Link and Sync - can't understand results

[SkiDad]

1985 Force 125

OK, so i never have fully checked the link and sync on my engine except for the fact that the carbs both opened fully at the same time. Well the lower carb opened up just a hair past flat. But it always accelerated very smoothly.

Anyhow out of curiosity, i unhooked the ball link at the tower, and thought I would check where the cam touches the roller. the bottom line hit about center to the roller.. so I adjusted the eccentric screw on the roller so it hit between the 2 lines - not a huge amount of adjustment. Seemed to make the bottom carb open up about dead flat (again not much of a change)

here is what I noticed on the water yesterday -- it didn't accelerate as strongly or smoothly - everything is slower - 4000 rpm is now 25 mph instead of 28. But WOT jumped from 5200 to 5400 but speed dropped 1-2 mph.

I just can't understand that result at all - the only thing i really changed was loosening and re-tightening the bar link and that eccentric screw - before I put it back can someone explain what changed and why ?

 

[Jiggz]

This is a shot in the dark, when you changed the setting of the eccentric screw with the cam I believe that changed the WOT timing too. Can you verify the WOT timing?

 

[jerryjerry05]

Timing didn't change when he moved that link.
It would only change if he moved the top turnbuckle.
Unless you added a bigger load(extra weight) the 4000 should still get you 28.
You should have gotten 54-5500 all along.
Remove the extra weight and see what you get.

One of the top post is a linc and sinc.Do that.
My carbs, the butterfly's don't all end up even on full throttle.
Some go past the level on full throttle.

 

[SkiDad]

so I put the eccentric roller about where it was originally and i'm getting about 26 at 4000 - so a hair better but my top rpm dropped back to 5200 but now at 34 mph instead of the consistent 37 I got before i started fiddlin. Still confused why such a small adjustment did all of this. All my trips are with the same 5 people and same stuff.

do i need to put any pressure on the bar link end when i tighten or leave loose ? - i tried to but maybe I'm doing something wrong here.

all I can think is the the carbs were slightly open before ? right now they close fully and the same time.

i read the carb sync sticky and I've done all of this (well i didn't re-check my timing but I haven't changed that)

in my mind same RPM = same speed - how can the same RPM produce a lower speed.

 

[foodfisher]

Spun Prop?