Acceleration anomoly?

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redglbx
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Re: Acceleration anomoly?

#46

Post by redglbx »

Mick, Usually if you’re accelerating like your 5000-5500rpm experience and slightly back off and the acceleration increases is a sign of it being lean ,,,,, BUT, with the vacuum slides it is really hard to say that with any confidence. On our GL’s when you back the throttle off like that, it should be lowering the slides which will reduce the airflow ( richening the fuel mix) but also lowering the needles back into the secondary mains (leaning the fuel mix) ,,, so which is it ?

Very hard to say without running it with a Lambda sensor (air/fuel ratio gauge) which it is….. My advice would be to pull the carbs out and check to see that the jetting actually is the correct ‘Keihin jetting and that it hasn’t been modified or been replaced with poor Chinese eBay jetting. Also a good time to check that the air jets under the cap haven’t been reversed. I don’t have that info available right now but is easily checked in your factory service manual. OE Keihin jets have their trademark “star” engraved/stamped into them and should be visible on the jets.

And as has been said above these just aren’t torque monsters, they tend to be a little bit slower reving because of their heavier crank weights, just the nature of the beast. But with careful carb setup and sync they really aren’t that bad either. But you need to know what you actually have and not assume that someone else did them correctly.

Also, I prefer to set the ignition timing dynamically using a degree wheel to verify the actual ignition timing of the pairs vs static timing which tends to make the ignition timing 6-8 degrees off. My .02
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Re: Acceleration anomoly?

#47

Post by Whiskerfish »

redglbx wrote: Thu Jan 12, 2023 8:51 amSNIP
Also a good time to check that the air jets under the cap haven’t been reversed. I don’t have that info available right now but is easily checked in your factory service manual. OE Keihin jets have their trademark “star” engraved/stamped into them and should be visible on the jets.SNIP
For the Air jets I just remember that the big one goes to the outboard side of the carb.
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Re: Acceleration anomoly?

#48

Post by Bloodhound »

I'd imagine most have read about the split timing that , you can't get the timing correct and have to split the difference :IDTS: , I can tell you this is caused by a stamped out points plate it is inaccurate if you muck around and slot the points and plate on the right side point, you can achieve perfect timing I think the left set of points is fixed to point plate and adv/retard by rotating plate . Still not easy but achieved it on mine .
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Re: Acceleration anomoly?

#49

Post by dontwantapickle »

We all know that the common practice is to synch the carbs at idle rpms (900-1000) and call it good.
I have stumbled on an alternative method.

While tuning on my racing bike, I had the carbs set up and synched perfectly (at idle).
With my vacuum gauges still hooked up, I took the rpms up to 3000 (full ignition advance)
and noticed that all 4 carbs were pretty far off.
Since my goal was for the best performance at high speed, I Of course re-synched the carbs at 3000 rpms.

I am 100% confident that doing this was beneficial.

So much so that the last 2 racks of carburetors that I have went through have been synched the same way.
There are no issues doing this, the bikes all start easily and are optimally tuned for the rpm that they run.

With all of the old Goldwing mechanics here, I am surprised to never see this method discussed.
I can't believe that I am the first to discover this.

Another note: I do most tuning with a wideband AFR lambda sensor and I have found that the pilot screw
settings have no effect on the afr at higher rpms.

***DISCLAIMER: I ain't no "guru" or "approved" carburetor guy; so take any advice I give with a grain of salt, YMMV. ***
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Re: Acceleration anomoly?

#50

Post by gltriker »

Mickster wrote: Wed Jan 11, 2023 11:27 am Yes, I have taken it out and zoomed around some rural highways.


With wide open throttle and getting the bike up to about 5000/5500 rpm in 5th gear and then backing off to about 3/4 throttle the bike actually speeds up. As a side note, about 5500 rpm is when it really kicks in like a nitro boost.

Mickster! What is your bike's indicated, or better yet, actual ground speed at 5,000rpm, in 5th gear?
I'd guess around 90mph if your bike's stock tachometer display is accurate at a true 5,000rpm engine speed.

