V-Twin Carburetor Synchronization

On Jun 27, 2:28 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
wrote:
> Rob Kleinschmidt wrote:
> >Check that before you dick with the carbs any more.
>
> The motorcycle is only two years old, and the front carburetor's idle passage
> is all gummed up.
>
> The OP can get the front cylinder to run on the transition ports or on needle
> drool, but the vacuum isn't equal because one butterfly is open more than the
> other.
>
> If he closes the butterfly on the low cylinder to get more vacuum, the
> butterfly will block the transition ports (which aren't supposed to be
> uncovered at idle anyway, and the needle will stop drooling gas and the
> engine will run on one cylinder.

You figure it's still running on the idle circuit at 50mph ?
He's reporting two separate issues, one at speed, one at idle.
Seems like idle wouldn't figure in at 50 mph.

I'd check the compression at this point just because it's good
elimination technique and easy to do. Not at all unheard of to
have valve problems and worth knowing for sure before
dicking with any troublesome tuning problems.

Carb cleaner, fuel filters and new gas ought to be somewhere
in that troubleshooting scenario too I guess.
 >> Stay informed about: V-Twin Carburetor Synchronization 

Croosh wrote:

>What would be the next thing to do? Panic, take my medicine and take
>the bike to my friendly neighborhood Honda Stealer?

No, it's time to drill out the EPA anti-tamper plugs so you can clean out the
idle mixture ports and passages properly.

It has been 30 days since I told you that you needed to clean out your idle
passages and ports. Dirty idle passages and ports are the main problem with
carbureted motorcycles.

You can probably drill a small pilot hole in the anti-tamper plug, screw a
small sheet metal screw into the plug, and pull it out with a pair of pliers.

Be careful when you drill the anti-tamper plug. You don't want to hit the
idle mixture screw with the drill, wrecking the screwdriver slot.

(If you took your Shadow to a $tealer$hip and asked the mechanic to remove
the anti-tamper plugs, he would probably refuse, claiming that he could be
fined $10K for doing that. He would offer to sell you a new carburetor for
$700, though. But there is probably a paragraph in the shop manual that tells
him how to do this. There may even be a special Honda tool for removing the
anti-tamper plugs. One article I read on www.factorypro.com said that Honda
was using a d-shaped plug.)

Before you remove the idle mixture screws, turn them all the way clockwise,
while counting the turns.

Write the number of full turns and fractions of turns down on a piece of
paper.

Keep each screw, spring, washer and tiny rubber o-ring separate, so you can
put the right screw back in its own carburetor.

Once you have removed the screws, squirt aerosol carburetor cleaner down the
hole each idle mixture screw came out of.

The idle mixture port, idle jet, pilot air jet, and the three transition
ports next to the
throttle butterfly are all connected by passages. If you squirt carburetor
cleaner in any of the holes, it has to come out all the other four holes.

The pilot air jet is either in the mouth of the carb, or it's under the
diaphragm.

It doesn't matter where it's at, if you squirt carn cleaner through it, the
carb cleaner will squirt out the other four holes.

If you squirt carb cleaner through the idle jet, it has to come out the other
four holes.

To get a strong flow of carburetor cleaner out of all the holes, cover three
of them with your fingers while you squirt carb cleaner through one of the
remaining holes.

Once you get a good flow of carb cleaner out of ALL the ports and jets,
reinstall the idle mixture screwsand turn them clockwise until they seat
lightly.

Then turn the screws back out the same number of turns you wrote down. This
will probably be around 1/2 to 1 full turn, since your carbs have #40 idle
jets.

Now you can reinstall your carbs. Turn the master idle knob all the way out
so the throttle butterfly on the lead carburetor is completely closed.

Turn the synchronizer screw so the other carb's butterfly is completely
closed.

Adjust the synchronizer screw so that the second carb's throttle butterfly
begins to move at the exact same time the lead carb's butterfly begins to
move.

Start the engine and warm it up. Now you can adjust the idle mixture. Amateur
mechanics have a hard time understanding the function of the idle mixture
screw
and they think that the idle RPM should keep increasing as they turn it
further and further counterclockwise.

Amateur mechanics don't understand that some carbs have HUGE idle jets and if
they open the idle mixture screw more than half a turn they are drowning the
engine in gasoline.

By the same token, some carbs have smaller idle jets and the idle screws can
be opened 2.5 to 3.0 turns to adjust the mixture.

