust float levels on various vehicles I've maintained in the past
but for this bike you need a special tool to measure the actual fuel
level, according to the manual I've got. The requirement of myriad
special tools to maintain this bike is a pain in the ass that I
consider a failing of this and other motorcycles of this type. It may
make the Yamaha mechanic happy, but not the owner. The bike appears
to me to be inordinately complicated in the way it was engineered,
hence, the potential for many different problems that are not easily
traced. Will keep trying, eventually will stumble upon the cause or
causes of the current problem, and will post them here. Thanks for
your help.
Posted by =?TIS-620?B?4s3BIMGz1SC70bfgwS on December 7, 2009, 8:44 am
> This was always the way to adjust float levels on various vehicles
> I've maintained in the past but for this bike you need a special tool to
> measure the actual fuel level, according to the manual I've got.
You can probably make a fuel level tool out of a piece of clear
plastic tubing and some kind of home made adapter that can be screw
into the float bowl drain
screw.
The recommended fuel level is probably around 1.0 ~ 1.5 mm below the
float bowl gasket surface.
> Will keep trying, eventually will stumble upon the cause or
> causes of the current problem, and will post them here. Thanks for
> your help.
Have you tried the old trick of turning the idle speed all the way
down? Just turn the master idle screw (or two idle speed screws if the
carbs aren't interconnected)
all the way counterclockwise to close the throttle butterflies and
make the engine vacuum high enough to suck fuel out of the float
bowls.
That old trick goes back to the days of British 500cc thumpers...
Posted by flybywire on May 10, 2010, 12:53 pm
try longer spark plugs the normal Yam ones are short
cheers
Mike
> Over the past couple of years, the bike hasn't started right up as it
> did for the first 3 years I owned it. The starter didn't turn over as
> authoritatively, but it did start after a few turns of the crank. At
> the end of this past summer, in which I rode it very little, the bike
> now won't start up at all with the starter. You can push start it to
> get it going but it takes a number of tries down a long hill to
> accomplish it. The last time I did that, I went about a mile down
> this friggin' hill before it started up, and then only after I'd
> opened the throttle up all the way. The odd thing is, once the bike
> is running and warm, it will start up using the starter motor without
> a problem.
> When I first began experiencing the initial hints of the
> developing problem a couple of years ago, I called the Yamaha dealer
> from which I bought the bike. The mechanic there told me he suspected
> I needed a new battery because batteries don't last long in the desert
> heat (it gets up to 118 degrees here and is over 105 for months on
> end). Once the starter simply wouldn't turn the engine over with any
> authority at all and the bike wouldn't start up anymore, the batter
> was the first thing I replaced. Oddly, the new one needed charging
> straight from the dealer before I could use it in the bike, but once
> charged for 2-3 hours, it seemed to work alright. Unfortunately, that
> wasn't the problem.
> I then thought it must be a fuel issue because of the long hot
> summer and the fact that I hadn't put fuel into the bike for 2-3
> months. Gasoline sitting in this kind of heat can turn to varnish in a
> fairly short time. In fact, I'd already experienced the same "won't
> start" problem with two other small engines left sitting here and the
> carbeurator jets were clogged with varnish. Once cleaned, the engines
> started up easily again. So I tried carb cleaner on the motorcycle,
> but to no effect, then tore the bike down to the carbs, removed them,
> and disassembled them. Everything inside the carbs was functioning
> well and it was absolutely clean -- bummer! I reassembled the
> carbs. I then checked the fuel pump/front coil assembly before
> reassembling the fuel system and the front cylinder plug wire
> practically dropped off the plug boot. That must be it, I thought,
> feeling rather stupid for not finding it before tearing into the
> machine to the extent I had. I pushed the plug wire back into the
> pointed metal "spear" inside the boot and then turned it clockwise
> until it gripped tightly onto the threads of the "spear." Sure
> enough, once I'd put the coil/fuel pump assembly back onto the bike,
> the carbs back onto the intake manifolds, the surge tank onto the
> carbs (what a hassle) and the air cleaner back onto the surge tank,
> cleaning up everything as I went and routing the many wires and
> electrical connectors at the neck of the frame a little more sensibly
> than the Yamaha assembler had done in building the bike, I started it
> up without a problem. It still didn't fire right up like it did right
> out of the shop but it started after only a turn or two of the
> crank.
> I thought I'd fixed the problem and took a long ride on it
> without any difficulty arising. It ran fine. Unfortunately, a few
> days later, when I tried to start the bike again, the same problem
> remained. I just got through taking a closer look at the electrical
> system after charging up the original battery, putting it in the bike,
> and proceeding to charge the new battery. Everything looks fine. All
> the connectors, diodes, relays, igniter, etc, are clean and appear to
> be functioning correctly. Have I tested them all? No, I can't say I
> have, not yet, anyway. Charging the old battery, I found out
> immediately, made no difference. The starter turns over, yes, but not
> as quickly as it ought to and certainly not authoritatively enough to
> start the bike up. What a pain in the ass! Yup, it just might be the
> starter motor, I figured, but you have to drain the oil and remove the
> gas tank, blah blah blah, to check it out. It sounds like the other
> tear downs I've already tried. BTW, when you turn over the engine
> with the starter, it cuts out with a loud noise after a few turns.
