Pilot Screw Adjustment: DigiSync Tachometer Feature

[DK]

Maybe the better name for this topic would be "Using The DigiSync".

Anyway, does anyone know whether or not the tachometer feature of the version 2 DigiSync accurate enough to use for setting the pilot screw?

As I interpret the Bon S instruction sheet, it is accurate so long as only one carb is connected  to each vacuum port, thus making Valk readings accurate.  However, the question remains as to whether it is accurate enough.

Dan

[Patrick]

I Don't know what you're talking about. That said, the sync is performed thru vacuum readings.
What you are talking about is apparently some new fangled thing. Some one must be trying to reinvent the wheel, which may be OK. But, I still adjust them according to vacuum readings.



Oooopps, As Roseann Roseanna Danna used to say, never mind. Boy, I had a huge brain fart. I was thinking carburetor sync and not pilot adjustment. I hope I didn't screw anyone up.
Any new good way of setting the pilots I think is a good thing because Hondas way isn't worth a crap.

[BonS]

Maybe the better name for this topic would be "Using The DigiSync".

Anyway, does anyone know whether or not the tachometer feature of the version 2 DigiSync accurate enough to use for setting the pilot screw?

As I interpret the Bon S instruction sheet, it is accurate so long as only one carb is connected  to each vacuum port, thus making Valk readings accurate.  However, the question remains as to whether it is accurate enough.

Dan

I have a customer in Canada that routinely rebuilds carbs and syncs them for his customers. He, too, is using the Dig Sync tach function for setting mixture screws. I put in quite a bit of effort in perfecting the tach function so it would be better than a full-range tach at idle speeds. He is going to get back to me on how the Digi Sync works for him.

The one-port-to-one-carb relationship is important for the rpm numbers to be interpreted 1:1. Thus 950 rpm reads "950". If two cylinders are pumping on one carb port then the "950" will display a different number. That said, the readout is stable and useable for detecting small changes in rpm while adjusting the pilot screws.

[DK]

Thanks Bon, I went ahead & set them per your tach read outs and all seems well. Very well.

My carbs were badly out of sync and the pilot screws were 1/2 to 3/4 turns more open as compared to the final settings achieved using the DigiSync. Haven't ridden enough to compare before & after mileage, but the exhaust no longer has the overrich smell. The improvement is remarkable. I'm going to leave my .38's installed for the Smokies trip.

Thank you for making the DigiSync available at such a reasonable price for such a quality piece of equipment that needs to be available to anyone riding a Valk. I wish I had one years ago when I was trying to sync my Austin-Healey 3000 with three SU's.

Patrick, see section 5-22 of the Valkyrie Shop Manual.

Dan

[Pappy!]

I set your Canada guy up with your information after letting him know about your set-up. I take it he has it and is already using it?
He does do a Hell of a lot of Magna and Vmax carbs. He was happy to see what you are building and even more pleased that you would build and supply him with one.

[BonS]

Thanks Bon, I went ahead & set them per your tach read outs and all seems well. Very well.

My carbs were badly out of sync and the pilot screws were 1/2 to 3/4 turns more open as compared to the final settings achieved using the DigiSync. Haven't ridden enough to compare before & after mileage, but the exhaust no longer has the overrich smell. The improvement is remarkable. I'm going to leave my .38's installed for the Smokies trip.

Thank you for making the DigiSync available at such a reasonable price for such a quality piece of equipment that needs to be available to anyone riding a Valk. I wish I had one years ago when I was trying to sync my Austin-Healey 3000 with three SU's.

Patrick, see section 5-22 of the Valkyrie Shop Manual.

Dan

That's great to hear DK. This is why I do it! I too remember the Uni-Syn days and the Carb-Stix, and the Carb Tune and . . .

I'm working with a fellow on this beast. It has extremely aggressive cams and it going to require some extra work to tame. We're having fun now!

[BonS]

I set your Canada guy up with your information after letting him know about your set-up. I take it he has it and is already using it?
He does do a Hell of a lot of Magna and Vmax carbs. He was happy to see what you are building and even more pleased that you would build and supply him with one.

I haven't heard from him yet. I don't know if that's good or bad!?

[Pappy!]

How bout I check for ya?

[BonS]

How bout I check for ya?