It doesn't matter either way, the amateur mechanic will open the idle screws
4 or 5 turns and make the idle mixture so rich the idle RPM slows down and
the engine wants to stall.

So the amateur mechanic turns the master idle knob up. This uncovers the
three acceleration transition ports under the throttle butterfly. The
transition ports are NOT controlled by the idle mixture screws.

Now the idle mixture is so rich a 4-cylinder engine goes "toot-toot toot-toot
toot" while it idles, and V-twins idle even rougher.

Maybe the engine clears out when the rider gives the engine a lot of throttle,
and maybe he's happy with the acceleration, but he is mystified by the lack
of response to turning the idle mixture screw at the specified idle RPM. The
screw doesn't seem to do anything.

That's because he's working backwards.

The whole idea of adjusting the idle mixture is to get the engine to runs
smoothly at the smallest butterfly opening and with the fewest turns out of
the idle mixture screws.

So, the procedure is to start the engine and warm it up, set the master idle
knob so the engine idles at the specified RPM, then turn the idle mixture
screws clockwise 1/4 of a turn at a time.

If the idle RPM increases, turn the master idle knob down. Then turn the idle
mixture screws clockwise another 1/4 turn. If the idle RPM rises, turn the
master idle knob down.

If the idle RPM decreases when you turn the idle mixture screws in, you've
found the critical point, turn them both back out 1/8th of a turn.

After you have the idle mixture and idle RPM set, you can play with your U-
tube manometer.

http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=1304531

5: SCREW SET

33: JET, MAIN (#105)

34: JET, MAIN (#108)

35: JET, SLOW (#40)

--
Message posted via MotorcycleKB.com
http://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200706/1
 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jun 27, 8:47 am, "Albrecht via MotorcycleKB.com" <u33665@uwe>
wrote:
> Croosh wrote:
> >What would be the next thing to do? Panic, take my medicine and take
> >the bike to my friendly neighborhood Honda Stealer?
>
> No, it's time to drill out the EPA anti-tamper plugs so you can clean out the
> idle mixture ports and passages properly.
>
> It has been 30 days since I told you that you needed to clean out your idle
> passages and ports. Dirty idle passages and ports are the main problem with
> carbureted motorcycles.
>
> You can probably drill a small pilot hole in the anti-tamper plug, screw a
> small sheet metal screw into the plug, and pull it out with a pair of pliers.
>
> Be careful when you drill the anti-tamper plug. You don't want to hit the
> idle mixture screw with the drill, wrecking the screwdriver slot.
>
> (If you took your Shadow to a $tealer$hip and asked the mechanic to remove
> the anti-tamper plugs, he would probably refuse, claiming that he could be
> fined $10K for doing that. He would offer to sell you a new carburetor for
> $700, though. But there is probably a paragraph in the shop manual that tells
> him how to do this. There may even be a special Honda tool for removing the
> anti-tamper plugs. One article I read onwww.factorypro.comsaid that Honda
> was using a d-shaped plug.)
>
> Before you remove the idle mixture screws, turn them all the way clockwise,
> while counting the turns.
>
> Write the number of full turns and fractions of turns down on a piece of
> paper.
>
> Keep each screw, spring, washer and tiny rubber o-ring separate, so you can
> put the right screw back in its own carburetor.
>
> Once you have removed the screws, squirt aerosol carburetor cleaner down the
> hole each idle mixture screw came out of.
>
> The idle mixture port, idle jet, pilot air jet, and the three transition
> ports next to the
> throttle butterfly are all connected by passages. If you squirt carburetor
> cleaner in any of the holes, it has to come out all the other four holes.
>
> The pilot air jet is either in the mouth of the carb, or it's under the
> diaphragm.
>
> It doesn't matter where it's at, if you squirt carn cleaner through it, the
> carb cleaner will squirt out the other four holes.
>
> If you squirt carb cleaner through the idle jet, it has to come out the other
> four holes.
>
> To get a strong flow of carburetor cleaner out of all the holes, cover three
> of them with your fingers while you squirt carb cleaner through one of the
> remaining holes.
>
> Once you get a good flow of carb cleaner out of ALL the ports and jets,
> reinstall the idle mixture screwsand turn them clockwise until they seat
> lightly.
>
> Then turn the screws back out the same number of turns you wrote down. This
> will probably be around 1/2 to 1 full turn, since your carbs have #40 idle
> jets.
>
> Now you can reinstall your carbs. Turn the master idle knob all the way out
> so the throttle butterfly on the lead carburetor is completely closed.
>
> Turn the synchronizer screw so the other carb's butterfly is completely
> closed.
>
> Adjust the synchronizer screw so that the second carb's throttle butterfly
> begins to move at the exact same time the lead carb's butterfly begins to
> move.
>
> Start the engine and warm it up. Now you can adjust the idle mixture. Amateur
> mechanics have a hard time understanding the function of the idle mixture
> screw
> and they think that the idle RPM should keep increasing as they turn it
> further and further counterclockwise.
>
> Amateur mechanics don't understand that some carbs have HUGE idle jets and if
> they open the idle mixture screw more than half a turn they are drowning the
> engine in gasoline.
>
> By the same token, some carbs have smaller idle jets and the idle screws can
> be opened 2.5 to 3.0 turns to adjust the mixture.
>
> It doesn't matter either way, the amateur mechanic will open the idle screws
> 4 or 5 turns and make the idle mixture so rich the idle RPM slows down and
> the engine wants to stall.
>
> So the amateur mechanic turns the master idle knob up. This uncovers the
> three acceleration transition ports under the throttle butterfly. The
> transition ports are NOT controlled by the idle mixture screws.
>
> Now the idle mixture is so rich a 4-cylinder engine goes "toot-toot toot-toot
> toot" while it idles, and V-twins idle even rougher.
>
> Maybe the engine clears out when the rider gives the engine a lot of throttle,
> and maybe he's happy with the acceleration, but he is mystified by the lack
> of response to turning the idle mixture screw at the specified idle RPM. The
> screw doesn't seem to do anything.
>
> That's because he's working backwards.
>
> The whole idea of adjusting the idle mixture is to get the engine to runs
> smoothly at the smallest butterfly opening and with the fewest turns out of
> the idle mixture screws.
>
> So, the procedure is to start the engine and warm it up, set the master idle
> knob so the engine idles at the specified RPM, then turn the idle mixture
> screws clockwise 1/4 of a turn at a time.
>
> If the idle RPM increases, turn the master idle knob down. Then turn the idle
> mixture screws clockwise another 1/4 turn. If the idle RPM rises, turn the
> master idle knob down.
>
> If the idle RPM decreases when you turn the idle mixture screws in, you've
> found the critical point, turn them both back out 1/8th of a turn.
>
> After you have the idle mixture and idle RPM set, you can play with your U-
> tube manometer.
>
> http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=1304531
>
> 5: SCREW SET
>
> 33: JET, MAIN (#105)
>
> 34: JET, MAIN (#108)
>
> 35: JET, SLOW (#40)
>
> --
> Message posted via MotorcycleKB.comhttp://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200706/1

