1988 Yamaha 130 dies at transition to high RPM

[usna1970]

1988 Yamaha 130 HP Carburator pilot screw adjustment

I adjusted the idle screw and the 4 pilot screws on the two Nikki carburetors and the engine is running smoothly and transitions from mid to high speed well now. The Yamaha service manual specs for the 1988 Yamaha V4 130 hp 2-st pilot screws are 5/8 to 1 1/8 however the engine dies at those settings. The engine runs best at 2 1/8 turns which incidentally is the correct spec for the 140 hp engine. Should I be concerned? I understand that a fuel mixture that is too lean can damage the engine. If I understand the Nikki carburator correctly the pilot screws control the amount of air/fuel mixture to the piston chamber so the additional turns out from spec should result in a richer mixture. Am I safe in running the engine with these settings?

[TownsendsFJR1300]

I believe your correct and resetting is indeed running richer. You can check the plugs to verify but just it running better tells me your good.

The settings are out a bit. On another thread (see below) another member had a similar issue(very rough running at a certain RPM, between high and low RPM's).

He ran a shock treatment of Yamaha's RingFree (5 gallons) and that alone cleaned his carb (apparently) and fixed his issue. You may consider doing the same. It cleans both the fuel system and top end.

IME, the RF is really good stuff, I run it in everything gas engine I own.

https://www.shopyamaha.com/product/d...?b=Search&d=34


Here's his thread, some interesting reading:
http://www.yamahaoutboardparts.com/f...e-th28109.html


And thanks for the update!
.

[99yam40]

the point is something is not right and you had to adjust out of spec to make up for the plugging of something.
strange you had the same problem with all of the carbs and not just one tho.

are you sure the carbs and there jets are original

[usna1970]

Carbs and jets should be original. I purchased the boat and engine in 1990 from the original owner who was local to me. Everything appeared to be new at the time so I doubt if there was any substutition of parts.

[usna1970]

I've been using Chevron Techron Injector Cleaner as an additive and will try the Yamaha additive in my next tank of fuel.

[TownsendsFJR1300]

I've been using Chevron Techron Injector Cleaner as an additive and will try the Yamaha additive in my next tank of fuel.

Use it at the shock amount of 2 oz / gallon.

Hopefully, that should clear out any crap...