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The Carburetors that came on the USA model 66V motors are originally set to meet EPA emissions guidelines. Yamaha achieved these goals by using the catalytic converter and leaning out the jetting on the carbs. The problem was they had no low end punch, to make up for this they added the accelerator pump. This gives a squirt of gas to the #1 & #3 carbs just off idle, and helped solve the lean low end issue.
When tuners started upgrading these motors they removed the problem laden catalytic converter, and replaced them with a d-plate, They then opened up the air flow to the carburetors to allow the motor to breathe better, as a result rejetting became necessary.
It was quickly discovered that the OEM jetting was extremely lean in the midrange, it was so lean that cruising at 4k-5k rpms for an extended period would cause an engine seizure. (infamous midrange seizure)
As the jetting size was increased to remove the midrange lean condition and improve the top end performance another issue appeared "low end bog" this was now a rich condition from too much fuel. This condition was solved by removing the accelerator pump.
The carb settings for the 66V motors that we see repeated over and over again, were developed quite some time ago. They have withstood the test of time and man.
Carb settings with accelerator pump removed or disabled and after market F/A's (Flame Arrestors): These settings will work on both US and non US models.
1200R Aftermarket F/A's (Flame Arrestors) chokes intact
Currently to my knowledge, there is no known jetting solution that will work for removing the accelerator pump and keeping the stock air box.
Many members have tried this, and there has been no reliable jetting set-up that has been reported to have worked.
If you have tried this and have been successful, please post your results for others to use. We welcome any proven solution.
I have not and will not try this. I have never owned a stock air box, and I enjoy the benefits of the 10%+ performance increase provided by the after market FA's.
If your hull is wet, fix the problem, add an aftermarket bilge and run water socks if necessary. Riva also made a nice splash gaurd for the carbs with after market F/A's.
If your on a budget, remove the inlet piping and drill holes in your stock air box to let it breath.
Please do not PM me asking for a solution for this. After explaining it countless times over the years, I have decided to post here in the hopes of never having to repeat myself again.
When tuners started upgrading these motors they removed the problem laden catalytic converter, and replaced them with a d-plate, They then opened up the air flow to the carburetors to allow the motor to breathe better, as a result rejetting became necessary.
It was quickly discovered that the OEM jetting was extremely lean in the midrange, it was so lean that cruising at 4k-5k rpms for an extended period would cause an engine seizure. (infamous midrange seizure)
As the jetting size was increased to remove the midrange lean condition and improve the top end performance another issue appeared "low end bog" this was now a rich condition from too much fuel. This condition was solved by removing the accelerator pump.
The carb settings for the 66V motors that we see repeated over and over again, were developed quite some time ago. They have withstood the test of time and man.
Carb settings with accelerator pump removed or disabled and after market F/A's (Flame Arrestors): These settings will work on both US and non US models.
1200R Aftermarket F/A's (Flame Arrestors) chokes intact
- 110 Pilot jets, 1 turn out on low speed adjusters
- 120 main jets, 1-1/2 turn out on high speed adjusters
- 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure.
- 110 Pilot jets, 1 turn out on low speed adjusters.
- 125 Main jets 1-1/4 turn out on high speed adjusters
- 1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure.
Currently to my knowledge, there is no known jetting solution that will work for removing the accelerator pump and keeping the stock air box.
Many members have tried this, and there has been no reliable jetting set-up that has been reported to have worked.
If you have tried this and have been successful, please post your results for others to use. We welcome any proven solution.
I have not and will not try this. I have never owned a stock air box, and I enjoy the benefits of the 10%+ performance increase provided by the after market FA's.
If your hull is wet, fix the problem, add an aftermarket bilge and run water socks if necessary. Riva also made a nice splash gaurd for the carbs with after market F/A's.
If your on a budget, remove the inlet piping and drill holes in your stock air box to let it breath.
Please do not PM me asking for a solution for this. After explaining it countless times over the years, I have decided to post here in the hopes of never having to repeat myself again.
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