Albrecht,
I remeber your post 30 days ago I was not ignoring it, I was just
procrastenating (don't feel too comfortable messing with the mixture).
Since the plugs looked intact, I figured that previous owner didn't
mess with that...
I cleaned the carbs to my best ability without messing with the pilot
jet. I soaked the think in carb cleaner overnight (after removing all
rubber parts), and the squorted a full can of gumoff carb cleaner into
every hole and cravice.
My Honda Manual has been ordered over a month ago, and it's still
being "printed". I was able to find a pdf version on the net (for an
older model, but carbs are almost the same , with only small
difference in the float chamber). It has good instructions how to
ajdust the misture etc.
Yesterday i ordered an inductive tachometer with good resolution.
When everything comes, I will try to clean/adjust the pilot jet.
 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jun 27, 1:15 pm, Rayvan <rvannul....DeleteThis@cachevision.com> wrote:
> On Jun 26, 2:03 pm, chas <chass....DeleteThis@gmail.com> wrote:
>
> > Just trade it in for a Suzuki Savage and you'll never have this
> > problem again
>
> Yes. Especially as a bike ages. It's *so* nice to never need to sync.
> --
> Rayvan

Hm... that woul be counter-intuitive.
Normal path is to get 750CC, figure that it's too whimpy, go to
1100CC. Then ride 1100CC , figure that 1800CC is even better and so on
and on... Just kidding
On the serious note, I tried Savage (my younger brother has Boulevard
S40), and although i like the "style", it's way too small for me. I
have fairly long legs , and even shadow 750 is almost not big
enough...

Regards
Yuriy
 >> Stay informed about: V-Twin Carburetor Synchronization 

Albrecht via MotorcycleKB.com wrote:
> (If you took your Shadow to a $tealer$hip and asked the mechanic to remove
> the anti-tamper plugs, he would probably refuse, claiming that he could be
> fined $10K for doing that. He would offer to sell you a new carburetor for
> $700, though. But there is probably a paragraph in the shop manual that tells
> him how to do this.

