WOT throttle stop question

[Taxus812]

I fully synced the linkage and carb, following the service manual. Everything seemed clean until I reached the last step to adjust the wide-open throttle stop.

That step has you advance the throttle to the wide open position and check the throttle shaft pins on the carburetors are both verticle. My assumption is they will both be exactly verticle (or adjusted utill they are precisely verticle).

This is where my issue is. My upper is about 2 deg more open than the lower in the WOT position. Both throttles are evenly snapped shut in the idol position and move simultaneously, and the cam follower has a small gap. Is this adjustable? My only thought is that there is wear in the link pin retainers or the link pin itself is bent slightly.

The picture does look even, but it isn't. The bottom is slightly off from the top.

Any help is always appreciated.

1991 Johnson 48hp

 

[brodmann]

The first section on syncing the carburetors should show you how to remove the slack from the linkages. That's what corrects that.

 

[Taxus812]

The first section on syncing the carburetors should show you how to remove the slack from the linkages. That's what corrects that.

Thank you
No slack and they move exactly at the same time. This is what is puzzling.
The pins are at the same position as each other at idol and off from each other slightly at WOT. Geometry should have kept them symmetrical I would think. I was just unsure if Johnson intended that to be by design.

I fired up the parts cannon and ordered retaining pins since there was a lot of play in them anyway I also ordered a new link pin for good measure. I don't know what the previous owner did or didn't do. I figured it wouldn't hurt and it was like $7.

outside of that, it's the throttle itself I guess (bent?).

 

[havoc_squad]

There is no slack. That is what is puzzling. the pins are at the same position at idol and off from each other at WOT.

I'm willing to guess yes it is off. There is a specific procedure mentioned to take the slack out of the carb that does not have the throttle arm on it.

It is described in my factory service manual, it is located in the synchronization and linkage adjustment section:
1. First loosen the carb lever adjusting screw on the carb that is linked to the carb with the throttle arm. (The slaved/linked carbs).
2. Press downward on tab of the adjusting link of the slaved/linked carb linked to remove backlash.
3. Tighten the screw before you release the downward pressure.
4. Check your work, making sure they close and open the exact same time and exact same level.

 

[Taxus812]

I'm willing to guess yes it is off. There is a specific procedure mentioned to take the slack out of the carb that does not have the throttle arm on it.

It is described in my factory service manual
1. First loosen the carb lever adjusting screw on the carb that is linked to the carb with the throttle arm. (The slaved/linked carbs).
2. Press downward on tab of the adjusting link of the slaved/linked carb linked to remove backlash.
3. Tighten the screw before you release the downward pressure.
4. Check your work, making sure they close and open the exact same time and exact same level.

humm..
Followed that method with one exception.

1. Loosened the top carb (slave) adjusting the screw
2. Rotated both throttle shafts to let them snap shut
3. I can't press down on the adjusting tab of the top carb to remove slack. I have to press up lightly (right side bottom of slaved carb adjustment tab) to remove slack.
4. then tighten the screw.
5. verified they move exactly at the same time,

Gonna have to review it again in the daylight.

 

[havoc_squad]

humm..
Followed that method with one exception.

1. Loosened the top carb (slave) adjusting the screw
2. Rotated both throttle shafts to let them snap shut
3. I can't press down on the adjusting tab of the top carb to remove slack. I have to press up lightly (right side bottom of slaved carb adjustment tab) to remove slack.
4. then tighten the screw.
5. verified they move exactly at the same time,

Gonna have to review it again in the daylight.

The principal of that procedure is what is most important, it is expected if the master is in the middle and you have a top slaved carb, then it would be in the inverse direction to remove slack.

 

[jimmbo]

Both Carbs have to be fully Closed at Idle. No Exceptions

 

[Crosbyman]

old style carbs draw idle fuel from the upper idle circuit hence the need to close the inbound air supply to force fuel extraction from the upper idle cct.

see older carb operation.... same thing today !!

 

[Taxus812]

old style carbs draw idle fuel from the upper idle circuit hence the need to close the inbound air supply to force fuel extraction from the upper idle cct.

see older carb operation.... same thing today !!
View attachment 389470

Thanks, it is appreciated.
Both of my carbs are fully closed at Idol. I pulled the airbox off to validate that they were fully closed (and not loose). The slack between master and slave is out, and they sync. When fully opened, there is a 1-degree difference in verticle pin position on the slave vs. the master. I suspect I have that same 1-degree difference in pin position at Idol, but I can't tell. I may work out a throttle position amplifier to test that theory. If that is the case, I must ensure nothing is bent.

The link retaining pins do have a lot of side-to-side slop. That could mess up the throw distance (I don't know the impact). It's an easy test, so I await replacements before I check it again.

 

[jimmbo]

Throttle Position Amplifier? Just loosen the god damn Linkage between the Carbs, insure they are both fully closed, then tighten the Linkage

 

[tphoyt]

I’m having a rough day so far but you brought a smile to my face Jimbo. Thx for that

 

[Taxus812]

Throttle Position Amplifier? Just loosen the god damn Linkage between the Carbs, insure they are both fully closed, then tighten the Linkage

um that is exactly what I did. They don't align. Dont be a ****.

 

[jimmbo]

um that is exactly what I did. They don't align. Dont be a ****.

If you are referring to a Pin, who cares, I doubt there was much Precision in drilling a pin to keep the Shaft from sliding out. What would matter is that both Carbs are Closed.

 

[Taxus812]

If you are referring to a Pin, who cares, I doubt there was much Precision in drilling a pin to keep the Shaft from sliding out. What would matter is that both Carbs are Closed.

Thank You,
Then, it's not an issue. That is what I was looking for.
I questioned because the service manual stated they must be "exactly verticle" at WOT. The tolerances in the syncing were to the mm, which threw up a red flag. This old motor had lots of worn parts and was way out of spec from years of people tweaking.