RSV Main Jets

[Rick Butler]

Guys,

 

Have any of you went into your carbs and replaced your main jets with the same jet size? And does anyone know why Yamaha in their infinite wisdom uses 122.5 jets in #1 & 2, a 117.5 in #3 and a 120.0 in #4?

 

The reason I ask is a friend of mine took his 06 with a Dyna 3000, Barons Nasty Boy slip- ons, needles shimmed and K&Ns and put it on dyno at a Yamaha shop. They started at 72.3HP and 74.05 lbs torque and ended up with 74.95Hp and 73.84 lbs. And they did this by installing 115.0 main jets in all carbs.

 

My first thought is that they don't know what the heck they are doing, but how did they end up with an increase in HP.

 

I have only messed (considerably) with 86-93 carbs and know that they came with 125.0 mains. And (in 89) with a DynoJet V-Boost kit (which they stopped offering in 92) with 150 mains and a few other pilot jet changes, I could get close to 100HP on a dyno. With these RSV carbs, I'm back on virgin ground.

 

Curious minds need to know,

 

Rick

[pegscraper]

staggered main jet thread

[Condor]

Guys,

 

Have any of you went into your carbs and replaced your main jets with the same jet size? And does anyone know why Yamaha in their infinite wisdom uses 122.5 jets in #1 & 2, a 117.5 in #3 and a 120.0 in #4?

 

The reason I ask is a friend of mine took his 06 with a Dyna 3000, Barons Nasty Boy slip- ons, needles shimmed and K&Ns and put it on dyno at a Yamaha shop. They started at 72.3HP and 74.05 lbs torque and ended up with 74.95Hp and 73.84 lbs. And they did this by installing 115.0 main jets in all carbs.

 

My first thought is that they don't know what the heck they are doing, but how did they end up with an increase in HP.

 

I have only messed (considerably) with 86-93 carbs and know that they came with 125.0 mains. And (in 89) with a DynoJet V-Boost kit (which they stopped offering in 92) with 150 mains and a few other pilot jet changes, I could get close to 100HP on a dyno. With these RSV carbs, I'm back on virgin ground.

 

Curious minds need to know,

 

Rick

 

Rick I hope this thread turns up some interesting dialog, but I gotta ask... Is that all the HP these 2ndGens are putting out?? I thought it was around 98hp. Or are they taking the 98 off the crank, and 72-75hp off the rear wheel.... Can't explain the reason for the difference between the 125 and the 115.

[pegscraper]

Those are rear wheel numbers. If you check the history section, you'll see 2nd gens are rated at 1 more hp than 1st gens are.

[Rick Butler]

Thanks Lynn,

 

I don't know how I could have missed Goose's earlier post? But again he is just as curious as I am at times.

 

But now that I have you, did the early Royal Star carbs use the same mains on each cylinder? And I don't think they used the AIS did they?

 

I'm guessing that it has something to do with the AIS and emmisions, but I would have thought that #1 & #3 would have used the same mains since they fire 180 degrees from each other. The 70 degree over and underlap is between #3 and #2 and #4 to #1.

 

Curious minds still need to know,

 

Rick

[pegscraper]

The early Royal Stars with the 28mm carbs had all one size main jet. They were not staggered like the later Ventures are. And they did not have the AIS either. When I swapped 32mm carbs onto my bike, I stayed with all one size jet, like my bike had been. I figured I could watch plugs and mufflers and decide if I thought they needed to be staggered. With four mufflers, it's real easy to tell what's going on in each cylinder. In two years I can't see any need for it. All plugs and all mufflers look the same to me. The 1st gen Ventures and the VMXs also use just one size main jet. I completely fail to see any rhyme or reason for staggered jetting on the 2nd gens.

[BuddyRich]

For Emissions ?

[93 venture]

I hate to stick my foot in my mouth, but do you think it just may cause a inbalance of the cylinders to make it sound more like a harley.

[az1103]

I hate to stick my foot in my mouth, but do you think it just may cause a inbalance of the cylinders to make it sound more like a harley.

 

I would say that's highly unlikely. First because I don't believe Yama would mess with emission requirements for that, and secondly because there is nothing you can do to this engine to make it sound like that primitive smog-maker.

[93 venture]

Did i kill this post or what? :rotfl: