Carb Floats - twisted?

[dan filipi]

pistolpete » 12 minutes ago[/url]":twuq9ccs]

dan filipi » Tue Feb 10, 2015 9:37 am[/url]":twuq9ccs]
Gerry, I heard the 'spit back' (as I call it) twice in that video.
That spit back often results in a hard kick back against engine rotation in my experiences.
What do you suppose causes that? The single carb mod I have on has never done that, not once ever even though the stock rack did it bad on the same engine so I believe the cause not to be ignition or timing related.
There isn't much talk about it on the forums though I know lots of bike's do it.

Dan,
The carbs are over 30 years old and the jetting can be worn causing a rich fuel mixture at cold starts. I have noticed that the "chuffing" is caused by this issue and it will spit back but if the air filter is in place it is much less. I do not believe that it will cause harm to the engine.

Pistol

Ok let's say it is caused by over rich from worn jets.
Why is this not addressed in 'rebuilding' them?
Common belief on the forums is the jets don't wear so I'm confused now.
I'm not trying to put anyone on the spot but that spitting is crazy and not right. Seems to me to be a true 'rebuild' to 100% performance then jets should be replaced?

 

[mcgovern61]

FYI:

Backfiring through the carb (spitting or coughing) usually occurs in the morning when a carb's air/fuel mixture is a bit too lean. This usually goes away once the engine warms-up.

 

[AApple]

Mine will do that if it hasn't been started in a few days. When I ride everyday, it never occurs, regardless of ambient temps. I have to assume it is because at least one of the carb's fuel level is low, or something like that. Once it runs for a couple of minutes, it will stop, and idle just fine. I agree, it sure sounds like something would be getting hammered pretty good when it happens....
Anyway, glad Gerry's runs so sweeeeet! :good:

 

[dan filipi]

Ok so the spitting goes away once it's warmed up but that isn't acceptable to me.
Why specifically does it do it and what is the fix.
I'm sure when these bikes were new, they didn't spit during warm up at the dealer.

 

[joedrum]

mcgovern61 » Tue Feb 10, 2015 1:53 pm[/url]":8xxo395k]
FYI:

Backfiring through the carb (spitting or coughing) usually occurs in the morning when a carb's air/fuel mixture is a bit too lean. This usually goes away once the engine warms-up.

along with the choke on oldwings is throttle bump ...and is actually what keeps the motor going when cold than choke dose ... it fools people into thinking only reason it wont run is it lean and cold ...yes it is cold but not lean is the the same cold as hot mostly... its the temp that changes things ... i have found that the biggest problem at idle and just off idle is first air ....

the sync setting screws do one thing adjust the throttle plate for air... not to make the needles of a gauge set the same but to run a oldwing ... in fact i never use them ..there no reason ... there easy to bench set ..pass that it me ..i dont need no help from gauges.....once mix crew base setting are done ...it time to start and tune....it well probably run ok but will have spit and pops going on in places .....go right there with throttle lock if you have it ....now is time to adjust air at each carb ....and like mix screw adjusting one then rpm ways kept at bad spot with throttle lock you can get air the best you can at the worse spot .....always know the one carb cant be adjusted it kind of rules ...say you you got to run good there now no spits or pops ...try other spots ... for me once this is done it seems your there as it will run super ....but from here you can drop back to idle now ..and you will see more response from mix screws as the air has been adjusted ....whew all said to get to this point ...without air adjusted to the motor not gauges ..the mix screw setting dosnt stand a chance and is impossible to read feel whatever...why most just set it....but it will now and you can go around the carbs and get it done even better adjust idle but you most like be very good already ....

i will also have say stock racks are very complex vacume operated throttles that is a spyder web of syncing of so many factors and all the blab above means nothing if the rack is not up to par in all ways ...stock racks can down from the slightest of things ...there is no way this tech should ever be consider performance like in any way ....there are many myths out there about there capabilities ......there is a lot of preventive tech here going on to keep rider input under control ..it comes at a huge price in complicity and slowness .....myths about single carbs cant perform ...i have found without a doubt in my mind 4 slow carb dont beat one fast acting rider input control two stage carb that covers entire rpm zone of motor .... one day in like to try and mod a 75 stock rack to cable operated ...that might be the do all mod fuel induction ... :thanks:

 

[mcgovern61]

dan filipi » Tue Feb 10, 2015 2:03 pm[/url]":2w1lw5pc]
Ok so the spitting goes away once it's warmed up but that isn't acceptable to me.
Why specifically does it do it and what is the fix.
I'm sure when these bikes were new, they didn't spit during warm up at the dealer.

