Re: Bike won't start after carb cleaning.

Your idle jets are all plugged up. Remove the idle mixture screws and
spray Berryman's B12 or STP or GumOut carb cleaner through all the
idle mixture ports, including the three acceleration transition ports
located near the lower edge of the throttle butterflies.

The engine draws fuel through the idle jets and air through the pilor
air jet which may be in the inlet bell or under the rubber diaphragm.
Then the mixture goes off to the single idle mixture port behind the
idle mixture screw and to the three acceleration ports.

Spraying carb cleaner through the pilot air jet and the idle jet
should result in a strong stream of fuel air mixture coming out of
each port.

I cannot advise you as to how many turns open your idle mixture screws
should be, because it depends on the area of the orifice in the idle
jet, and the area varies exponentially as to the square of the radius
of the jet.

Some bikes have tiny idle jets, like #30 to #35 and they need the idle
mixture screw to be turned out 3 to 3-1/2 turns.

Other bikes have huge #40 to #45 idle jets and the idle mixture screw
only needs to be turned out 1/4 of a turn.

When starting the motorcycle, the choke should be fully "ON" and the
throttle should be fully closed to avoid uncovering the three
acceleration transition ports, which makes the idle mixture far too
rich.

Posted by Eat Dirt on April 9, 2008, 12:46 pm

> > Is there a trick to getting this bike to start nicely again?

> Your idle jets are all plugged up. Remove the idle mixture screws and

> spray Berryman's B12 or STP or GumOut carb cleaner through all the

> idle mixture ports, including the three acceleration transition ports

> located near the lower edge of the throttle butterflies.

> The engine draws fuel through the idle jets and air through the pilor

> air jet which may be in the inlet bell or under the rubber diaphragm.

> Then the mixture goes off to the single idle mixture port behind the

> idle mixture screw and to the three acceleration ports.

> Spraying carb cleaner through the pilot air jet and the idle jet

> should result in a strong stream of fuel air mixture coming out of

> each port.

> I cannot advise you as to how many turns open your idle mixture screws

> should be, because it depends on the area of the orifice in the idle

> jet, and the area varies exponentially as to the square of the radius

> of the jet.

> Some bikes have tiny idle jets, like #30 to #35 and they need the idle

> mixture screw to be turned out 3 to 3-1/2 turns.

> Other bikes have huge #40 to #45 idle jets and the idle mixture screw

> only needs to be turned out 1/4 of a turn.

> When starting the motorcycle, the choke should be fully "ON" and the

> throttle should be fully closed to avoid uncovering the three

> acceleration transition ports, which makes the idle mixture far too

> rich.

Thanks, I did what you said and I have cleaned the air mixture screws,
which were indeed dirty. I also fully cleaned each and every tiny hole
by spraying carb cleaner through them. Now I feel that this carb is
fully clean. But I suspect I found a problem: my diaphragm and its
cylinder may not be working as it should. What do you think of this?
The manual says that in order to test it, I should place the carb
upright, cover the inlet air hole, push the cylinder way up and time
it as it slowly descends. It claims it should take over 10 seconds.
Well, in my test one of them took 6 seconds while the other only took
3 secons. Is this bad? I hope I don't have to replace these as I
suspect they'd cost a small fortune. But could this be causing
starting problems and causing the bike to run lean as well?

I plan to install the carb back on the bike later tonight to test it.
Although I'm now wondering if I'd be better first bringing it to a
mechanic to properly adjust the float levels. The bike is clearly
running very lean (white spark plug contacts, overheating, need for
the choke to be on, etc). Do you think this to be a good idea too?
Thanks for the help.

Posted by Rick Cortese on April 9, 2008, 1:37 pm

Eat Dirt wrote:

<snip>

> Thanks, I did what you said and I have cleaned the air mixture screws,

> which were indeed dirty. I also fully cleaned each and every tiny hole

> by spraying carb cleaner through them. Now I feel that this carb is

> fully clean. But I suspect I found a problem: my diaphragm and its

> cylinder may not be working as it should. What do you think of this?

It should still start with a bad diaphragm. A bad diaphragm just makes
it so it won't take full throttle.

Sorry if I missed it in another post, but are you sure you didn't pinch
a gas line when you bolted the tank back on? I do this myself more often
then I would like to admit.

Anyway, the little brass drain plugs on the bottom of the carburetor are
a wonderful diagnostic device. What I do is with the petcock in the OFF
position remove the plug and catch the gas that falls. If it is the
~right volume I turn the petcock on and see if there is adequite flow.
If gas flows with the petcock off, time to replace the petcock.