Why should I want to know. ??? I've never felt an opportunity materialized to present my need-to-know inquiry in the Forum until this particular Topic came along. tumb2

Around 5 years ago I was curious how many mph trike's speedometer ground speed readings were, "off". The gauge display error deviation, I reckon.
According to a GPS app on my cell phone, riding steadily at 80 GPS calculated mph , my trike's speedometer display was approximately 3-5mph "fast."
If I remember somewhat correctly, trike's tachometer reading was approximately 5,100 rpm at the GPS measured 80mph.

WAIT.... WHAT! :shock: YOU SAY

trike's GM rear axle ratio is 3.73 to 1, and worn, still legal tread depth 215-60-16 rear tires O.D. was approximately 26 inches; within a 1/4 inch O.D. of a stock GL1000 rear tire spec. . the STOCK configuration GL1000 final drive ratio is 3.40 to 1. ~10% increase of mechanical advantage, but notably reduced ground speed results at identical engine speed comparisons.
~90mph was the highest speed it and I ever travelled at. Very smooth and flat road. Cautiously. Once. Exhilarating. Trike never misbehaved during the mile or so we travelled at 90, then I slowed down to 60-ish. Good 'nuff
anyways...
Trike's 1975 engine, under load, comes alive at/above 4,000rpm, GPS 60mph in 5th gear; generally speaking, most other 1975-1977 GL1000 owners echo the same observation with a well tuned and correctly running stock engine, too.

I have zero, in person, dynamic experience with any other person's GL1000.
Never able to ride a 2 wheeled motorized vehicle after my 18th birthday. Although trike runs well, I will never know how it compares to an unmolested (not triked!) 1975 GL1000.
Even though I haven't sat on trike going on 3 years, I appreciate, even more now, the challenges and rewards of participating in this Club and contributing what I can.

Keep On Keepin' On, Mickster ! action1




Respectfully, no, I don't want to hear about changing carburetor jets and dynamometer runs now ;)
Last edited by gltriker on Fri Jan 13, 2023 7:03 am, edited 2 times in total.
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Re: Acceleration anomoly?

#51

Post by gltriker »

dontwantapickle wrote: Fri Jan 13, 2023 2:28 am We all know that the common practice is to synch the carbs at idle rpms (900-1000) and call it good.
I have stumbled on an alternative method.

While tuning on my racing bike, I had the carbs set up and synched perfectly (at idle).
With my vacuum gauges still hooked up, I took the rpms up to 3000 (full ignition advance)
and noticed that all 4 carbs were pretty far off. Now, I need to know more Respectfully inquiring, how many inches of vacuum were they displaying, below 1000rpm? 8 or 9ish
Since my goal was for the best performance at high speed, I Of course re-synched the carbs at 3000 rpms. How many inches of vacuum were the re-synched gauges displaying at 3000rpm?

I am 100% confident that doing this was beneficial. I agree tumb2

So much so that the last 2 racks of carburetors that I have went through have been synched the same way. How many turns out from seated do you set the pilot mixture screws at?
There are no issues doing this, the bikes all start easily and are optimally tuned for the rpm that they run.

With all of the old Goldwing mechanics here, I am surprised to never see this method discussed.
I can't believe that I am the first to discover this.

Another note: I do most tuning with a wideband AFR lambda sensor and I have found that the pilot screw
settings have no effect on the afr at higher rpms. Agreed. The #35 slow fuel jet controls the total volume discharged

***DISCLAIMER: I ain't no "guru" or "approved" carburetor guy; so take any advice I give with a grain of salt, YMMV. ***
Very interesting post, dontwantapickle tumb2

I apologize for marking it up, but I don't know what other strategy I might have used.
Last edited by gltriker on Fri Jan 13, 2023 8:28 am, edited 1 time in total.
Cliff (74yrs ;) )

Keep your eyes and ears open and you'll learn something new, everyday. tumb2

New users please visit our "Shop Talk" for common tips and help: <---jdvorchak
http://www.ngwclub.com/forum/page/ST
^^^^^^^click up here^^^^^ :oldies

RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi tumb2
"Can't see the paint when your looking thru the handlebars..........." -Oldewing ;)
"I'd rather Ride than Shine" -RAT tumb2 Me Too!!

