Topic: 750 F2 # 1 on mine does not run at all at idle.

[pdeg]

Hi guys ... finally found this forum, and what a blessing.

I too have a 750 F2.. and sorry to hijack this thread with a couple of newb queries...

# 1 on mine does not run at all at idle.. stick my finger in the inlet and it sort of runs.
Stick my finger in the others and the motor slows...
This bike has had probs with # 1 since I have owned it... 10 years...  Cutting in an out.
Sick of it.  Riding without an air cleaner.. as you accelarate you can hear #1 sucking... even though it
is  is firing.
Tried adjusting #1 down .. think it was out of balance .. but ran out of adjustment

I was about to pull the heads off thinking that the compression was low.. but after reading
a few similar threads I am beginning to think that I have  carb probs.   I have put a compression
gauge on the motor and #1 reads the same as the rest.

 I have the carbs off on my coffee table now (I am single)     They are the ones with the screw
on float covers.  The one that barely gets a mention in the manuals :-)

To the questions...
1. Putting aside the low versus high debate on the floats.  The spec on mine says 26mm.  ?
    Is that from the gasket to the top of the float?  Bottom of the float ?

2.  If I have them upside down.  I also have to consider the fact that there is a spring in the "valves".
     So this height may change with the weight of the fuel on them... or do the specs take this into
     account.

3.  I am presuming that the clear hose idea.... is to put a  piece of clear hose on the drains, and with the
     carbs in the bike..... I put this hose vertical next to the float and it will tell me what the actual
     fuel height.... Very clever .. would never have thought of that.     In this scenario .. how far below
     the gasket should the fuel level be.

4.  If the idle circuit is blocked ... which hole(s) should I get stuck into with the compressed air?

5.  Is there supposed to be an O ring on the idle screw .. is this important ?

Many tx for any advice .. and again I am sorry to hijack this thread... should I have started another ?

Cheers
Peter

PS...  Started this topic as a cut and paste from one I hijacked... will paste replies from there

[pdeg]

Offline DukieFrankenkit

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Re: Motor stalls out when cornering...
« Reply #32 on: June 22, 2012, 12:15:37 pm »

    Quote


To the questions...
1. Putting aside the low versus high debate on the floats.  The spec on mine says 26mm.  ?
    Is that from the gasket to the top of the float?  Bottom of the float ?

With the carb measuring tool (or one you fabricate yourself set to 26mm) you should get a reading at 26mm when the tool touches the float to where the float tang barely touches the tip of the float valve.

2.  If I have them upside down.  I also have to consider the fact that there is a spring in the "valves".
     So this height may change with the weight of the fuel on them... or do the specs take this into
     account.

See above

3.  I am presuming that the clear hose idea.... is to put a  piece of clear hose on the drains, and with the
     carbs in the bike..... I put this hose vertical next to the float and it will tell me what the actual
     fuel height.... Very clever .. would never have thought of that.     In this scenario .. how far below
     the gasket should the fuel level be.

You are just performing this test if you have further problems with one or two carbs after adjusting the float height to check the actual fuel level in each carb bowl. It should be below the gasket, no set amount.

4.  If the idle circuit is blocked ... which hole(s) should I get stuck into with the compressed air?

Compressed air in all orifices along with carb cleaner along with wire cleaning is what I do.

5.  Is there supposed to be an O ring on the idle screw .. is this important ?

Yes. Yes.

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CB750 K3 cafe | (2) 1986 VFR750F

[pdeg]

Offline Spanner 1

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Re: Motor stalls out when cornering...
« Reply #34 on: June 22, 2012, 11:26:45 pm »

    Quote

pdeg..... your carb float level on your F2 750 is 14.5mm.... not 26mm. 26mm is correct for the K0 thru' K6 bikes .... None of the screw-off float bowl carbs were 26mm.... either 12.5mm or 14.5mm.
Need to read-up on the 'Carb Facts' area of the Forum and learn how to take out the jets for cleaning and how to clean and prove  the air bleeds. As you already have the carbs off, now's the time  No shortcuts, you will only have to do it over....
« Last Edit: June 22, 2012, 11:34:26 pm by Spanner 1 »
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In the garage; CB750 K1 taking a rest , K4 parts bike and K8 on the road... + 'Prince Charles', my wifeys CB 650
'Wish I could ride across the country starting tomorrow, well , whats actually stopping me?... I might have to get back to you on that '.