This may take longer to tell then it is worth, but you really have to
flush the carbs in the right direction or verify flow. That is, when you
use the little tube that came with your carb cleaner to spray cleaner
into the slow jet, it should have a steady stream of cleaner comming out
of a tiny hole on the engine side of the butterfly valve. It will also
come out one of the holes on the intake side of the carburator if you
have the idle screw out a couple of turns.

Sometimes the little flakes/crud form is between the jet and this exit.
I just pull a steel wire out of a wire brush to poke it open. Ditto for
the slow jet.

Rick

Posted by on April 11, 2008, 2:12 pm

> Eat Dirt wrote:

> It should still start with a bad diaphragm. A bad diaphragm just makes

> it so it won't take full throttle.

> Sometimes the little flakes/crud form is between the jet and this exit.

> I just pull a steel wire out of a wire brush to poke it open. Ditto for

> the slow jet.

> Rick

Not sure how a thread about a bike not starting turns into an idiotic
debate on how sniffing carb cleaner to kill you and cause your wife to
give birth to a 7 headed monster but for those that actually tried to
help, here's an update:
Installed the carb after a 4th attempt at cleaning it - and the thing
fired right up! Wow, I couldn't believe it. It's like a new bike now
and works absolutely well (despite being too lean). Here's what I
think happened (for those thread jackers that have a hard on for carb
cleaner you'll like this). I had initially used Yamaha's combustion
chamber cleaner to clean out the very gross varnish and greenish sand
that was the inside of both carbs, due to a friend's recommendation. I
noticed that it left a somewhat thick, very shiny and slippery residue
on everything it touched. I figured that gasoline would just clean
that out once gas run through it. Well, it actually didn't. A guy at
local shop said that some of the jets need to be exceptionally clean
as it is very sensitive to anything (the jets responsible for idling
and starting). Suspecting the combustion cleaner was the problem, I
picked up a can of carb cleaner (thread hijackers, pay attention) and
completely cleaned everything over again, leaving a dry, crisp
surface. I also sprayed it through every hole, which inevitably
backsprayed onto my eyes and face. Guess what folks: I can still see
and despite even tasting it, I managed to survive.

I still have one problem though: bike is still running too lean. I
have set the air screws to only half a turn despite the manual
recommendation for 1.75 turns from completely closed. I figured that
by letting less air in that it would richen the mixture. Well, I still
get a whitish spark plug and I noticed the engine seems to be running
very hot even though this is an air cooled bike and the bike was
mostly idling in place. However I no longer need to have the choke on
for the bike to idle, which is a sign that I'm on the right path.

What can I do to richen the mixture? I don't think replacing the jets
to be the answer as previous to my carb cleaning the bike was running
properly, as seen on the old spark plugs that looked 'normal'. Any
tweaks I can do?

Posted by Mark Olson on April 11, 2008, 2:20 pm

esteves.grace@gmail.com wrote:

> I still have one problem though: bike is still running too lean. I

> have set the air screws to only half a turn despite the manual

> recommendation for 1.75 turns from completely closed. I figured that

> by letting less air in that it would richen the mixture. Well, I still

> get a whitish spark plug and I noticed the engine seems to be running

> very hot even though this is an air cooled bike and the bike was

> mostly idling in place. However I no longer need to have the choke on

> for the bike to idle, which is a sign that I'm on the right path.

> What can I do to richen the mixture? I don't think replacing the jets

> to be the answer as previous to my carb cleaning the bike was running

> properly, as seen on the old spark plugs that looked 'normal'. Any

> tweaks I can do?

Are you *sure* the idle mixture screws on these '83 GPz305 carbs are
actually air screws and not fuel screws? If they are anything like the
TK carbs on my '82 GPz550 they are fuel, not air screws, so turning
them further in will in fact lean out the idle and part throttle mixture.

--
'01 SV650SK1 '99 EX250-F13 '98 ZG1000-A13
OMF #7

Page 1 of 11 1 2 3 > last >>

Similar Threads	Posted
Re: Bike won't start after carb cleaning.	April 8, 2008, 12:19 pm
Re: Bike won't start after carb cleaning.	April 9, 2008, 2:17 pm
Helmet Cleaning	September 10, 2007, 7:34 am
Help with cleaning the inside of a H4 headlamp	April 10, 2007, 3:51 pm
Help with cleaning small miltipin connectors.	April 2, 2007, 2:25 pm
Cleaning fork seals instead of replacing them	March 24, 2007, 11:50 am
81 Virago 750 won't start	August 29, 2007, 10:27 am
GT380 engine won't start	July 5, 2007, 6:06 am
1982 Yamaha 650 - no start	July 9, 2008, 8:22 pm
GPZ600R ('86 I believe) Won't Start, Tried Everything, Any ideas please?	July 28, 2008, 12:42 am

XML Sitemap