Cliff

'75 GL1000 home built trike; http://www.ngwclub.com/forum/viewtopic.php?f=30&t=39996
October,2017 BOTM :shock: https://nakedgoldwingsclub.com/forum/page/Welcome

previous rides:
1953 H-D Servi-car, naked, 1969-1978 (serial#53G1559 committed to memory!)
1980 CB900 Custom (triked) 1997-2003 .... R.I.P.
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Re: Acceleration anomoly?

#52

Post by Whiskerfish »

dontwantapickle wrote: Fri Jan 13, 2023 2:28 amSnip

With all of the old Goldwing mechanics here, I am surprised to never see this method discussed.
I can't believe that I am the first to discover this.
SNIP
For a very long time in the helicopter community there has been discussion regarding tracking main rotor blades at ground flat pitch verses under a load in flight. Some Blade combinations were such that you could adjust them to within limits on the ground or in flight, but not both. Same concept I believe.

About adjusting synch at advance rpm, I have done this a couple times. Yes there generally is a fair amount of disparity if you set them at idle and then check higher. But it seems like once adjusted at higher rpm the split at idle was less than the other way around. For daily riders I did not find the performance difference at all signifcant. I think for many the smoother engine at idle is more concerning.
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and a whole garage full of possibilities!!

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Re: Acceleration anomoly?

#53

Post by pidjones »

dontwantapickle wrote: Fri Jan 13, 2023 2:28 am ***DISCLAIMER: I ain't no "guru" or "approved" carburetor guy; so take any advice I give with a grain of salt, YMMV. ***
Hmmm. Don't you hold a land speed record on your GL1000? For me, that qualifies as Guru for speed-tuning at least.
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Re: Acceleration anomoly?

#54

Post by Whiskerfish »

pidjones wrote: Fri Jan 13, 2023 8:20 am
dontwantapickle wrote: Fri Jan 13, 2023 2:28 am ***DISCLAIMER: I ain't no "guru" or "approved" carburetor guy; so take any advice I give with a grain of salt, YMMV. ***
Hmmm. Don't you hold a land speed record on your GL1000? For me, that qualifies as Guru for speed-tuning at least.
action1 action1 action1 action1 action1 action1 action1 action1 action1
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"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
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and a whole garage full of possibilities!!

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Re: Acceleration anomoly?

#55

Post by gltriker »

:)
Last edited by gltriker on Sat Jan 14, 2023 1:05 am, edited 4 times in total.
Cliff (74yrs ;) )

Keep your eyes and ears open and you'll learn something new, everyday. tumb2

New users please visit our "Shop Talk" for common tips and help: <---jdvorchak
http://www.ngwclub.com/forum/page/ST
^^^^^^^click up here^^^^^ :oldies

RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi tumb2
"Can't see the paint when your looking thru the handlebars..........." -Oldewing ;)
"I'd rather Ride than Shine" -RAT tumb2 Me Too!!

Cliff

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October,2017 BOTM :shock: https://nakedgoldwingsclub.com/forum/page/Welcome

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Re: Acceleration anomoly?

#56

Post by Sidecar Bob »

I feel the acceleration in the seat of my pants on the 'Wing. That's good enough for me.
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Re: Acceleration anomoly?

#57

Post by dontwantapickle »

gltriker wrote: Fri Jan 13, 2023 6:50 am
dontwantapickle wrote: Fri Jan 13, 2023 2:28 am
While tuning on my racing bike, I had the carbs set up and synched perfectly (at idle).
With my vacuum gauges still hooked up, I took the rpms up to 3000 (full ignition advance)
and noticed that all 4 carbs were pretty far off. Now, I need to know more Respectfully inquiring, how many inches of vacuum were they displaying, below 1000rpm? 8 or 9ish
Since my goal was for the best performance at high speed, I Of course re-synched the carbs at 3000 rpms. How many inches of vacuum were the re-synched gauges displaying at 3000rpm?