> If anyone has any ideas on what might be wrong with this infernal
> machine, I'd like to hear it. The mechanic at the Yamaha dealer
> characterized this bike as "bullet proof." What a load. Those guys
> are so full of shit sometimes. Yes, these motorcycles are much more
> complex than they used to be and you probably need to have to have all
> sorts of diagnostic equipment and special tools to trace a problem to
> its source without all this hit or miss nonsense, but "bullet
> proof?" My asshole. I've had more than any bike's share of minor
> problems with this motorcycle. It has never shifted easily, even
> after the original clutch was replaced. I've always suspected that a
> shifting fork may be slightly bent, not enough for the Yamaha folks to
> know it, or at least to admit it,, but enough for me to know it. I've
> changed the oil so many times to make it shift/run smoother, I can't
> tell you. I've also had to adjust the valves about four times and the
> bike only has 12,000 miles on it. Anytime you run this bike at all
> hard, and by that I mean running it the way it ought to run normally,
> the valves go out of adjustment, which is why I usually take things
> very easy on it and just cruise around in no big hurry. It looks
> brand new but has never run as well as it should. Frankly, I'm
> beginning to think I got stuck with a lemon.
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> > after trying to start it, as if it's flooding. That ought to tell
> > someone in the know something.
> This problem, whatever it is, is probably not electrical at all, it's
> probably a carburetor problem, combined with a lack of understanding
> of how constant vacuum carbs work.
> Maybe you have a sticky/leaky float valve on one carb. I know that my
> Yamaha FZR1000 has at least one sticky/leaky float valve because of
> the backfires when I start the engine the first time in the spring and
> also when roll off the throttle the first few rides of the year.
> I live in an area where the temperature gets up to 100 degrees every
> day for half the year, and the other half the year it's cold and foggy
> and riding is no fun at all.
> So my carbs plug up if I don't ride for a few months.
> I add fuel stabilizer to the gasoline before storing the bike for the
> winter and I also add about five ounces of Berryman B12 Choke and
> Carburetor Cleaner to a full tank of gasoline every spring.
> B12 contains solvents like acetone, toluene, methyl ethyl ketone and
> xylene which dissolve gum and varnish quickly.
> But I will often hear one or two really loud and scary backfires when
> trying to start the engine for the first time. And I get the smell of
> unburned gasoline, but nothing runs out the float bowl overflow hose.
> (If a backfire actually causes the engine to rotate backwards a
> fraction of a turn, this can jam up the starter clutch and that would
> be a major disaster for my engine, because the starter clutch is
> buried deep inside the engine and I would need to remove the engine
> and split the crankcases to repair it. Your starter clutch is much
> more accessible.)
> Berryman B12 comes in both liquid and aerosol cans so it can either be
> added to the fuel directly or used to clean out the jets and passage
> directly.
> Your carburetors probably have a small hole in the intake bellmouth,
> and, if you
> squirt B12 (or GumOut or STP or other clear carburetor cleaner) down
> the smaller of the two holes, that will clean out the idle mixture
> circuit.
> The larger of the two holes in the intake is the "choke". Actually you
> don't have a flat plate type choke like a car's carburetor used to
> have.
> The cold starting enrichener circuit has a little valve that allows
> air to bypass the throttle butterfly and the air rushing through the
> air passage sucks gasoline directly out of the float bowl.
> When you start an engine that is equipped with a cold starting
> enrichener, the drill is to move the "choke" lever or knob to the full
> on position and leave the throttle twist grip alone and push the
> starter button until the engine acts like it wants to start.
> Then you can help the start by twisting the throttle grip a little
> bit. What you're actually doing when you twist the throttle is adding
> AIR to the excessively rich mixture, so it's not surprising that you
> smell raw gasoline for that reason.
> An old trick to starting a stubborn engine is to turn the master idle
> speed control knob all the way counterclockwise until the throttle
> butterflies are completely closed.
> When you crank the engine with the electric starter you get MORE
> engine vacuum to suck fuel through the idle jets and passages and
> through the cold starting enrichener because the throttle butterflies
> are fully closed.
> Then, when the engine starts, you can twist the throttle and hold it
> open until the engine warms up and then you can turn the master idle
> knob clockwise to adjust the idle speed to normal.
> There's another thing to understand about the smell of unburned
> gasoline after starting.
> The engine needs a rich fuel air ratio to start, and if the carbs are
> plugged up (or a float valve is stuck shut) the affected cylinder will
> only fire every eighth stroke (four turns of the crankshaft) instead
> of every fourth stroke (two turns of the crank) and it will blow
> unburned gasoline out the exhaust pipe.