Help!! Any carb rebuild experts out there?

cSickNick · #1 08-19-2003, 01:35 AM

I decided to rebuild the carbs on the old '87 Yamaha 115HP. Pretty straight forward, but a few things have me confused;

1) The Seloc manual states that the main jet "has the greater numerical number embossed on it face("60", small air hole)". Is this correct?? When i dissembled, the main jet location had the smaller numerical number "16"jets, larger air opening.

2) The original pilot screws have a taper, then a step in diameter and continue to taper. The replacement ones have a straight taper, no "step". My bet is to stay with the originals?

3) The dealer that sold the kit says to use the new pilot screws and back out 1 1/2 turns. My common since says to use the originals screws and port 2 1/8", star 1 7/8" back out according to the book.

4) What spark plugs do you recommend B8HS-10 or BR8HS-10? One dealer says "R" type, the other says no "R", motor and book do not state "R". My common since says use "R" because of 2-way radio and GPS.

Thanks Nick

barnacle · #2 08-19-2003, 07:57 PM

Nick I am not a Yamaha man but if the engine was running ok with the jets that are in them then you should keep that size in them. Alot of times a dealer has to rejet a engine to get them to run right. If it has been rebuilt then most likey the jets were richened up some. As for the Seloc manual throw it in the trash and order a OEM manual from your dealer. I would use the R plug. Not knowing the year of your engine there is a good chance the r plug was out yet when the engine was produced.

cSickNick · #3 08-22-2003, 06:27 PM

Hi Joe,

Thanks for the reply.

I should have been clearer on the jet question. I am not planning to change jets. During the rebuild i found the small air hole(# 60, idle?) jets at the top closer to the pilot screws. The larger air hole (#16, main?) jets were at the bottom closer to the float bowl. I believe this is correct, however the Seloc book states the jet size in reverse? I know, your right trash it. (they also have wiring diagrams for the V4, that show 6 spark plugs? ... more bad info)

I ran it last night with original pilot screws at 1 1/2 turns out and it runs fine. Not sure if or how i would fine tune from there.

Curious on your reasoning towards "R" plugs. If there is no noise with non "R" plugs, should i stick with them?

- Nick