How many turns out from seated do you set the pilot mixture screws at?
gltriker,
Best answers I can give:
When using my gauges, synching at idle always ending up between 5 - 8 inches of vacuum.
After synching at full advance, the numbers are pretty much the same.

Since there is a bit of variability between different racks of carbs and between sets of gauges,
I don't put much emphasis on the actual numbers but more on getting the same number on all 4 carburetors.

As Whiskerfish stated:
when syching the carbs at idle and then increasing the rpm and synching again, after the rpms are dropped back
to idle, the synch isn't as far off as it was.
For example;
If the carbs were synched perfectly at idle and all drawing exactly 6 inches of vacuum,
When the rpms are increased to 3000, there could be as much as a 3 inch difference between individual carbs.
When the carburetors are synched perfectly at 3000 rpm and then the engine speed returned to idle,
There may be only 1 inch variation between carburetors.

I don't have an answer for this but do find it interesting.

I think that the differences in vacuum at different engine speeds could be due to a couple of different things.
.maybe slightly sticker slides as they are raised higher in the bore.
.maybe vacuum leaks.
.maybe a slightly different spring rate between carb slides.

Maybe a combination of all of these add up to make a significant difference.
Like someone posted earlier... everything affects everything.


I follow Mikes advice and set all pilots to 3 turns out. It works well for me.
Last edited by dontwantapickle on Sun Jan 15, 2023 11:08 pm, edited 3 times in total.
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Re: Acceleration anomoly?

#58

Post by dontwantapickle »

Long ago, when I first discovered the magic of carburetor synchronization
while working on the old air cooled twins (triumph, norton, etc),
being young and poor, I used the drill bit under the butterfly method.

When I graduated to the next step and started using the Mercury Carb Stix,
one of the first things that I remember doing was revving the motor and sucking all of the mercery into the engine.
(Vowing to learn from my mistake, that is probably when I fell into the routine of just synching at idle.)

Now that I'm using actual vacuum gauges, I have no reservations revving the engines with the gauges attached.

Honestly,
Whether any of this has anything much to do with decreasing the flat spot on the Goldwings,
I'd guess probably not too much.
But I spend much more time riding above 3000 rpm than I do sitting at idle so
it just makes sense to me to try to make the bike run best where I use it.

And again... everything affects everything.
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Re: Acceleration anomoly?

#59

Post by Whiskerfish »

dontwantapickle wrote: Sun Jan 15, 2023 5:32 pm SNIP
And again... everything affects everything.
You might find this interesting https://ngwclub.com/forum/viewtopic.php ... um#p160748
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!

Psst. oh and by the way CHANGE YOUR BELTS!!!!
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Re: Acceleration anomoly?

#60

Post by GW Hobo »

dontwantapickle wrote: Fri Jan 13, 2023 2:28 am We all know that the common practice is to synch the carbs at idle rpms (900-1000) and call it good.
I have stumbled on an alternative method.

While tuning on my racing bike, I had the carbs set up and synched perfectly (at idle).
With my vacuum gauges still hooked up, I took the rpms up to 3000 (full ignition advance)
and noticed that all 4 carbs were pretty far off.
Since my goal was for the best performance at high speed, I Of course re-synched the carbs at 3000 rpms.

I am 100% confident that doing this was beneficial.

So much so that the last 2 racks of carburetors that I have went through have been synched the same way.
There are no issues doing this, the bikes all start easily and are optimally tuned for the rpm that they run.

With all of the old Goldwing mechanics here, I am surprised to never see this method discussed.
I can't believe that I am the first to discover this.

Another note: I do most tuning with a wideband AFR lambda sensor and I have found that the pilot screw
settings have no effect on the afr at higher rpms.

***DISCLAIMER: I ain't no "guru" or "approved" carburetor guy; so take any advice I give with a grain of salt, YMMV. ***
Interesting take - thanks for this. I may try this for my top speed problem.
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