Yamaha 130 v4 missing a cylinder at low rpms

[Spirosdes]

Hello to all,
I am glad that this forum came back to life again!
I have a problem with my outboard is 130 v4 1996,at low rpms between 1000-1700 rpms is shaking very bad like it missing a cylinder,so far i make some searching to identify the problem with no lack!What i've done
1)Cleaned the carbs twice on ultrasonic also i rebuild them and i got them also to a mechanic to cleaned them to!
2)Changed fuel pump 3)Work it from external tank!
4)Checked ignition timing by light and it's spot on
5)Checked Stator, trigger,cdi with dva adaptor all values in spec
6)changed spark plugs
The only thing that make it work better was when i turn pilot screws to 7/8 of a turn besides the 1 1/8 which was earlier but the problem is still there.
Also i have a picture of spark plugs and the right one it seems that is running lean and the others rich!
Also i have a video at 1300rpms that is the problem obvious https://youtube.com/shorts/IN9JYe2blkg?feature=share.
Any help i will appreciate it.

[99yam40]

did you use your timing light to see if each plug was sparking steady while this shaking is going on?
have you checked compression to make sure all cylinders are even?
what are the specs on the pilot screws?
have you tried adjusting them one at a time instead of all the same?
if one cylinder is not getting enough fuel,(lean plug) you need to see why that one is so different than the others.
does this motor have more that one fuel pump?

[Spirosdes]

Actually i didn't use the timing light when this shaking going on but at idle and all the cylinders was firing steadily, also i checked compression and all the cylinders are equal within 10% margin.
The specs for pilot screws from factory are 7/8 +- 1/4 ,i tried to adjust them one by one but is very difficult do to so because its v4 engine and the changes are not so easy to understand if changing only one pilot screw,i checked everything and nothing is different and it has only one fuel pump.

[99yam40]

Actually i didn't use the timing light when this shaking going on but at idle and all the cylinders was firing steadily, also i checked compression and all the cylinders are equal within 10% margin.
The specs for pilot screws from factory are 7/8 +- 1/4 ,i tried to adjust them one by one but is very difficult do to so because its v4 engine and the changes are not so easy to understand if changing only one pilot screw,i checked everything and nothing is different and it has only one fuel pump.

if you did not check each plug while the motor was shaking(problem showed up) how can you say that is not a problem causing the shaking?

Are you saying the motor idles fine, but coming off of ide is when the problem starts?
does it (problem ) go away at higher RPM?
does all plugs have good spark all of the time?
if so I would say you have an off idle port that is plugged causing a lean mixture during the transition from idle jets to Main jets.

if that is true, you might be able to ID which Cylinder by giving it more fuel with the pilot screw to help it transition

[Spirosdes]

The motor idles fine at 750-800 rpms and *****ing at 600 rpms but the problem start happening at 1000 rpms to 1700 after that gap the motor is running great and the wot rpms are at 5800.
I thought it also that is a problem in the transition from idle port to main jet thats why i clean them twice in ultrasonic to get in the passages which is difficult to get.
I thought that the cylinder causing this is from the picture i posted is the last right spark.
If all sparks have good spark all the time i don't really can tell but thats why i test all the ignition system with the dva adaptor.
I will give a try with your recommendation to richen up the suspicious cylinder and i will post back with the results.

[zenoahphobic]

I would also look at your linkages to your carbs and to the ignition advance, they also transition with cam. The carbs might also go out of sync through wobbly worn out sections, and you can never rule out play in the butterfly shafts.

[Spirosdes]

I also thought about it and i went through all the procedure of link and sync and checked also if it was any play at the butterflys also i found out that i have a flat spot on roller cam and i replaced it so i believe that all of this is ok.

[robert graham]

Everything on the motor that moves or slides or has any movement at all really needs a drop of oil a couple of times a year…..that roller cam with the flat spot was almost certainly dry and not turning. I use a mixture of motor oil with just a bit of STP type oil stabilizer in it to make a lubricant that sticks to all parts very well…..an ounce of prevention as they say….