Please and thank you!

[BonS]

I want to do this adjustment and DK you've nailed it. The following is an excerpt from the service manual (5-22). I want to be sure that I do this right! Please correct my shorthand summary below wherever I've strayed:

In step 1,2,3 and 4 we adjust the mixture screws to factory settings, warm up the engine and set the idle speed to 900 rpm.

In step 5 we're enriching all carbs by 1/2 turn out from their nominal starting point.

Can you elaborate on step 6? I take it to mean that all carburetors are enriched by 1/2 turn and then the increase of rpm is noted. If there is any gain then ALL carbs are again enriched by 1/2, the rpm checked for increase and repeated until no rpm increase is noted.

Idle is again set to 900 rpm in step 7.

In steps 8 & 9, and starting with carburetor #1, each mixture screw is turned in until a 50 rpm drop is noted and then it is backed out by 1 whole turn. After backing the mixture screw by 1 turn this is its final setting and we move on to the next carburetor.

For extended high altitude operation repeat this procedure at or near the desired elevation.

Comments? Questions? Concerns?

INITIAL OPENING:
         '97 GL1500C/CT:
           Except California type : 1-3/4 turns out
           California type           : 2 turns out

         GL1500CF, After '97 GL15OOC/CT:
            Except California type : 2-1/4 turns out
            California type           : 2-3/8 turns out

1.  Turn the pilot screw clockwise until it seats lightly, then
     back it out to the specification given. This is an initial setting
     prior to the final pilot screw adjustment.

2.  Warm up the engine to operating temperature. Stop and
     go driving for 10 minutes is sufficient.

3.  Stop the engine and connect a tachometer according to
     the tachometer manufacturer's instructions ( A Digi Sync will do).

4.  Start the engine and adjust the idle speed with the throttle
     stop screw. IDLE SPEED: 900 +/- 100 rpm.

5.  Turn each pilot screw 1/2 turn out from the initial setting.

6.  If the engine speed increases by 50 rpm or more, turn each
     pilot screw out by successive in 1/2 turn increments until
     engine speed does not increase.

7.  Adjust the idle speed with the throttle stop screw.

8.  Turn the No.1 carburetor #1 pilot screw in until the engine
     speed drops by 50 rpm.

9.  Turn the #1 carburetor pilot screw out to the final opening
     from the position obtained in step 8 by 1 complete turn out.

     FINAL OPENING: 1 turn out

10. Adjust the idle speed with the throttle stop screw.

11. Perform steps 8, 9 and 10 for the No. 2, 3, 4, 5 and 6
     carburetor pilot screws.

[westnek]

Maybe the better name for this topic would be "Using The DigiSync".

Anyway, does anyone know whether or not the tachometer feature of the version 2 DigiSync accurate enough to use for setting the pilot screw?

As I interpret the Bon S instruction sheet, it is accurate so long as only one carb is connected  to each vacuum port, thus making Valk readings accurate.  However, the question remains as to whether it is accurate enough.

Dan
hi dan west here.is this write up about mixture screws on carbs? and are we talking of doing this with a tach and no vacuum instruments- our old carbs on cars we turned in till rpm.s drop then back out screw until rpms stay steady ,,repeat step ,stopping at rpm which read the highest ..can it be done on valk carbs this way?''starting at 2 1/2  turns  out from bottoming  screw ,then make a final adjustment  to each carb==maybe I'm on the wrong highway   but old farts like me take the wrong road every so often oh ! and what size D shaped adjuster is used   thanks    dan   

[BonS]

Maybe the better name for this topic would be "Using The DigiSync".

Anyway, does anyone know whether or not the tachometer feature of the version 2 DigiSync accurate enough to use for setting the pilot screw?

As I interpret the Bon S instruction sheet, it is accurate so long as only one carb is connected  to each vacuum port, thus making Valk readings accurate.  However, the question remains as to whether it is accurate enough.