[pdeg]

Compressed air in all orifices along with carb cleaner along with wire cleaning is what I do

Wire cleaning ?  Everthing I read says not to stick wire in there.. but at this point
will try anything .... what sort of wire ?  I am thinking some very thin copper stuff,
like the winding on an electric motor... thin and flexible.

pdeg..... your carb float level on your F2 750 is 14.5mm.... not 26mm. 26mm is correct for the K0 thru' K6 bikes .... None of the screw-off float bowl carbs were 26mm.... either 12.5mm or 14.5mm.
Need to read-up on the 'Carb Facts' area of the Forum and learn how to take out the jets for cleaning and how to clean and prove  the air bleeds. As you already have the carbs off, now's the time  No shortcuts, you will only have to do it over....


Interesting .. can somebody give me a link to that section ... have been trawling for a while and
cannot find it

Tx guys
Peter

[pdeg]

Have beem reading some more .. was a sub forum .. duh 

Found this thread
http://forums.sohc4.net/index.php?topic=37634.25
with a link to the manual
http://www.mediafire.com/?5ttzdg9yyuz
  .. yippee 

And you are correct ... is 14.5 on the floats.

Sorry .. .still a couple of newb questions....

1.  Is the idle mixture screw an air bleed or fuel ?  Most the texts say that M/C carbs bleed air
     on the idle mixture screw.. hence in is richer...

2. If I did take a brave pill and tried to pull out the low speed jet (a press fit).  How would I do that ?
     Would I get  a pair of pliers and extract it like a tooth ?

Tx
Peter

[HondaMan]

Have beem reading some more .. was a sub forum .. duh 

Found this thread
http://forums.sohc4.net/index.php?topic=37634.25
with a link to the manual
http://www.mediafire.com/?5ttzdg9yyuz
  .. yippee 

And you are correct ... is 14.5 on the floats.

Sorry .. .still a couple of newb questions....

1.  Is the idle mixture screw an air bleed or fuel ?  Most the texts say that M/C carbs bleed air
     on the idle mixture screw.. hence in is richer...

2. If I did take a brave pill and tried to pull out the low speed jet (a press fit).  How would I do that ?
     Would I get  a pair of pliers and extract it like a tooth ?

Tx
Peter

Your carbs should be either PD41 or PD42 type (it shows right on the side of the carb bodies). All of the PD carbs use fuel-metering idle air screws, for better accuracy (it was done to meet emissions standards, mostly). They are also calibrated pretty lean in most bikes, with 105 mainjets. If you can get some, the 110 size mainjet will improve the overall performance.

But, back to the basic questions...
Usually, these bikes display vacuum leaks in the rubber hoses that clamp to the head. The rubber is hard now, so either stronger, wider hose clamps are needed, or new rubber, or you can just soak them in xylene for a couple of days, then wait a day to dry out, then install them and they will "shrink to fit" again for a couple more years. If you can also find some oil of wintergreen to add to the xylene (50/50 mix), they will stay soft for years (and smell good!).

The small vacuum leaks affect the carbs most at idle, when the throttle is mostly closed. This lowers the amount of vacuum across the idle jet's orifice, reducing the amount of fuel it sweep in. Also, if the tiny emulsifier holes on the tips of the idle jets are even partially plugged, not enough air can get in to lift the fuel from the jet, so even if the  tiny idle jet is clear, the emulsifier holes can cause troubles. This is difficult with the PD42 carbs in particular, which had press-in idle jets (in the US, not sure about 'down under' bikes.).

[lucky]

IS the accelerator pump system working?
Do you see fuel squirt out of the nozzle when you turn the throttle with the engine off???  Check that #1 nozzle.

[pdeg]

Snaps in line ... click to enlarge.  These smart phone cameras are cool .... the flash in next to the lens.

Your carbs should be either PD41 or PD42 type (it shows right on the side of the carb bodies).

Correct .. Not sure what number though.

All of the PD carbs use fuel-metering idle air screws, for better accuracy (it was done to meet emissions standards, mostly).

Tx for that ... I got the feeling that it was running richer when I unscrewed them.  Interestingly adjusting
the screw appears to do very little.. at idle anyway

They are also calibrated pretty lean in most bikes, with 105 mainjets. If you can get some, the 110 size mainjet will improve the overall performance.

Yep   105s .. Will certainly try.  1978... anti-pollution .. sigh 

Usually, these bikes display vacuum leaks in the rubber hoses that clamp to the head.

This has recently been replaced ..so is not too bad... but will renew the clamps though.. so I get get some
heft on it 

There seem to be some amazing chemicals out there ... but they are described with their brand names.
Most of which are US.. 
Xylene... where would I find that ?? on the paint thinner isle ?  Oil of wintergreen sounds like a fountain of youth
elixir     What is it exactly and how would I get hold of some..   Will try to get hold of some
milkstone remover too.... had to google that    Does it eat aluminium ?

