V6 yamaha carb tuning

**Bruce C** · 03-14-2018, 08:44 AM

i have been playing with a 2.6 yamaha and have been looking for some 34 or 36 mm carbs with no luck. I have a set of single float 32mm carbs that i would like to use until i can locate the right ones as the season is approaching and i just picked up a boat. The engine had some port work, tight heads (approx 130psi), horizontal reeds, 225 excel tuner and exhaust divider. Also has finger ports. Ive built it from parts i bought here, heads are hydro tec.

How do these old yamaha carbs work in terms of tuning? I can see that yamaha had different size carbs on the same block for the 150, 175, and 200. If i run these 32 mm carbs from a 1987 200 will they be lean? Should i jet up?

Im thinking that they will obviously restrict the motor and not allow it to make full use of the mods but shouldnt the carb run at the correct AF mixture regardless of whats behind it? I could be completely wrong and would like to hear from some yamaha guys.

**Dingie 2** · 03-14-2018, 09:10 AM

Any time you add more compression and or ignition timing you will need to add fuel , jet up . I would start with a couple sizes larger jet than make a few wot runs read the plugs and piston tops and give that yamaha what it is asking for . You can tune both the carbs but may see a little more RPM with the larger carbs when tuned correct . Joe R

**Bruce C** · 03-14-2018, 09:21 AM

Originally Posted by Dingie 2

Any time you add more compression and or ignition timing you will need to add fuel , jet up . I would start with a couple sizes larger jet than make a few wot runs read the plugs and piston tops and give that yamaha what it is asking for . You can tune both the carbs but may see a little more RPM with the larger carbs when tuned correct . Joe R

Would you suggest mid range and main jets be upped a couple sizes? I havent tried sourcing jets yet, are they still sold from yamaha?