I know what you mean, but it sounds like the Honda Shop Manual states:
"Don't pull the anti-tamper plugs - sell the idiot a $700 carb..."

--
"Outback" Jon - KC2BNE
outback_jon DeleteThis @ver.no.sp.am.izon.net
AMD Opteron 146 (@2. and 6.1 GHz of other AMD power...
http://folding.stanford.edu - got folding? Team 48435

2006 ZG1000A Concours "Blueline" COG# 7385 CDA# 0157
1980 CB750F SuperSport "CoolerKing"
 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jun 27, 4:45 pm, Croosh <ycro... DeleteThis @gmail.com> wrote:
> On Jun 27, 1:15 pm, Rayvan <rvannul... DeleteThis @cachevision.com> wrote:
>
> > On Jun 26, 2:03 pm, chas <chass... DeleteThis @gmail.com> wrote:
>
> > > Just trade it in for a Suzuki Savage and you'll never have this
> > > problem again
>
> > Yes. Especially as a bike ages. It's *so* nice to never need to sync.
> > --
> > Rayvan
>
> Hm... that woul be counter-intuitive.
> Normal path is to get 750CC, figure that it's too whimpy, go to
> 1100CC. Then ride 1100CC , figure that 1800CC is even better and so on
> and on... Just kidding
> On the serious note, I tried Savage (my younger brother has Boulevard
> S40), and although i like the "style", it's way too small for me. I
> have fairly long legs , and even shadow 750 is almost not big
> enough...

Rumour has it that there are some 883cc, 1200cc and even some 1550cc
two cylinder bikes available that never need carb (or throttle body)
syncs.
--
Rayvan
 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jun 27, 4:53 pm, Rob Kleinschmidt <Rkleinsch1216....TakeThisOut@aol.com> wrote:
> On Jun 27, 4:15 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
> wrote:
>
> > Rob Kleinschmidt wrote:
> > >You figure it's still running on the idle circuit at 50mph ?
>
> > Oh, yes. CV carbs get 75% of the gas they use from the idle jet.
>
> Uhhh...not on a Bing CV carb anyway.

Or any CV carb....

>
> The idle jet supplies most of the fuel to 1/8 - 1/4 throttle.

Just like any CV carb.

--
Rayvan
 >> Stay informed about: V-Twin Carburetor Synchronization 

Rob Kleinschmidt wrote:

>Check that before you dick with the carbs any more.

The motorcycle is only two years old, and the front carburetor's idle passage
is all gummed up.

The OP can get the front cylinder to run on the transition ports or on needle
drool, but the vacuum isn't equal because one butterfly is open more than the
other.

If he closes the butterfly on the low cylinder to get more vacuum, the
butterfly will block the transition ports (which aren't supposed to be
uncovered at idle anyway, and the needle will stop drooling gas and the
engine will run on one cylinder.

--
Message posted via MotorcycleKB.com
http://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200706/1
 >> Stay informed about: V-Twin Carburetor Synchronization 

Rob Kleinschmidt wrote:

>You figure it's still running on the idle circuit at 50mph ?

Oh, yes. CV carbs get 75% of the gas they use from the idle jet.

Problem is, most riders don't understand how a CV carb works at idle, very
small throttle settings and larger throttle settings.

They think that the idle mixture screw (if they even know it exists) controls
all the
gasoline that comes through the idle jet.

It doesn't. The idle mixer screw is a trimmer on the idle circuit. At most,
it controls 1/4 of the fuel that comes out of the idle jet.

If the idle jet is around a #40 to #45, the idle mixture screw will be turned
almost fully closed. When a carb has an idle jet that large, its very easy
for the single
idle mixture port to get plugged with gum and varnish.

The other 75% of the fuel that comes through the idle jet comes out the three
transition ports that are controlled by the throttle butterfly.

As the rider wants to accelerate away from a stop, he opens the throttle.

But doing that causes vacuum downstream of the throttle butterfly to decrease.


That's OK, there are three transition ports that can flow fuel to accelerate
engine speed.

Problem is when the single idle mixture port gets plugged up and the engine
won't run on both cylinders until it warms up or the throttle is opened.

The newbie tries to ride using 1/4 throttle all the time, but he can't
control the motorcycle very well at parking lot speeds if he always has to
keep the throttle slightly open.