Well, I cannot speak for the GW when new, but I did have a Suzuki GN400 when it was new and if I turned off the choke too soon when cold, that engine would pop and often stall (it was only a single cylinder 400).

I have to be clear that when I follow the choke instructions in the OEM manual and allow the engine to warm it does not pop at all!

I will have to find where I read about the popping being related to the gas not being fully atomized when the intakes and engine are cold. If the choke is opened too early in a cold engine, I think it creates a lean condition?

 

[pistolpete]

Dan and all,
Nearly 100% of the time our test engine starts right up without the chuffing when we rebuild a set.
But always the set is made to run correctly before it ships.
Gerry said that it chuffed some but his was a start slightly different from the book.

Worn jets can be replaced for the most part but where should we make a decision to replace them? The customer wants his set to run the engine well and I believe that we do that for nearly 100% of our customers. The chuffing has never been an issue with our builds.
We have also seen needle jets that are severely worn and we encourage our customers to replace them if they are too bad. Some will and some will not.

Pistol

 

[dan filipi]

Just trying to understand.....

So if the engine is cold and spits with choke opened, that would be a lean condition. Would it not?
How then would worn jets come into play? A worn jet would let too much gas pass so how could this be causing a lean condition?
Gerry's last post and pistolpete's last post seem to contradict one another.

 

[mcgovern61]

Here is that article I read some time ago. Great explanations!

https://www.hemmings.com/mus/stories/200 ... tips2.html

 

[joedrum]

cv carbs introduce lean condition instantly off idle has nothing to do with jetting it has to do with rider has input of one thing throttle plate air ...but not gas charge ...so it goes lean spit and pops till the vacume lifts the slide and charge starts ...it a total air problem ... all manufector seemed to jump on the cv carb thing it wasnt just honda ... it is simply not simple set up and very complex to dial in to work good through out rpm zone ... at low rpm is the worse ..oldwings all dressed are heavy loads and brings cv carb faults to surface quick ....getting to the root of the problem with cv carbs is not discount its trying to solve things ...im with dan worn jets and other stuff like that has no part in the spit and pop problem that can be so huge ....it is an over done tech problem to the max...... solving it so wings wont hammer up steep gravel drives like mine would be huge.....

 

[dan filipi]

mcgovern61 » Today, 1:24 pm[/url]":2fw0duzj]
Here is that article I read some time ago. Great explanations!

https://www.hemmings.com/mus/stories/200 ... tips2.html

Thanks for the link Gerry, it was a good long read but I do understand the why and operation behind a choke system and why it's needed.
This doesn't explain why an oldwing spits back, often counter rotation and not only when cold. Mine would do it sometimes after it's been warmed up too, certainly not as often but it did do it.

In my old days running carbs on cars, I would get backfire into the carb when cold if the choke wasn't set right but I can't recall ever having one fire back on itself against engine rotation like an oldwing does.

 

[pistolpete]

joedrum » Tue Feb 10, 2015 4:42 pm[/url]":3aa355o5]
cv carbs introduce lean condition instantly off idle has nothing to do with jetting it has to do with rider has input of one thing throttle plate air ...but not gas charge ...so it goes lean spit and pops till the vacume lifts the slide and charge starts ...it a total air problem ... all manufector seemed to jump on the cv carb thing it wasnt just honda ... it is simply not simple set up and very complex to dial in to work good through out rpm zone ... at low rpm is the worse ..oldwings all dressed are heavy loads and brings cv carb faults to surface quick ....getting to the root of the problem with cv carbs is not discount its trying to solve things ...im with dan worn jets and other stuff like that has no part in the spit and pop problem that can be so huge ....it is an over done tech problem to the max...... solving it so wings wont hammer up steep gravel drives like mine would be huge.....

I dissagree.
Perhaps to some the CV carb is relatively complex but I see it a as the interim next step after the lift slide set up and before CFI. The GL1100 has several things going for it over the GL1000 carbs. Among them is the accelerator pump, considerably smaller throats and much better fitting and near vertical throttle plates. All of these modifications have made them a more effective carb set up.

Opening the throttle plate will instantly inject aerated fuel into the throat and uncovers the transfer ports for additional air enriched fuel to enter the engine. These conditions allow the engine rpm to increase as well as to allow a further pressure drop in the carburetor.
The slide is offset by this pressure drop and lifts to open the jet needle. It is all accomplished in a matter of milliseconds.

I am not as eloquent as some but I am pretty sure this is what happens and especially after more than 1000 rebuilds.