Dan

hi dan west here.is this write up about mixture screws on carbs? and are we talking of doing this with a tach and no vacuum instruments- our old carbs on cars we turned in till rpm.s drop then back out screw until rpms stay steady ,,repeat step ,stopping at rpm which read the highest ..can it be done on valk carbs this way?''starting at 2 1/2  turns  out from bottoming  screw ,then make a final adjustment  to each carb==maybe I'm on the wrong highway   but old farts like me take the wrong road every so often oh ! and what size D shaped adjuster is used   thanks    dan   

Yup, mixture screws on the carbs. We talking about using the high resolution RPM function on the Digi Sync to set them. The fact that the Digi Sync uses vacuum to derive the rpm is the only reason that vacuum is mentioned. For me, I haven't done the factory method for setting the mixture screws so I'm trying to make sure that I fully understand their recommended method. Are there other ways such as you describe, quite likely. But for me I'd like to do the factory method and then perhaps consider other ways.

The D adjuster I have is like this one. I added a knob from Sears to it to make it easy to turn.
http://www.amazon.com/Motion-Pro-Replacement-D-Shaped-08-0242/dp/B003CMWC4U/ref=sr_1_6?ie=UTF8&qid=1431477198&sr=8-6&keywords=carburetor+D+tool

[BINOVC]

At step 6 (if RPM increases by 50 or more), do you return the RPM back to 900 at each 1/2 turn out?  Or just keep going until the RPM stops rising, and at this point re-adjust back to 900?

[DK]

I want to do this adjustment and DK you've nailed it. The following is an excerpt from the service manual (5-22). I want to be sure that I do this right! Please correct my shorthand summary below wherever I've strayed:

In step 1,2,3 and 4 we adjust the mixture screws to factory settings, warm up the engine and set the idle speed to 900 rpm.

In step 5 we're enriching all carbs by 1/2 turn out from their nominal starting point.

Can you elaborate on step 6? I take it to mean that all carburetors are enriched by 1/2 turn and then the increase of rpm is noted. If there is any gain then ALL carbs are again enriched by 1/2, the rpm checked for increase and repeated until no rpm increase is noted.

Idle is again set to 900 rpm in step 7.

In steps 8 & 9, and starting with carburetor #1, each mixture screw is turned in until a 50 rpm drop is noted and then it is backed out by 1 whole turn. After backing the mixture screw by 1 turn this is its final setting and we move on to the next carburetor.

For extended high altitude operation repeat this procedure at or near the desired elevation.

Comments? Questions? Concerns?

INITIAL OPENING:
         '97 GL1500C/CT:
           Except California type : 1-3/4 turns out
           California type           : 2 turns out

         GL1500CF, After '97 GL15OOC/CT:
            Except California type : 2-1/4 turns out
            California type           : 2-3/8 turns out

1.  Turn the pilot screw clockwise until it seats lightly, then
     back it out to the specification given. This is an initial setting
     prior to the final pilot screw adjustment.

2.  Warm up the engine to operating temperature. Stop and
     go driving for 10 minutes is sufficient.

3.  Stop the engine and connect a tachometer according to
     the tachometer manufacturer's instructions ( A Digi Sync will do).

4.  Start the engine and adjust the idle speed with the throttle
     stop screw. IDLE SPEED: 900 +/- 100 rpm.

5.  Turn each pilot screw 1/2 turn out from the initial setting.

6.  If the engine speed increases by 50 rpm or more, turn each
     pilot screw out by successive in 1/2 turn increments until
     engine speed does not increase.

7.  Adjust the idle speed with the throttle stop screw.

8.  Turn the No.1 carburetor #1 pilot screw in until the engine
     speed drops by 50 rpm.

9.  Turn the #1 carburetor pilot screw out to the final opening
     from the position obtained in step 8 by 1 complete turn out.

     FINAL OPENING: 1 turn out

10. Adjust the idle speed with the throttle stop screw.

11. Perform steps 8, 9 and 10 for the No. 2, 3, 4, 5 and 6
     carburetor pilot screws.

Bon,

I interpret step six to mean that we are to turn out the pilot screw of all, each and every carb, collectively, to the point that further increase of any individual carb does not result in increasing rpm. That being accomplished, each individual carb is then separately and individually decreased to the precise point that it causes a decrease of 50 rpm & then increased one turn out of the pilot screw; then restoring rpm to that established by the step 6 procedure using the idle adjustment & then going to each successive carb & repeating the procedure thereby resulting in each carb making an identical contribution to engine rpm and presumably an equal contribution throughout the entire rpm range.