Every time he rolls the throttle all the way off, the engine goes back to
running on the clean carburetor.

The newbie rider doesn't know how his CV carb works and some clown who
knows only a little more wisely tells the newbie that his carbs need
synchronizing, when all that is really needed is a chemical cleaning with B12
or other solvent in the gas tank.

Carburetor synchronizing is about the dumbest notion possible, considering
the precision nature of the modern CV carburetor.

What is supposed to wear out in the first several thousand miles of operation
that will cause the carbs to suddenly need synchronization?

Carb synchronization is a bread and butter business for $tealer$hip mechanic$

>He's reporting two separate issues, one at speed, one at idle.
>Seems like idle wouldn't figure in at 50 mph.

Well, idle fuel does matter. Most big bore motorcycles are running at 1/4
throttle or less at highway speeds, and the straight part of the needle is
usually still in the needle jet.

--
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 >> Stay informed about: V-Twin Carburetor Synchronization 

Rob Kleinschmidt wrote:
>On Jun 27, 4:15 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
>wrote:

>> Oh, yes. CV carbs get 75% of the gas they use from the idle jet.
>
>Uhhh...not on a Bing CV carb anyway.

Bing CV's work just like Mikuni or Keihin CV's. There is an idle port
downstream of the butterfly and there are transition ports that are covered
by the butterfly when the engine is idling.

BMW airhead owners occasionally made the mistake of installing the throttle
butterflies on the wrong side of the throttle shafts when rebuilding their
cabrs and they couldn't adjust the idle mixture.
>
>The idle jet supplies most of the fuel to 1/8 - 1/4 throttle.

When synchronizing the carburetors you want the butterflies closed and the
engine is supposed to get enough air to idle through the air jet.

>At 50 mph, I'd expect it to be running mostly on the needle
>rather than the idle jet.

As the butterfly opens further and further, vacuum in the carburetor drops
off and it cannot pull fuel through the tiny idle ports so easily. But it has
an easier time pulling fuel through the needle jet because there is less
restriction.

There is a point, somewhere around half throttle where the increasing fuel
flow past the needle and the decreasing fuel flow through the idle jet are
equal. This point is called the "crossover point".

BMW airhead owners who wanted better fuel mileage for bragging rights found
they could lower the needle or install a different idle jet.

--
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 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jun 27, 7:01 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
wrote:
> Rob Kleinschmidt wrote:
> >On Jun 27, 4:15 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
> >wrote:
> >> Oh, yes. CV carbs get 75% of the gas they use from the idle jet.
>
> >Uhhh...not on a Bing CV carb anyway.
>
> Bing CV's work just like Mikuni or Keihin CV's. There is an idle port
> downstream of the butterfly and there are transition ports that are covered
> by the butterfly when the engine is idling.
>
> BMW airhead owners occasionally made the mistake of installing the throttle
> butterflies on the wrong side of the throttle shafts when rebuilding their
> cabrs and they couldn't adjust the idle mixture.
>
>
>
> >The idle jet supplies most of the fuel to 1/8 - 1/4 throttle.
>
> When synchronizing the carburetors you want the butterflies closed and the
> engine is supposed to get enough air to idle through the air jet.

I think you mean "almost closed". On mine, the spec is 1.5
turns of the idle speed screw.

> >At 50 mph, I'd expect it to be running mostly on the needle
> >rather than the idle jet.

> There is a point, somewhere around half throttle where the increasing fuel
> flow past the needle and the decreasing fuel flow through the idle jet are
> equal. This point is called the "crossover point".

As I said, I've seen needle problems show up anywhere from
~2500 - 3500 RPM. Seems unlikely there was an idle or transition
problem at 50 mph.

The most interesting question to my mind is why one cylinder would
pull more vacuum at idle and the other cylinder pull more at higher
RPMs. I'm not 100% sure of his particular idle adjust mechanism, so it
could be a matter of simple adjustment.

OTOH, there is a real possibility that his problems may have
started a while ago and be totally unrelated to tuning. That's
why I suggest he first make sure that he's starting with a
problem that can really be fixed by adjusting jets. This would
be particularly true if he has to go to the trouble of drilling
out an epoxy cap first. If carb cleaner won't fix it, check
the compression before breaking out the drill.

