So, i've been doing some looking and based on some advice i was given before, i'm looking to upgrade my carburetor jets.
What size and brand would be preferred/recommended?
Also, when replaced, is there any tips or tricks when syncing them or should I have a shop preform the work?
All help would be greatly appreciated! Thanks y'all!
Phoenix, hot summer, go with #42 pilots and #115 or #117.5 mains.
Shim the jet needle 1/2 step.
Carb sync is about balancing airflow...no change.
If you want to use an ignition advance and/or aftermarket header, different jets from above may be needed.
Cheers.
Pat
Pat?
what type of exhaust would you use stock or other? like for a 91 1200 currently running stock. just made my first purchased with rpm engine guards so to be back other purchases little at a time piece by piece
Quote from: dbc on June 14, 2021, 01:25:51 PM
Pat?
what type of exhaust would you use stock or other? like for a 91 1200 currently running stock. just made my first purchased with rpm engine guards so to be back other purchases little at a time piece by piece
Hello David, I currently use the oem SS head tubes with the oem collector box then I use aftermarket Cobra F1R slip on mufflers. I like the oem look with the lighter weight benefits offered by the aftermarket slip ons.
Those stock FJ mufflers must weigh in at 20 lbs a piece, so the weight savings is considerable.
There are better, more efficient flowing exhaust systems than the stock Yamaha set up.
The 4 into 1 systems offered by Supertrapp and Kerker I recall flow the best in the high RPM ranges. The 4 into 2 into 1 systems by Hindle, Yoshumira and others I recall had better flow in the mid range power band.
When looking at the exhaust systems by themselves, you were only looking at 5 maybe 7 horsepower gains...however when you combined the volumetric efficiency of a aftermarket system with UniPods and a 5* ignition advance rotor, and proper jetting....it was common to get a 15 to 20 horsepower gain.
Stock FJ's that were dynoing at 100/105 rwhp, were now getting 115/125 rwhp with the combined effects of aftermarket intake, exhaust and ignition advances....and of course proper jetting.
As our Carb Guru David Raforth taught us, with the increase in volumetric efficiency (less restrictive intake and exhaust mods) it's the lower air velocity passing thru the carbs (thus lower slide position and lower jet needle position) that causes the lean condition....and thus the reason you need to add fuel to the lower slide position.
http://www.fjowners.com/index.php?topic=4714.0 (http://www.fjowners.com/index.php?topic=4714.0)
Cheers Pat
Quote from: Pat Conlon on June 14, 2021, 03:41:04 PM
Quote from: dbc on June 14, 2021, 01:25:51 PM
Pat?
what type of exhaust would you use stock or other? like for a 91 1200 currently running stock. just made my first purchased with rpm engine guards so to be back other purchases little at a time piece by piece
Hello David, I currently use the oem SS head tubes with the oem collector box then I use aftermarket Cobra F1R slip on mufflers. I like the oem look with the lighter weight benefits offered by the aftermarket slip ons.
Those stock FJ mufflers must weigh in at 20 lbs a piece, so the weight savings is considerable.
There are better, more efficient flowing exhaust systems than the stock Yamaha set up.
The 4 into 1 systems offered by Supertrapp and Kerker I recall flow the best in the high RPM ranges. The 4 into 2 into 1 systems by Hindle, Yoshumira and others I recall had better flow in the mid range power band.
When looking at the exhaust systems by themselves, you were only looking at 5 maybe 7 horsepower gains...however when you combined the volumetric efficiency of a aftermarket system with UniPods and a 5* ignition advance rotor, and proper jetting....it was common to get a 15 to 20 horsepower gain.
Stock FJ's that were dynoing at 100/105 rwhp, were now getting 115/125 rwhp with the combined effects of aftermarket intake, exhaust and ignition advances....and of course proper jetting.
As our Carb Guru David Raforth taught us, with the increase in volumetric efficiency (less restrictive intake and exhaust mods) it's the lower air velocity passing thru the carbs (thus lower slide position and lower jet needle position) that causes the lean condition....and thus the reason you need to add fuel to the lower slide position.
http://www.fjowners.com/index.php?topic=4714.0 (http://www.fjowners.com/index.php?topic=4714.0)
Cheers Pat
All great information, as usual.
The only thing I'd add is degreeing the cam - which should also end a lot of the blow back through the carbs.