As I perceive the procedure, if properly done, it will result in each carb making an equal contribution of one turn of the pilot screw beyond an established baseline of engine rpm and success could be verified by increasing or decreasing the pilot screw of each individual carb one turn, then observing whether it affects rpm; then going beyond one turn until rpm is affected and then restoring the setting and going on to each of the remaining carbs with the same test. As I have it in my mind, doing this verification procedure should achieve near identical results with each carb if properly set.

Another proof this interpretation of step six would be to do a second round of increases per the step 6 procedure and see if any further increases are achieved by further opening of any or the pilot screws. If it does increase, we may be in an infinity loop and wrong.

Simply put, exceed a baseline with all carbs, gradually back each carb down until it affects the base line and then add one turn out of the pilot screw to each carb.

Thanks for your question. I originally thought you were reading it incorrectly but after further thought I think you were correct.

I hate manuals originally written in a foreign language and translated to English. Honda, however, is better than most. BMW is the worst by far. Some of the Chinese consumer stuff, speakers, appliances, etc. are ridiculous & often even funny. Haven't seen an unintended vulgar or risqué one yet, but I'm sure I will at some point.

I hope this is right, criticism is welcome.

Dan

[soundude]

Hi Bon , DK
Its been a long time since I posted, I have been doing alot of research on this exact matter.
So let me suggest, there are two methods to honda's idle drop. Honda had a general manual with the procedure for multiple carbs. No.5 carb #1 if the RPM increases by 50 turn each screw a 1/2 turn out.
But in the general manual No. 5carb #1 if the RPM increases by 50 turn the screw a additional 1/2 turn out till it stops increasing. then proceed to do other carbs. then proceed to step 8.

Then on the CBX 6cyl. procedure is wild, I'll insert youtube link.. found it interesting.

https://www.youtube.com/watch?v=Qa-iJ30rDzs

Then another is turn each mixture to get the peak idle, then proceed to no. 8...

[98valk]

Hi Bon , DK
Its been a long time since I posted, I have been doing alot of research on this exact matter.
So let me suggest, there are two methods to honda's idle drop. Honda had a general manual with the procedure for multiple carbs. No.5 carb #1 if the RPM increases by 50 turn each screw a 1/2 turn out.
But in the general manual No. 5carb #1 if the RPM increases by 50 turn the screw a additional 1/2 turn out till it stops increasing. then proceed to do other carbs. then proceed to step 8.

Then on the CBX 6cyl. procedure is wild, I'll insert youtube link.. found it interesting.

https://www.youtube.com/watch?v=Qa-iJ30rDzs

Then another is turn each mixture to get the peak idle, then proceed to no. 8...

u can always use example #2, for idle richness/leaness.  what I use and then go from there for idle mixture screw adjustment.
https://fboignition.com/articles/sparkplugreading

[turtle254]

Hey, 98valk
Does the Std carb springs run richer than the IS carb springs?
Std springs = rich
Is springs = lean
And why?
Thanks

[98valk]

Hey, 98valk
Does the Std carb springs run richer than the IS carb springs?
Std springs = rich
Is springs = lean
And why?
Thanks

The size of the carb throat determines the amount of air velocity going through. High velocity will draw more fuel up through the needle well.
so std springs keep the throat smaller, more velocity.
The softer I/S springs allow the carb throat to be larger, hence less velocity.

So I/S springs will provide better mpg overall. 
Bottom line they are part of tuning the air/fuel ratio just like the jets are.

[Knapdog]

The Digisync is one of my better buys.
One thing I've noticed is, without the Digisync I was setting the 900rpm revs on the "turn knob" just under the 1000 mark. When I used the Digisync,  900 is actually much closer to what appears to be the "500rpm" mark.

[turtle254]

Hey, 98valk
Does the Std carb springs run richer than the IS carb springs?
Std springs = rich
Is springs = lean
And why?
Thanks

The size of the carb throat determines the amount of air velocity going through. High velocity will draw more fuel up through the needle well.
so std springs keep the throat smaller, more velocity.
The softer I/S springs allow the carb throat to be larger, hence less velocity.

So I/S springs will provide better mpg overall. 
Bottom line they are part of tuning the air/fuel ratio just like the jets are.

Thanks, that's what I was finding.