What is the recommendation for something I can put in a bucket to dump them in
to give the a good clean to start with ?  Truck wash ??

tiny emulsifier holes on the tips of the idle jets

My mains had blocked emulsion tubes.  Where in the idle circuit are theirs .. under the non
removable jet ? Under the jet in the body of the carb ?  I was thinking I may get a thin piece
of copper wire .and put a tiny hook on the end and see if  I can dig them out..

Along with a spray can of carby cleaner.. with the little tube  (nozzle) in it.  Our carby cleaner
here appears to be acetone (thinners) ..  is there a better chemical that may remove rubbish ?

From the snaps .. there appears to be 2 idle circuit  holes coming out in the throat of of the carb ... is that true ?  is it worth digging around in them ??

Many tx for the help.
Peter

[Spanner 1]

pdeg... with respect you have a lot to learn  ( but that's why your here, right ! )...... the slow jets are removable and must be removed !!.... Just grad 'em with a pliers ( o.k., wrap the jet with a rag if you want ) and pull/twist them out..... now jet must be clear thru' it, bottom to top and side emulsion holes must be clear....... I use an E guitar string ( smallest string on the guitar ) to open the jet. Can be hard to clear. Held up to a light at just the correct angle, light must be visible thru' it. Side holes , the same.
Then move on to the air bleeds, are they proven clear ?....... lots of good info about carb cleaning here, do a search... good luck....

[pdeg]

pdeg... with respect you have a lot to learn  ( but that's why your here, right ! )...... the slow jets are removable and must be removed !!.... Just grad 'em with a pliers ( o.k., wrap the jet with a rag if you want ) and pull/twist them out..... now jet must be clear thru' it, bottom to top and side emulsion holes must be clear....... I use an E guitar string ( smallest string on the guitar ) to open the jet. Can be hard to clear. Held up to a light at just the correct angle, light must be visible thru' it. Side holes , the same.
Then move on to the air bleeds, are they proven clear ?....... lots of good info about carb cleaning here, do a search... good luck....

yes ... but I am so afraid    How hard do I have to pull ??  Would heating up the surrounding metal help ?
How many times can I pull them before they do not stay in ?

When I shoved a can of carby cleaner up the idle mixture adjust screw hole ... a stream
came out of air bleed in the intake ...

[Terry in Australia]

G'Day Mate, don't be afraid, if you fcuk them up I'll send you another set, for cheap. Get a set of vice-grips and twist your pilot jet out (it's only pressed in, and not hard to get out or back in again) and hold it up to the light, I'm betting you won't see daylight.

You won't be able to blow out the blockage with compressed air, if you try you'll lauch it like a .22 projectile, and probably kill your cat. I bought a set of oxy welder tip cleaners and the finest one does a good job of removing the crap therein. While it's out get a can of carb cleaner and pump it thru the (now unblocked) jet, and that particular idle cirsuit.

If you need any more info, PM me. Cheers, Terry.

[pdeg]

Mmmm .. will be PMing and grovelling for a price I suspect..

Tried to pull it off using multi grips and all I succeeded in doing was marking/damaging the jet. 
Do you think I may have more luck with vice grips ?  Is really hard to get anything in there.
Bloody Honda .. what made them think that the jet will never have to come out. ?

Will have to come out one way or another.

I stick some silicon hose on it .. and sucked.  Stuck the other end on my tongue and it was still
sticking some 5 minutes later !  This baby is BLOCKED !

Certainly open to any suggestions ...  I suspect that my wishy washy approach is not helping.
Need to get stuck in ...  just need to get a good purchase.

 

[Spanner 1]

Grab it with a vise grips then, if you can't pull it out with a pliers  ... just pull it out. Plier  marks on the sides don't matter at all, no effect on operation of the jet... just pull it out....jeez !

[Terry in Australia]

Yeah, what Spanny said mate, although I suppose you could crush the pilot jet if you put too much pressure on it. Having said that, once it's out you can always replace it, so no biggie. Be as rough as you like mate, if you buggar them, I've got another set of carbs here with your name on them!  

[lucky]

DO NOT USE a welders torch cleaner on a jet!! It will enlarge the hole in the jet.
Use a #10 guitar string.

The stock idle jet is .013 thousandths or larger.

[pdeg]

That may depend on what sizes come on the cleaner ....

Anyway .. I read the guitar string idea on another post .. and as I walk past
a music store on the way home from work, I bought one. $3 natch.
Is a high E apparently    Was 11 thou.  says so on the packet...

Spent 1/2 hour digging around, thinking that there would not be a hole on the end
of the idle jet .. and suddenly it went through    Yah.
BTW.. does anybody have picture of an extracted jet ?

Stick the tubing on it and it now sucks and blows like a whales blowhole.

