310RD Main Jet? I'm Running Lean?

[NIXITFIXIT]

Today March 20,2022 I started a 2003 Blaster after a complete motor rebuild top to bottom. This is a project I started to help out a local friend in Martinsville, Indiana. This quad was completely abused. I personally am an avid Honda TRX250R owner and this is my first Yamaha Blaster build. Here's my question: When I started the quad it idled just fine and then started to ramp up in rpm's to the point I just shut it down. My first thought was I have an air leak, but I was a little puzzled due to the fact I put the motor through a leak down test prior to putting the motor in the frame and it passed? When placing the motor back into the frame I did remove the head because I didn't think it would fit in the frame opening fully assembled. I ended up performing another leak down this afternoon and I placed 8 pounds of pressure and actually let it sit there for over 13 minutes with no air loss! I sprayed soap water everywhere looking for a leak. With that said I turned my attention to the carburetor because I did put a rebuild kit on it. I noticed that the main jet was labeled 310RD, I don't have a bunch of different size jets for a Mikuni carbs, I run Kehin on my Hondas. Listed below are some details on this project Blaster, let me know if something looks funny or provide me some advice on what to try next to reduce the lean condition.
2003 Blaster Details

• Martinsville Indiana Elevation = 604'
• OEM Mikuni Carburetor, Main = 310RD / Pilot = 32.5 / Needle = 5J22 / Clip Position = 2
• OEM TORES in operation
• Fuel/Air Screw = 1 1/2 Turns Out
• FMF Gold series full pipe.
• New Air Filter Element (not foam), looks like a K&N but not!
• Spark Plug = NGK BR8ES / .025" gap.
• Reeds looked good no light showing, no chips, etc.
• Stock Bore Size with an aftermarket cylinder.
• Carb has its autolube pump removed and carb is blocked off.
• Gas is 87 octane with a 32:1 ratio mix, using Yamalube oil.

Additional Thoughts

• Could the TORES be causing a lean condition?
• Could I just be idled too high?
• Is 310RD main jet too small, 310 seems like a big number jet?
• There is very little to no smoke when running!

 

[blasterBruce]

Today March 20,2022 I started a 2003 Blaster after a complete motor rebuild top to bottom. This is a project I started to help out a local friend in Martinsville, Indiana. This quad was completely abused. I personally am an avid Honda TRX250R owner and this is my first Yamaha Blaster build. Here's my question: When I started the quad it idled just fine and then started to ramp up in rpm's to the point I just shut it down. My first thought was I have an air leak, but I was a little puzzled due to the fact I put the motor through a leak down test prior to putting the motor in the frame and it passed? When placing the motor back into the frame I did remove the head because I didn't think it would fit in the frame opening fully assembled. I ended up performing another leak down this afternoon and I placed 8 pounds of pressure and actually let it sit there for over 13 minutes with no air loss! I sprayed soap water everywhere looking for a leak. With that said I turned my attention to the carburetor because I did put a rebuild kit on it. I noticed that the main jet was labeled 310RD, I don't have a bunch of different size jets for a Mikuni carbs, I run Kehin on my Hondas. Listed below are some details on this project Blaster, let me know if something looks funny or provide me some advice on what to try next to reduce the lean condition.
2003 Blaster Details

• Martinsville Indiana Elevation = 604'
• OEM Mikuni Carburetor, Main = 310RD / Pilot = 32.5 / Needle = 5J22 / Clip Position = 2
• OEM TORES in operation
• Fuel/Air Screw = 2 1/2 Turns Out
• FMF Gold series full pipe.
• New Air Filter Element (not foam), looks like a K&N but not!
• Spark Plug = NGK BR8ES / .025" gap.
• No work done to the reeds because it was glued in position, maybe I should look at the reeds?
• Stock Bore Size with an aftermarket cylinder.

I see no mention of pre mix and or stock oil injection being used, If pre mix double check that the oil injection nipple is blocked off on carb body.

 

[NIXITFIXIT]

I see no mention of pre mix and or stock oil injection being used, If pre mix double check that the oil injection nipple is blocked off on carb body.

This quad is premix, let me check the carb if blocked off.

 

[NIXITFIXIT]

This quad is premix, let me check the if blocked off.

Yes it blocked off by the yellow cap.

 

[NIXITFIXIT]

I will try and post a video of what I'm talking about.

 

[NIXITFIXIT]

I'm going to disassemble the entire carb and carefully clean all parts. I had the quad apart for about a month and or so waiting on case halves. Its possible that some dust and debris could have gotten into the carburetor restricting fuel flow? I also don't have a fuel filter going to the carburetor, maybe a contaminate clogged a jet or something?

 

[NIXITFIXIT]

I'm going to disassemble the entire carb and carefully clean all parts. I had the quad apart for about a month and or so waiting on case halves. Its possible that some dust and debris could have gotten into the carburetor restricting fuel flow? I also don't have a fuel filter going to the carburetor, maybe a contaminate clogged a jet or something?

I completely disassembled the carb and carefully inspected all components. Two issues I noticed was 1. the screen located in the bottom of the carb where the "fuel valve seat" goes was either clogged or discolored. I cleaned with carb cleaner and used compressed air to clean, still looks the same but appeared to be open. 2. Missing the small washer that is on the pilot air screw? You have the screw which has the O-ring, washer, and spring, I'm missing the washer? How important do you think that is? I think that would have an effect on the number of turns?

 

[NIXITFIXIT]

SOLVED ISSUE!
I'm kind of embarrassed but the solve was the idle screw on the back of the TORES system was just turned way to far. I ended up turning it about 2 plus counter clockwise to reduce the idle and with the pilot air screw at 1.5 turns the quad is idling great. Just calmly put it through all its gears and was just as smooth. I'm really happy. I'm now ready to turn the quad over after I properly break it in.