I did however mis-read Gerry's post and had the "spit" mixed up with a worn jet (or possible PO increase) in size leading to a rich condition and a chuffing sound when idling.

One more small side note: I have observed needle jets worn so badly that even at idle the engine is overwhelmed by this rich condition and will smoke severely. All jets are "gauged" for proper size during the build process in our shop.

Pistol

 

[dan filipi]

Great discussion and going very well so far.

Thanks for all the input guys!

 

[pistolpete]

dan filipi » Tue Feb 10, 2015 6:00 pm[/url]":22lhnm18]

mcgovern61 » Today, 1:24 pm[/url]":22lhnm18]
Here is that article I read some time ago. Great explanations!

https://www.hemmings.com/mus/stories/200 ... tips2.html

Thanks for the link Gerry, it was a good long read but I do understand the why and operation behind a choke system and why it's needed.
This doesn't explain why an oldwing spits back, often counter rotation and not only when cold. Mine would do it sometimes after it's been warmed up too, certainly not as often but it did do it.

In my old days running carbs on cars, I would get backfire into the carb when cold if the choke wasn't set right but I can't recall ever having one fire back on itself against engine rotation like an oldwing does.

Dan,

Please explain for me what are the physics involved with your GW attempting to counter-rotate? I have heard stories but never had it laid out for me.
Thanx

Pistol

 

[dan filipi]

Well what will happen when it spits, the engine will slow down just as if you had a cross firing plug wire on a car or a leaking intake valve.
Hard to explain but there is a definite kick back against the engine rotation.
I think I have a video on youtube but it sounds just like what I heard in Gerry's video.

 

[pistolpete]

dan filipi » Tue Feb 10, 2015 7:32 pm[/url]":2tcnsdox]
Well what will happen when it spits, the engine will slow down just as if you had a cross firing plug wire on a car or a leaking intake valve.
Hard to explain but there is a definite kick back against the engine rotation.
I think I have a video on youtube but it sounds just like what I heard in Gerry's video.

Cool, but what if the carb was taken out of the equation? Wouldn't this action require some sort of detenation in order for a counter rotating impact to occur?

Thanks
Pistol

 

[Ansimp]

That counter rotation that you have described Dan I have only experienced when the battery or starter motor are faulty and not allowing full rotational speed.
And how could I forget ignition timing :doh:

 

[dan filipi]

pistolpete » 10 minutes ago[/url]":wqj1gfk5]

dan filipi » Tue Feb 10, 2015 7:32 pm[/url]":wqj1gfk5]
Well what will happen when it spits, the engine will slow down just as if you had a cross firing plug wire on a car or a leaking intake valve.
Hard to explain but there is a definite kick back against the engine rotation.
I think I have a video on youtube but it sounds just like what I heard in Gerry's video.

Cool, but what if the carb was taken out of the equation? Wouldn't this action require some sort of detenation in order for a counter rotating impact to occur?

Thanks
Pistol

Usually yes but I have gone through every other component on the engine, ignition and head/valves replacements etc with little to no change.

 

[pistolpete]

Ansimp » Tue Feb 10, 2015 7:51 pm[/url]":2f07rcqj]
That counter rotation that you have described Dan I have only experienced when the battery or starter motor are faulty and not allowing full rotational speed.

It would also seem that a detention could occur in the case of "dieseling" or ignition before tdc.

 

[joedrum]

well pete i agree 1100 carbs are better than 1000 but .... but it still a huge problem just off idle ... smaller throats and stuff help as it brings more vacume to slides along with quicker gas plus accelerator pump... but 1100 carbs fall flat at higher rpm and the oldwing motor is capable of more ....when i say there complicated its in comparison to a cable ,,, thats what all this cv stuff replaced ...in this view ..its very complicated and hard to match efficiency of of simple cable in no way could it ever beat a cable lift to provide gas charge as quick ..to me its plain and simple the problem ... why these carb are so hard to dial in and so on ... its also why they will never be a performance type carb ever against something of more performance design ....

my work with the 1200 modded motor ..c5 ignition...weber carb has taught me what truly these motors are capable of... it aint all c5 either cause i had the stock carbs first with the c5 .. the 1200 modded motor took the stock rack cv system way beyond it design ... and complete redo in slide springs vacume holes and stuff that to hard to mod ... i went weber from there its been a total lesson in power the more i get the carb modded to oldwing motor the more power i get ... and this is all way above what stock carbs are capable of ... all this points to the cv air system as why stock carbs cant get it done at low rpm ...my bike has a ton of power off idle and dont loose it in the rpm zone anywhere ....