Does not solve the problem of the emulsion jet though..... but I am halfway there.
Extraction still an option... still scared 

Interestingly ... I stuck a bit of wire in the slow jet and the mixture adjust screw.
These match the 2 holes in the throat of the carby.  And it appears the jet feeds both.
So you get load from the jet and then adjusted with  more from the idle screw.
Picture below.

You can stick your fingers into the throat and block off these holes and your thumb
can block off the adjust screw hole...  so there is some scope there to try and blow
out the emulsion tube with carby cleaner...... trouble is that I would not be able to tell......

BTW.. does anybody have picture of an extracted jet ?

The saga continues...

[w1sa]

If the guitar string thru the idle jet does not fix the problem, it is not likely that spraying carb cleaner and air into the emulsion chamber alone is going to properly clean and clear whatever crud blockage is there...............you will (most likely) still have to extract and clean the emulsion tube.

[pdeg]

Concur....

Hence my request for picture of an extracted jet....
I was thinking that I could put a little hook on the end of the wire and try and dig them out... but want
to get a mental picture of what they look like.

Bit like dentistry

I must be driving the extraction boys mad..

[w1sa]

I think the slow jets should look like these..........

[pdeg]

Many, many tx.  That matches what it feels like on the end of the wire.
35 was the size on the side of them
Plus I can see how far it goes down.

And those holes on the side are really tiny ... I will really be struggling with a bit
of wire

And are they for sale ?

If I can some new ones....quickly .. would be just as easy to mangle the old ones
pulling them out and put in some new ones..

Tx again

Peter

[w1sa]

No problem..............like the other guys said.....some marring on the lower section from extraction does not render the jet useless....good luck

[Spanner 1]

here's a well known tune called 'Just Pull Em Out' played on the didger....
http://youtu.be/DC9w4KWEgJE

[pdeg]

Found the web site  ... .$35  inc air freight.... order already in

http://www.siriusconinc.com/pro-detail.php?pid=&product_id=1107

Cannot go wrong

[phil71]

Use a set of guitar strings and PB blaster before you bother win air. Drag them thru every passage over and over.

[lucky]

That may depend on what sizes come on the cleaner ....

Anyway .. I read the guitar string idea on another post .. and as I walk past
a music store on the way home from work, I bought one. $3 natch.
Is a high E apparently    Was 11 thou.  says so on the packet...

Spent 1/2 hour digging around, thinking that there would not be a hole on the end
of the idle jet .. and suddenly it went through    Yah.
BTW.. does anybody have picture of an extracted jet ?

Stick the tubing on it and it now sucks and blows like a whales blowhole.

Does not solve the problem of the emulsion jet though..... but I am halfway there.
Extraction still an option... still scared 

Interestingly ... I stuck a bit of wire in the slow jet and the mixture adjust screw.
These match the 2 holes in the throat of the carby.  And it appears the jet feeds both.
So you get load from the jet and then adjusted with  more from the idle screw.
Picture below.

You can stick your fingers into the throat and block off these holes and your thumb
can block off the adjust screw hole...  so there is some scope there to try and blow
out the emulsion tube with carby cleaner...... trouble is that I would not be able to tell......

BTW.. does anybody have picture of an extracted jet ?

The saga continues...

Guitar strings can be purchased for electric guitars in 9's.10,s up to 13 even.

The idle jet is .013 so your .011 wire will work.

[pdeg]

Got it...

Recommend vice grips.  You can separately adjust the force to grab the jet versus
the force to extract it...

And after all that ... the emulsion tube was clean as a whistle.

I have highlighted the actual jet position in the attached picture.  The emulsion
part in under that.

My latest theory is that when I shoved a can of carby cleaner (with the tube on)
into the idle mixture screw.... there must be a passageway going across from that
to the jet cavity (containing the emulsion tube) and then out to the  bleed hole
in the mouth of the carby.  Arrow in the picture...

Or it could have just been clean all along.

Anyway.. will press on.
Tx for the  advice and moral support guys.
Peter

[pdeg]

Just an update .... had to put go away for a week or so....

Came back last night, and did a static balance on the carbs using
a 1.5 mm drill bit. Another great idea I gleaned from this forum.

Now I have the correct float height settings .. mine came up about 3-4 mm or so
Mmmm ... so that  will "fattened" it up a bit....

Put them back on the bike.  Hint... I wiped a bit of dishwashing liquid around
the inside of the spacers, and the carbs slipped right in.. smooth as.

Kicked it over .. and it is a new bike... smooth and running on all 4.
Pulls like a train from idle.
Top stuff...  Using the old spit on finger onto the exhaust outlets.. .seems #1 is
still a bit lazy....still.

Now to go for a run and get that howl out of the 4 into 1....

Still no accelerator pump.. will start a new thread.
And need to balance the carbs ..  saw a great thread on a home made one
using a pet bottle...

Tx for the help guys.