A compression check is pretty easy. Best is with carbs
removed and the +12 lead disconnected from the spark
coil. When I'm feeling lazy, I'll run it with the carbs wide
open and the plugs just shorted out. This is good enough
to detect any gross imbalances, which is what you really
care about here.
t
 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jun 27, 2:28 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
wrote:
> Rob Kleinschmidt wrote:
> >Check that before you dick with the carbs any more.
>
> The motorcycle is only two years old, and the front carburetor's idle passage
> is all gummed up.
>
> The OP can get the front cylinder to run on the transition ports or on needle
> drool, but the vacuum isn't equal because one butterfly is open more than the
> other.
>
> If he closes the butterfly on the low cylinder to get more vacuum, the
> butterfly will block the transition ports (which aren't supposed to be
> uncovered at idle anyway, and the needle will stop drooling gas and the
> engine will run on one cylinder.
>
> --
> Message posted via MotorcycleKB.comhttp://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200706/1

Hi all!
I checked the compression, and it's spot-on in both cylinders, so...
I ended up taking the carb apart again, this time I drilled out EPA
plugs, took out EVERYTHING, soaked everything in carb cleaner,
reassembled the thing and bribed a local Harley shop to adjust the
mixture (costed me $30 and a 6-pack of nice porter ) After that the
carbs synced on the first go-around, and are very at the low and the
high end. No afterfires and no excessive vibration (3rd gear feels
like 5th felt at 50MPH).

Now, there is one more annoyance I have not dealt with: the bike
"starves" after about 10 minutes at freeway spped (at least it did
befire the ajustment, and I've been avoiding the slab afterwards).
Basically it would loose power, stall and refuse to start for about 5
minutes. I suspected the gas tank (vacuum build-up) but opening the
tank doesn't help. I get good spark on both cylinders (I checked [the
stupid way]).
My suspects are: blockage of the gas line/pump problem (engine gets
enough gas at normal speed but starves at high spped), overheating
(carb gets too hot and vaporazes the gas) or electical problem.
Does anyone have any experience with such problem?

Thank you
Yuriy
 >> Stay informed about: V-Twin Carburetor Synchronization 

On Jul 2, 10:25 pm, Croosh <ycro... DeleteThis @gmail.com> wrote:
> On Jun 27, 2:28 pm, "Albrecht via MotorcycleKB.com" <u33665@uwe>
> wrote:
>
>
>
> > Rob Kleinschmidt wrote:
> > >Check that before you dick with the carbs any more.
>
> > The motorcycle is only two years old, and the front carburetor's idle passage
> > is all gummed up.
>
> > The OP can get the front cylinder to run on the transition ports or on needle
> > drool, but the vacuum isn't equal because one butterfly is open more than the
> > other.
>
> > If he closes the butterfly on the low cylinder to get more vacuum, the
> > butterfly will block the transition ports (which aren't supposed to be
> > uncovered at idle anyway, and the needle will stop drooling gas and the
> > engine will run on one cylinder.
>
> > --
> > Message posted via MotorcycleKB.comhttp://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200706/1
>
> Hi all!
> I checked the compression, and it's spot-on in both cylinders, so...
> I ended up taking the carb apart again, this time I drilled out EPA
> plugs, took out EVERYTHING, soaked everything in carb cleaner,
> reassembled the thing and bribed a local Harley shop to adjust the
> mixture (costed me $30 and a 6-pack of nice porter ) After that the
> carbs synced on the first go-around, and are very at the low and the
> high end. No afterfires and no excessive vibration (3rd gear feels
> like 5th felt at 50MPH).
>
> Now, there is one more annoyance I have not dealt with: the bike
> "starves" after about 10 minutes at freeway spped (at least it did
> befire the ajustment, and I've been avoiding the slab afterwards).
> Basically it would loose power, stall and refuse to start for about 5
> minutes. I suspected the gas tank (vacuum build-up) but opening the
> tank doesn't help. I get good spark on both cylinders (I checked [the
> stupid way]).
> My suspects are: blockage of the gas line/pump problem (engine gets
> enough gas at normal speed but starves at high spped), overheating
> (carb gets too hot and vaporazes the gas) or electical problem.
> Does anyone have any experience with such problem?

My gravity feed tank has a fine mesh filter above the petcock
that used to get clogged with peeled off fragments of red
tank liner. I refinished the tank with POR-15 and haven't had
trouble since.

Is this gravity feed or pump ? If it's pump feed, I don't know that
opening the tank would make a difference. If it's gravity feed,
definitely look for a mesh filter inside the tank.


>
> Thank you
> Yuriy
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